Choice of Lesson (Bấm chuột vào ô sổ xuống bên dưới và chọn bài kiểm tra)

Level A Level B Level C TOEFL Incorrect word TOEFL Reading Comprehension Synonym word TOEFL

Monday, July 30, 2007

Trinh do C - Bai 65

Trình độ C - Bài 65

1. The boy fell into the river and was ________ along by the fast current.




2. In a greengrocer's shop there is a lot of ________ when fruit and vegetables are not sold.




3. If you don't know what the words means, why don't you look it ________ the dictionary?




4. - Do I have to make that French course? - No, you ________.




5. He had no way of making a fire so he had to eat the fish ________.




6. Her plane takes ________ at 3 p.m.




7. The child was told to ________ for being rude to his uncle.




8. I'll have to ________ to you, otherwise he will hear.




9. "I'll call ________ you at 6 o'clock," said James.




10. Try to write your figures clearly, the way Anne ________.




11. The concert was so ________ that the audience went to sleep.




12. When Mike entered the room, he looked rather pale and in ________ of a shave.




13. The traffic lights ________ to green, and the cars drove on.




14. Many people escaped ________ prison camps during the last war.




15. How long have you been working ________ this exercise?




16. I hope they will never be able to ________ his offer.




17. After I had discussed my plans with Professor Watkins I ________ to work on my dissertation.




18. Absenteeism per employee ________ out at 4 days a year.




19. The storm played ________ the cross-channel ferry crossings.




20. If you've got a ________ of cards, I'll show you some tricks.






Trinh do C - Bai 64

Trình độ C - Bài 64

1. He ________ the office when I arrived.




2. He will do the work and then send you the ________ for it.




3. My brother is always late for appointments. He seems to be ________ of leaving the house on time.




4. Sarah would not ________ her parent's advice about her choice of career.




5. Unfortunately, Sally has never been too friendly to Jim and keeps him at a ________.




6. I ________ rather go to Ireland than Scotland for my holiday.




7. Our company is a small organization with only a few ________.




8. Catching the earlier train will give us the ________ to do some shopping.




9. I've ________ had time to read the report so I can't give an opinion on it.




10. She ________ have rushed to the airport like that. The plane was delayed by several hours.




11. Several new hotels have been built along the coast, and they have helped the tourist business ________.




12. Margaret looked embarrassed ________ than pleased when she won the prize.




13. He has been waiting for this letter for days, and at ________ it has come.




14. This year his company made a ________ but next year we hope to make a profit.




15. Even though he was often cruel ________ his dog, it remained faithful to him.




16. We expect a great deal ________ you, Smith.




17. She is well-qualified in typing and very efficient ________ her work.




18. If he ________ me to tell it to him, I would do so with pleasure.




19. I do not believe that this preposterous scheme is ________ of our serious consideration.




20. She's an excellent manager. She runs a really tight ________.






Trinh do C - Bai 63

Trình độ C - Bài 63

1. I shouldn't imagine there is ________ on earth who can answer that question.




2. Children in large families learn how to get ________ with other people.




3. Hello. Is that 21035? Please put me ________ to the manager.




4. ________ pleasant it is to sit here in the shade!




5. I'm going to ________ my dress dry-cleaned.




6. I'm afraid Grandfather's writing is becoming more and more ________.




7. They had to ________ some trees that had been standing for over a hundred years.




8. I ________ rather not go by coach, if you don't mind.




9. "Thank goodness you have come ________!" she exclaimed in relief.




10. It was a magnificent car which must have belonged to a very ________ person.




11. I'll give George your message the ________ I see him.




12. I had a ________ problem with my computer when I started to use it.




13. She is very stubborn, so it will be difficult to ________ her to go.




14. In the car park the detective came face ________ face with spy.




15. I can't afford a TV so we'll just have to do ________ one for the moment.




16. He is intent ________ passing the examination, but I'm doubtful about his chances.




17. ________ the evening Dick and Mark will meet again.




