全文获取类型
收费全文 | 40934篇 |
免费 | 5352篇 |
国内免费 | 2482篇 |
学科分类
数理化 | 48768篇 |
出版年
2024年 | 93篇 |
2023年 | 422篇 |
2022年 | 526篇 |
2021年 | 652篇 |
2020年 | 1141篇 |
2019年 | 1092篇 |
2018年 | 1044篇 |
2017年 | 1060篇 |
2016年 | 1181篇 |
2015年 | 1018篇 |
2014年 | 1971篇 |
2013年 | 3311篇 |
2012年 | 2064篇 |
2011年 | 2641篇 |
2010年 | 2393篇 |
2009年 | 2590篇 |
2008年 | 2779篇 |
2007年 | 2784篇 |
2006年 | 2292篇 |
2005年 | 2222篇 |
2004年 | 1920篇 |
2003年 | 1820篇 |
2002年 | 1552篇 |
2001年 | 1259篇 |
2000年 | 1204篇 |
1999年 | 1110篇 |
1998年 | 1025篇 |
1997年 | 854篇 |
1996年 | 673篇 |
1995年 | 613篇 |
1994年 | 500篇 |
1993年 | 374篇 |
1992年 | 335篇 |
1991年 | 329篇 |
1990年 | 266篇 |
1989年 | 183篇 |
1988年 | 173篇 |
1987年 | 159篇 |
1986年 | 147篇 |
1985年 | 143篇 |
1984年 | 133篇 |
1983年 | 74篇 |
1982年 | 122篇 |
1981年 | 106篇 |
1980年 | 85篇 |
1979年 | 96篇 |
1978年 | 59篇 |
1977年 | 51篇 |
1976年 | 31篇 |
1973年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
1.
2.
Simulating numerically the sound radiation of a rolling tire requires the solution of a very large and sparse gyroscopic eigenvalue problem. Taking advantage of the automated multi-level substructuring (AMLS) method it can be projected to a much smaller gyroscopic problem, the solution of which however is still quite costly since the eigenmodes are non-real and complex arithmetic is necessary. This paper discusses the application of AMLS to huge gyroscopic problems and the numerical solution of the AMLS reduction. A numerical example demonstrates the efficiency of AMLS. 相似文献
3.
关于一类二次哈密尔顿系统在二次扰动下的极限环个数问题 总被引:2,自引:0,他引:2
本文研究了一类具有两个鞍点和一个中心的通用二次哈密尔顿向量场在二次扰动下的三参数开折,证明极限环的最小上界为2。 相似文献
4.
5.
Yoel Shkolnisky Mark Tygert Vladimir Rokhlin 《Applied and Computational Harmonic Analysis》2006,21(3):413-420
Many signals encountered in science and engineering are approximated well by bandlimited functions. We provide suitable error bounds for the approximation of bandlimited functions by linear combinations of certain special functions—the prolate spheroidal wave functions of order 0. The coefficients in the approximating linear combinations are given explicitly via appropriate quadrature formulae. 相似文献
6.
Exact closed-form solutions are exhibited for the Hopf equation for stationary incompressible 3D Navier-Stokes flow, for the cases of homogeneous forced flow (including a solution with depleted nonlinearity) and inhomogeneous flow with arbitrary boundary conditions. This provides an exact method for computing two- and higher-point moments, given the mean flow. 相似文献
7.
M. Gorkunov M. Lapine E. Shamonina K.H. Ringhofer 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(3):263-269
Effective magnetic properties of a composite meta-material consisting of periodically arranged circular conductive elements
are studied theoretically. A general expression for the effective bulk permeability is obtained with mutual effects and lattice
ordering being taken into account. The resonance frequency of the permeability is found to be strongly dependent on the size
and shape of the unit cell. Frequency dispersion of the permeability is studied with special attention paid to the frequency
range, where negative values of the permeability are possible. Corresponding recommendations for optimisation of the meta-materials
with negative permeability are made. The results are confirmed by numerical simulations of the finite structure behaviour
in an external magnetic field.
Received 19 April 2002 Published online 31 July 2002 相似文献
8.
A. V. Bobylev 《Journal of statistical physics》2006,124(2-4):371-399
It is well-known that the classical Chapman-Enskog procedure does not work at the level of Burnett equations (the next step after the Navier-Stokes equations). Roughly speaking, the reason is that the solutions of higher equations of hydrodynamics (Burnett's, etc.) become unstable with respect to short-wave perturbations. This problem was recently attacked by several authors who proposed different ways to deal with it. We present in this paper one of possible alternatives. First we deduce a criterion for hyperbolicity of Burnett equations for the general molecular model and show that this criterion is not fulfilled in most typical cases. Then we discuss in more detail the problem of truncation of the Chapman-Enskog expansion and show that the way of truncation is not unique. The general idea of changes of coordinates (based on analogy with the theory of dynamical systems) leads finally to nonlinear Hyperbolic Burnett Equations (HBEs) without using any information beyond the classical Burnett equations. It is proved that HBEs satisfy the linearized H-theorem. The linear version of the problem is studied in more detail, the complete Chapman-Enskog expansion is given for the linear case. A simplified proof of the Slemrod identity for Burnett coefficients is also given. 相似文献
9.
Benjamin J. K. Evans Susan M. Scott Antony C. Searle 《General Relativity and Gravitation》2002,34(10):1675-1684
We have developed a new tool for numerical work in General Relativity: GRworkbench. We discuss how GRworkbench's implementation of a numerically-amenable analogue to Differential Geometry facilitates the development of robust and chart-independent numerical algorithms. We consider, as an example, geodesic tracing on two charts covering the exterior Schwarzschild space-time. 相似文献
10.
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