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   9441篇
  免费   753篇
  国内免费   517篇
化学   1294篇
晶体学   147篇
力学   707篇
综合类   72篇
数学   6932篇
物理学   1559篇
  2024年   21篇
  2023年   83篇
  2022年   109篇
  2021年   125篇
  2020年   247篇
  2019年   245篇
  2018年   244篇
  2017年   264篇
  2016年   269篇
  2015年   225篇
  2014年   393篇
  2013年   904篇
  2012年   337篇
  2011年   530篇
  2010年   527篇
  2009年   605篇
  2008年   662篇
  2007年   605篇
  2006年   515篇
  2005年   468篇
  2004年   417篇
  2003年   363篇
  2002年   331篇
  2001年   264篇
  2000年   220篇
  1999年   219篇
  1998年   171篇
  1997年   170篇
  1996年   147篇
  1995年   112篇
  1994年   104篇
  1993年   78篇
  1992年   67篇
  1991年   54篇
  1990年   50篇
  1989年   33篇
  1988年   41篇
  1987年   25篇
  1986年   43篇
  1985年   45篇
  1984年   58篇
  1983年   40篇
  1982年   50篇
  1981年   42篇
  1980年   38篇
  1979年   45篇
  1978年   30篇
  1977年   17篇
  1976年   21篇
  1973年   12篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
131.
We investigate the six-dimensional Schrödinger equation for a three-body system with central pair interactions of a more general form than Coulomb interactions. Regular general and special physical solutions of this equation are represented by infinite asymptotic series in integer powers of the distance between two particles and in the sought functions of the other three-body coordinates. Constructing such functions in angular bases composed of spherical and bispherical harmonics or symmetrized Wigner D-functions is reduced to solving simple recursive algebraic equations. For projections of physical solutions on the angular bases functions, we derive boundary conditions at the pair impact point.  相似文献   
132.
Subgame Consistent Cooperative Solutions in Stochastic Differential Games   总被引:3,自引:1,他引:2  
Subgame consistency is a fundamental element in the solution of cooperative stochastic differential games. In particular, it ensures that: (i) the extension of the solution policy to a later starting time and to any possible state brought about by the prior optimal behavior of the players would remain optimal; (ii) all players do not have incentive to deviate from the initial plan. In this paper, we develop a mechanism for the derivation of the payoff distribution procedures of subgame consistent solutions in stochastic differential games with transferable payoffs. The payoff distribution procedure of the subgame consistent solution can be identified analytically under different optimality principles. Demonstration of the use of the technique for specific optimality principles is shown with an explicitly solvable game. For the first time, analytically tractable solutions of cooperative stochastic differential games with subgame consistency are derived.  相似文献   
133.
An intuitive definition of standing gravitational waves is proposed. Some main classes of exact vacuum solutions are searched for standing gravitational waves, in most cases with a negative result. Only some Einstein–Rosen waves meet the conditions.  相似文献   
134.
Banach空间中二阶积分-微分方程的初值问题   总被引:5,自引:0,他引:5  
使用锥理论及单调迭代技术,首先讨论了Banach空间中一阶积分-微分方程初值问题的最小最大解的存在性,并在此基础上讨论了带有一阶微分项的二阶积分-微分方程初值问题的最小最大解的存在性。  相似文献   
135.
First order dynamic inclusions on time scales   总被引:1,自引:0,他引:1  
In this paper, we study existence of solutions of first order dynamic inclusions on time scales with general boundary conditions. Both the ∇-derivative and Δ-derivative cases are considered. Examples are presented to illustrate that the Δ-derivative case needs more restrictive assumptions.  相似文献   
136.
This paper deals with two mixed nonlinear boundary value problems depending on a parameter λ. For each of them we prove the existence of at least three generalized solutions when λ lies in an exactly determined open interval. Usefulness of this information on the interval is then emphasized by means of some consequences. Our main tool is a very recent three critical points theorem stated in [Topol. Methods Nonlinear Anal. 22 (2003) 93-104].  相似文献   
137.
Weakly conducting fluid flows in an electric field in the presence of phase interfaces are investigated theoretically and experimentally. The object of the investigation is an axisymmetric jet. The analysis is carried out within the framework of electrohydrodynamics (EHD) with allowance for surface charge transfer on mobile interfaces. The jet shape is calculated at large distances from the outflow point. The theoretical and experimental data are compared for Newtonian and polymeric fluids.  相似文献   
138.
关于非线性多目标规划问题非劣解解法的探讨   总被引:3,自引:0,他引:3  
陈伟 《运筹与管理》2003,12(3):32-37
非线性多目标规划是一类复杂的规划问题,由于其往往没有最优解,因此求其非劣解具有重要的意义。本首先探讨了无约束条件下非线性多目标规划的解法,然后提出了有约束条件下非线性多目标规划的一种解法。所述方法具有一定的普遍意义。  相似文献   
139.
In this paper we obtain some sufficient conditions for the existence of non-constant periodic solutions of the following planar system with six delaysOur approach is based on the continuation theorem of the coincidence degree.  相似文献   
140.
This paper deals with the analysis of an M/M/c queueing system with setup times. This queueing model captures the major characteristics of phenomena occurring in production when the system consists in a set of machines monitored by a single operator. We carry out an extensive analysis of the system including limiting distribution of the system state, waiting time analysis, busy period and maximum queue length. AMS subject classification: 90B22, 60K25  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