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   31330篇
  免费   5675篇
  国内免费   3464篇
化学   22325篇
晶体学   350篇
力学   1806篇
综合类   136篇
数学   3000篇
物理学   12852篇
  2024年   136篇
  2023年   697篇
  2022年   1205篇
  2021年   1387篇
  2020年   1401篇
  2019年   1378篇
  2018年   1172篇
  2017年   1052篇
  2016年   1596篇
  2015年   1526篇
  2014年   1958篇
  2013年   2417篇
  2012年   2899篇
  2011年   2919篇
  2010年   1906篇
  2009年   1815篇
  2008年   2047篇
  2007年   1796篇
  2006年   1675篇
  2005年   1317篇
  2004年   1010篇
  2003年   785篇
  2002年   770篇
  2001年   602篇
  2000年   473篇
  1999年   599篇
  1998年   514篇
  1997年   500篇
  1996年   494篇
  1995年   430篇
  1994年   349篇
  1993年   287篇
  1992年   281篇
  1991年   225篇
  1990年   202篇
  1989年   151篇
  1988年   92篇
  1987年   80篇
  1986年   104篇
  1985年   73篇
  1984年   37篇
  1983年   44篇
  1982年   28篇
  1981年   22篇
  1980年   7篇
  1979年   4篇
  1976年   1篇
  1975年   1篇
  1957年   4篇
  1923年   1篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
111.
In this paper, we investigate the Novikov equation with weak dissipation terms. First, we give the local well-posedness and the blow-up scenario. Then, we discuss the global existence of the solutions under certain conditions. After that, on condition that the compactly supported initial data keeps its sign, we prove the infinite propagation speed of our solutions, and establish the large time behavior. Finally, we also elaborate the persistence property of our solutions in weighted Sobolev space.  相似文献   
112.
Implicit and explicit characterizations of the solutions to the following constrained best interpolation problem $$\min \left\{ {\left\| {Tx - z} \right\|:x \in C \cap A^{ - 1} d} \right\}$$ are presented. Here,T is a densely-defined, closed, linear mapping from a Hilbert spaceX to a Hilbert spaceY, A: X→Z is a continuous, linear mapping withZ a locally, convex linear topological space,C is a closed, convex set in the domain domT ofT, anddAC. For the case in whichC is a closed, convex cone, it is shown that the constrained best interpolation problem can generally be solved by finding the saddle points of a saddle function on the whole space, and, if the explicit characterization is applicable, then solving this problem is equivalent to solving an unconstrained minimization problem for a convex function.  相似文献   
113.
114.
115.
Angular distributions of elastic and inelastic scattering have been measured for152Sm+12C at 63.2 MeV and148Nd+16O at 90.9 MeV. An evident interference pattern in the inelastic scattering has been observed for the first time in a strong Coulomb coupling system.We are indebted to Dr. S. Pieper for supplying the Ptolemy Program. One of us (Chenglie Jiang) would like to acknowledge the Argonne National Laboratory for the opportunity given, to perform theoretical calculations with the code Ptolemy during his visit there. Thanks are also due to Mr. H. Folger (GSI, Germany) for supplying the targets. This work was supported in part by China National Nature Science Fundation.  相似文献   
116.
117.
Letf:XX be a selfmap of a compact connected polyhedron, andA a nonempty closed subset ofX. In this paper, we shall deal with the question whether or not there is a mapg:XX homotopic tof such that the fixed point set Fixg ofg equalsA. We introduce a necessary condition for the existence of such a mapg. It is shown that this condition is easy to check, and hence some sufficient conditions are obtained.Partially supported by the Natural Science Foundation of Liaoning University.  相似文献   
118.
119.
In this paper we study a particular class of primal-dual path-following methods which try to follow a trajectory of interior feasible solutions in primal-dual space toward an optimal solution to the primal and dual problem. The methods investigated are so-called first-order methods: each iteration consists of a long step along the tangent of the trajectory, followed by explicit recentering steps to get close to the trajectory again. It is shown that the complexity of these methods, which can be measured by the number of points close to the trajectory which have to be computed in order to achieve a desired gain in accuracy, is bounded by an integral along the trajectory. The integrand is a suitably weighted measure of the second derivative of the trajectory with respect to a distinguished path parameter, so the integral may be loosely called a curvature integral.  相似文献   
120.
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