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   19440篇
  免费   271篇
  国内免费   125篇
教育   13737篇
科学研究   2236篇
各国文化   188篇
体育   1620篇
综合类   12篇
文化理论   174篇
信息传播   1869篇
  2021年   130篇
  2020年   252篇
  2019年   382篇
  2018年   510篇
  2017年   484篇
  2016年   471篇
  2015年   322篇
  2014年   408篇
  2013年   3656篇
  2012年   364篇
  2011年   426篇
  2010年   311篇
  2009年   336篇
  2008年   355篇
  2007年   374篇
  2006年   369篇
  2005年   357篇
  2004年   329篇
  2003年   330篇
  2002年   313篇
  2001年   319篇
  2000年   337篇
  1999年   337篇
  1998年   196篇
  1997年   208篇
  1996年   245篇
  1995年   227篇
  1994年   180篇
  1993年   194篇
  1992年   264篇
  1991年   281篇
  1990年   281篇
  1989年   310篇
  1988年   246篇
  1987年   262篇
  1986年   262篇
  1985年   303篇
  1984年   249篇
  1983年   244篇
  1982年   214篇
  1981年   203篇
  1980年   185篇
  1979年   305篇
  1978年   219篇
  1977年   220篇
  1976年   179篇
  1975年   162篇
  1974年   183篇
  1973年   155篇
  1971年   138篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
33.
34.
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   
35.
Richard H. Beyler 《Minerva》2006,44(3):251-266
In responding to incidents of internal ‘indiscipline’, the Kaiser Wilhelm Society many times asserted its authority, sometimes in cooperation with agencies of the Nazi regime. Following the Second World War, however, the KWS represented itself as having been intrinsically anti-Nazi. This essay describes the assumptions inherent in this view, and points to its wider implications for post-war German science.  相似文献   
36.
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   
37.
38.
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   
39.
40.
Ordinary markets allow parties, not the state, to value property and projects. But they do not account for subjective value in such traditional contexts as condemnation. An awareness of these nonmarket values helps overcome any categorical opposition to the use of the contingent valuation method (CVM) to value cultural and environmental resources. But accurate CVM should measure all values, positive or negative, tononowners; it should apply generally to any substitute projects; and it should seek to account for diminishing marginal value of additional resource units. CVM should be used only to aggregate nonmarket preferences, not to skew the political debate to cultural or environmental objectives.  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