全文获取类型
收费全文 | 2468篇 |
免费 | 218篇 |
国内免费 | 155篇 |
专业分类
化学 | 146篇 |
晶体学 | 3篇 |
力学 | 223篇 |
综合类 | 14篇 |
数学 | 1503篇 |
物理学 | 952篇 |
出版年
2024年 | 3篇 |
2023年 | 25篇 |
2022年 | 33篇 |
2021年 | 37篇 |
2020年 | 74篇 |
2019年 | 73篇 |
2018年 | 73篇 |
2017年 | 67篇 |
2016年 | 62篇 |
2015年 | 60篇 |
2014年 | 110篇 |
2013年 | 194篇 |
2012年 | 111篇 |
2011年 | 148篇 |
2010年 | 115篇 |
2009年 | 173篇 |
2008年 | 193篇 |
2007年 | 170篇 |
2006年 | 134篇 |
2005年 | 114篇 |
2004年 | 133篇 |
2003年 | 117篇 |
2002年 | 103篇 |
2001年 | 71篇 |
2000年 | 59篇 |
1999年 | 61篇 |
1998年 | 51篇 |
1997年 | 49篇 |
1996年 | 39篇 |
1995年 | 27篇 |
1994年 | 27篇 |
1993年 | 22篇 |
1992年 | 26篇 |
1991年 | 8篇 |
1990年 | 5篇 |
1989年 | 9篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 8篇 |
1985年 | 13篇 |
1984年 | 9篇 |
1983年 | 3篇 |
1982年 | 3篇 |
1981年 | 5篇 |
1980年 | 2篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有2841条查询结果,搜索用时 0 毫秒
971.
A semiclassical theory of a dissipative Henon—Heiles system is proposed. Based on -scaling of an equation for the evolution of the Wigner quasiprobability distribution function in the presence of dissipation and thermal diffusion, we derive a semiclassical equation for quantum fluctuations, governed by the dissipation and the curvature of the classical potential. We show how the initial quantum noise gets amplified by classical chaotic diffusion, which is expressible in terms of a correlation of stochastic fluctuations of the curvature of the potential due to classical chaos, and ultimately settles down to equilibrium under the influence of dissipation. We also establish that there exists a critical limit to the expansion of phase space. The limit is set by chaotic diffusion and dissipation. Our semiclassical analysis is corroborated by numerical simulation of a quantum operator master equation. 相似文献
972.
Chengyue Li 《Journal of Mathematical Analysis and Applications》2010,365(2):510-516
This paper gives a direct, short and unified proof of Rabinowitz's Theorem, Grossinho-Minhós-Tersian's Theorem and Tersian-Chaparova's Theorems on existence of homoclinic orbits for second order periodic Hamiltonian systems, fourth and sixth order periodic ordinary differential equations, respectively, by Brezis-Nirenberg type Mountain Pass Lemma. 相似文献
973.
T. J. Bridges 《Journal of Nonlinear Science》1994,4(1):221-251
Summary The governing equations for three-dimensional time-dependent water waves in a moving frame of reference are reformulated in
terms of the energy and momentum flux. The novelty of this approach is that time-independent motions of the system—that is,
motions that are steady in a moving frame of reference—satisfy a partial differential equation, which is shown to be Hamiltonian.
The theory of Hamiltonian evolution equations (canonical variables, Poisson brackets, symplectic form, conservation laws)
is applied to the spatial Hamiltonian system derived for pure gravity waves. The addition of surface tension changes the spatial
Hamiltonian structure in such a way that the symplectic operator becomes degenerate, and the properties of this generalized
Hamiltonian system are also studied. Hamiltonian bifurcation theory is applied to the linear spatial Hamiltonian system for
capillary-gravity waves, showing how new waves can be found in this framework. 相似文献
974.
基于保守超混沌信号,提出一种数字图像加密算法.该算法利用一个5维保守超混沌系统产生5通道时间序列对原图像分别进行RGB三基色像素级和比特级置乱,再对置乱的RGB三基色作异或操作.在此基础上,利用其中一个通道的时间序列作为密钥分别进行一次正向异或操作的扩散和S盒处理,一次反向异或操作的扩散与S盒处理及置乱,得到加密的图像.最后利用直方图、信息熵、密钥空间等安全性指标对该加密算法进行测试,并与一个五维耗散超混沌系统应用于图像加密的实例进行对比.数值结果表明保守混沌应用到数字图像加密的算法具有更高的安全性和可靠性. 相似文献
975.
Matthias Kriesell 《Graphs and Combinatorics》2002,18(3):565-571
A. Saito conjectured that every finite 3-connected line graph of diameter at most 3 is hamiltonian unless it is the line
graph of a graph obtained from the Petersen graph by adding at least one pendant edge to each of its vertices. Here we shall
see that a line graph of connectivity 3 and diameter at most 3 has a hamiltonian path.
Received: May 31, 2000 Final version received: August 17, 2001
RID="*"
ID="*" This work has partially been supported by DIMATIA, Grant 201/99/0242, Grant Agency of the Czech Republic
AMS subject classification: 05C45, 05C40 相似文献
976.
A bubble expands adiabatically and translates in an incompressible and inviscid liquid. We investigate the number of equilibrium
points of the bubble and the nature of stability of the bubble at these points. We find that there is only one equilibrium
point and the bubble is stable there. 相似文献
977.
Partially observed control systems described by analytic semigroup are considered. Finite-dimensional feedback control based on FEM approximations and accounting for incomplete observations is constructed. It is shown that this feedback control provides uniform stability (in time) of the originally unstable system. The main novel feature of the problem is that both—control and observation operators—are modeled by fully unbounded operators as they frequently arise in modeling of smart sensors and actuators. This contributes to technical difficulties at the level of perturbation theory for analytic semigroups. It is shown that a careful and rather special approximation in the area of support of the unbounded control/observation operators allows to obtain the right stability estimates. Theoretical results are illustrated with several examples of control problems governed by heat and plate equations. 相似文献
978.
Wenxiu MA 《数学年刊B辑(英文版)》2012,33(2):207-224
A class of non-semisimple matrix loop algebras consisting of triangular block matrices is introduced and used to generate bi-integrable couplings of soliton equations from zero curvature equations.The variational identities under non-degenerate,symmetric and ad-invariant bilinear forms are used to furnish Hamiltonian structures of the resulting bi-integrable couplings.A special case of the suggested loop algebras yields nonlinear bi-integrable Hamiltonian couplings for the AKNS soliton hierarchy. 相似文献
979.
S.V. LototskyB.L. Rozovskii D. Seleši 《Stochastic Processes and their Applications》2012,122(3):808-843
The Malliavin derivative, the divergence operator (Skorokhod integral), and the Ornstein-Uhlenbeck operator are extended from the traditional Gaussian setting to nonlinear generalized functionals of white noise. These extensions are related to the new developments in the theory of stochastic PDEs, in particular elliptic PDEs driven by spatial white noise and quantized nonlinear equations. 相似文献
980.
We study the fluctuation theorem formulated in terms of the currents present in a Hamiltonian system with coupled mass and energy transport. To drive the system out of equilibrium, we assume it to be connected to two ideal thermodynamical baths. The fluctuation symmetry is, thus, expressed in terms of the joint probability distribution of energy and particle currents in the system. This relation is verified numerically for the stationary state in the Spinning Lorentz Gas (SLG), driven out of equilibrium by temperature and/or chemical potential differences between the baths, as well as in the presence of an applied field. 相似文献