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   1299167篇
  免费   29585篇
  国内免费   7659篇
化学   644346篇
晶体学   20080篇
力学   73986篇
综合类   102篇
数学   238494篇
物理学   359403篇
  2021年   13443篇
  2020年   15882篇
  2019年   15998篇
  2016年   27292篇
  2015年   20560篇
  2014年   30263篇
  2013年   74102篇
  2012年   35892篇
  2011年   31341篇
  2010年   35695篇
  2009年   38375篇
  2008年   31179篇
  2007年   26352篇
  2006年   33864篇
  2005年   25647篇
  2004年   27664篇
  2003年   26416篇
  2002年   27837篇
  2001年   26210篇
  2000年   23451篇
  1999年   21857篇
  1998年   20758篇
  1997年   20770篇
  1996年   20967篇
  1995年   19059篇
  1994年   18492篇
  1993年   18030篇
  1992年   17752篇
  1991年   18095篇
  1990年   17312篇
  1989年   17383篇
  1988年   16942篇
  1987年   16956篇
  1986年   15840篇
  1985年   22299篇
  1984年   23607篇
  1983年   19856篇
  1982年   21560篇
  1981年   20800篇
  1980年   20138篇
  1979年   20238篇
  1978年   21601篇
  1977年   21162篇
  1976年   20849篇
  1975年   19541篇
  1974年   19173篇
  1973年   19650篇
  1972年   14176篇
  1968年   12055篇
  1967年   12398篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
921.
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   
922.
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   
923.
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   
924.
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   

925.
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   

926.
927.
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   
928.
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   
929.
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   
930.
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