全文获取类型
收费全文 | 1846篇 |
免费 | 900篇 |
国内免费 | 75篇 |
专业分类
化学 | 36篇 |
晶体学 | 1篇 |
力学 | 466篇 |
综合类 | 25篇 |
数学 | 508篇 |
物理学 | 1785篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 36篇 |
2021年 | 55篇 |
2020年 | 42篇 |
2019年 | 26篇 |
2018年 | 24篇 |
2017年 | 46篇 |
2016年 | 61篇 |
2015年 | 49篇 |
2014年 | 90篇 |
2013年 | 131篇 |
2012年 | 146篇 |
2011年 | 130篇 |
2010年 | 150篇 |
2009年 | 137篇 |
2008年 | 175篇 |
2007年 | 168篇 |
2006年 | 183篇 |
2005年 | 149篇 |
2004年 | 87篇 |
2003年 | 131篇 |
2002年 | 110篇 |
2001年 | 126篇 |
2000年 | 81篇 |
1999年 | 65篇 |
1998年 | 68篇 |
1997年 | 74篇 |
1996年 | 36篇 |
1995年 | 39篇 |
1994年 | 28篇 |
1993年 | 27篇 |
1992年 | 33篇 |
1991年 | 22篇 |
1990年 | 17篇 |
1989年 | 12篇 |
1988年 | 6篇 |
1987年 | 13篇 |
1986年 | 9篇 |
1985年 | 10篇 |
1984年 | 4篇 |
1983年 | 4篇 |
1982年 | 2篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1957年 | 2篇 |
排序方式: 共有2821条查询结果,搜索用时 0 毫秒
11.
B R Sitaram 《Pramana》1995,44(4):295-302
The invariants of chaotic bounded Hamiltonian systems and their relation to the solutions of the first variational equations
of the equations of motion are studied. We show that these invariants are characterized by the fact that they either lose
the property of differentiability as functions on phase space or that a certain formal power series defined in terms of the
derivatives of the invariants has zero radius of convergence. For a specific example, we show that the former possibility
appears to apply. 相似文献
12.
从非线性自回归模型Xt+1=-αXtλ+1+βXt+γ出发,通过变量替换Xt=aYt,推出三参数混沌动力学系统模型Yt+1=kYt(1-Ytλ)+c;采用线性回归与非线性回归相结合的改进的混合法,对模型参数作了估计;实际研究表明,该模型可以用于对国内生产总值GDP增长的研究. 相似文献
13.
Stadia are popular models of chaotic billiards introduced by Bunimovich in 1974. They are analogous to dispersing billiards
due to Sinai, but their fundamental technical characteristics are quite different. Recently many new results were obtained
for various chaotic billiards, including sharp bounds on correlations and probabilistic limit theorems, and these results
require new, more powerful technical apparatus. We present that apparatus here, in the context of stadia, and prove “regularity”
properties.
相似文献
14.
15.
16.
We introduce an interesting hierarchy of rational order chaotic maps that possess an invariant measure. In contrast to the
previously introduced hierarchy of chaotic maps [1–5], with merely entropy production, the rational order chaotic maps can
simultaneously produce and consume entropy. We compute the Kolmogorov-Sinai entropy of these maps analytically and also their
Lyapunov exponent numerically, where the obtained numerical results support the analytical calculations. 相似文献
17.
We study infinite-dimensional systems of ordinary differential equations having applications in some popular and important physical problems. The appearance of infinite-dimensional space–time chaos is considered, namely, the bifurcations and critical phenomena that occur in the phase space of the systems and explain some physical problems are described. 相似文献
18.
This paper presents a simple chaotic circuit consisting of two capacitors, one linear two-port VCCS and one time-state-controlled
impulsive switch. The impulsive switch causes rich chaotic and periodic behavior. The circuit dynamics can be simplified into
a one-dimensional return map that is piecewise linear and piecewise monotone. Using the return map, we clarify parameter conditions
for existence of chaotic and periodic attractors and coexistence state of attractors. 相似文献
19.
The shock structure problem is one of the classical problems of fluid mechanics and at least for non-reacting dilute gases it has been considered essentially solved. Here we present a few recent findings, to show that this is not the case. There are still new physical effects to be discovered provided that the numerical technique is general enough to not rule them out a priori. While the results have been obtained for dense fluids, some of the effects might also be observable for shocks in dilute gases. 相似文献
20.