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   277779篇
  免费   2291篇
  国内免费   880篇
化学   133990篇
晶体学   4397篇
力学   14540篇
综合类   11篇
数学   50361篇
物理学   77651篇
  2020年   1732篇
  2019年   1931篇
  2018年   12375篇
  2017年   12308篇
  2016年   9423篇
  2015年   3001篇
  2014年   3828篇
  2013年   9385篇
  2012年   10117篇
  2011年   18098篇
  2010年   11124篇
  2009年   11511篇
  2008年   13493篇
  2007年   15532篇
  2006年   6905篇
  2005年   7316篇
  2004年   6985篇
  2003年   6983篇
  2002年   5853篇
  2001年   6375篇
  2000年   4907篇
  1999年   3662篇
  1998年   2932篇
  1997年   2838篇
  1996年   2792篇
  1995年   2557篇
  1994年   2407篇
  1993年   2260篇
  1992年   2887篇
  1991年   2799篇
  1990年   2730篇
  1989年   2755篇
  1988年   2776篇
  1987年   2783篇
  1986年   2655篇
  1985年   3364篇
  1984年   3358篇
  1983年   2640篇
  1982年   2757篇
  1981年   2802篇
  1980年   2581篇
  1979年   2923篇
  1978年   2902篇
  1977年   3006篇
  1976年   2840篇
  1975年   2574篇
  1974年   2525篇
  1973年   2493篇
  1972年   1720篇
  1968年   1714篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
This paper analyzes the compromise social choice correspondence derived from the τ-value of digraph games. Monotonicity of this correspondence is shown. A connection between several properties of social choice correspondences based on game theoretical solutions and game theoretical properties of the underlying solutions is given. Applications to several game theoretic solutions are provided.  相似文献   
63.
64.
We examine several interesting relationships and expressions involving Fourier-Feynman transform, convolution product and first variation for functionals in the Fresnel class F(B) of an abstract Wiener space B. We also prove a translation theorem and Parseval's identity for the analytic Feynman integral. This revised version was published online in June 2006 with corrections to the Cover Date.  相似文献   
65.
66.
We carried out detailed calculations for photorefractive wave-mixing switches based on one of three crystals with high electro-optic coefficients, namely, BaTiO3, Strontium Barium Niobate (SBN (0.75)), and Potasium Sodium Strontium Barium Niobate (KNSBN). A comparison of results for the three crystals shows that a 0_-cut BaTiO3 crystal is suitable for a longitudinal switch and requires a voltage of about 80 for a 2-mm-thick crystal to induce sufficient phase mismatch. The electrodes must be transparent for the incident and diffracted beams. A 45_-cut SBN (0.75) crystal, however, is suitable for a lateral switch and requires a voltage of about 150 for a 1-mm-wide crystal. The electrodes do not need to be transparent.  相似文献   
67.
The dependence of the strangeness saturation factor on the system size, centrality and energy is studied in relativistic heavy-ion collisions.  相似文献   
68.
A longitudinal dc electric discharge in a submerged high-pressure supersonic air jet is described. Photographs of the discharge are provided. The experimental voltage across the discharge gap and the discharge current are given for two resistances of the resistor that limits the discharge current over a certain range of the discharge channel length along the air flow. The current-voltage discharge characteristic is provided at a constant discharge length. The main discharge characteristics are obtained from a comparison of the experimental and theoretical results calculated on the basis of the simplest model.  相似文献   
69.
Results of measuring the monochromatic sound field with a dipping probe in the deep ocean are presented. The sound speed profile in the region of measurements had a minimum at a depth of 1600 m. The experiment was carried out in the Atlantic Ocean with the use of two vessels separated by a distance of approximately four ray cycles (~240 km). The experimental data are compared with the calculations based on a new concept of the Brillouin waves for describing the vertical structure of the sound field produced by rays. It is shown that a satisfactory agreement between experiment and calculation can be achieved by fitting the parameters of the experiment. Such a procedure allows one to refine or even to determine the experimental conditions, which not are always known. The proposed method of calculation offers an opportunity for solving inverse problems of ocean acoustics.  相似文献   
70.
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