全文获取类型
收费全文 | 27688篇 |
免费 | 2586篇 |
国内免费 | 1545篇 |
专业分类
化学 | 734篇 |
晶体学 | 54篇 |
力学 | 6288篇 |
综合类 | 271篇 |
数学 | 19087篇 |
物理学 | 5385篇 |
出版年
2024年 | 44篇 |
2023年 | 285篇 |
2022年 | 282篇 |
2021年 | 424篇 |
2020年 | 763篇 |
2019年 | 703篇 |
2018年 | 743篇 |
2017年 | 770篇 |
2016年 | 787篇 |
2015年 | 653篇 |
2014年 | 1147篇 |
2013年 | 2713篇 |
2012年 | 1156篇 |
2011年 | 1558篇 |
2010年 | 1310篇 |
2009年 | 1682篇 |
2008年 | 1614篇 |
2007年 | 1660篇 |
2006年 | 1517篇 |
2005年 | 1319篇 |
2004年 | 1181篇 |
2003年 | 1158篇 |
2002年 | 1087篇 |
2001年 | 932篇 |
2000年 | 917篇 |
1999年 | 853篇 |
1998年 | 737篇 |
1997年 | 637篇 |
1996年 | 504篇 |
1995年 | 358篇 |
1994年 | 331篇 |
1993年 | 252篇 |
1992年 | 247篇 |
1991年 | 215篇 |
1990年 | 163篇 |
1989年 | 107篇 |
1988年 | 79篇 |
1987年 | 87篇 |
1986年 | 69篇 |
1985年 | 106篇 |
1984年 | 131篇 |
1983年 | 78篇 |
1982年 | 79篇 |
1981年 | 79篇 |
1980年 | 63篇 |
1979年 | 64篇 |
1978年 | 56篇 |
1977年 | 36篇 |
1976年 | 28篇 |
1974年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
111.
The application of some recently proposed algebraic multilevel methods for the solution of two-dimensional finite element problems on nonuniform meshes is studied. The locally refined meshes are created by the newest vertex mesh refinement method. After the introduction of this refinement technique it is shown that, by combining levels of refinement, a preconditioner of optimal order can be constructed for the case of local refinement along a line. Its relative condition number is accurately estimated. Numerical tests demonstrating the performance of the proposed preconditioners will be reported in a forthcoming paper. 相似文献
112.
Identification of nonlinear elliptic equations 总被引:1,自引:0,他引:1
An optimization theoretic approach and algorithm for the estimation of state-dependent coefficients in nonlinear elliptic equation is presented. It is based on a splitting method combined with convex analysis techniques. Convergence of the algorithm is established and numerical examples are included.The research of K. Kunisch was supported in part by a grant from the Bundesministerium für Wissenschaft und Forschung, Austria. 相似文献
113.
The aim of this paper is to present construction of finite element multiscaling function with three coefficients. In order to illuminate the result, two examples are given finally. 相似文献
114.
In this work two non-local problems for the parabolic-hyperbolic type equation with non-characteristic line of changing type
are considered. Unique solvability of these problems is proven. The uniqueness of the solution is proven by the method of
energy integrals and the existence is proven by the method of integral equations. 相似文献
115.
A. S. Kholodov Ya. A. Kholodov 《Computational Mathematics and Mathematical Physics》2006,46(9):1560-1588
Previously formulated monotonicity criteria for explicit two-level difference schemes designed for hyperbolic equations (S.K. Godunov’s, A. Harten’s (TVD schemes), characteristic criteria) are extended to multileveled, including implicit, stencils. The characteristic monotonicity criterion is used to develop a universal algorithm for constructing high-order accurate nonlinear monotone schemes (for an arbitrary form of the desired solution) based on their analysis in the space of grid functions. Several new fourth-to-third-order accurate monotone difference schemes on a compact three-level stencil and nonexpanding (three-point) stencils are proposed for an extended system, which ensures their monotonicity for both the desired function and its derivatives. The difference schemes are tested using the characteristic monotonicity criterion and are extended to systems of hyperbolic equations. 相似文献
116.
L. E. Payne G. A. Philippin V. Proytcheva 《Mathematical Methods in the Applied Sciences》2007,30(15):1885-1898
In this paper, we investigate the continuous dependence on the geometry and the initial time for solutions u( x , t) of a class of nonlinear parabolic initial‐boundary value problems. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
117.
118.
B. M. Azizur Rahman A. K. M. Saiful Kabir Muttukrishnan Rajarajan Kenneth T. V. Grattan 《Optical and Quantum Electronics》2005,37(1-3):171-183
Modal solutions of planar photonic crystal waveguides with rectangular air-holes are presented by using a rigorous full-vectorial finite element-based approach. The effective indices, mode field profiles, spot-sizes, power confinements, modal hybridness, beat lengths and group velocity dispersions are shown for the fundamental and higher order modes of the quasi-TE and TM polarizations. 相似文献
119.
Yang Zuosheng 《国际流体数值方法杂志》2005,47(12):1423-1430
A complete boundary integral formulation for compressible Navier–Stokes equations with time discretization by operator splitting is developed using the fundamental solutions of the Helmholtz operator equation with different order. The numerical results for wall pressure and wall skin friction of two‐dimensional compressible laminar viscous flow around airfoils are in good agreement with field numerical methods. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
120.
We demonstrate that a pair of additive quintic equations in at least 34 variables has a nontrivial integral solution, subject only to an 11-adic solubility hypothesis. This is achieved by an application of the Hardy–Littlewood method, for which we require a sharp estimate for a 33.998th moment of quintic exponential sums. We are able to employ p-adic iteration in a form that allows the estimation of such a mean value over a complete unit square, thereby providing an approach that is technically simpler than those of previous workers and flexible enough to be applied to related problems. 相似文献