18. When he was washing his shirt in the bathroom, the telephone ________.




19. I am afraid, Mr Jones, that the bank is obliged to refuse your application for an extended ________.




20. The delay to the fight was brought ________ by bad weather.






Trinh do C - Bai 62

Trình độ C - Bài 62

1. The ________ thing about travelling by train rather than by car is that you can sleep or read during the journey.




2. I let the phone ring several times before I ________ the receiver.




3. We have arranged special insurance to cover medical ________ in the event of an accident.




4. Everyone who applies for a job with the company is given an intelligence ________.




5. If you hear the baby ________, please tell me.




6. In the last few weeks, a record number of cars ________.




7. He thought ________ getting a new job for a long time, but in the end he decided not to.




8. Of course I'm a Christian ________ I expect everyone who works here to be a Christian too.




9. I'm disgusted ________ your behaviour!




10. You forgot to thank Aunt Jane ________ her present.




11. I'm not very fond ________ dancing.




12. I was afraid of mentioning it ________ him.




13. We have a ________ future ahead with little comfort, food or hope.




14. She ________ me all about her new job when we meet next Thursday.




15. He ________ for Paris last Saturday.




16. I would have bought that camera, if I ________ money.




17. As soon as you ________ to the station, you'll meet Dick who is waiting for you at the entrance door.




18. If I had more time, I ________ some of those articles.




19. I'd be very ________ to go to Japan one day.




20. The product has been a great success. We're doing a roaring ________ in it.






Trinh do C - Bai 61

Trình độ C - Bài 61

1. He stood on one leg, ________ against the wall, while he took off his shoe.




2. ________ of all of us who are here tonight, I would like to thank Mr Jones for his talk.




3. It was a complete ________; I never meant to hurt her!




4. When I was in the hotel my money ________.




5. ________ to an accident in the High Street, traffic is moving very slowly on the London Road.




6. I am going to have a short rest as I ________ a headache.




7. Wild ducks always fly in a definite ________.




8. There was a robbery at the bank, and the police are looking ________ the matter.




9. I'm not sure how old he is but he must be ________ for 70.




10. The sky is ________ so I don't think it will rain.




11. It tasted so ________ of lemon that the other flavours were lost.




12. I am not in the least ________ about his opinion.




13. Whenever you go to the sales, you ________ your money buying things that nobody wants.




14. Paris lies ________ the river Seine.




15. At the end of the day we watch a little television ________ going to bed.




16. Mr Handforth could have continued working until he was 65, but he decided to ________ early.




17. It is obvious to everyone that he is not responsible ________ this mistake.




18. The sergeant's orders were perfectly ________.




19. She's obviously going to get a top job soon. She's a real high ________.




20. The boy looks like his father and the girl takes ________ her mother.






List of search engines

From Wikipedia, the free encyclopedia

Jump to: navigation, search

(The entries are in alphabetical order within each category.)

Contents


General search engines

Open source search engines

Metasearch engines

See also: Metasearch engine

Regional search engines

People search engines

Email-based search engines

Visual search engines

Answer-based search engines

Google-based search engines

Yahoo!-based search engines

Windows-Live-based search engines

Ask.com-based search engines

Job search engines

See also: Job search engine and Category:Job search engines

Forum search engines

Blog search engines

News search engines

Multimedia search engines

Code search engines

BitTorrent search engines

These search engines work across the BitTorrent protocol.

Accountancy search engines

Medical search engines

Property search engines

Business search engines

Comparison shopping search engines

Geographic search engines

Social search engines

  • Google Co-op is a platform provided by Google that allows web developers to feature specialized information in web searches, refine and categorise queries, and create customized search engines
  • Rollyo
  • Wink provides web search by analyzing user contributions such as bookmarks and feedback
See also: Social search and Relevance feedback

Search engines for kids

Desktop search engines

See also: Desktop search

Legal

Defunct search engines

See also

External links

Search engine

From Wikipedia, the free encyclopedia

Jump to: navigation, search


Google search is the world's most popular search engine.
Google search is the world's most popular search engine.

A search engine is an information retrieval system designed to help find information stored on a computer system, such as on the World Wide Web, inside a corporate or proprietary network, or in a personal computer. The search engine allows one to ask for content meeting specific criteria (typically those containing a given word or phrase) and retrieves a list of items that match those criteria. This list is often sorted with respect to some measure of relevance of the results. Search engines use regularly updated indexes to operate quickly and efficiently.

