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   565505篇
  免费   6940篇
  国内免费   4227篇
化学   283447篇
晶体学   9026篇
力学   27659篇
综合类   279篇
数学   76493篇
物理学   179768篇
  2021年   4568篇
  2020年   5010篇
  2019年   5624篇
  2018年   13123篇
  2017年   13733篇
  2016年   13293篇
  2015年   7076篇
  2014年   10433篇
  2013年   23812篇
  2012年   21452篇
  2011年   30823篇
  2010年   21202篇
  2009年   21183篇
  2008年   27202篇
  2007年   29530篇
  2006年   18135篇
  2005年   20573篇
  2004年   17031篇
  2003年   15560篇
  2002年   14078篇
  2001年   15245篇
  2000年   11647篇
  1999年   8852篇
  1998年   7237篇
  1997年   7051篇
  1996年   6762篇
  1995年   5998篇
  1994年   5813篇
  1993年   5517篇
  1992年   6404篇
  1991年   6473篇
  1990年   6216篇
  1989年   6196篇
  1988年   5923篇
  1987年   6032篇
  1986年   5678篇
  1985年   7238篇
  1984年   7295篇
  1983年   5955篇
  1982年   6135篇
  1981年   5953篇
  1980年   5662篇
  1979年   6208篇
  1978年   6267篇
  1977年   6275篇
  1976年   6149篇
  1975年   5709篇
  1974年   5589篇
  1973年   5654篇
  1972年   3967篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
141.
Algebraic methods in quantum mechanics: from molecules to polymers   总被引:2,自引:0,他引:2  
We present a brief review of algebraic techniques developed and applied in molecular spectroscopy in the last five years. We also outline perspectives for new applications of the Lie algebraic method in the first decade of the new century. Received 21 November 2001  相似文献   
142.
It is shown that any finite dimensionalC 0 manifold (connected and Hausdorff but otherwise unrestricted) has an atlas of cardinality not greater than that of the continuum; while if it has a Hölder continuous pseudo-Riemannian metric then there is a countable atlas.  相似文献   
143.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 4, pp. 624–629, October, 1991.  相似文献   
144.
Cognitive style refers to differences that can be perceived in individuals due to differing cognitive structures. There has been a large amount of research on how cognitive style affects managerial decision-making, particularly in the context of management information systems, but little or no attempt to relate these findings to operational research. This paper reviews the findings of cognitive-style research from the perspective of operational research, and draws a number of useful inferences concerning the matching of OR aids to managers, the presentation of information and recommendations, the use and acceptance of OR, and the structure of OR groups. Further, it is argued that cognitive-style findings help to give a justification to the move towards ‘soft’ approaches to analysis.  相似文献   
145.
146.
Partially supported by the general research fund at the University of Kansas  相似文献   
147.
Selected experiences in the control of contamination and the threat it poses to the quality of analytical date are discussed in the context of the whole analytical process from collection of marine environmental samples, through handling and radiochemical separation, to the final interpretation of results. Examples include a demonstration of the contamination introduced during sediment core sectioning, contamination of sea water by a ship's pumping system, and the effect of filtration on the apparent partitioning of radionuclides between solid and liquid phases of sea water.  相似文献   
148.
149.
The objective of this research is to evaluate a new methodology, data envelopment analysis (DEA), as a tool for measuring and evaluating the operational efficiency of US Air Force organizations. This study involves the application of DEA to locate possible inefficiencies in the performance of US Air Force real-property maintenance activities. Dynamic behaviour, as exhibited via window analyses, is reviewed along with static counterparts. The testing was done in close coordination with Air Force officials, who reviewed the results for accuracy, validity and relevance. We conclude that this type of efficiency analysis does have value for the Air Force, where it can serve as a guide to auditors, budget programmers, managers and others in measuring, evaluating and enhancing operational efficiency.  相似文献   
150.
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