全文获取类型
收费全文 | 27836篇 |
免费 | 3244篇 |
国内免费 | 1768篇 |
专业分类
化学 | 1960篇 |
晶体学 | 17篇 |
力学 | 3125篇 |
综合类 | 317篇 |
数学 | 19269篇 |
物理学 | 8160篇 |
出版年
2024年 | 61篇 |
2023年 | 285篇 |
2022年 | 327篇 |
2021年 | 434篇 |
2020年 | 837篇 |
2019年 | 827篇 |
2018年 | 769篇 |
2017年 | 699篇 |
2016年 | 795篇 |
2015年 | 679篇 |
2014年 | 1241篇 |
2013年 | 2428篇 |
2012年 | 1326篇 |
2011年 | 1668篇 |
2010年 | 1615篇 |
2009年 | 1784篇 |
2008年 | 1868篇 |
2007年 | 1819篇 |
2006年 | 1540篇 |
2005年 | 1555篇 |
2004年 | 1295篇 |
2003年 | 1243篇 |
2002年 | 1080篇 |
2001年 | 829篇 |
2000年 | 789篇 |
1999年 | 763篇 |
1998年 | 698篇 |
1997年 | 572篇 |
1996年 | 455篇 |
1995年 | 374篇 |
1994年 | 314篇 |
1993年 | 206篇 |
1992年 | 201篇 |
1991年 | 212篇 |
1990年 | 179篇 |
1989年 | 102篇 |
1988年 | 104篇 |
1987年 | 101篇 |
1986年 | 99篇 |
1985年 | 94篇 |
1984年 | 89篇 |
1983年 | 45篇 |
1982年 | 90篇 |
1981年 | 75篇 |
1980年 | 53篇 |
1979年 | 57篇 |
1978年 | 39篇 |
1977年 | 32篇 |
1976年 | 24篇 |
1973年 | 16篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
Sh. R. Shakirov 《Theoretical and Mathematical Physics》2007,153(2):1477-1486
We propose a method for constructing systems of polynomial equations that define submanifolds of degenerate binary forms of
an arbitrary degeneracy degree.
__________
Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 153, No. 2, pp. 147–157, November, 2007. 相似文献
142.
Wei Mingjun Zhu Wanzhen 《Annals of Differential Equations》2007,23(4):511-518
In this paper we consider the system of classical particles coupled with a Klein-Gordon field in two dimensions.We establish a-priori-bounds on the solutions of this system with initial data satisfying a size restriction derived from conservation of energy.This result,together with the smoothing of"velocity averaging",yields the existence of global weak solutions to the corresponding restricted initial value problem.The size restriction is necessary since energy of the system is indefinite.Finally,we show that the weak solutions preserve the total mass. 相似文献
143.
Various tests have been carried out in order to compare the performances of several methods used to solve the non-symmetric linear systems of equations arising from implicit discretizations of CFD problems, namely the scalar advection-diffusion equation and the compressible Euler equations. The iterative schemes under consideration belong to three families of algorithms: relaxation (Jacobi and Gauss-Seidel), gradient and Newton methods. Two gradient methods have been selected: a Krylov subspace iteration method (GMRES) and a non-symmetric extension of the conjugate gradient method (CGS). Finally, a quasi-Newton method has also been considered (Broyden). The aim of this paper is to provide indications of which appears to be the most adequate method according to the particular circumstances as well as to discuss the implementation aspects of each scheme. 相似文献
144.
An efficient preconditioner is developed for solving the Helmholtz problem in both high and low frequency (wavenumber) regimes. The preconditioner is based on hierarchical unknowns on nested grids, known as incremental unknowns (IU). The motivation for the IU preconditioner is provided by an eigenvalue analysis of a simplified Helmholtz problem. The performance of our preconditioner is tested on the iterative solution of two‐dimensional electromagnetic scattering problems. When compared with other well‐known methods, our technique is shown to often provide a better numerical efficacy and, most importantly, to be more robust. Moreover, for the best performance, the number of IU levels used in the preconditioner should be designed for the coarsest grid to have roughly two points per linear wavelength. This result is consistent with the conventional sampling criteria for wave phenomena in contrast with existing IU applications for solving the Laplace/Poisson problem, where the coarsest grid comprises just one interior point. © 2007 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2007 相似文献
145.
We construct separation variables for the Kovalevskaya–Goryachev–Chaplygin gyrostat for arbitrary values of the parameters. We show that different separation variables can be constructed for the same integrable system if different integrals of motion are chosen. 相似文献
146.
Numerical analysis for stochastic age-dependent population equations with Poisson jumps 总被引:1,自引:0,他引:1
In this paper, stochastic age-dependent population equations with Poisson jumps are considered. In general, most of stochastic age-dependent population equations with jumps do not have explicit solutions, thus numerical approximation schemes are invaluable tools for exploring their properties. The main purpose of this paper is to develop a numerical Euler scheme and show the convergence of the numerical approximation solution to the true solution. 相似文献
147.
M. Benchohra 《Journal of Mathematical Analysis and Applications》2003,286(1):307-325
In this paper, we shall establish sufficient conditions for the existence of integral solutions for some nondensely defined evolution impulsive differential inclusions in Banach spaces with nonlocal conditions. 相似文献
148.
T. Roubíček 《Journal of Optimization Theory and Applications》2007,132(1):41-50
Existence of a Nash equilibrium in a noncooperative game governed by the one-dimensional Burgers equation, proposed in the
case of pointwise controls in Ref. 1, is proved under data qualifications that guarantee the diffusion term in the Burgers’
equation to be dominant enough with respect to the uniform convexity of the payoffs.
This work was partly supported by Grants 201/03/0934 (GA čR) and MSM 0021620839 (MšMT čR). Inspiring discussions with Angel
M. Ramos are acknowledged. 相似文献
149.
B. Ivorra A. M. Ramos B. Mohammadi 《Journal of Optimization Theory and Applications》2007,135(3):549-561
This paper has two objectives. We introduce a new global optimization algorithm reformulating optimization problems in terms
of boundary-value problems. Then, we apply this algorithm to a pointwise control problem of the viscous Burgers equation,
where the control weight coefficient is progressively decreased. The results are compared with those obtained with a genetic
algorithm and an LM-BFGS algorithm in order to check the efficiency of our method and the necessity of using global optimization
techniques. 相似文献
150.
文章讨论无界区域上GBBM方程的Cauchy问题,对方程的解进行了先验估计,并证明了在H1弱拓扑中整体吸引子的存在性. 相似文献