全文获取类型
收费全文 | 1091篇 |
免费 | 78篇 |
国内免费 | 68篇 |
专业分类
化学 | 364篇 |
晶体学 | 7篇 |
力学 | 112篇 |
综合类 | 2篇 |
数学 | 177篇 |
物理学 | 575篇 |
出版年
2024年 | 1篇 |
2023年 | 16篇 |
2022年 | 16篇 |
2021年 | 23篇 |
2020年 | 22篇 |
2019年 | 14篇 |
2018年 | 22篇 |
2017年 | 32篇 |
2016年 | 26篇 |
2015年 | 28篇 |
2014年 | 58篇 |
2013年 | 70篇 |
2012年 | 52篇 |
2011年 | 74篇 |
2010年 | 71篇 |
2009年 | 83篇 |
2008年 | 56篇 |
2007年 | 70篇 |
2006年 | 61篇 |
2005年 | 43篇 |
2004年 | 50篇 |
2003年 | 39篇 |
2002年 | 28篇 |
2001年 | 24篇 |
2000年 | 20篇 |
1999年 | 22篇 |
1998年 | 14篇 |
1997年 | 24篇 |
1996年 | 12篇 |
1995年 | 15篇 |
1994年 | 11篇 |
1993年 | 19篇 |
1992年 | 12篇 |
1991年 | 25篇 |
1990年 | 12篇 |
1989年 | 24篇 |
1988年 | 13篇 |
1987年 | 9篇 |
1986年 | 5篇 |
1985年 | 7篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1979年 | 1篇 |
1976年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有1237条查询结果,搜索用时 93 毫秒
991.
We study
Maker–Breaker games played on the edge set of the complete graph on vertices. In the following four games — perfect matching game, Hamilton cycle game, star factor game and path factor game, our goal is to determine the least number of moves which Maker needs in order to win these games. Moreover, for all games except for the star factor game, we show how first player can win in the strong version of these games. 相似文献
992.
A. Korepanov Z. Kosloff I. Melbourne 《Annales de l'Institut Henri Poincaré (C) Analyse Non Linéaire》2018,35(4):859-885
We prove statistical limit laws for sequences of Birkhoff sums of the type where is a family of nonuniformly hyperbolic transformations.The key ingredient is a new martingale–coboundary decomposition for nonuniformly hyperbolic transformations which is useful already in the case when the family is replaced by a fixed transformation T, and which is particularly effective in the case when varies with n.In addition to uniformly expanding/hyperbolic dynamical systems, our results include cases where the family consists of intermittent maps, unimodal maps (along the Collet–Eckmann parameters), Viana maps, and externally forced dispersing billiards.As an application, we prove a homogenisation result for discrete fast–slow systems where the fast dynamics is generated by a family of nonuniformly hyperbolic transformations. 相似文献
993.
Ivan Oseledets 《Linear algebra and its applications》2010,432(6):1492-1500
We obtain a simple tensor representation of the kernel of the discrete d-dimensional gradient operator defined on tensor semi-staggered grids. We show that the dimension of the nullspace grows as O(nd-2), where d is the dimension of the problem, and n is one-dimensional grid size. The tensor structure allows fast orthogonalization to the kernel. The usefulness of such procedure is demonstrated on three-dimensional Stokes problem, discretized by finite differences on semi-staggered grids, and it is shown by numerical experiments that the new method outperforms usually used stabilization approach. 相似文献
994.
In this paper, we present a simple and efficient method for rotating a spherical harmonic expansion. This is a well-studied problem, arising in classical scattering theory, quantum mechanics and numerical analysis, usually addressed through the explicit construction of the Wigner rotation matrices. We show that rotation can be carried out easily and stably through “pseudospectral” projection, without ever constructing the matrix entries themselves. Existing fast algorithms, based on recurrence relations, are subject to a variety of instabilities, limiting the effectiveness of the approach for expansions of high degree. 相似文献
995.
We develop a fast sweeping method for the factored eikonal equation. By decomposing the solution of a general eikonal equation as the product of two factors: the first factor is the solution to a simple eikonal equation (such as distance) or a previously computed solution to an approximate eikonal equation. The second factor is a necessary modification/correction. Appropriate discretization and a fast sweeping strategy are designed for the equation of the correction part. The key idea is to enforce the causality of the original eikonal equation during the Gauss–Seidel iterations. Using extensive numerical examples we demonstrate that (1) the convergence behavior of the fast sweeping method for the factored eikonal equation is the same as for the original eikonal equation, i.e., the number of iterations for the Gauss–Seidel iterations is independent of the mesh size, (2) the numerical solution from the factored eikonal equation is more accurate than the numerical solution directly computed from the original eikonal equation, especially for point sources. 相似文献
996.
The black-box fast multipole method 总被引:1,自引:0,他引:1
A new O(N) fast multipole formulation is proposed for non-oscillatory kernels. This algorithm is applicable to kernels K(x,y) which are only known numerically, that is their numerical value can be obtained for any (x,y). This is quite different from many fast multipole methods which depend on analytical expansions of the far-field behavior of K , for |x-y| large. Other “black-box” or “kernel-independent” fast multipole methods have been devised. Our approach has the advantage of requiring a small pre-computation time even for very large systems, and uses the minimal number of coefficients to represent the far-field, for a given L2 tolerance error in the approximation. This technique can be very useful for problems where the kernel is known analytically but is quite complicated, or for kernels which are defined purely numerically. 相似文献
997.
M. Nikl G.P. Pazzi E. Mihokova D. Ehrentraut R.T. Williams 《Journal of luminescence》2009,129(12):1564-13828
Photoluminescence spectra and decays under pulsed N2 (337 nm) laser excitation were measured for hydrothermally grown bulk and liquid-phase epitaxy (LPE)-grown film ZnO samples within 9-300 K. Temperature dependence of integrated spectra over the exciton and visible spectral regions was evaluated using a model involving standard energy barrier processes. Decay curves measured within a broad time window (10 ns-1 ms) and with extreme signal/background ratio (five orders of magnitude) point to complex decay mechanism in which the exponential and inverse power-law processes can coexist. There is no straightforward interconnection between the observed temperature dependence of integrated visible photoluminescence intensity and its decay shape over the 9-300 K temperature interval. 相似文献
998.
999.
1000.
Mathilde Giffard Michel Bardet Beate Bersch Jacques Covs Sabine Hediger 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2009,200(1):153-160
The effect of selective pulses on the apparent carbon longitudinal relaxation is investigated in three fully 13C-labeled systems, histidine as a model system and two proteins MerP and YajG. It is shown that the longitudinal relaxation of a selectively excited carbon spin is greatly enhanced, mainly because of fast spin-diffusion. This relaxation enhancement allows reducing the time necessary for polarization recovery between two experiments. This effect can be exploited either to improve the sensitivity of NMR experiments or to reduce the experimental time. Using selective carbon excitation combined with fast pulsing on fully 13C-labeled proteins, a sensitivity improvement of 20–45% over standard cross-polarization methods is predicted from the measured relaxation times. 相似文献