首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   3980篇
  免费   49篇
  国内免费   6篇
教育   2512篇
科学研究   509篇
各国文化   25篇
体育   322篇
综合类   8篇
文化理论   43篇
信息传播   616篇
  2022年   21篇
  2021年   23篇
  2020年   52篇
  2019年   72篇
  2018年   139篇
  2017年   181篇
  2016年   156篇
  2015年   97篇
  2014年   119篇
  2013年   633篇
  2012年   131篇
  2011年   158篇
  2010年   129篇
  2009年   91篇
  2008年   85篇
  2007年   124篇
  2006年   65篇
  2005年   84篇
  2004年   75篇
  2003年   68篇
  2002年   60篇
  2001年   88篇
  2000年   77篇
  1999年   68篇
  1998年   59篇
  1997年   52篇
  1996年   57篇
  1995年   29篇
  1994年   39篇
  1993年   25篇
  1992年   57篇
  1991年   48篇
  1990年   40篇
  1989年   45篇
  1988年   37篇
  1987年   36篇
  1986年   39篇
  1985年   41篇
  1984年   44篇
  1983年   26篇
  1982年   39篇
  1981年   28篇
  1980年   19篇
  1979年   39篇
  1978年   34篇
  1977年   24篇
  1976年   22篇
  1974年   22篇
  1972年   25篇
  1971年   22篇
排序方式: 共有4035条查询结果,搜索用时 15 毫秒
31.
32.
In Information Retrieval, since it is hard to identify users’ information needs, many approaches have been tried to solve this problem by expanding initial queries and reweighting the terms in the expanded queries using users’ relevance judgments. Although relevance feedback is most effective when relevance information about retrieved documents is provided by users, it is not always available. Another solution is to use correlated terms for query expansion. The main problem with this approach is how to construct the term-term correlations that can be used effectively to improve retrieval performance. In this study, we try to construct query concepts that denote users’ information needs from a document space, rather than to reformulate initial queries using the term correlations and/or users’ relevance feedback. To form query concepts, we extract features from each document, and then cluster the features into primitive concepts that are then used to form query concepts. Experiments are performed on the Associated Press (AP) dataset taken from the TREC collection. The experimental evaluation shows that our proposed framework called QCM (Query Concept Method) outperforms baseline probabilistic retrieval model on TREC retrieval.  相似文献   
33.
34.
BACKGROUND: The analysis included forty-one academic health sciences library (HSL) Websites as captured in the first two weeks of January 2001. Home pages and persistent navigational tools (PNTs) were analyzed for layout, technology, and links, and other general site metrics were taken. METHODS: Websites were selected based on rank in the National Network of Libraries of Medicine, with regional and resource libraries given preference on the basis that these libraries are recognized as leaders in their regions and would be the most reasonable source of standards for best practice. A three-page evaluation tool was developed based on previous similar studies. All forty-one sites were evaluated in four specific areas: library general information, Website aids and tools, library services, and electronic resources. Metrics taken for electronic resources included orientation of bibliographic databases alphabetically by title or by subject area and with links to specifically named databases. RESULTS: Based on the results, a formula for determining obligatory links was developed, listing items that should appear on all academic HSL Web home pages and PNTs. CONCLUSIONS: These obligatory links demonstrate a series of best practices that may be followed in the design and construction of academic HSL Websites.  相似文献   
35.
This study is a social media analysis on the use of Twitter at Historically Black Colleges and University (HBCU) libraries. While information science researchers have begun examining how libraries use social media, the vast majority of these studies are situated at large flagship research-intensive universities. Additionally, there currently exist deficiencies in research on social media deployment at HBCU libraries. We leverage, the IBM Watson's analytic engine, to systemically examine over 23,000, tweets over an eighteen-month period, around a set of objective measures including propagation of retweets and sentiment to assess follower engagement. The analysis found little evidence of follower engagement with library generated content. However, we observed a substantial volume of library tweets coalesced around institutional boosterism, rather than library related phenomena. This non-library related content represented the vast majority of retweets, but paradoxically was propagated by non-followers. Additionally, tweets relating to institutional boosterism produced the most positive sentiment within the data.  相似文献   
36.
The current state of the Russian Science Citation Index is analyzed. Several areas for its further development identified by long-standing active users, such as data searching, refinement, and storage; current user alerts; data input with the Science Index license; patent information; and the application programming interface (API) are investigated.  相似文献   
37.
38.
39.
This article considers the dynamics and specifics of training highly qualified scientific staff (philosophy doctors and doctors of sciences) in the field of information security and data protection in a 10-year period of 2004–2013 in basic research specialties as classified by the Higher Attestation Commission (VAC) of the Ministry of Education and Science of the Russian Federation.  相似文献   
40.
This paper demonstrates the application of module arithmetic for controlling the level of information security by a new technique referred as integer splitting. The basic definitions and concepts of the method are provided. The mathematical function of arising transformation is described in detail; its properties were studied and the basic theorems were proven that justify the use of splitting in practical applications. An active system was designed and characteristic cases of its operation are considered.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号