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   21277篇
  免费   273篇
  国内免费   124篇
教育   14920篇
科学研究   2400篇
各国文化   227篇
体育   1692篇
综合类   15篇
文化理论   178篇
信息传播   2242篇
  2020年   270篇
  2019年   414篇
  2018年   535篇
  2017年   540篇
  2016年   524篇
  2015年   342篇
  2014年   419篇
  2013年   4075篇
  2012年   425篇
  2011年   451篇
  2010年   343篇
  2009年   362篇
  2008年   389篇
  2007年   408篇
  2006年   387篇
  2005年   382篇
  2004年   364篇
  2003年   349篇
  2002年   332篇
  2001年   318篇
  2000年   350篇
  1999年   337篇
  1998年   205篇
  1997年   221篇
  1996年   264篇
  1995年   246篇
  1994年   217篇
  1993年   221篇
  1992年   290篇
  1991年   303篇
  1990年   306篇
  1989年   333篇
  1988年   275篇
  1987年   286篇
  1986年   287篇
  1985年   304篇
  1984年   281篇
  1983年   293篇
  1982年   236篇
  1981年   230篇
  1980年   220篇
  1979年   304篇
  1978年   267篇
  1977年   237篇
  1976年   193篇
  1975年   182篇
  1974年   183篇
  1973年   173篇
  1972年   146篇
  1971年   149篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
33.
34.
35.
36.
Quantum algorithms are a field of growing interest within the theoretical computer science as well as the physics community. Surprisingly, although the number of researchers working on the subject is ever-increasing, the number of quantum algorithms found so far is quite small. In fact, the task of designing new quantum algorithms has been proven to be extremely difficult. In this paper we give an overview of the known quantum algorithms and briefly describe the underlying ideas. Roughly, the algorithms presented are divided into hidden subgroup type algorithms and in amplitude amplification type algorithms. While the former deal with problems of group-theoretical nature and have the promise to yield strong separations of classical and quantum algorithms, the latter have been proved to be a prolific source of algorithms in which a polynomial speed-up as compared to classical algorithms can be achieved. We also discuss quantum algorithms which do not fall under these two categories and give a survey of techniques of general interest in quantum computing such as adiabatic computing, lower bounds for quantum algorithms, and quantum interactive proofs.  相似文献   
37.
Medicine has made increasing use of meta-analysis, largely as a quantitative procedure for combining results of clinical trials. Meta-analysis begins with a comprehensive review of the literature. The next step is a systematic analysis of the quality and content of each study. Finally, results are combined statistically and conclusions are drawn from this new overview of the data. This paper presents a brief historical perspective on the use of meta-analysis in medicine with emphasis on the medical library. The authors conclude that in the future, medical librarians will play a significant role in the application of this useful technique.  相似文献   
38.
39.
40.
Chaos theory, informational needs, and natural disasters   总被引:2,自引:0,他引:2  
This study applies chaos theory to a system-wide analysis of crisis communication in a natural disaster. Specifically, we analyze crisis communication during the 1997 Red River Valley flood in Minnesota and North Dakota. This flood, among the worst in modern American history, consumed entire metropolitan areas, displacing thousands of people. The conditions and decisions leading to the disaster, and the subsequent reactions are retraced. Communication related to river crest predictions (fractals), the shock at the magnitude of the crisis (cosmology episode), novel forms of reorganizing (self-organization), and agencies that aided in establishing a renewed order (strange attractors) are evaluated. Ultimately, we argue that preexisting sensemaking structures favoring rationalized, traditional views of a complex system led officials to make inappropriately unequivocal predictions and ultimately diminished the effectiveness of the region's crisis communication and planning.  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