全文获取类型
收费全文 | 5899篇 |
免费 | 843篇 |
国内免费 | 504篇 |
专业分类
化学 | 314篇 |
晶体学 | 9篇 |
力学 | 489篇 |
综合类 | 132篇 |
数学 | 5533篇 |
物理学 | 769篇 |
出版年
2024年 | 17篇 |
2023年 | 67篇 |
2022年 | 67篇 |
2021年 | 115篇 |
2020年 | 174篇 |
2019年 | 160篇 |
2018年 | 190篇 |
2017年 | 247篇 |
2016年 | 256篇 |
2015年 | 144篇 |
2014年 | 245篇 |
2013年 | 491篇 |
2012年 | 286篇 |
2011年 | 322篇 |
2010年 | 267篇 |
2009年 | 331篇 |
2008年 | 332篇 |
2007年 | 365篇 |
2006年 | 383篇 |
2005年 | 300篇 |
2004年 | 250篇 |
2003年 | 272篇 |
2002年 | 285篇 |
2001年 | 247篇 |
2000年 | 212篇 |
1999年 | 185篇 |
1998年 | 169篇 |
1997年 | 140篇 |
1996年 | 91篇 |
1995年 | 104篇 |
1994年 | 88篇 |
1993年 | 63篇 |
1992年 | 53篇 |
1991年 | 49篇 |
1990年 | 36篇 |
1989年 | 22篇 |
1988年 | 23篇 |
1987年 | 21篇 |
1986年 | 17篇 |
1985年 | 28篇 |
1984年 | 25篇 |
1983年 | 9篇 |
1982年 | 17篇 |
1981年 | 17篇 |
1980年 | 18篇 |
1979年 | 13篇 |
1978年 | 8篇 |
1977年 | 12篇 |
1976年 | 4篇 |
1936年 | 3篇 |
排序方式: 共有7246条查询结果,搜索用时 15 毫秒
41.
We present a new verified optimization method to find regions for Hénon systems where the conditions of chaotic behaviour
hold. The present paper provides a methodology to verify chaos for certain mappings and regions. We discuss first how to check
the set theoretical conditions of a respective theorem in a reliable way by computer programs. Then we introduce optimization
problems that provide a model to locate chaotic regions. We prove the correctness of the underlying checking algorithms and
the optimization model. We have verified an earlier published chaotic region, and we also give new chaotic places located
by the new technique. 相似文献
42.
Summary We investigate the transition from two-frequency quasiperiodicity to chaotic behavior in a model for a quasiperiodically driven
magnetoelastic ribbon. The model system is a two-frequency parametrically driven Duffing oscillator. As a driving parameter
is increased, the route to chaos takes place in four distinct stages. The first stage is a torus-doubling bifurcation. The
second stage is a transition from the doubled torus to a strange nonchaotic attractor. The third stage is a transition from
the strange nonchaotic attractor to a geometrically similar chaotic attractor. The final stage is a hard transition to a much
larger chaotic attractor. This latter transition arises as the result of acrisis, the characterization of which is one of our primary concerns. Numerical evidence is given to indicate that the crisis arises
from the collision of the chaotic attractor with the stable manifold of a saddle torus. Intermittent bursting behavior is
present after the crisis with the mean time between bursts scaling as a power law in the distance from the critical control
parameter; τ ∼ (A-Ac)-α. The critical exponent is computed numerically, yielding the value α=1.03±0.01. Theoretical justification is given for the
computed critical exponent. Finally, a Melnikov analysis is performed, yielding an expression for transverse crossings of
the stable and unstable manifolds of the crisis-initiating saddle torus. 相似文献
43.
Hua Nie Jian-hua Wu 《应用数学学报(英文版)》2006,22(2):257-264
This paper is concerned with the unstirred chemostat model with two-species and one non-reproducingresource.The global attractivity of the positive steady-state solutions of the original system is established.Moreover,the effects of the growth rate on the unique positive equilibrium of the single population model arestudied. 相似文献
44.
This paper proposes a new method that extends the efficient global optimization to address stochastic black-box systems. The
method is based on a kriging meta-model that provides a global prediction of the objective values and a measure of prediction
uncertainty at every point. The criterion for the infill sample selection is an augmented expected improvement function with
desirable properties for stochastic responses. The method is empirically compared with the revised simplex search, the simultaneous
perturbation stochastic approximation, and the DIRECT methods using six test problems from the literature. An application
case study on an inventory system is also documented. The results suggest that the proposed method has excellent consistency
and efficiency in finding global optimal solutions, and is particularly useful for expensive systems. 相似文献
45.
This article studies the inshore-offshore fishery model with impulsive diffusion. The existence and global asymptotic stability of both the trivial periodic solution and the positive periodic solution are obtained. The complexity of this system is also analyzed. Moreover, the optimal harvesting policy are given for the inshore subpopulation, which includes the maximum sustainable yield and the corresponding harvesting effort. 相似文献
46.
Piotr Szopa 《Mathematical Methods in the Applied Sciences》2007,30(3):331-346
In this paper, we prove the existence and uniqueness of a global solution for 2‐D micropolar fluid equation with periodic boundary conditions. Then we restrict ourselves to the autonomous case and show the existence of a global attractor. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
47.
具有时滞的非自治的捕食-食饵系统的全局吸引 总被引:1,自引:0,他引:1
考虑一个具有离散时滞的非自治的捕食—食饵系统。系统是由3种群组成的,其中一个为捕食者,另两个为食饵种群。本文的目的是给出时滞对系统的持续生存是无害的,从而确定了系统的周期解全局吸引的条件。 相似文献
48.
This paper develops a theory for the global solution of nonconvex optimization problems with parameter-embedded linear dynamic systems. A quite general problem formulation is introduced and a solution is shown to exists. A convexity theory for integrals is then developed to construct convex relaxations for utilization in a branch-and-bound framework to calculate a global minimum. Interval analysis is employed to generate bounds on the state variables implied by the bounds on the embedded parameters. These bounds, along with basic integration theory, are used to prove convergence of the branch-and-bound algorithm to the global minimum of the optimization problem. The implementation of the algorithm is then considered and several numerical case studies are examined thoroughly 相似文献
49.
Using the iterative scheme we prove the local existence and uniqueness of solutions of the spherically symmetric Einstein-Vlasov-Maxwell system with small initial data. We prove a continuation criterion to global in-time solutions. 相似文献
50.
具有种内互惠作用的Lotka-Volterra互惠共存模型 总被引:1,自引:0,他引:1
对具有种内互惠作用的Lotka-Volterra互惠共存模型进行了完整的全局分析,得到了一些新的结果。 相似文献