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   2536篇
  免费   324篇
  国内免费   147篇
化学   48篇
力学   273篇
综合类   26篇
数学   1071篇
物理学   733篇
综合类   856篇
  2024年   4篇
  2023年   20篇
  2022年   26篇
  2021年   27篇
  2020年   53篇
  2019年   45篇
  2018年   46篇
  2017年   75篇
  2016年   72篇
  2015年   67篇
  2014年   104篇
  2013年   167篇
  2012年   132篇
  2011年   122篇
  2010年   120篇
  2009年   152篇
  2008年   152篇
  2007年   172篇
  2006年   164篇
  2005年   183篇
  2004年   122篇
  2003年   125篇
  2002年   110篇
  2001年   90篇
  2000年   91篇
  1999年   63篇
  1998年   51篇
  1997年   40篇
  1996年   46篇
  1995年   39篇
  1994年   40篇
  1993年   39篇
  1992年   41篇
  1991年   28篇
  1990年   32篇
  1989年   23篇
  1988年   14篇
  1987年   21篇
  1986年   19篇
  1985年   13篇
  1984年   7篇
  1983年   2篇
  1982年   11篇
  1981年   7篇
  1980年   9篇
  1979年   6篇
  1978年   4篇
  1977年   3篇
  1976年   3篇
  1957年   1篇
排序方式: 共有3007条查询结果,搜索用时 797 毫秒
71.
An analytical method is developed to study the two-mode quantum Rabi model. For certain specific parameter conditions, especially for the resonant conditions, we obtain an infinite number of the exact solutions of the eigenfunctions and associated energies. It is shown that there exist new types of the exact energies which do not correspond to the level-crossings. Our analytical method may find applications in some related models.  相似文献   
72.
We obtain the energy spectrum and all the corresponding eigenfunctions of N-body Bose and Fermi systems with Quadratic Pair Potentials in one dimension. The original first excited state or energy level is disappeared in one dimension, which results from the operation of symmetry or antisymmetry of identical particles. In two and higher dimensions, we give the energy spectrum and the analytical ground state wave functions and the degree of degeneracy. By comparison, we refine Avinash Khare's results by making some items in his article precisely.  相似文献   
73.
In this paper,we show that for any given planar cubic algebraic curves defined by a quadratic Hamiltonian vector field,we can always have their exact explicit parametric representations. We use a model of micro-structured solid to show an application of our conclusions.  相似文献   
74.
目的 求解Burgers-Huxley方程,得到该方程的精确解.方法 用齐次平衡原则求解Burgers-Huxley方程并利用符号计算软件Mathetnatica对方程进行化简.结果 得到了BurgersHuxley方程6种不同形式的行波解.结论 齐次平衡法是求解某些非线性偏微分方程的有效工具之一,具有一定的普适性.  相似文献   
75.
In this paper, we prove controllability results for a two-dimensional semilinear heat equation with mixed boundary conditions. It is well-known that mixed boundary conditions can present a singular behaviour of the solution. First, we will prove global Carleman estimates then we will use these inequalities to obtain controllability results.  相似文献   
76.
By adding one variable to the equality-or inequality-constrained minimization problems, a new simple penalty function is proposed. It is proved to be exact in the sense that under mild assumptions, the local minimizers of this penalty function are precisely the local minimizers of the original problem, when the penalty parameter is sufficiently large.  相似文献   
77.
78.
This paper is concerned with the generalized nonlinear Schrödinger equation with parabolic law and dual‐power law. Abundant explicit and exact solutions of the generalized nonlinear Schrödinger equation with parabolic law and dual‐power law are derived uniformly by using the first integral method. These exact solutions are include that of extended hyperbolic function solutions, periodic wave solutions of triangle functions type, exponential form solution, and complex hyperbolic trigonometric function solutions and so on. The results obtained confirm that the first integral method is an efficient technique for analytic treatment of a wide variety of nonlinear systems of partial DEs. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   
79.
In this paper, we deal with the approximate controllability for control systems described by a class of hemivariational inequalities. Firstly, we introduce the concept of mild solutions for hemivariational inequalities. Then the approximate controllability is formulated and proved by utilizing a fixed-point theorem of multivalued maps and properties of generalized Clarke subdifferential.  相似文献   
80.
The performance of 18 density functional approximations has been tested for a very challenging task, the calculations of rate constants for radical‐molecule reactions in aqueous solution. Despite of the many difficulties involved in such an enterprise, six of them provide high quality results, and are recommended to that purpose. They are LC‐ωPBE, M06‐2X, BMK, B2PLYP, M05‐2X, and MN12SX, in that order. This trend was obtained using experimental data as reference. The other relevant aspects used in this benchmark are: (i) the SMD model for mimicking the solvent; (ii) the conventional transition state, the zero‐curvature tunneling correction, and the limit imposed by diffusion for the calculation of the rate constants. Even though changing any of these aspects might alter the trend in performance, at least, when using them, the aforementioned functionals can be successfully used to obtain high quality kinetic data for the kind of reactions investigated in this work. © 2014 Wiley Periodicals, Inc.  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