全文获取类型
收费全文 | 525篇 |
免费 | 105篇 |
国内免费 | 37篇 |
专业分类
化学 | 116篇 |
晶体学 | 1篇 |
力学 | 82篇 |
综合类 | 11篇 |
数学 | 235篇 |
物理学 | 222篇 |
出版年
2024年 | 3篇 |
2023年 | 2篇 |
2022年 | 19篇 |
2021年 | 17篇 |
2020年 | 17篇 |
2019年 | 18篇 |
2018年 | 26篇 |
2017年 | 14篇 |
2016年 | 25篇 |
2015年 | 14篇 |
2014年 | 24篇 |
2013年 | 56篇 |
2012年 | 30篇 |
2011年 | 38篇 |
2010年 | 29篇 |
2009年 | 31篇 |
2008年 | 32篇 |
2007年 | 41篇 |
2006年 | 35篇 |
2005年 | 27篇 |
2004年 | 18篇 |
2003年 | 23篇 |
2002年 | 23篇 |
2001年 | 6篇 |
2000年 | 14篇 |
1999年 | 14篇 |
1998年 | 7篇 |
1997年 | 6篇 |
1996年 | 4篇 |
1995年 | 9篇 |
1994年 | 9篇 |
1993年 | 1篇 |
1991年 | 2篇 |
1990年 | 7篇 |
1989年 | 1篇 |
1988年 | 1篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1982年 | 1篇 |
1981年 | 4篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 4篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1973年 | 1篇 |
排序方式: 共有667条查询结果,搜索用时 0 毫秒
71.
1 IntroductionThispaperisdevotedtostudywhatkindofdiscreteschemesofthefollowing 2n dimen sionalHamiltoniansystemswithparameterinnormalform u=J2n H uT, H =H(u ,λ) ,(1 )whereu∈R2n,λ∈R ,H∈Ck+1(R2n×R ,R) ,k≥ 6,andJ2n =0In-In 0 ,In:unitmatrixofordernhasthepropertyofinheritinghom… 相似文献
72.
Qian-shun Chang Bo-ling GuoInstitute of Applied Mathematics Academy of Mathematics System Sciences Chinese Academy of Sciences Beijing ChinaInstitute of Applied Physics Computational Mathematics Beijing China 《应用数学学报(英文版)》2002,18(2):201-214
Abstract In this paper, a dissipative Zakharov equations are discretized by difference method.We make priorestimates for the algebric system of equations. It is proved that for each mesh size,there exist attractors forthe discretized system.The bounds of the Hausdorff dimensions of the discrete attractors are obtained,and thevarious bounds are dependent of the mesh sizes. 相似文献
73.
Weisheng Niu 《Journal of Mathematical Analysis and Applications》2011,374(1):166-177
We first establish the local well-posedness for the nonuniform weakly dissipative b-equation which includes both the weakly dissipative Camassa-Holm equation and the weakly dissipative Degasperis-Procesi equation as its special cases. We then study the blow-up phenomena and the long time behavior of the solutions. Two blow-up results are established for certain initial profiles. Moreover, two sufficient conditions for the decay of the solutions are presented. 相似文献
74.
Arnaud Debussche Gianmario Tessitore 《Stochastic Processes and their Applications》2011,121(3):407-426
In this paper we study ergodic backward stochastic differential equations (EBSDEs) dropping the strong dissipativity assumption needed in Fuhrman et al. (2009) [12]. In other words we do not need to require the uniform exponential decay of the difference of two solutions of the underlying forward equation, which, on the contrary, is assumed to be non-degenerate.We show the existence of solutions by the use of coupling estimates for a non-degenerate forward stochastic differential equation with bounded measurable nonlinearity. Moreover we prove the uniqueness of “Markovian” solutions by exploiting the recurrence of the same class of forward equations.Applications are then given for the optimal ergodic control of stochastic partial differential equations and to the associated ergodic Hamilton-Jacobi-Bellman equations. 相似文献
75.
