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   20996篇
  免费   1053篇
  国内免费   2421篇
化学   7733篇
晶体学   222篇
力学   724篇
综合类   124篇
数学   9944篇
物理学   5723篇
  2024年   34篇
  2023年   240篇
  2022年   345篇
  2021年   345篇
  2020年   540篇
  2019年   530篇
  2018年   492篇
  2017年   477篇
  2016年   466篇
  2015年   506篇
  2014年   890篇
  2013年   1286篇
  2012年   695篇
  2011年   1589篇
  2010年   1124篇
  2009年   1304篇
  2008年   1520篇
  2007年   1443篇
  2006年   1095篇
  2005年   1028篇
  2004年   860篇
  2003年   784篇
  2002年   834篇
  2001年   585篇
  2000年   489篇
  1999年   500篇
  1998年   446篇
  1997年   370篇
  1996年   335篇
  1995年   278篇
  1994年   307篇
  1993年   298篇
  1992年   282篇
  1991年   221篇
  1990年   206篇
  1989年   224篇
  1988年   182篇
  1987年   201篇
  1986年   190篇
  1985年   199篇
  1984年   182篇
  1983年   129篇
  1982年   87篇
  1981年   64篇
  1980年   57篇
  1979年   39篇
  1978年   46篇
  1977年   30篇
  1976年   28篇
  1974年   23篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
A Yang–Mills theory in a purely symplectic framework is developed. The corresponding Euler–Lagrange equations are derived and first integrals are given. We relate the results to the work of Bourgeois and Cahen on preferred symplectic connections.  相似文献   
82.
In this paper, we discuss the local and global existence ofweak solutions for some hyperbolic–parabolic systems modellingchemotaxis.  相似文献   
83.
This paper deals with perturbations of the Ornstein-Uhlenbeck operator on L2-spaces with respect to a Gaussian measure μ. We perturb the generator of the Ornstein-Uhlenbeck semigroup by a certain unbounded, non-linear drift, and show various properties of the perturbed semigroup such as compactness and positivity. Strong Feller property, existence and uniqueness of an invariant measure are discussed as well.  相似文献   
84.
 We have investigated the effects of the magnetic field which is directed perpendicular to the well on the binding energy of the hydrogenic impurities in an inverse parabolic quantum well (IPQW) with different widths as well as different Al concentrations at the well center. The Al concentration at the barriers was always xmax=0.3. The calculations were performed within the effective mass approximation, using a variational method. We observe that IPQW structure turns into parabolic quantum well with the inversion effect of the magnetic field and donor impurity binding energy in IPQW strongly depends on the magnetic field, Al concentration at the well center and well dimensions.  相似文献   
85.
本篇文章首先定义了向量变分不等式的严格可行点概念,其次在假设了映射是强(D)-伪单调的情况下,证明了向量变分不等式解集非空有界与其严格可行点存在的等价性问题,推广了在数量变分不等式上得到的相应结果.  相似文献   
86.
In this paper one specifies the ergodic behavior of the 2D-stochastic Navier–Stokes equation by giving a Large Deviation Principle for the occupation measure for large time. It describes the exact rate of exponential convergence. The considered random force is non-degenerate and compatible with the strong Feller property.  相似文献   
87.
In this paper we study a Ginzburg–Landau model which describes the behaviour of a superconducting material including thermal effects. We extend the traditional formulation of the problem, by introducing the temperature as an additional state variable. Accordingly, together with the Gor’kov–Eliashberg system, we introduce an evolution equation for the absolute temperature. We examine in detail the case which allows only variations of the concentration of superconducting electrons and of the temperature, neglecting the electromagnetic field. For this problem existence and uniqueness of the solution are shown. Finally we analyze the asymptotic behaviour of the solutions, proving that the system possesses a global attractor.  相似文献   
88.
Let M be a separable metric space consisting of more than one point. We construct perfectly normal dense subspaces ZMc2 and (under additional set-theoretic assumption) YMc which are not collectionwise Hausdorff.  相似文献   
89.
In this article we investigate some integral functional inequalities of Bellman–Bihari type for piecewise-continuous functions with some fixed points of discontinuity. We also prove a new analogy and generalization of results which were obtained by Bellman and Bihari to integro-sum inequalities with delay and discontinuities that do not belong to Lipschitz’s type.  相似文献   
90.
This paper is concerned with information revelation in single-item auctions. We compute how much data needs to be transmitted in three strategically equivalent auctions—the Vickrey auction, the English auction and the recently proposed bisection auction—and show that in the truth-telling equilibrium the bisection auction is the best performer.  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