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   508663篇
  免费   4302篇
  国内免费   1498篇
化学   255298篇
晶体学   7569篇
力学   23643篇
综合类   21篇
数学   71411篇
物理学   156521篇
  2021年   3303篇
  2020年   3693篇
  2019年   4327篇
  2018年   12222篇
  2017年   12787篇
  2016年   11488篇
  2015年   5604篇
  2014年   7960篇
  2013年   20063篇
  2012年   18020篇
  2011年   27293篇
  2010年   18061篇
  2009年   17932篇
  2008年   24653篇
  2007年   27465篇
  2006年   15686篇
  2005年   18991篇
  2004年   14923篇
  2003年   13694篇
  2002年   11989篇
  2001年   12120篇
  2000年   9793篇
  1999年   7218篇
  1998年   6308篇
  1997年   6313篇
  1996年   5827篇
  1995年   5132篇
  1994年   5010篇
  1993年   5069篇
  1992年   5461篇
  1991年   5560篇
  1990年   5290篇
  1989年   5254篇
  1988年   5255篇
  1987年   5074篇
  1986年   4868篇
  1985年   6500篇
  1984年   6821篇
  1983年   5584篇
  1982年   6104篇
  1981年   5901篇
  1980年   5599篇
  1979年   5859篇
  1978年   6181篇
  1977年   5974篇
  1976年   6187篇
  1975年   5653篇
  1974年   5707篇
  1973年   6198篇
  1972年   3982篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
171.
An estimate of the factors which influence the rate of growth of filamentary silicon crystals in a standard chloride system using a quartz reactor with hot walls is given. It is shown that a diffusion form of crystallization is observed under the conditions investigated.Voronezh State Technical University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 22–26, October, 1995.  相似文献   
172.
Nonperturbative nolocal structure of QCD vacuum is well described by instanton model. Specific helicity and flavor structure of zero modes of quarks, in instanton field allows simultaneously to explain some important features of low-and high-energy hadron phenomemology. The basic characteristics of hadron spectrum, partonic sum rules, heavyquark potential etc within the instanton liquid model are briefly discussed.  相似文献   
173.
The microhardness and content of carbon in electroplated gold coatings were studied as influenced by the operation time of citrate and citrate-phosphate gold-plating electrolytes. Such physicomechanical properties as porosity, microhardness, internal stress, plasticity, and microstructure of electroless-plated and electroplated nickel coatings were studied and analyzed.  相似文献   
174.
This paper reports on the first experimental observation of quantum-well states and sp-type resonances in thin single-crystal gold, silver, and copper layers formed on single-crystal W(110) surfaces, which result from spatial localization of Bloch-type electronic wave functions in a quantum well with potential barriers at the vacuum/metal and metal/W(110) interfaces. The quantization of the valence-band electronic structure in Au/W(110), Ag/W(110), and Cu/W(110) systems was studied experimentally using angle-resolved photoelectron spectroscopy.  相似文献   
175.
Using an integral theory of grating diffraction we calculate efficiencies greater than 100% if a coating with gain is taken into account. A connection with guided modes is conjectured. The application in optical computing seems to be possible.  相似文献   
176.
Physics and Mathematics Division with Computational Center of the Bashkir Branch of the USSR Academy of Sciences. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 80, No. 3, pp. 470–473, September, 1989.  相似文献   
177.
178.
In this paper, the authors studied certain properties of the estimate of Liang and Krishnaiah (1985, J. Multivariate Anal. 16, 162–172) for multivariate binary density. An alternative shrinkage estimate is also obtained. The above results are generalized to general orthonormal systems.  相似文献   
179.
This paper presents an alternative to the beta continuous probability distribution for risk analysis. Particular attention has been given to two major applications of distributions, namely project management risk and critical path analysis (PERT). In conjunction with the beta, the triangular and normal distributions are frequently employed in order to give sufficient robustness to risk analysis. The beta distribution, as used in PERT, has a major theoretical implementation flaw. The new distribution was developed to give a possible alternative method of assessing risk. It is shown that the requirement to estimate the most pessimistic variate may be replaced by the probability to exceed the mode. Proposals for other simplifications in risk analysis are discussed. Practical means to validate the most appropriate distributions for risk analysis are outlined, and a cost-data case study is included.  相似文献   
180.
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