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   4618篇
  免费   291篇
  国内免费   180篇
化学   878篇
晶体学   17篇
力学   498篇
综合类   46篇
数学   3081篇
物理学   569篇
  2024年   8篇
  2023年   63篇
  2022年   46篇
  2021年   87篇
  2020年   103篇
  2019年   128篇
  2018年   122篇
  2017年   121篇
  2016年   127篇
  2015年   119篇
  2014年   193篇
  2013年   465篇
  2012年   223篇
  2011年   234篇
  2010年   197篇
  2009年   296篇
  2008年   293篇
  2007年   295篇
  2006年   236篇
  2005年   202篇
  2004年   196篇
  2003年   139篇
  2002年   128篇
  2001年   110篇
  2000年   113篇
  1999年   98篇
  1998年   84篇
  1997年   86篇
  1996年   69篇
  1995年   48篇
  1994年   57篇
  1993年   37篇
  1992年   47篇
  1991年   27篇
  1990年   27篇
  1989年   29篇
  1988年   16篇
  1987年   24篇
  1986年   23篇
  1985年   12篇
  1984年   23篇
  1983年   15篇
  1982年   14篇
  1981年   18篇
  1980年   19篇
  1979年   19篇
  1978年   15篇
  1977年   12篇
  1976年   14篇
  1974年   5篇
排序方式: 共有5089条查询结果,搜索用时 15 毫秒
31.
In this paper,we discuss a large number of sets of global parametric sufficient optimality condi-tions under various gcneralized (η,ρ)-invexity assumptions for a semi-infinite minmax fractional programmingproblem.  相似文献   
32.
In this paper, we prove the existence and uniqueness of a global solution for 2‐D micropolar fluid equation with periodic boundary conditions. Then we restrict ourselves to the autonomous case and show the existence of a global attractor. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   
33.
In this paper we obtain the existence of periodic solutions for nonlinear ``invariance' problems monitored by impulsive differential inclusions subject to impulse effects.

  相似文献   

34.
In this paper, by means of the method of upper and lower solutions and monotone iterative technique, the existence of maximal and minimal solutions of the boundary value problems for first order impulsive delay differential equations is established.  相似文献   
35.
In this paper, we exhibit a unified treatment of the mixed initial boundary value problem for second order (in time) parabolic linear differential equations in Banach spaces, whose boundary conditions are of a dynamical nature. Results regarding existence, uniqueness, continuous dependence (on initial data) and regularity of classical and strict solutions are established. Moreover, several examples are given as samples for possible applications.

  相似文献   

36.
In this paper we give necessary and sufficient conditions for the existence of a C> 0-semigroup in L 1(I) (I real interval) generated by a second-order differential operator when suitable boundary conditions at the endpoints are imposed.  相似文献   
37.
The load-carrying capacity of circular plates made of a fiber-reinforced composite and loaded with axisymmetric transverse forces under axisymmetric boundary conditions is investigated. The plates can be freely supported or clamped along their contour. To the known yield condition used, in the plane of main bending moments, there correspond irregular hexagons, which depend on the mechanical properties of composite constituents and some characteristic geometrical parameters. It is shown that, depending on the ratio of ultimate radial and circumferential bending moments, in the plastic state, the circular plates (the central part of the clamped plates) take the form of a cone or a frustum of cone. For each of the cases, the limit load is found, which is a function of the above-mentioned mechanical parameters. The statically allowable fields of bending moments and the corresponding allowable fields of deflection rates are determined. The solutions found are exact. Special cases for the freely supported plates are analyzed, and the results obtained are presented in the form of graphs.__________Translated from Mekhanika Kompozitnykh Materialov, Vol. 41, No. 2, pp. 177–192, March–April, 2005.  相似文献   
38.
Existence theory is developed for the equation ?(u)=F(u), where ? is a formally self-adjoint singular second-order differential expression and F is nonlinear. The problem is treated in a Hilbert space and we do not require the operators induced by ? to have completely continuous resolvents. Nonlinear boundary conditions are allowed. Also, F is assumed to be weakly continuous and monotone at one point. Boundary behavior of functions associated with the domains of definitions of the operators associated with ? in the singular case is investigated. A special class of self-adjoint operators associated with ? is obtained.  相似文献   
39.
An electromagnetic diffraction problem in a wedge shaped region is reduced to a system of coupled functional difference equations by means of Sommerfeld integrals and Malyuzhinets theorem. By introducing an integral operator it is shown that the solutions of this system of functional equations can be defined in terms of integral representations whose kernels are solutions of a singular integral equation of Cauchy-Carleman type for which an explicit solution is given.  相似文献   
40.
We present in this paper a domain decomposition method to treat faults in geological basin modeling. The particularity of this model is that the faults whose widths are very small in comparison with the basin size, are not characterized as subdomains any more but as interfaces between sedimentary blocks. The originality of this work lies in the formulation of this new fault model and in the definition and the computation of the interface conditions between the subdomains. To cite this article: E. Flauraud et al., C. R. Mecanique 331 (2003).  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