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   109759篇
  免费   1606篇
  国内免费   628篇
化学   46823篇
晶体学   1031篇
力学   7308篇
综合类   1篇
数学   37344篇
物理学   19486篇
  2023年   161篇
  2022年   160篇
  2021年   386篇
  2020年   610篇
  2019年   600篇
  2018年   10714篇
  2017年   10525篇
  2016年   6903篇
  2015年   1649篇
  2014年   1279篇
  2013年   1998篇
  2012年   5886篇
  2011年   12751篇
  2010年   6833篇
  2009年   7092篇
  2008年   8733篇
  2007年   10644篇
  2006年   2312篇
  2005年   3206篇
  2004年   3123篇
  2003年   3247篇
  2002年   2096篇
  2001年   555篇
  2000年   605篇
  1999年   414篇
  1998年   426篇
  1997年   502篇
  1996年   573篇
  1995年   398篇
  1994年   426篇
  1993年   414篇
  1992年   339篇
  1991年   329篇
  1990年   286篇
  1989年   261篇
  1988年   260篇
  1987年   273篇
  1986年   225篇
  1985年   415篇
  1984年   369篇
  1983年   309篇
  1982年   378篇
  1981年   314篇
  1980年   331篇
  1979年   283篇
  1978年   258篇
  1977年   235篇
  1976年   221篇
  1975年   202篇
  1974年   171篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
We discuss the length of the longest directed cycle in the sparse random digraph , constant. We show that for large there exists a function such that a.s. The function where is a polynomial in . We are only able to explicitly give the values , although we could in principle compute any .  相似文献   
3.
Mathematical Programming - We provide a control-theoretic perspective on optimal tensor algorithms for minimizing a convex function in a finite-dimensional Euclidean space. Given a function...  相似文献   
4.
Computational Optimization and Applications - It has been shown that a global minimizer of a smooth determinant of a matrix function corresponds to the largest cycle of a graph. When it exists,...  相似文献   
5.
Journal of Dynamics and Differential Equations - In this paper we study the local and global well posedness of a fractional dissipative Klein–Gordon–Schrödinger type system in...  相似文献   
6.
Measuring angles in the Euclidean plane is a well-known topic, but for general normed planes there exists a variety of different concepts. These can be of a special kind, e.g. also preserving special orthogonality types. But these concepts are no angle measures in the sense of measure theory since they are not additive. This motivates us to define a new angle measure for normed planes that is in fact a measure in the sense of measure theory. Furthermore, we look at related types of rotation and reflection.  相似文献   
7.
We analyze isolated resonance curves (IRCs) in single-degree-of-freedom systems possessing nonlinear damping. Through the combination of singularity theory and the averaging method, the onset and merging of IRCs, which coincide to isola and simple bifurcation singularities, respectively, can be analytically predicted. Numerical simulations confirm the accuracy of the analytical developments. Another important finding of this paper is that we unveil a geometrical connection between the topology of the damping force and IRCs. Specifically, we demonstrate that extremas and zeros of the damping force correspond to the appearance and merging of IRCs. Considering a damping force possessing several minima and maxima confirms the general validity of the analytical result. It also evidences a very complex scenario for which different IRCs are created, co-exist and then merge together to form a super IRC which eventually merges with the main resonance peak.  相似文献   
8.
We give the parameter version of a localization theorem for the Bergman metric near the boundary points of strictly pseudoconvex domains. The approximation theorem for square integrable holomorphic functions on such domains in the spirit of Graham-Kerzman is proved in the hereby paper, as well.  相似文献   
9.
10.
The paper presents an interphase cohesive zone model (CZM) incorporating stress multi-axiality devised to capture, by simplified micro-modeling, the influence of the in-plane strain and stress state in the mechanical response of the CZM. Moreover, the model is able to account for the Poisson-related effect in the interphase, which can play an important role in the modeling of heterogeneous masonry elements. From the constitutive point of view, the proposed formulation couples damage and friction by addressing a smooth transition from a quasi-brittle response to a residual frictional behavior described by a Coulomb law with unilateral contact. As in-plane stresses are accounted for, damage activation and evolution are governed by a Drucker–Prager law with linear softening. A predictor-corrector procedure based on a backward Euler scheme is detailed for integrating the nonlinear evolutive problem together with the related tangent operator which consistently linearizes the algorithmic strategy. This framework is embedded into a kinematically-enriched finite element interphase formulation incorporating stress multi-axiality. The modeling features of the resulting numerical tool are tested both at the local level, for the typical interphase point, and in meso-structural tests consisting of brick-mortar triplets, investigating the capability of the proposed model and numerical procedure to simulate the brick-mortar decohesion mechanism during confined slip tests.  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