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   8564篇
  免费   452篇
  国内免费   574篇
化学   1804篇
晶体学   32篇
力学   96篇
综合类   92篇
数学   6411篇
物理学   1155篇
  2023年   27篇
  2022年   60篇
  2021年   53篇
  2020年   45篇
  2019年   213篇
  2018年   237篇
  2017年   96篇
  2016年   50篇
  2015年   71篇
  2014年   565篇
  2013年   864篇
  2012年   420篇
  2011年   753篇
  2010年   604篇
  2009年   689篇
  2008年   617篇
  2007年   500篇
  2006年   415篇
  2005年   281篇
  2004年   246篇
  2003年   220篇
  2002年   154篇
  2001年   171篇
  2000年   169篇
  1999年   206篇
  1998年   200篇
  1997年   172篇
  1996年   208篇
  1995年   203篇
  1994年   187篇
  1993年   176篇
  1992年   103篇
  1991年   36篇
  1990年   22篇
  1989年   19篇
  1988年   23篇
  1987年   23篇
  1986年   16篇
  1985年   51篇
  1984年   63篇
  1983年   47篇
  1982年   51篇
  1981年   54篇
  1980年   38篇
  1979年   37篇
  1978年   38篇
  1977年   29篇
  1976年   20篇
  1975年   17篇
  1973年   12篇
排序方式: 共有9590条查询结果,搜索用时 483 毫秒
61.
In this paper, we study the global existence and the asymptotic behavior of classical solution of the Cauchy problem for quasilinear hyperbolic system with constant multiple and linearly degenerate characteristic fields. We prove that the global C1 solution exists uniquely if the BV norm of the initial data is sufficiently small. Based on the existence result on the global classical solution, we show that, when the time t tends to the infinity, the solution approaches a combination of C1 traveling wave solutions. Finally, we give an application to the equation for time-like extremal surfaces in the Minkowski space-time R1+n.  相似文献   
62.
We give general conditions on a generator of a C0-semigroup (resp. of a C0-resolvent) on Lp(E,μ), p ≥ 1, where E is an arbitrary (Lusin) topological space and μ a σ-finite measure on its Borel σ-algebra, so that it generates a sufficiently regular Markov process on E. We present a general method how these conditions can be checked in many situations. Applications to solve stochastic differential equations on Hilbert space in the sense of a martingale problem are given. Dedicated to Giuseppe Da Prato on the occasion of his 70th birthday  相似文献   
63.
Summary. The perfectly matched layer (PML) is an efficient tool to simulate propagation phenomena in free space on unbounded domain. In this paper we consider a new type of absorbing layer for Maxwell's equations and the linearized Euler equations which is also valid for several classes of first order hyperbolic systems. The definition of this layer appears as a slight modification of the PML technique. We show that the associated Cauchy problem is well-posed in suitable spaces. This theory is finally illustrated by some numerical results. It must be underlined that the discretization of this layer leads to a new discretization of the classical PML formulation. Received May 5, 2000 / Published online November 15, 2001  相似文献   
64.
Under some general continuous and compact conditions, the existence problems of fiked points andd coupled fixed points for increasing operators are studied. an application, we utilize the results obtained to study the existence of solutions for differential inclusions in Banach spaces.  相似文献   
65.
Summary We show that each holomorphic Wiener function has a skeleton which is intrinsic from several viewpoints. In particular, we study the topological aspects of the skeletons by using the local Taylor expansion for holomorphic Wiener functions.Supported in part by the Grant-in-Aid for Science Research 03740120 Min. Education  相似文献   
66.
Summary. In this paper we are interested in two phase flow problems in porous media. We use a Dual Mesh Method to discretize this problem with finite volume schemes. In a simplified case (elliptic - hyperbolic system) we prove the convergence of approximate solutions to the exact solutions. We use the Dual Mesh Method in physically complex problems (heterogeneous cases with non constant total mobility). We validate numerically the Dual Mesh Method on practical examples by computing error estimates for different test-cases. Received March 21, 1997 / Revised version received October 13, 1997  相似文献   
67.
张国平 《物理》2006,35(5):424-427
在原子、分子和纳米材料中的高次谐波为非线性光学开辟了一个崭新的研究领域.其响应时间之短、能量之高,引起了人们的高度重视.目前的研究达到了白热化的程度.还有很多问题没有解决.文章首先简要地介绍了这一个新的领域.然后用一个简单的例子引出有名的辐射截断方程,最后用C60作为一个例子说明如何详细地计算辐射能量谱.  相似文献   
68.
In ergodic MDPs we consider stationary distributions of policies that coincide in all but n states, in which one of two possible actions is chosen. We give conditions and formulas for linear dependence of the stationary distributions of n+2 such policies, and show some results about combinations and mixtures of policies.  相似文献   
69.
In this paper we study random orderings of the integers with a certain invariance property. We describe all such orders in a simple way. We define and represent random shuffles of a countable set of labels and then give an interpretation of these orders in terms of a class of generalized riffle shuffles.  相似文献   
70.
This paper examines the steady state behaviour of a batch arrival queue with two phases of heterogeneous service along and Bernoulli schedule vacation under multiple vacation policy, where after two successive phases service or first vacation the server may go for further vacations until it finds a new batch of customer in the system. We carry out an extensive stationary analysis of the system, including existence of stationary regime, queue size distribution of idle period process, embedded Markov chain steady state distribution of stationary queue size, busy period distribution along with some system characteristics.  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