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   1356881篇
  免费   29687篇
  国内免费   7759篇
化学   671228篇
晶体学   20940篇
力学   76032篇
综合类   108篇
数学   245877篇
物理学   380142篇
  2021年   13490篇
  2020年   15934篇
  2019年   16048篇
  2018年   15691篇
  2017年   14421篇
  2016年   29151篇
  2015年   21141篇
  2014年   30474篇
  2013年   74413篇
  2012年   38785篇
  2011年   37792篇
  2010年   39362篇
  2009年   41747篇
  2008年   36754篇
  2007年   33205篇
  2006年   35191篇
  2005年   30694篇
  2004年   30617篇
  2003年   28576篇
  2002年   28893篇
  2001年   27159篇
  2000年   23894篇
  1999年   22091篇
  1998年   20887篇
  1997年   20887篇
  1996年   21063篇
  1995年   19134篇
  1994年   18602篇
  1993年   18133篇
  1992年   17909篇
  1991年   18218篇
  1990年   17425篇
  1989年   17522篇
  1988年   17077篇
  1987年   17110篇
  1986年   15951篇
  1985年   22447篇
  1984年   23713篇
  1983年   19925篇
  1982年   21631篇
  1981年   20876篇
  1980年   20200篇
  1979年   20318篇
  1978年   21680篇
  1977年   21252篇
  1976年   20912篇
  1975年   19586篇
  1974年   19243篇
  1973年   19723篇
  1972年   14181篇
排序方式: 共有10000条查询结果,搜索用时 9 毫秒
971.
Space-time directional Lyapunov exponents are introduced. They describe the maximal velocity of propagation to the right or to the left of fronts of perturbations in a frame moving with a given velocity. The continuity of these exponents as function of the velocity and an inequality relating them to the directional entropy is proved.  相似文献   
972.
Summary The main purpose of this paper is to introduce the concepts of η-sets, ηζ-sets,η-continuity and ηζ-continuity and to obtain a decomposition of continuity.  相似文献   
973.
The paper mentioned above is a contribution of the authors to Volume 18 (2002) of this journal, see . Recently, J. Domsta pointed out to us that the proof of Theorem 4.2 in that paper contains an error. The purpose of this addendum is to present a correct argument for it.  相似文献   
974.
A test for a function to be a solution of an elliptic PDE is given in terms of extensions, as solutions, from the boundaries inside the domains belonging to an isotopic family. It generalizes a result of Ehrenpreis for spheres moved along a straight line.

  相似文献   

975.
We give sufficient conditions for Sobolev and Lipschitz functions in terms of their lower scaled-oscillation. The sharpness of these conditions is shown by examples. Our examples also show that a Stepanov-type differentiability theorem does not hold under the boundedness assumption of the lower scaled-oscillation.

  相似文献   

976.
977.
An expression for the ratio of the glass transition temperature to the melting temperature, T g/T m, was derived with allowance for fluctuations of the packing factor in the amorphous state. This relationship made it possible to describe the actual range of variation in T g/T m depending on a change in the packing factor in the crystalline state k o, cr. The proposed approach forms the basis for the method of determination of increments in the packing ratio k o, cr and formulation of the principles of selection of experimental data for calculations. The glass transition temperatures in polyethylene depending on the type of unit cell were calculated.  相似文献   
978.
The feasibility of an 84 GHz, 500 kW, CW gyrotron for ECRH on an experimental tokamak will be presented in this paper. Mode competition and mode selection procedures are carefully investigated by considering various candidate modes and the TE10,4 mode is chosen as the operating mode. A conventional cylindrical cavity resonator with weak input and output tapers and parabolic roundings is considered for interaction studies. Self-consistent, both single mode and time-dependent, calculations are carried out and power and efficiencies are computed for a typical set of beam parameters. The results show that an output power of well over 500 kW, CW and efficiency around 40% can be reached without a depressed collector.  相似文献   
979.
We give a coring version for the duality theorem for actions and coactions of a finitely generated projective Hopf algebra. We also provide a coring analogue for a theorem of H.-J. Schneider, which generalizes and unifies the duality theorem for finite Hopf algebras and its refinements. This paper was written while the first author visited the Mathematics Departments of Syracuse University and California State University Dominguez Hills. He would like to thank both departments for their hospitality.  相似文献   
980.
The interferometric intensity patterns from a 2D shearing interferometer are shown and discussed. The intensity patterns can be obtained in two different approaches incorporating differential and extended wavefront controlled displacements. The reliable directional sensitivity of this interferometer allows the optimization of the measurement parameters to estimate the wavefront of the intensity patterns by regularization techniques.  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