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   60524篇
  免费   3953篇
  国内免费   3898篇
化学   20295篇
晶体学   411篇
力学   7488篇
综合类   634篇
数学   17771篇
物理学   21776篇
  2024年   46篇
  2023年   495篇
  2022年   778篇
  2021年   1154篇
  2020年   1275篇
  2019年   1346篇
  2018年   1195篇
  2017年   1407篇
  2016年   1679篇
  2015年   1339篇
  2014年   1983篇
  2013年   3982篇
  2012年   2379篇
  2011年   2726篇
  2010年   2165篇
  2009年   3504篇
  2008年   3805篇
  2007年   4224篇
  2006年   3559篇
  2005年   2965篇
  2004年   2501篇
  2003年   2766篇
  2002年   3076篇
  2001年   2306篇
  2000年   2208篇
  1999年   1863篇
  1998年   1874篇
  1997年   1145篇
  1996年   960篇
  1995年   934篇
  1994年   937篇
  1993年   721篇
  1992年   753篇
  1991年   507篇
  1990年   474篇
  1989年   379篇
  1988年   336篇
  1987年   326篇
  1986年   292篇
  1985年   265篇
  1984年   268篇
  1983年   157篇
  1982年   219篇
  1981年   209篇
  1980年   155篇
  1979年   188篇
  1978年   140篇
  1977年   131篇
  1976年   82篇
  1973年   45篇
排序方式: 共有10000条查询结果,搜索用时 937 毫秒
111.
Examples are worked out using a new equation proposed in the previous paper to show that it has new physical predictions for mesoscopic systems.  相似文献   
112.
We solve the word problem of the identity x(yz) = (xy)(yz) by investigating a certain group describing the geometry of that identity. We also construct a concrete realization of the one-generated free algebra relative to the above identity. Received March 23, 2001; accepted in final form July 6, 2002.  相似文献   
113.
结合Liapunov泛函,研究了具连续时滞Lienard方程概周期解的存在唯一性和安全一致渐进稳定性。  相似文献   
114.
A convective flow CO laser composed of polytetrafluoroethylene discharge tubes, nickel–chromium steel components, a cupric heat exchanger and other components is described. Operating in liquid nitrogen condition, output power of 60 W has been obtained from a non-selective cavity.  相似文献   
115.
We study the probabilistic consequences of the choice of the basic number field in the quantum formalism. We demonstrate that by choosing a number field for a linear space representation of quantum model it is possible to describe various interference phenomena. We analyse interference of probabilistic alternatives induced by real, complex, hyperbolic (Clifford) and p‐adic representations.  相似文献   
116.
平行机半在线排序问题研究(Ⅰ)   总被引:15,自引:1,他引:14  
对半在线平行机排序问题的研究进展作了详细综述和进一步探讨。文章给出半在线排序问题的背景、定义、分类和求解。介绍它们定义和在不同机器环境和目标函数下半在线排序问题分类,以及第一类半在线模型的近似算法的设计及其竞争比分析。  相似文献   
117.
We establish the existence and stability of multidimensional transonic shocks for the Euler equations for steady potential compressible fluids. The Euler equations, consisting of the conservation law of mass and the Bernoulli law for the velocity, can be written as a second-order, nonlinear equation of mixed elliptic-hyperbolic type for the velocity potential. The transonic shock problem can be formulated into the following free boundary problem: The free boundary is the location of the transonic shock which divides the two regions of smooth flow, and the equation is hyperbolic in the upstream region where the smooth perturbed flow is supersonic. We develop a nonlinear approach to deal with such a free boundary problem in order to solve the transonic shock problem. Our results indicate that there exists a unique solution of the free boundary problem such that the equation is always elliptic in the downstream region and the free boundary is smooth, provided that the hyperbolic phase is close to a uniform flow. We prove that the free boundary is stable under the steady perturbation of the hyperbolic phase. We also establish the existence and stability of multidimensional transonic shocks near spherical or circular transonic shocks.

  相似文献   

118.
The five relative equilibria of the three-body problem give rise to solutions where the bodies rotate rigidly around their center of mass. For these solutions, the moment of inertia of the bodies with respect to the center of mass is clearly constant. Saari conjectured that these rigid motions are the only solutions with constant moment of inertia. This result will be proved here for the planar problem with three nonzero masses with the help of some computational algebra and geometry.

  相似文献   

119.
Equilibrium Problems with Applications to Eigenvalue Problems   总被引:5,自引:0,他引:5  
In this paper, we consider equilibrium problems and introduce the concept of (S)+ condition for bifunctions. Existence results for equilibrium problems with the (S)+ condition are derived. As special cases, we obtain several existence results for the generalized nonlinear variational inequality studied by Ding and Tarafdar (Ref. 1) and the generalized variational inequality studied by Cubiotti and Yao (Ref. 2). Finally, applications to a class of eigenvalue problems are given.  相似文献   
120.
By further generalizing the skew-symmetric triangular splitting iteration method studied by Krukier, Chikina and Belokon (Applied Numerical Mathematics, 41 (2002), pp. 89–105), in this paper, we present a new iteration scheme, called the modified skew-Hermitian triangular splitting iteration method, for solving the strongly non-Hermitian systems of linear equations with positive definite coefficient matrices. We discuss the convergence property and the optimal parameters of this new method in depth. Moreover, when it is applied to precondition the Krylov subspace methods like GMRES, the preconditioning property of the modified skew-Hermitian triangular splitting iteration is analyzed in detail. Numerical results show that, as both solver and preconditioner, the modified skew-Hermitian triangular splitting iteration method is very effective for solving large sparse positive definite systems of linear equations of strong skew-Hermitian parts.  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