全文获取类型
收费全文 | 3922篇 |
免费 | 522篇 |
国内免费 | 300篇 |
专业分类
化学 | 261篇 |
晶体学 | 6篇 |
力学 | 322篇 |
综合类 | 83篇 |
数学 | 3457篇 |
物理学 | 615篇 |
出版年
2024年 | 9篇 |
2023年 | 36篇 |
2022年 | 31篇 |
2021年 | 71篇 |
2020年 | 107篇 |
2019年 | 100篇 |
2018年 | 123篇 |
2017年 | 166篇 |
2016年 | 153篇 |
2015年 | 109篇 |
2014年 | 142篇 |
2013年 | 318篇 |
2012年 | 173篇 |
2011年 | 213篇 |
2010年 | 165篇 |
2009年 | 182篇 |
2008年 | 212篇 |
2007年 | 259篇 |
2006年 | 241篇 |
2005年 | 207篇 |
2004年 | 181篇 |
2003年 | 191篇 |
2002年 | 210篇 |
2001年 | 181篇 |
2000年 | 147篇 |
1999年 | 138篇 |
1998年 | 107篇 |
1997年 | 97篇 |
1996年 | 63篇 |
1995年 | 76篇 |
1994年 | 52篇 |
1993年 | 41篇 |
1992年 | 42篇 |
1991年 | 32篇 |
1990年 | 20篇 |
1989年 | 15篇 |
1988年 | 19篇 |
1987年 | 13篇 |
1986年 | 10篇 |
1985年 | 9篇 |
1984年 | 17篇 |
1983年 | 6篇 |
1982年 | 7篇 |
1981年 | 9篇 |
1980年 | 16篇 |
1979年 | 9篇 |
1978年 | 4篇 |
1977年 | 7篇 |
1975年 | 2篇 |
1936年 | 1篇 |
排序方式: 共有4744条查询结果,搜索用时 31 毫秒
21.
具有避难所的非自治竞争系统的持续生存和全局稳定性 总被引:2,自引:0,他引:2
考虑一个四缀块模型,其中一缀块里有三个竞争种群,另外三个分别是它们的避难所,并且种群能在竞争缀块和各自的避难所间相互扩散.在一定的条件下,我们给出了此模型的持续生存,周期性和全局稳定性. 相似文献
22.
Song Jiang 《Mathematische Nachrichten》1998,190(1):169-183
We consider initial boundary value problems for the equations of the one-dimensional motion of a viscous, heat-conducting gas with density-dependent viscosity that decreases (to zero) with decreasing density. We prove that if the viscosity does not decrease to zero too rapidly, then smooth solutions exist globally in time. 相似文献
23.
GLOBAL ATTRACTOR OF A SPATIALLY DISCRETIZED REACTION-DIFFUSION SYSTEM WITH HAMILTONIAN STRUCTURE 总被引:1,自引:0,他引:1
1HamiltonianStructureinReaction-DifusionsystemConsiderasystemofreaction-difusionequationsut=uxx+f(u,v)vt=vxx+g(u,v){(1.1)wher... 相似文献
24.
Gabriele Bonanno 《Journal of Global Optimization》1998,12(1):101-104
In this note we introduce a suitable class of functionals, including the class of integral functionals, and prove that any (strict) local minimum of a functional of this class, defined on a decomposable space, is a (strict) global minimum. So, the recent result obtained by Giner in [1] is specified and extended. 相似文献
25.
In this paper, we investigate a constrained optimization problem with a quadratic cost functional and two quadratic equality constraints. It is assumed that the cost functional is positive definite and that the constraints are both feasible and regular (but otherwise they are unrestricted quadratic functions). Thus, the existence of a global constrained minimum is assured. We develop a necessary and sufficient condition that completely characterizes the global minimum cost. Such a condition is of essential importance in iterative numerical methods for solving the constrained minimization problem, because it readily distinguishes between local minima and global minima and thus provides a stopping criterion for the computation. The result is similar to one obtained previously by the authors. In the previous result, we gave a characterization of the global minimum of a constrained quadratic minimization problem in which the cost functional was an arbitrary quadratic functional (as opposed to positive-definite here) and the constraints were at least positive-semidefinite quadratic functions (as opposed to essentially unrestricted here). 相似文献
26.
V.I. Fernández A. Iucci C.M. Naón 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(1):53-56
We present an extension of the Tomonaga-Luttinger model in which left and right-moving particles have different Fermi velocities.
We derive expressions for one-particle Green's functions, momentum-distributions, density of states, charge compressibility
and conductivity as functions of both the velocity difference ε and the strength of the interaction β. This allows us to identify
a novel restricted region in the parameter space in which the system keeps the main features of a Luttinger liquid but with
an unusual behavior of the density of states and the static charge compressibility κ. In particular κ diverges on the boundary
of the restricted region, indicating the occurrence of a phase transition.
Received 20 May 2002 / Received in final form 23 August 2002 Published online 19 November 2002 相似文献
27.
A globally convergent Newton method for solving strongly monotone variational inequalities 总被引:14,自引:0,他引:14
Variational inequality problems have been used to formulate and study equilibrium problems, which arise in many fields including economics, operations research and regional sciences. For solving variational inequality problems, various iterative methods such as projection methods and the nonlinear Jacobi method have been developed. These methods are convergent to a solution under certain conditions, but their rates of convergence are typically linear. In this paper we propose to modify the Newton method for variational inequality problems by using a certain differentiable merit function to determine a suitable step length. The purpose of introducing this merit function is to provide some measure of the discrepancy between the solution and the current iterate. It is then shown that, under the strong monotonicity assumption, the method is globally convergent and, under some additional assumptions, the rate of convergence is quadratic. Limited computational experience indicates the high efficiency of the proposed method. 相似文献
28.
Tatsien Li 《Mathematical Methods in the Applied Sciences》2006,29(13):1543-1553
By means of a direct and constructive method based on the theory of semi‐global C2 solution, the local exact boundary observability and an implicit duality between the exact boundary controllability and the exact boundary observability are shown for 1‐D quasilinear wave equations with various boundary conditions. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
29.
Jean-Franç ois Coulombel Thierry Goudon 《Transactions of the American Mathematical Society》2007,359(2):637-648
We construct global smooth solutions to the multidimensional isothermal Euler equations with a strong relaxation. When the relaxation time tends to zero, we show that the density converges towards the solution to the heat equation.
30.
三种群食物链交错扩散模型的整体 总被引:1,自引:0,他引:1
本文应用能量估计方法和Gagliardo-Nirenberg型不等式证明了一类强耦合反应扩散系统整体解的存在性和一致有界性,该系统是带自扩散和交错扩散项的三种群Lotka-Volterra食物链模型.通过构造Lyapunov函数给出了该模型正平衡点全局渐近稳定的充分条件. 相似文献