全文获取类型
收费全文 | 34551篇 |
免费 | 5181篇 |
国内免费 | 1917篇 |
专业分类
化学 | 2765篇 |
晶体学 | 201篇 |
力学 | 6763篇 |
综合类 | 360篇 |
数学 | 18537篇 |
物理学 | 13023篇 |
出版年
2024年 | 85篇 |
2023年 | 348篇 |
2022年 | 476篇 |
2021年 | 598篇 |
2020年 | 945篇 |
2019年 | 888篇 |
2018年 | 869篇 |
2017年 | 994篇 |
2016年 | 1035篇 |
2015年 | 861篇 |
2014年 | 1597篇 |
2013年 | 2939篇 |
2012年 | 1669篇 |
2011年 | 2071篇 |
2010年 | 1761篇 |
2009年 | 2088篇 |
2008年 | 2164篇 |
2007年 | 2193篇 |
2006年 | 2003篇 |
2005年 | 1821篇 |
2004年 | 1650篇 |
2003年 | 1646篇 |
2002年 | 1437篇 |
2001年 | 1245篇 |
2000年 | 1171篇 |
1999年 | 1049篇 |
1998年 | 888篇 |
1997年 | 795篇 |
1996年 | 598篇 |
1995年 | 499篇 |
1994年 | 411篇 |
1993年 | 398篇 |
1992年 | 315篇 |
1991年 | 287篇 |
1990年 | 224篇 |
1989年 | 175篇 |
1988年 | 155篇 |
1987年 | 140篇 |
1986年 | 98篇 |
1985年 | 138篇 |
1984年 | 157篇 |
1983年 | 79篇 |
1982年 | 114篇 |
1981年 | 115篇 |
1980年 | 87篇 |
1979年 | 87篇 |
1978年 | 90篇 |
1977年 | 63篇 |
1976年 | 44篇 |
1971年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
151.
基于正弦灰度变换的X光图像增强 总被引:11,自引:0,他引:11
介绍了灰度变换法的几种形式 ,提出了一种正弦非线性变换法 ,对三幅数字X光医学图像进行了处理 ,获得了令人满意的对比度增强效果 ,证明该方法有效而实用 相似文献
152.
Dirichlet boundary value problems for perturbed second-order differential equations on a half line are investigated in this paper. The methods mainly depend on the calculus of variations to the classical functionals. Sufficient conditions are obtained for the existence of the solutions. 相似文献
153.
Kiyoshi Mochizuki 《Journal of Mathematical Analysis and Applications》2007,326(1):582-588
We show that the energy of solutions to the initial boundary value problem for the wave equation in exterior domains with a dissipation which is localized only near infinity tends to zero as the time goes to infinity. We do not make any geometrical condition like star-shapedness on the boundary. 相似文献
154.
本文研究具有受迫性的广义二维KdV-Burgers方程的周期行波解,为了获得周期行波解的存在唯一性定理,使唤用特定系数法和Schauder不动点定理获得了受迫广义KdV-Burgers方程周期行波解存在唯一性的条件.并获得了周期行波解的一些先验估计式. 相似文献
155.
An infinite row of periodically spaced, identical rigid circularcylinders is excited by an acoustic line source which is parallelto the generators of the cylinders. A method for calculatingthe scattered field accurately and efficiently is presented.When the cylinders are sufficiently close together, Rayleigh–Blochsurface waves that propagate energy to infinity along the arrayare excited. An expression is derived which enables the amplitudesof these surface waves to be computed without requiring thesolution to the full scattering problem. 相似文献
156.
Based on the theory of calculus of variation, some suffcient conditions are given for some Euler-Lagrangcequations to be equivalently represented by finite or even infinite many Hamiltonian canonical equations. Meanwhile,some further applications for equations such as the KdV equation, MKdV equation, the general linear Euler Lagrangeequation and the cylindric shell equations are given. 相似文献
157.
S. P. Popov 《Computational Mathematics and Mathematical Physics》2006,46(6):983-994
Numerical solutions to three systems of integrable evolutionary equations from the Toda lattice hierarchy are analyzed. These are the classical Toda lattice, the second local dispersive flow, and the second extended dispersive flow. Special attention is given to the properties of soliton solutions. For the equations of the second local flow, two types of solitons interacting in a special manner are found. Solutions corresponding to various initial data are qualitatively outlined. 相似文献
158.
Linear complexity and linear complexity profile are important characteristics of a sequence for applications in cryptography
and Monte-Carlo methods.
The nonlinear congruential method is an attractive alternative to the classical linear congruential method for pseudorandom
number generation.
Recently, a weak lower bound on the linear complexity profile of a general nonlinear congruential pseudorandom number generator
was proven by Gutierrez, Shparlinski and the first author. For most nonlinear generators a much stronger lower bound is expected.
Here, we obtain a much stronger lower bound on the linear complexity profile of nonlinear congruential pseudorandom number
generators with Dickson polynomials. 相似文献
159.
160.
We present the explicit form of the symplectic structure of anti-self-dual Yang-Mills (ASDYM) equations in Yang’s J- and K-gauges in order to establish the bi-Hamiltonian structure of this completely integrable system. Dirac’s theory of constraints is applied to the degenerate Lagrangians that yield the ASDYM equations. The constraints are second class as in the case of all completely integrable systems which stands in sharp contrast to the situation in full Yang-Mills theory. We construct the Dirac brackets and the symplectic 2-forms for both J- and K-gauges. The covariant symplectic structure of ASDYM equations is obtained using the Witten-Zuckerman formalism. We show that the appropriate component of the Witten-Zuckerman closed and conserved 2-form vector density reduces to the symplectic 2-form obtained from Dirac’s theory. Finally, we present the Bäcklund transformation between the J- and K-gauges in order to apply Magri’s theorem to the respective two Hamiltonian structures. 相似文献