Without further qualification, search engine usually refers to a Web search engine, which searches for information on the public Web. Other kinds of search engine are enterprise search engines, which search on intranets, personal search engines, and mobile search engines. Different selection and relevance criteria may apply in different environments, or for different uses.

Some search engines also mine data available in newsgroups, databases, or open directories. Unlike Web directories, which are maintained by human editors, search engines operate algorithmically or are a mixture of algorithmic and human input.


Contents


History

The very first tool used for searching on the Internet was Archie.[1] The name stands for "archive" without the "v". It was created in 1990 by Alan Emtage, a student at McGill University in Montreal. The program downloaded the directory listings of all the files located on public anonymous FTP (File Transfer Protocol) sites, creating a searchable database of file names; however, Archie did not index the contents of these files.

The rise of Gopher (created in 1991 by Mark McCahill at the University of Minnesota) led to two new search programs, Veronica and Jughead. Like Archie, they searched the file names and titles stored in Gopher index systems. Veronica (Very Easy Rodent-Oriented Net-wide Index to Computerized Archives) provided a keyword search of most Gopher menu titles in the entire Gopher listings. Jughead (Jonzy's Universal Gopher Hierarchy Excavation And Display) was a tool for obtaining menu information from specific Gopher servers. While the name of the search engine "Archie" was not a reference to the Archie comic book series, "Veronica" and "Jughead" are characters in the series, thus referencing their predecessor.

Timeline
Note: "Launch" refers only to web
availability of original crawl-based
web search engine results.
Year Engine Event
1993 Aliweb Launch
1994 WebCrawler Launch
JumpStation Launch
Infoseek Launch

Lycos Launch
1995 AltaVista Launch (part of DEC)
Excite Launch
1996 Dogpile Launch
Inktomi Founded
HotBot Founded

Ask Jeeves Founded
1997 Northern Light Launch
1998 Google Launch
1999 AlltheWeb Launch
Naver Launch
Teoma Founded
Vivisimo Founded
2000 Baidu Founded
2003 Info.com Launch
2004 Yahoo! Search Final launch

A9.com Launch
2005 MSN Search Final launch
Ask.com Launch
AskMeNow Launch
2006 wikiseek Founded
Quaero Founded
Ask.com Launch
Live Search Launch
ChaCha Beta Launch
Quintura Beta Launch
2007 wikiseek Launched
Tokenizer Launched

The first Web search engine was Wandex, a now-defunct index collected by the World Wide Web Wanderer, a web crawler developed by Matthew Gray at MIT in 1993. Another very early search engine, Aliweb, also appeared in 1993, and still runs today. JumpStation (released in early 1994) used a crawler to find web pages for searching, but search was limited to the title of web pages only. One of the first "full text" crawler-based search engine was WebCrawler, which came out in 1994. Unlike its predecessors, it let users search for any word in any webpage, which became the standard for all major search engines since. It was also the first one to be widely known by the public. Also in 1994 Lycos (which started at Carnegie Mellon University) was launched, and became a major commercial endeavor.

Soon after, many search engines appeared and vied for popularity. These included Excite, Infoseek, Inktomi, Northern Light, and AltaVista. In some ways, they competed with popular directories such as Yahoo!. Later, the directories integrated or added on search engine technology for greater functionality.

Search engines were also known as some of the brightest stars in the Internet investing frenzy that occurred in the late 1990s. Several companies entered the market spectacularly, receiving record gains during their initial public offerings. Some have taken down their public search engine, and are marketing enterprise-only editions, such as Northern Light.

Google

Around 2001, the Google search engine rose to prominence. Its success was based in part on the concept of link popularity and PageRank. The number of other websites and webpages that link to a given page is taken into consideration with PageRank, on the premise that good or desirable pages are linked to more than others. The PageRank of linking pages and the number of links on these pages contribute to the PageRank of the linked page. This makes it possible for Google to order its results by how many websites link to each found page. Google's minimalist user interface is very popular with users, and has since spawned a number of imitators.

