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   28765篇
  免费   396篇
  国内免费   19篇
教育   20243篇
科学研究   2593篇
各国文化   296篇
体育   2715篇
综合类   7篇
文化理论   238篇
信息传播   3088篇
  2021年   284篇
  2020年   446篇
  2019年   663篇
  2018年   882篇
  2017年   833篇
  2016年   810篇
  2015年   486篇
  2014年   654篇
  2013年   5180篇
  2012年   606篇
  2011年   662篇
  2010年   519篇
  2009年   541篇
  2008年   598篇
  2007年   560篇
  2006年   504篇
  2005年   443篇
  2004年   464篇
  2003年   381篇
  2002年   403篇
  2001年   554篇
  2000年   603篇
  1999年   527篇
  1998年   305篇
  1997年   290篇
  1996年   360篇
  1995年   295篇
  1994年   306篇
  1993年   263篇
  1992年   437篇
  1991年   442篇
  1990年   406篇
  1989年   458篇
  1988年   398篇
  1987年   385篇
  1986年   387篇
  1985年   446篇
  1984年   354篇
  1983年   359篇
  1982年   304篇
  1981年   297篇
  1980年   316篇
  1979年   411篇
  1978年   314篇
  1977年   285篇
  1976年   245篇
  1975年   201篇
  1974年   220篇
  1973年   216篇
  1971年   194篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
Searching online information resources using mobile devices is affected by small screens which can display only a fraction of ranked search results. In this paper we investigate whether the search effort can be reduced by means of a simple user feedback: for a screenful of search results the user is encouraged to indicate a single most relevant document. In our approach we exploit the fact that, for small display sizes and limited user actions, we can construct a user decision tree representing all possible outcomes of the user interaction with the system. Examining the trees we can compute an upper limit on relevance feedback performance. In this study we consider three standard feedback algorithms: Rocchio, Robertson/Sparck-Jones (RSJ) and a Bayesian algorithm. We evaluate them in conjunction with two strategies for presenting search results: a document ranking that attempts to maximize information gain from the user’s choices and the top-D ranked documents. Experimental results indicate that for RSJ feedback which involves an explicit feature selection policy, the greedy top-D display is more appropriate. For the other two algorithms, the exploratory display that maximizes information gain produces better results. We conducted a user study to compare the performance of the relevance feedback methods with real users and compare the results with the findings from the tree analysis. This comparison between the simulations and real user behaviour indicates that the Bayesian algorithm, coupled with the sampled display, is the most effective. Extended version of “Evaluating Relevance Feedback Algorithms for Searching on Small Displays, ” Vishwa Vinay, Ingemar J. Cox, Natasa Milic-Frayling, Ken Wood published in the proceedings of ECIR 2005, David E. Losada, Juan M. Fernández-Luna (Eds.), Springer 2005, ISBN 3-540-25295-9  相似文献   
142.
Chinese Studies Librarianship in North America   总被引:1,自引:0,他引:1  
Although American libraries had begun collecting Chinese language materials in the 19th century, notably the United States Library of Congress in 1869, Yale in 1878, Harvard in 1879, and Berkeley in 1896, East Asian studies librarianship in North America, including China studies librarianship, was not fully developed until the 1960s. There was no formal organization that represented the interest of Chinese studies librarians because there were few of them and most of them were China scholars rather than trained librarians. More than 100 years later, the number of Chinese studies librarians in North America has increased considerably, primarily in response to the demand in the field of China studies and more recently to the needs of immigrant population and the general public who has an interest in China.This paper traces the history and growth of Chinese studies librarianship in North America, documents the development of the professional organization that represents Chinese studies librarians, and exami.  相似文献   
143.
In 2001, the Regenstrief Institute for Health Care and the Indiana University School of Medicine (IUSM) began an IAIMS planning effort to create a vision and a tactical plan for the first Integrated Advanced Information Management Systems (IAIMS) implementation to cross a large area and include unaffiliated institutions. A number of elements made this planning effort unique. Among these elements were the existence of a network infrastructure that supported the Indianapolis Network for Patient Care, the existence of a mature medical informatics program at the Regenstrief Institute, and the existence of a wide-area knowledge network fostered by the IUSM libraries. However, the leadership for a strong information technology role in the IUSM that could promote collaboration in support of education and research across the diverse Indianapolis hospital systems had been lacking. By bringing together various groups, each with a commitment to improve health care quality and public health across the Indianapolis metropolitan area, regardless of individual institutional affiliation, the strategic directions for I3-Indianapolis IAIMS Initiative have been defined and the foundations for a third generation IAIMS construct have been laid in Indianapolis, Indiana.  相似文献   
144.
