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   9205篇
  免费   809篇
  国内免费   342篇
化学   1231篇
晶体学   51篇
力学   624篇
综合类   67篇
数学   5631篇
物理学   2752篇
  2023年   85篇
  2022年   103篇
  2021年   195篇
  2020年   258篇
  2019年   223篇
  2018年   222篇
  2017年   199篇
  2016年   239篇
  2015年   186篇
  2014年   329篇
  2013年   917篇
  2012年   376篇
  2011年   412篇
  2010年   374篇
  2009年   476篇
  2008年   498篇
  2007年   566篇
  2006年   455篇
  2005年   379篇
  2004年   299篇
  2003年   334篇
  2002年   345篇
  2001年   324篇
  2000年   346篇
  1999年   263篇
  1998年   275篇
  1997年   175篇
  1996年   134篇
  1995年   131篇
  1994年   131篇
  1993年   90篇
  1992年   104篇
  1991年   87篇
  1990年   79篇
  1989年   74篇
  1988年   58篇
  1987年   74篇
  1986年   48篇
  1985年   96篇
  1984年   70篇
  1983年   40篇
  1982年   56篇
  1981年   26篇
  1980年   29篇
  1979年   35篇
  1978年   22篇
  1977年   35篇
  1976年   24篇
  1974年   15篇
  1973年   13篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
The F- F+-photoconversion in oxygen-deficient corundum, induced by 210 nm irradiation at different temperatures, was analyzed. It was shown that the dosimetric trap and known deep trap contribute little to these transformations. The dose dependencies of detectors in initial and sensitized states were studied. The interactive processes between different traps in TLD-500 were examined directly.  相似文献   
32.
The control of piecewise-deterministic processes is studied where only local boundedness of the data is assumed. Moreover the discount rate may be zero. The value function is shown to be solution to the Bellman equation in a weak sense; however the solution concept is strong enough to generate optimal policies. Continuity and compactness conditions are given for the existence of nonrelaxed optimal feedback controls.  相似文献   
33.
K. Kubilius 《Acta Appl Math》2003,78(1-3):233-242
We consider the integral equation driven by a standard Brownian motion and by a fractional Brownian motion. Sufficient conditions under which the equation has a weak solution are obtained.  相似文献   
34.
35.
36.
37.
The notion of random attractor for a dissipative stochastic dynamical system has recently been introduced. It generalizes the concept of global attractor in the deterministic theory. It has been shown that many stochastic dynamical systems associated to a dissipative partial differential equation perturbed by noise do possess a random attractor. In this paper, we prove that, as in the case of the deterministic attractor, the Hausdorff dimension of the random attractor can be estimated by using global Lyapunov exponents. The result is obtained under very natural assumptions. As an application, we consider a stochastic reaction-diffusion equation and show that its random attractor has finite Hausdorff dimension.  相似文献   
38.
该文利用算子半群的方法给出了取值于具有左不变度量的完备可分群的齐次Levy过程是复合Poisson过程的弱极限这一结论.  相似文献   
39.
集值Lebesgue—Stieltjes积分   总被引:8,自引:2,他引:6  
本文首先刻划了B(R_ )上的集值测度,其次建立了(R_ B(R_ ))上的集值Lebesgue-Stieltjes积分.最后,进—步建立了集值随机Lebesgue-Stietjes积分的理论.  相似文献   
40.
We develop a production policy that controls work-in-process (WIP) levels and satisfies demand in a multistage manufacturing system with significant uncertainty in yield, rework, and demand. The problem addressed in this paper is more general than those in the literature in three aspects: (i) multiple products are processed at multiple workstations, and the capacity of each workstation is limited and shared by multiple operations; (ii) the behavior of a production policy is investigated over an infinite-time horizon, and thus the system stability can be evaluated; (iii) the representation of yield and rework uncertainty is generalized. Generalizing both the system structure and the nature of uncertainty requires a new mathematical development in the theory of infinite-horizon stochastic dynamic programming. The theoretical contributions of this paper are the existence proofs of the optimal stationary control for a stochastic dynamic programming problem and the finite covariances of WIP and production levels under the general expression of uncertainty. We develop a simple and explicit sufficient condition that guarantees the existence of both the optimal stationary control and the system stability. We describe how a production policy can be constructed for the manufacturing system based on the propositions derived.  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