Google and most other web engines utilize not only PageRank but more than 150 criteria to determine relevancy.[2] The algorithm "remembers" where it has been and indexes the number of cross-links and relates these into groupings. PageRank is based on citation analysis that was developed in the 1950s by Eugene Garfield at the University of Pennsylvania. Google's founders cite Garfield's work in their original paper. In this way virtual communities of webpages are found. Teoma's search technology uses a communities approach in its ranking algorithm. Nippon Electric Corporation|NEC Research Institute has worked on similar technology. Web link analysis was first developed by Jon Kleinberg and his team while working on the CLEVER project at IBM's Almaden Research Center. Google is currently the most popular search engine.

Yahoo! Search

The two founders of Yahoo!, David Filo and Jerry Yang, Ph.D. candidates in Electrical Engineering at Stanford University, started their guide in a campus trailer in February 1994 as a way to keep track of their personal interests on the Internet. Before long they were spending more time on their home-brewed lists of favourite links than on their doctoral dissertations. Eventually, Jerry and David's lists became too long and unwieldy, and they broke them out into categories. When the categories became too full, they developed subcategories ... and the core concept behind Yahoo! was born. In 2002, Yahoo! acquired Inktomi and in 2003, Yahoo! acquired Overture, which owned AlltheWeb and AltaVista. Despite owning its own search engine, Yahoo! initially kept using Google to provide its users with search results on its main website Yahoo.com. However, in 2004, Yahoo! launched its own search engine based on the combined technologies of its acquisitions and providing a service that gave pre-eminence to the Web search engine over the directory.

Microsoft

The most recent major search engine is MSN Search (evolved into Live Search), owned by Microsoft, which previously relied on others for its search engine listings. In 2004, it debuted a beta version of its own results, powered by its own web crawler (called msnbot). In early 2005 , it started showing its own results live, and ceased using results from Inktomi, now owned by Yahoo!. In 2006, Microsoft migrated to a new search platform - Live Search, retiring the "MSN Search" name in the process.

Baidu

Due to the difference between hanzi and the Roman alphabet, the Chinese search market did not boom until the introduction of Baidu in 2000.[citation needed]

Top Providers

Market Share worlwide as of June, 2007 [3]
Google (all) - above 74%
Google.com - 51.53%
Yahoo! Web Sites - 12.16%
Google UK - 9.51%
MSN - 4.34%
Google AdSense for Content - 3.51%
Google Canada - 3.17%
AOL - 2.06%
Top U.S. Search Providers by Searches, May 2007:

Provider Searches (000) Share of Total Searches (%)
Google 4,033,277 56.3
Yahoo 1,540,949 21.5
MSN/Windows Live 605,400 8.4
AOL 381,961 5.3
Ask.com 142,418 2.0
My Web Search 61,784 0.9
Comcast 34,908 0.5
EarthLink 33,461 0.5
My Way 30,122 0.4
Dogpile.com 26,295 0.4
Other 275,365 3.8
All search 7,165,940 100.0
Source: Nielsen//NetRatings, 2007