Fatemeh Shakeri Mehdi Dehghan 《Numerical Methods for Partial Differential Equations》2011,27(5):1055-1071
This article presents a technique based on the hybrid Legendre tau‐finite difference method to solve the fourth order wave equation which arises in the elasto‐plastic‐microstructure models for longitudinal motion of an elasto‐plastic bar. Illustrative examples and numerical results obtained using new technique demonstrate that the proposed approach is efficient in treating longitudinal equation of ealsto‐plastic bar. © 2010 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 27: 1055–1071, 2011 相似文献
76.
77.
The evolution of a granular gas of viscoelastic particles in the homogeneous cooling state is studied. The velocity distribution function of granular particles and the time dependence of the mean kinetic energy of particles (granular temperature) are found. The noticeable deviation of the distribution function from the Maxwell distribution and its non-monotonous evolution are established. The perturbation theory with respect to the small dispersion parameter is elaborated and the analytical expressions for the asymptotic time dependence of the velocity distribution function and the granular gas temperature are derived. 相似文献
78.
Asynchronously tuned elementary cellular automata (AT-ECA) are described with respect to the relationship between active and passive updating, and that spells out the relationship between synchronous and asynchronous updating. Mutual tuning between synchronous and asynchronous updating can be interpreted as the model for dissipative structure, and that can reveal the critical property in the phase transition from order to chaos. Since asynchronous tuning easily makes behavior at the edge of chaos, the property of AT-ECA is called the unfolded edge of chaos. The computational power of AT-ECA is evaluated by the quantitative measure of computational universality and efficiency. It shows that the computational efficiency of AT-ECA is much higher than that of synchronous ECA and asynchronous ECA. 相似文献
79.
Using algebraic. analysis method for periodic orbits of Hknon map, we derive the boundary equations of stable window and Lyapunov exponent plateau region on the space of nonintegrability parameter A and dissipation parameter J. Ekom the real root of these equations, we obtain the plateau width of Lyapunov exponent Wp = Ap,max - Ap,min and the stable tvindorv width Ws = Ap,max - Ap,min for high periodic orbits. The calculated result of plateau structure ratio α4 = Wp/WS for period-4 orbit agrees with the conjectural analytical formula: α4 = 2J2/(1+J4). Hence our result presents further evidence of universal dependence of Lyapunov exponent plateau structure on the dissipation parameter for period doubling cascade attractors of nonlinear system in transition from order to chaos. 相似文献
80.
Recently new novel magnetic phases were shown to exist in the asymptotic steady states of spin systems coupled to dissipative environments at zero temperature. Tuning the different system parameters led to quantum phase transitions among those states. We study, here, a finite two-dimensional Heisenberg triangular spin lattice coupled to a dissipative Markovian Lindblad environment at finite temperature. We show how applying an inhomogeneous magnetic field to the system at different degrees of anisotropy may significantly affect the spin states, and the entanglement properties and distribution among the spins in the asymptotic steady state of the system. In particular, applying an inhomogeneous field with an inward (growing) gradient toward the central spin is found to considerably enhance the nearest neighbor entanglement and its robustness against the thermal dissipative decay effect in the completely anisotropic (Ising) system, whereas the beyond nearest neighbor ones vanish entirely. The spins of the system in this case reach different steady states depending on their positions in the lattice. However, the inhomogeneity of the field shows no effect on the entanglement in the completely isotropic (XXX) system, which vanishes asymptotically under any system configuration and the spins relax to a separable (disentangled) steady state with all the spins reaching a common spin state. Interestingly, applying the same field to a partially anisotropic (XYZ) system does not just enhance the nearest neighbor entanglements and their thermal robustness but all the long-range ones as well, while the spins relax asymptotically to very distinguished spin states, which is a sign of a critical behavior taking place at this combination of system anisotropy and field inhomogeneity. 相似文献