全文获取类型
收费全文 | 4485篇 |
免费 | 668篇 |
国内免费 | 499篇 |
专业分类
化学 | 1459篇 |
晶体学 | 42篇 |
力学 | 955篇 |
综合类 | 76篇 |
数学 | 890篇 |
物理学 | 2230篇 |
出版年
2024年 | 4篇 |
2023年 | 51篇 |
2022年 | 106篇 |
2021年 | 129篇 |
2020年 | 121篇 |
2019年 | 100篇 |
2018年 | 106篇 |
2017年 | 186篇 |
2016年 | 205篇 |
2015年 | 176篇 |
2014年 | 243篇 |
2013年 | 411篇 |
2012年 | 292篇 |
2011年 | 340篇 |
2010年 | 255篇 |
2009年 | 287篇 |
2008年 | 275篇 |
2007年 | 290篇 |
2006年 | 259篇 |
2005年 | 215篇 |
2004年 | 224篇 |
2003年 | 202篇 |
2002年 | 151篇 |
2001年 | 118篇 |
2000年 | 94篇 |
1999年 | 108篇 |
1998年 | 94篇 |
1997年 | 92篇 |
1996年 | 77篇 |
1995年 | 63篇 |
1994年 | 62篇 |
1993年 | 48篇 |
1992年 | 39篇 |
1991年 | 35篇 |
1990年 | 22篇 |
1989年 | 25篇 |
1988年 | 23篇 |
1987年 | 13篇 |
1986年 | 12篇 |
1985年 | 14篇 |
1984年 | 12篇 |
1983年 | 5篇 |
1982年 | 11篇 |
1981年 | 8篇 |
1980年 | 9篇 |
1979年 | 16篇 |
1978年 | 8篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1973年 | 3篇 |
排序方式: 共有5652条查询结果,搜索用时 15 毫秒
11.
12.
13.
14.
I. J. Lozada J. C. Osorio D. V. Griffiths M. Cerrolaza 《Numerical Methods for Partial Differential Equations》2006,22(2):296-316
The semi‐analytical integration of an 8‐node plane strain finite element stiffness matrix is presented in this work. The element is assumed to be super‐parametric, having straight sides. Before carrying out the integration, the integral expressions are classified into several groups, thus avoiding duplication of calculations. Symbolic manipulation and integration is used to obtain the basic formulae to evaluate the stiffness matrix. Then, the resulting expressions are postprocessed, optimized, and simplified in order to reduce the computation time. Maple symbolic‐manipulation software was used to generate the closed expressions and to develop the corresponding Fortran code. Comparisons between semi‐analytical integration and numerical integration were made. It was demonstrated that semi‐analytical integration required less CPU time than conventional numerical integration (using Gaussian‐Legendre quadrature) to obtain the stiffness matrix. © 2005 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2006 相似文献
15.
We consider Markov processes built from pasting together pieces of strong Markov processes which are killed at a position
dependent rate and connected via a transition kernel. We give necessary and sufficient conditions for local absolute continuity
of probability laws for such processes on a suitable path space and derive an explicit formula for the corresponding likelihood
ratio process. The main tool is the consideration of the process between successive jumps – what we call ‘elementary experiments’
– and criteria for absolute continuity of laws of the process there. We apply our results to systems of branching diffusions
with interactions and immigrations.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
16.
平行机半在线排序问题研究(Ⅰ) 总被引:15,自引:1,他引:14
对半在线平行机排序问题的研究进展作了详细综述和进一步探讨。文章给出半在线排序问题的背景、定义、分类和求解。介绍它们定义和在不同机器环境和目标函数下半在线排序问题分类,以及第一类半在线模型的近似算法的设计及其竞争比分析。 相似文献
17.
18.
Noboru Nakatani 《Optical Review》2003,10(4):206-210
This paper describes a compulsorily phase locked differential interferometer using an orthogonally polarized light source of a modulated LD with high extinction ratio to reduce non-linearity of the interferometer caused by polarization cross-talk. The current modulated LD is used as a light source to make the interferometer compact and for the scanning phase of the interferometer. The interferometer is operated compulsorily at the maximum inclination point of the fringe intensity curve by fringe scanning and an electric system. A Wollaston prism of high extinction ratio (50 dB) is used to combine the polarizing beams and to make the polarization cross-talk very small. In one light source the polarized output beams are on the same propagation axis; in the other they have a small crossing angle (2.5 mrad ∼ 10 mrad) to completely exclude non-linearity of the interferometer causded by polarization cross-talk. Using jets of a gas mixture of nitrogen and ethylene, this interferometer was demonstrated to be useful in detecting the photothermal effect of a photothermal velocimeter under phase fluctuation in a turbulent flow. 相似文献
19.
20.