Challenges faced by search engines

  • The Web is growing much faster than any present-technology search engine can possibly index see distributed web crawling. In 2006, some users found major search-engines became slower to index new webpages. Time to index in MSN Search, slowing down in Dec-2005 & Jan-2006:(18-Jan-2006).
  • Many webpages are updated frequently, which forces the search engine to revisit them periodically.
  • The Web search queries one can make are currently limited to searching for key words, which may result in many Type I and type II errors positives, especially using the default whole-page search. Better results might be achieved by using a Proximity search (text) option with a search-bracket to limit matches within a paragraph or phrase, rather than matching random words scattered across large pages. Another alternative is using human operators to do the researching for the user with organic search engines.
  • Dynamically generated sites may be slow or difficult to index, or may result in excessive results, perhaps generating 500 times more webpages than average. Example: for a dynamic webpage which changes content based on entries inserted from a database, a search-engine might be requested to index 50,000 static webpages for 50,000 different parameter values passed to that dynamic webpage. The indexing is numerous in the dynamic webpages, they can also be shown by logical thinking: if one parameter-value generates 1 indexed webpage, 10 generate 10, and 1,000 parameter-values generate 1,000 webpages, etc. Also, some dictionary-page websites are indexed using dynamic pages: for example, search for page-counts of URLs containing variations of "dictionary.*" and observe the page-totals reported by the search-engines, perhaps in excess of 50,000 pages.
  • Many dynamically generated websites are not indexable by search engines; this phenomenon is known as the invisible web. There are list of search engines that specialize in crawling the invisible web by crawling sites that have dynamic content, require forms to be filled out, or are password protected.
  • Relevancy: sometimes the engine can't get what the person is looking for.
  • Some search-engines do not rank results by relevance, but by the amount of money the matching websites pay.
  • In 2006, hundreds of generated websites used tricks to manipulate a search-engine to display them in the higher results for numerous keywords. This can lead to some search engine results being polluted with linkspam or bait-and-switch pages which contain little or no information about the matching phrases. The more relevant webpages are pushed further down in the results list, perhaps by 500 entries or more.
     LSPAM:  The number of spam-links that slip past search-engine restrictions
is a company-proprietary secret. Hundreds of spam-links can be verified
by searching 24 variations of spelling "Da Vinci"/"Davinci" such as
"Devinchi" or "Davinche" and counting the matching links which contain
no relevant details, such as: "devinchi com. ketogenic
diet recipe kona coffee label" -- searches can be repeated
with numerous other rare words. (Such searches will yield definitive
results for years and will, of course, be the most current research on the
subject. See also: linkspam explaining proliferation of spam-pages.
  • Secure pages content hosted on HTTPS URLs pose a challenge for crawlers which either can't browse the content for technical reasons or won't index it for privacy reasons.

How search engines work

A search engine operates, in the following order

  1. Web crawling
  2. Indexing
  3. Searching

Web search engines work by storing information about a large number of web pages, which they retrieve from the WWW itself. These pages are retrieved by a Web crawler (sometimes also known as a spider) — an automated Web browser which follows every link it sees. Exclusions can be made by the use of robots.txt. The contents of each page are then analyzed to determine how it should be indexed (for example, words are extracted from the titles, headings, or special fields called meta tags). Data about web pages are stored in an index database for use in later queries. Some search engines, such as Google, store all or part of the source page (referred to as a cache) as well as information about the web pages, whereas others, such as AltaVista, store every word of every page they find. This cached page always holds the actual search text since it is the one that was actually indexed, so it can be very useful when the content of the current page has been updated and the search terms are no longer in it. This problem might be considered to be a mild form of linkrot, and Google's handling of it increases usability by satisfying user expectations that the search terms will be on the returned webpage. This satisfies the principle of least astonishment since the user normally expects the search terms to be on the returned pages. Increased search relevance makes these cached pages very useful, even beyond the fact that they may contain data that may no longer be available elsewhere.

When a user enters a query into a search engine (typically by using key words), the engine examines its index and provides a listing of best-matching web pages according to its criteria, usually with a short summary containing the document's title and sometimes parts of the text. Most search engines support the use of the boolean operators AND, OR and NOT to further specify the search query. Some search engines provide an advanced feature called proximity search which allows users to define the distance between keywords.

The usefulness of a search engine depends on the relevance of the result set it gives back. While there may be millions of webpages that include a particular word or phrase, some pages may be more relevant, popular, or authoritative than others. Most search engines employ methods to rank the results to provide the "best" results first. How a search engine decides which pages are the best matches, and what order the results should be shown in, varies widely from one engine to another. The methods also change over time as Internet usage changes and new techniques evolve.

Most Web search engines are commercial ventures supported by advertising revenue and, as a result, some employ the controversial practice of allowing advertisers to pay money to have their listings ranked higher in search results. Those search engines which do not accept money for their search engine results make money by running search related ads alongside the regular search engine results. The search engines make money every time someone clicks on one of these ads.

The vast majority of search engines are run by private companies using proprietary algorithms and closed databases, though some are open source.[citation needed]

Storage costs and crawling time

? This article or section may contain original research or unverified claims.
Please help Wikipedia by adding references. See the talk page for details.

