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   5767篇
  免费   633篇
  国内免费   192篇
化学   746篇
力学   466篇
综合类   52篇
数学   4087篇
物理学   1241篇
  2023年   46篇
  2022年   55篇
  2021年   112篇
  2020年   164篇
  2019年   140篇
  2018年   149篇
  2017年   162篇
  2016年   212篇
  2015年   133篇
  2014年   244篇
  2013年   653篇
  2012年   276篇
  2011年   285篇
  2010年   274篇
  2009年   297篇
  2008年   291篇
  2007年   309篇
  2006年   285篇
  2005年   280篇
  2004年   226篇
  2003年   218篇
  2002年   184篇
  2001年   181篇
  2000年   184篇
  1999年   130篇
  1998年   127篇
  1997年   115篇
  1996年   88篇
  1995年   81篇
  1994年   79篇
  1993年   53篇
  1992年   63篇
  1991年   53篇
  1990年   48篇
  1989年   38篇
  1988年   34篇
  1987年   27篇
  1986年   29篇
  1985年   45篇
  1984年   39篇
  1983年   17篇
  1982年   22篇
  1981年   18篇
  1980年   13篇
  1979年   20篇
  1978年   17篇
  1977年   23篇
  1976年   16篇
  1975年   7篇
  1973年   9篇
排序方式: 共有6592条查询结果,搜索用时 15 毫秒
81.
We explicitly discuss scalar Langevin type of equations where the deterministic part is linear, but where the integrated noise source is a non-linear diffusion process exhibiting superdiffusive behavior. We calculate transient and stationary probabilities and study the possibility of noise induced transitions from a unimodal to a bimodal probability shape. Illustrations from finance and dynamical systems are given.  相似文献   
82.
Our purpose is to characterize the multiparameter Gaussian processes, that is Gaussian sheets, that are equivalent in law to the Brownian sheet and to the fractional Brownian sheet. We survey multiparameter analogues of the Hitsuda, Girsanov and Shepp representations. As an application, we study a special type of stochastic equation with linear noise.   相似文献   
83.
混合交通OD分布与随机平衡分配组合模型及算法   总被引:4,自引:0,他引:4  
基于我国城市混合交通的特点,借助于Logit选择模型,建立了混合交通OD分布与随机平衡分配组合的数学规划模型,证明了模型最优解的等价性与唯一性,同时给出了算法和算例.  相似文献   
84.
This paper newly designs the recursive least-squares (RLS) fixed-lag smoother and filter using the covariance information in linear continuous-time stochastic systems. It is assumed that the signal is observed with additive white observation noise and the signal is uncorrelated with the observation noise. The estimators require the covariance information of the signal and the variance of the observation noise. The auto-covariance function of the signal is expressed in the semi-degenerate kernel form.  相似文献   
85.
Asymptotic expansions for the exponential growth rate, known as the Lyapunov exponent, and rotation numbers for two coupled oscillators driven by real noise are constructed. Such systems arise naturally in the investigation of the stability of steady-state motions of nonlinear dynamical systems and in parametrically excited linear mechanical systems. Almost-sure stability or instability of dynamical systems depends on the sign of the maximal Lyapunov exponent. Stability conditions are obtained under various assumptions on the infinitesimal generator associated with real noise provided that the natural frequencies are noncommensurable. The results presented here for the case of the infinitesimal generator having a simple zero eigenvalue agree with recent results obtained by stochastic averaging, where approximate ItÔ equations in amplitudes and phases are obtained in the sense of weak convergence.Dedicated to Thomas K. Caughey on the occasion of his 65th birthday.  相似文献   
86.
We discuss issues pertaining to the domination from above of the second-stage recourse function of a stochastic linear program and we present a scheme to majorize this function using a simpler sublinear function. This majorization is constructed using special geometrical attributes of the recourse function. The result is a proper, simplicial function with a simple characterization which is well-suited for calculations of its expectation as required in the computation of stochastic programs. Experiments indicate that the majorizing function is well-behaved and stable.  相似文献   
87.
Consider discrete storage processes that are modulated by environmental processes. Environmental processes cause interruptions in the input and/or output processes of the discrete storage processes. Due to the difficulties encountered in the exact analysis of such discrete storage systems, often Poisson flow and/or fluid flow models with the same modulating environmental processes are proposed as approximations for these systems. The analysis of Poisson flow and fluid flow models is much easier than that of the discrete storage processes. In this paper we give sufficient conditions under which the content of the discrete storage processes can be bounded by the Poisson flow and the fluid flow models. For example, we show that Poisson flow models and the fluid flow models developed by Kosten (and by Anick, Mitra and Sondhi) can be used to bound the performance of infinite (finite) source packetized voice/data communication systems. We also show that a Poisson flow model and the fluid flow model developed by Mitra can be used to bound the buffer content of a two stage automatic transfer line. The potential use of the bounding techniques presented in this paper, of course, transcends well beyond these examples.Supported in part by NSF grant DMS-9308149.  相似文献   
88.
We prove that the Hudson-Parthasarathy equation corresponds, up to unitary equivalence, to the strong resolvent limit of Schrödinger Hamiltonians in Fock space and that the symmetric form of this equation corresponds to the weak limit of the Schrödinger Hamiltonians.Translated fromMatematicheskie Zametki, Vol. 60, No. 5, pp. 726–750, November, 1996.  相似文献   
89.
In a general measure-theoretic context, it is proved that the action of a stochastic map on a pair of probability distributions can be characterized by the criterion of decreasing mixing distance.  相似文献   
90.
A class of circuit-switching open queueing networks is discussed. The main result of the paper is that if extra message flows are not too intensive and the path distribution is mainly concentrated on the paths of (graph) distance 1 (nearest neighbour connections), then the network has a unique stationary working regime, no matter how large the configuration graph of the network is. Standard properties of this regime are established such as decay of correlation and continuity.  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