OBJECTIVE: This article presents the results of complementary research studies on the behaviors of hospital clinicians in asking clinical questions and the relationship between asking of questions, outcome of information searches, and success in problem solving. METHODS: Triangulation in research methods--a combination of mailed questionnaires, interviews, and a randomized controlled study--was employed to provide complementary views of the research problems under study. RESULTS: The survey and interviews found that clinical problems (concerned mainly with therapy and equipment or technology) were expressed as statements rather than questions (average number of concepts = 1.7), that only slightly more than half (higher for doctors) of problems could be solved, and that the majority of clinical questions were not well formed. An educational workshop however improved clinicians' formulation of questions, but the use of structured prompting was found to improve building of hypotheses in the doctors' group without training. The workshop also improved satisfaction with the obtained information and success in problem solving. Nonetheless, for both the experimental and control groups, more structured and complete questions or statements did not mean higher success rates in problem solving or higher satisfaction with obtained information. CONCLUSION: The triangulation methods have gathered complementary evidence to reject the hypothesis that building well-structured clinical questions would mean higher satisfaction with obtained information and higher success in problem solving.  相似文献   
145.
OBJECTIVES: This paper explores the potential of multinomial logistic regression analysis to perform Web usage mining for an academic health sciences library Website. METHODS: Usage of database-driven resource gateway pages was logged for a six-month period, including information about users' network addresses, referring uniform resource locators (URLs), and types of resource accessed. RESULTS: It was found that referring URL did vary significantly by two factors: whether a user was on-campus and what type of resource was accessed. CONCLUSIONS: Although the data available for analysis are limited by the nature of the Web and concerns for privacy, this method demonstrates the potential for gaining insight into Web usage that supplements Web log analysis. It can be used to improve the design of static and dynamic Websites today and could be used in the design of more advanced Web systems in the future.  相似文献   
146.
147.
Der Burrows-Wheeler-Kompressionsalgorithmus hat als ein universelles Kompressionsverfahren in den letzten Jahren aufgrund seiner hervorragenden Kompressionsraten und hohen Verarbeitungsgeschwindigkeiten eine bemerkenswerte Beachtung erfahren. Das Herzstück des Algorithmus stellt die sogenannte Burrows-Wheeler-Transformation dar. Es handelt sich bei dieser Transformation um eine Permutation der Eingabedaten, welche Zeichen mit ähnlichem Kontext nahe beieinander anordnet. Die Transformation sowie die zugehörige Rücktransformation werden zusammen mit den weiteren Stufen des Algorithmus in einer gegenüber der Standardversion verbesserten Variante vorgestellt und die Ergebnisse mit denen anderer Datenkompressionsalgorithmen verglichen.  相似文献   
148.
The views of specialists (academics, librarians, publishers and information scientists) on trends in scholarly communications were canvassed by means of structured questions. A greater commonality of views was found than might have been expected.  相似文献   
149.
150.
Hayes, Glynn, and Shanahan (2005) defined self-censorship asthe withholding of one’s opinion around an audience perceivedto disagree with that opinion. They argued that people differin their willingness to self-censor and introduced an 8-itemself-report instrument, the Willingness to Self-Censor scale,to measure this individual difference. The results of an experimentalstudy presented here provide further evidence of the constructvalidity of the scale. Each participant in the study was presentedwith a hypothetical scenario that contained information suggestinga group of people the participant was conversing with abouta controversial topic held opinions that were either uniformlysimilar to or different from the participant’s own opinion.Four weeks prior, each participant had responded to the Willingnessto Self-Censor scale and a measure of dispositional shyness.As expected, the manipulation of the climate of opinion affectedwillingness to express an opinion to the group, but more soamong those who scored relatively high on the Willingness toSelf-Censor scale. These results support the notion that somepeople rely on information about the climate of opinion moreso than do others when they decide whether or not to voice theiropinion publicly, and they suggest that the Willingness to Self-Censorscale measures this individual difference.  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