Storage costs are not the limiting resource in search engine implementation. Simply storing 10 billion pages of 10 kbytes each (compressed) requires 100TB and another 100 TB or so for indexes, giving a total hardware cost of under $200k: 100 cheap PCs each with four 500GB disk drives.[citation needed]

However, a public search engine requires considerably more resources than this to calculate query results and to provide high availability. Also, the costs of operating a large server farm are not trivial.[citation needed]

Crawling 10B pages with 100 machines crawling at 100 pages/second would take 1M seconds, or 11.6 days on a very high capacity Internet connection. Most search engines crawl a small fraction of the Web (10-20% pages) at around this frequency or better, but also crawl dynamic websites (e.g. news sites and blogs) at a much higher frequency.[citation needed]

Geospatially enabled search engines

A recent enhancement to search engine technology is the addition of geocoding and geoparsing to the processing of the ingested documents being indexed, to enable searching within a specified locality (or region). Geoparsing attempts to match any found references to locations and places to a geospatial frame of reference, such as a street address, gazetteer locations, or to an area (such as a polygonal boundary for a municipality).[citation needed] Through this geoparsing process, latitudes and longitudes are assigned to the found places, and these latitudes and longitudes are indexed for later spatial query and retrieval. This can enhance the search process tremendously by allowing a user to search for documents within a given map extent, or conversely, plot the location of documents matching a given keyword to analyze incidence and clustering, or any combination of the two. See the list of search engines for examples of companies which offer this feature.

Vertical Search Engines

Vertical search engines or specialized search engines are search engines which specialize in specific content categories or that search within a specific medium. Popular search engines, such as Google or Yahoo!, are very effective when the user searches for web sites, web pages, or general information. Vertical search engines enable the user to find specific types of listings, thus making the search more customized to the user's needs.

Category-focused vertical search engines

This type of search engine searches for sites, pages, and other online content relevant to a specific area or category. Vertical search engines falling into this category include shopping search engines (such as Froogle or NexTag), government search engines (such as "Google US government search" and searchgov.com), legal search engines (such as law.com and lawcrawler), travel search engines (such as Travelocity and Expedia), financial search engines (such as Business.com and Hoovers), business search engines (such as knuru) and many others.

Media-focused search engines

This type of search engine focuses on searching within specific online media. This group includes the following subcategories, although this list is not exhaustive:

  1. Forum and discussion group search engines which scan discussion boards, forums, groups, answer pages and other "many to many" online media. Examples of search engines of this kind include Omgili and board-tracker.
  2. News group search engines which scan news groups worldwide. This category includes bincrawler, Google groups, knuru and many others.
  3. Blog search engines focus on searching web logs or "the blogosphere." Some of the members of this group are: Google Blog Search, Technorati, knuru, and Blog-search-engine.
  4. Mailing list search engines search in mailing lists. These include "list of lists" and E-Zine List
  5. Chat search engines search on chat rooms. Examples of this subcategory are Chatsearch and Search IRC.

Social search

Further information: Social search

Social search engines are a type of vertical search engine found on many websites[citation needed].

See also

Notes

The footnotes below are given in support of the statements above. Because some facts are proprietary secrets held by private companies and therefore not documented in journals, such facts are reasoned from facts that are public.

  • GBMW: Reports of 30-day punishment, re: Car maker BMW had its German website bmw.de delisted from Google, such as: Slashdot-BMW (05-Feb-2006).
  • INSIZ: Maximum size of webpages indexed by MSN/Google/Yahoo! ("100-kb limit"): Max Page-size (28-Apr-2006).
  1. ^ "Internet History - Search Engines" (from Search Engine Watch), Universiteit Leiden, Netherlands, September 2001, web: LeidenU-Archie.
  2. ^ Sergey Brin and Lawrence Page. The Anatomy of a Large-Scale Hypertextual Web Search Engine. Stanford University. 1998.
  3. ^ http://marketshare.hitslink.com/report.aspx?qprid=1

References

  • "Seeking Better Web Searches," Scientific American magazine (February 2005 Issue).

External links