全文获取类型
收费全文 | 56374篇 |
免费 | 8410篇 |
国内免费 | 6385篇 |
专业分类
化学 | 20727篇 |
晶体学 | 1231篇 |
力学 | 11903篇 |
综合类 | 745篇 |
数学 | 16586篇 |
物理学 | 19977篇 |
出版年
2024年 | 118篇 |
2023年 | 616篇 |
2022年 | 1229篇 |
2021年 | 1372篇 |
2020年 | 1845篇 |
2019年 | 1560篇 |
2018年 | 1570篇 |
2017年 | 2046篇 |
2016年 | 2481篇 |
2015年 | 1944篇 |
2014年 | 3058篇 |
2013年 | 4481篇 |
2012年 | 3594篇 |
2011年 | 3937篇 |
2010年 | 3327篇 |
2009年 | 3679篇 |
2008年 | 3584篇 |
2007年 | 3614篇 |
2006年 | 3311篇 |
2005年 | 3013篇 |
2004年 | 2625篇 |
2003年 | 2399篇 |
2002年 | 2041篇 |
2001年 | 1754篇 |
2000年 | 1684篇 |
1999年 | 1466篇 |
1998年 | 1385篇 |
1997年 | 1150篇 |
1996年 | 969篇 |
1995年 | 839篇 |
1994年 | 785篇 |
1993年 | 628篇 |
1992年 | 613篇 |
1991年 | 451篇 |
1990年 | 359篇 |
1989年 | 291篇 |
1988年 | 247篇 |
1987年 | 178篇 |
1986年 | 134篇 |
1985年 | 155篇 |
1984年 | 140篇 |
1983年 | 67篇 |
1982年 | 101篇 |
1981年 | 61篇 |
1980年 | 42篇 |
1979年 | 58篇 |
1978年 | 41篇 |
1977年 | 39篇 |
1976年 | 16篇 |
1957年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
171.
B. Szafran P. S
p J. Adamowski S. Bednarek 《Physica E: Low-dimensional Systems and Nanostructures》2003,18(4):523-529
We present a theoretical study of the charging spectra in natural and artificial atoms. We apply a model electrostatic potential created by a homogenously charged sphere. This model potential allows for a continuous passage from the Coulomb potential of the nucleus to parabolic confinement potential of quantum dots. We consider electron systems with N=1,…,10 electrons with the use of the Hartree–Fock method. We discuss the qualitative similarities and differences between the chemical potential spectrum of electron systems bound to nucleus and confined in quantum dots. 相似文献
172.
The authors study the bifurcation problems of rough heteroclinic loop connecting three saddle points for the case β1 > 1, β2 > 1, β3 < 1 and β1β2β3 < 1. The existence, number, coexistence and incoexistence of 2-point-loop, 1-homoclinic orbit and 1-periodic orbit are studied. Meanwhile, the bifurcation surfaces and existence regions are given. 相似文献
173.
We consider a splitting finite-difference scheme for an initial-boundary value problem for a two-dimensional nonlinear evolutionary
equation. The problem is split into nonlinear and linear parts. The linear part is also split into locally one-dimensional
equations. We prove the convergence and stability of the scheme in L
2 and C norms.
Printed in Lietuvos Matematikos Rinkinys, Vol. 45, No. 3, pp. 413–434, July–September, 2005. 相似文献
174.
175.
176.
K. S. Birdi 《Colloid and polymer science》1997,275(6):561-566
The surface tension versus temperature data of homologous series of n-alkanes and n-alkenes is analyzed. Critical temperatures are shown to be predicted from these data, with a very high precision, after some
corrections are made. The corrections are shown to arise from the effect of the critical pressure on the extrapolated data
to surface tension approaching zero.
Received: 29 October 1996 Accepted: 13 December 1996 相似文献
177.
178.
The thermal and thermo-elastic-plastic response of newly developed ceramic-metalfunctionally graded materials under a thermal shock load is studied.The materials are heated at the ce-ramic surface with a sudden high-intensity heat flux input,and cooled at the metal surface with aflowing liquid nitrogen.Emphasis is placed on two aspects:(1)the influence of the graded composi-tion of the materials on the temperature and stress response;and(2)the optimum design of the gradedcomposition from a unified viewpoint of the heat insulation property and stress relaxation property.Moreover,a comparison between the thermoelastic stress and the thermo-elastic-plastic stress is alsomade to indicate the plasticity effect. 相似文献
179.
映象方程多解问题的某些研究 总被引:1,自引:0,他引:1
本文用fp-同伦方法,在一定的技巧和变换的配合下,在紧性条件支持下,研究了赋范线性空间中一类集值映象方程的多解问题。还给出所得理论结果的一个应用。 相似文献
180.
Efficient Sequential Quadratic Programming Implementations for Equality-Constrained Discrete-Time Optimal Control 总被引:1,自引:0,他引:1
Efficient sequential quadratic programming (SQP) implementations are presented for equality-constrained, discrete-time, optimal control problems. The algorithm developed calculates the search direction for the equality-based variant of SQP and is applicable to problems with either fixed or free final time. Problem solutions are obtained by solving iteratively a series of constrained quadratic programs. The number of mathematical operations required for each iteration is proportional to the number of discrete times N. This is contrasted by conventional methods in which this number is proportional to N
3. The algorithm results in quadratic convergence of the iterates under the same conditions as those for SQP and simplifies to an existing dynamic programming approach when there are no constraints and the final time is fixed. A simple test problem and two application problems are presented. The application examples include a satellite dynamics problem and a set of brachistochrone problems involving viscous friction. 相似文献