全文获取类型
收费全文 | 24547篇 |
免费 | 2170篇 |
国内免费 | 1372篇 |
专业分类
化学 | 1913篇 |
晶体学 | 35篇 |
力学 | 2787篇 |
综合类 | 217篇 |
数学 | 18650篇 |
物理学 | 4487篇 |
出版年
2024年 | 51篇 |
2023年 | 244篇 |
2022年 | 217篇 |
2021年 | 370篇 |
2020年 | 655篇 |
2019年 | 701篇 |
2018年 | 674篇 |
2017年 | 687篇 |
2016年 | 699篇 |
2015年 | 605篇 |
2014年 | 1100篇 |
2013年 | 2474篇 |
2012年 | 1064篇 |
2011年 | 1376篇 |
2010年 | 1177篇 |
2009年 | 1604篇 |
2008年 | 1536篇 |
2007年 | 1527篇 |
2006年 | 1371篇 |
2005年 | 1085篇 |
2004年 | 1005篇 |
2003年 | 963篇 |
2002年 | 953篇 |
2001年 | 751篇 |
2000年 | 769篇 |
1999年 | 698篇 |
1998年 | 579篇 |
1997年 | 543篇 |
1996年 | 394篇 |
1995年 | 272篇 |
1994年 | 260篇 |
1993年 | 184篇 |
1992年 | 180篇 |
1991年 | 133篇 |
1990年 | 118篇 |
1989年 | 87篇 |
1988年 | 73篇 |
1987年 | 61篇 |
1986年 | 61篇 |
1985年 | 90篇 |
1984年 | 123篇 |
1983年 | 58篇 |
1982年 | 86篇 |
1981年 | 88篇 |
1980年 | 79篇 |
1979年 | 69篇 |
1978年 | 62篇 |
1977年 | 44篇 |
1976年 | 38篇 |
1974年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 546 毫秒
121.
122.
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
123.
Differential inequality method, bounding function method and topological degree are applied to obtain the existence criterions of at least one solution for the general fourth-order differential equations under nonlinear boundary conditions, and many existing results are complemented. 相似文献
124.
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
125.
In this paper we prove existence results for semilinear neutral functional differential inclusions with finite or infinite
delay in Banach spaces. Our theory makes use of analytic semigroups and fractional powers of closed operators, integrated
semigroups and cosine families.
相似文献
126.
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
127.
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
128.
Arup Baksi Bidyut Kumar Roy Rasajit Kumar Bera 《Mathematical and Computer Modelling》2006,44(11-12):1069-1079
The fundamental equations of the problems of generalized thermoelasticity with one relaxation parameter including heat sources in infinite rotating magneto-thermo-viscoelastic media have been derived in the form of a vector matrix differential equation in the Laplace transform domain for a one dimensional problem. These equations have been solved by the eigenvalue approach to determine deformations, stress, and temperature. The results have been compared to those available in the existing literature. The graphs have been drawn to show the effect of rotation in the medium. 相似文献
129.
130.
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