全文获取类型
收费全文 | 1942篇 |
免费 | 922篇 |
国内免费 | 88篇 |
专业分类
化学 | 80篇 |
晶体学 | 8篇 |
力学 | 478篇 |
综合类 | 33篇 |
数学 | 528篇 |
物理学 | 1825篇 |
出版年
2024年 | 1篇 |
2023年 | 7篇 |
2022年 | 23篇 |
2021年 | 54篇 |
2020年 | 43篇 |
2019年 | 28篇 |
2018年 | 27篇 |
2017年 | 48篇 |
2016年 | 70篇 |
2015年 | 50篇 |
2014年 | 97篇 |
2013年 | 138篇 |
2012年 | 153篇 |
2011年 | 134篇 |
2010年 | 156篇 |
2009年 | 142篇 |
2008年 | 179篇 |
2007年 | 179篇 |
2006年 | 192篇 |
2005年 | 159篇 |
2004年 | 93篇 |
2003年 | 137篇 |
2002年 | 112篇 |
2001年 | 134篇 |
2000年 | 87篇 |
1999年 | 70篇 |
1998年 | 77篇 |
1997年 | 77篇 |
1996年 | 36篇 |
1995年 | 39篇 |
1994年 | 31篇 |
1993年 | 28篇 |
1992年 | 34篇 |
1991年 | 23篇 |
1990年 | 19篇 |
1989年 | 14篇 |
1988年 | 6篇 |
1987年 | 14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2952条查询结果,搜索用时 953 毫秒
101.
102.
讨论了具有有界随机参数的随机Bonhoeffer-Van der Pol系统的随机混沌现象,并利用噪声对其进行控制.首先运用Chebyshev多项式逼近的方法,将随机Bonhoeffer-Van der Pol系统转化为等价的确定性系统,使原系统的随机混沌控制问题转换为等价的确定性系统的确定性混沌控制问题,继而可用Lyapunov指数指标来研究等价确定性系统的确定性混沌现象和控制问题.数值结果表明,随机Bonhoeffer-Van der Pol系统的随机混沌现象与相应的确定性Bonhoeffer-Van der Pol系统极为相似.利用噪声控制法可将混沌控制到周期轨道,但是在随机参数及其强度的影响下也呈现出一些特点. 相似文献
103.
基于稳定性理论,提出了一种状态反馈控制混沌的方法。介绍了该方法的控制原理以及各个预期的周期轨道反馈系数的选取原则。以Gibbs光学双稳系统为例,验证了该方法的有效性。数值结果表明,通过调节反馈系数,可以将系统控制在所需的目标轨道上。 相似文献
104.
105.
M. Porfiri E. M. Bollt D. J. Stilwell 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(4):481-486
Opinion compromise models can give insight into how groups of individuals may either come to form
consensus or clusters of opinion groups, corresponding to parties. We consider models where randomly
selected individuals interact pairwise. If the opinions of the interacting agents are not within a certain confidence
threshold, the agents retain their own point of view. Otherwise, they constructively dialogue and smooth their
opinions. Persuasible agents are inclined to compromise with interacting individuals. Stubborn individuals slightly
modify their opinion during the interaction. Collective states for persuasible societies include extremist minorities,
which instead decline in stubborn societies. We derive a mean field approximation for the compromise model in stubborn
populations. Bifurcation and clustering analysis of this model compares favorably with Monte Carlo analysis found in
the literature. 相似文献
106.
The spatial chaos of Bose-Einstein condensates in a cigar-shaped trap is studied. For a system with a steady current, we construct the general solution of the 1st-order equation. From the boundedness condition of the general solution, we obtain the Melnikov function predicting the onset of chaos. The unpredictability of the system's distribution of atom density is also theoretically analyzed. For a 23Na system meeting the perturbation condition, numerical simulations show the existence of chaos, which is in accordance with our analytical results. Numerical simulations of a 87 Rb system dissatisfying the perturbation condition also demonstrate that there exists chaos in the system. The case without a current is also investigated. 相似文献
107.
The Einstein–Podolsky–Rosen–Bohm (EPRB) experiment performed with random variable and spatially separated analyzers is a milestone
test in the controversy between Objective Local Theories (OLT) and Quantum Mechanics (QM). Only a few OLT are still possible.
Some of the surviving OLT (specifically, the so called non-ergodic theories) would be undetectable in the averaged statistical
values, but they may leave their trace in the time dynamics. For, while QM predicts random processes, the OLT of this kind
predict the existence of regularities that may be revealed as a low dimensional object in the phase space. We perform a numerical
analysis of the time-resolved data recorded in that experiment to unveil any hypothetical low dimensional dynamics that may
be present. We find no consistent indication of such dynamics except for one data file, the longest of all in the real time.
The possible causes of these dynamics are discussed.
相似文献
108.
Jean E. Burns 《Foundations of Physics》2007,37(12):1727-1737
Vacuum radiation causes a particle to make a random walk about its dynamical trajectory. In this random walk the root mean
square change in spatial coordinate is proportional to t
1/2, and the fractional changes in momentum and energy are proportional to t
−1/2, where t is time. Thus the exchange of energy and momentum between a particle and the vacuum tends to zero over time. At the end of
a mean free path the fractional change in momentum of a particle in a gas is very small. However, at the end of the mean free
path each particle undergoes an interaction that magnifies the preceding change, and the net result is that the momentum distribution
of the particles in a gas is randomized in a few collision times. In this way the random action of vacuum radiation and its
subsequent magnification by molecular interaction produces entropy increase. This process justifies the assumption of molecular
chaos used in the Boltzmann transport equation. 相似文献
109.
L. Wu S. Zhu Y. Ni 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,41(2):349-354
Combination of two basic types of synchronization, anticipatory
synchronization and lagged synchronization, is investigated
numerically between two coupled semiconductor lasers. It is found
that lagged synchronization produced by a backward coupling with a
suitable delay can combine with the originally hidden anticipatory
synchronization and produce a type of synchronization overcoming the
original lagged synchronization produced by a forward coupling. We
study the combination synchronization phenomenon when the delay of
the backward coupling is different from that of the original
anticipatory synchronization. Our results suggest that the
synchronization combination phenomenon might allow an interpretation
of an experimental observation by Sivaprakasam et al. [Phys.
Rev. Lett. 87, 154101 (2001)] that the anticipating time is
irrespective of the external-cavity round trip time, which to date remains to be understood. 相似文献
110.
R. Bachelard A. Antoniazzi C. Chandre D. Fanelli X. Leoncini M. Vittot 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,42(1):125-132
The intensity of an electromagnetic wave interacting self-consistently
with a beam of charged particles as in a free electron laser, displays large
oscillations due to an aggregate of particles, called the macro-particle. In
this article, we propose a strategy to stabilize the intensity by re-shaping
the macro-particle. This strategy involves the study of the linear stability
(using the residue method) of selected periodic orbits of a mean-field model. As
parameters of an additional perturbation are varied, bifurcations occur in the
system which have drastic effect on the modification of the self-consistent
dynamics, and in particular, of the macro-particle. We show how to obtain an
appropriate tuning of the parameters which is able to strongly decrease the
oscillations of the intensity without reducing its mean-value. 相似文献