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   657480篇
  免费   7701篇
  国内免费   2128篇
化学   354703篇
晶体学   9418篇
力学   28505篇
综合类   20篇
数学   80203篇
物理学   194460篇
  2021年   5015篇
  2020年   5641篇
  2019年   5975篇
  2018年   7288篇
  2017年   7082篇
  2016年   11620篇
  2015年   7894篇
  2014年   11630篇
  2013年   30288篇
  2012年   23050篇
  2011年   28531篇
  2010年   19283篇
  2009年   18976篇
  2008年   25913篇
  2007年   26096篇
  2006年   24508篇
  2005年   22130篇
  2004年   20329篇
  2003年   18037篇
  2002年   17640篇
  2001年   19554篇
  2000年   14923篇
  1999年   11888篇
  1998年   9798篇
  1997年   9454篇
  1996年   9384篇
  1995年   8419篇
  1994年   8199篇
  1993年   7892篇
  1992年   8872篇
  1991年   8799篇
  1990年   8372篇
  1989年   8139篇
  1988年   8258篇
  1987年   7996篇
  1986年   7659篇
  1985年   10309篇
  1984年   10514篇
  1983年   8496篇
  1982年   8888篇
  1981年   8883篇
  1980年   8389篇
  1979年   8845篇
  1978年   8976篇
  1977年   8950篇
  1976年   8794篇
  1975年   8353篇
  1974年   8196篇
  1973年   8356篇
  1972年   5540篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
The problem of the vector and axial-vector dominance of weak interactions within the framework of the quark model of superconductivity type is discussed.  相似文献   
32.
33.
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   
34.
35.
36.
37.
We consider the growth of a spherical crystal in a supersaturatedsolution. In the first part, existence and uniqueness resultsfor radially symmetric growth are obtained, provided that thesupersaturation is not too large; conversely, when the far-fieldsupersaturation exceeds a critical value, it is shown that theradially symmetric solution ceases to exist in finite time.In the second part, we examine the linear stability of a radiallysymmetric similarity solution (in which the radius grows ast?) to shape perturbations. The results are compared with previousquasi-static analyses, and, in particular, the critical radiusat which the crystal becomes unstable is found to be largerfor small supersaturations, but smaller for large supersaturations,than those predicted by the quasi-static analysis  相似文献   
38.
One obtains a formula for the transformation of a vector with a given covariance matrix. The sum of the squares of the components of the transformed vector is equal to a chi-square type quadratic form, constructed with the aid of the initial vector. Taking into account this property, one finds the components of the Pearson statistic, Pearson-Fisher statistic, etc.Translated from Veroyatnostnye Raspredeleniya i Matematicheskaya Statistika, pp. 337–350, 1986.  相似文献   
39.
Transport as a consequence of state-dependent diffusion   总被引:1,自引:0,他引:1  
Overdamped particles subject to a drift in a force field with sinusoidal space dependence and also a sinusoidally modulated space-dependent diffusion, with the same period as the drift, experience a net driving force. The resulting current depends on the amplitude of the modulation of the diffusion and is a periodic function of the phase difference between the sinusoidal drift and the sinusoidal modulation of the diffusion. For small modulation amplitudes a particle subject to state-dependent noise behaves the same way as a particle subject to thermal noise but with a drift which, in addition to the sinusoidal term, contains a net force term.Dedicated to Professor Harry Thomas on the occasion of his 60th birthday  相似文献   
40.
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