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   27527篇
  免费   1022篇
  国内免费   150篇
化学   18463篇
晶体学   280篇
力学   766篇
数学   2603篇
物理学   6587篇
  2023年   150篇
  2022年   448篇
  2021年   626篇
  2020年   494篇
  2019年   509篇
  2018年   434篇
  2017年   411篇
  2016年   812篇
  2015年   692篇
  2014年   939篇
  2013年   1654篇
  2012年   1955篇
  2011年   2222篇
  2010年   1392篇
  2009年   1231篇
  2008年   1868篇
  2007年   1611篇
  2006年   1654篇
  2005年   1385篇
  2004年   1238篇
  2003年   1043篇
  2002年   1012篇
  2001年   625篇
  2000年   557篇
  1999年   391篇
  1998年   249篇
  1997年   258篇
  1996年   321篇
  1995年   218篇
  1994年   228篇
  1993年   232篇
  1992年   189篇
  1991年   148篇
  1990年   154篇
  1989年   130篇
  1988年   84篇
  1987年   86篇
  1986年   64篇
  1985年   103篇
  1984年   72篇
  1983年   63篇
  1982年   81篇
  1981年   71篇
  1980年   48篇
  1979年   57篇
  1978年   63篇
  1977年   55篇
  1976年   54篇
  1975年   49篇
  1973年   43篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
141.
142.
Mechanics of Composite Materials - A three-dimensional ply-level modeling of multiple matrix cracking near an open hole in a quasi-isotropic composite laminate was performed. A mesh-independent...  相似文献   
143.
By the numerical simulation of the dynamics of the optical circularly polarized field in the Kerr-type medium, it has been shown that the binary collisions between wave solitons consisting of a few field oscillation cycles with respect to their energy characteristics exhibit the properties of the collisions of Schrödinger solitons. The corresponding spectral characteristics change according to the conservation of the soliton-like structure of the envelop. In dependence on the absolute difference of the field phases, there are three different interaction regimes: the passage of one structure through another, their repulsion, and the exact replication of one initial wave structure by another.  相似文献   
144.
We will introduce new functional equations (3) and (4) which are strongly related to well-known formulae (1) and (2) of number theory, and investigate the solutions of the equations. Moreover, we will also study some stability problems of those equations.  相似文献   
145.
Finite element analysis of fluid flow with moving free surface has been performed in 2‐D and 3‐D. The new VOF‐based numerical algorithm that has been proposed by the present authors (Int. J. Numer. Meth. Fluids, submitted) was applied to several 2‐D and 3‐D free surface flow problems. The proposed free surface tracking scheme is based on two numerical tools; the orientation vector to represent the free surface orientation in each cell and the baby‐cell to determine the fluid volume flux at each cell boundary. The proposed numerical algorithm has been applied to 2‐D and 3‐D cavity filling and sloshing problems in order to demonstrate the versatility and effectiveness of the scheme. The proposed numerical algorithm resolved successfully the free surfaces interacting with each other. The simulated results demonstrated applicability of the proposed numerical algorithm to the practical problems of large free surface motion. It has been also demonstrated that the proposed free surface tracking scheme can be easily implemented in any irregular non‐uniform grid systems and can be extended to 3‐D free surface flow problems without additional efforts. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   
146.
In this paper we introduce a new notion of infine nonsmooth functions and give several characterizations of infineness property. We prove alternative theorems with mixed constraints (i.e., inequality and equality constraints) being described by invex-infine nonsmooth functions. We establish a necessary and sufficient condition for a solution of a vector optimization problem involving mixed constraints to be a properly efficient solution.  相似文献   
147.
148.
149.
The frequency tuning range of waveguide oscillator and its stability depend sensitively on the dimension of the resonance cap. Therefore the driving-point impedances with the various dimensions of the resonance cap are calculated by using HFSS(High Frequency Simulation System). In this paper the comparisons between theoretical results of the driving-point impedances as a function of frequency and that of experimental results are described. The oscillation frequency range could be predicted by using the theoretical evaluation methods which are proposed. It shows that resonance cap size and disc height have an effect on the frequency tuning characteristics of Gunn oscillator.  相似文献   
150.
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