全文获取类型
收费全文 | 11067篇 |
免费 | 1534篇 |
国内免费 | 825篇 |
专业分类
化学 | 2257篇 |
晶体学 | 22篇 |
力学 | 3416篇 |
综合类 | 308篇 |
数学 | 3875篇 |
物理学 | 3548篇 |
出版年
2024年 | 21篇 |
2023年 | 121篇 |
2022年 | 259篇 |
2021年 | 312篇 |
2020年 | 423篇 |
2019年 | 307篇 |
2018年 | 330篇 |
2017年 | 416篇 |
2016年 | 451篇 |
2015年 | 391篇 |
2014年 | 479篇 |
2013年 | 865篇 |
2012年 | 556篇 |
2011年 | 621篇 |
2010年 | 506篇 |
2009年 | 582篇 |
2008年 | 583篇 |
2007年 | 607篇 |
2006年 | 631篇 |
2005年 | 590篇 |
2004年 | 525篇 |
2003年 | 530篇 |
2002年 | 401篇 |
2001年 | 365篇 |
2000年 | 353篇 |
1999年 | 307篇 |
1998年 | 288篇 |
1997年 | 228篇 |
1996年 | 220篇 |
1995年 | 176篇 |
1994年 | 161篇 |
1993年 | 119篇 |
1992年 | 122篇 |
1991年 | 98篇 |
1990年 | 86篇 |
1989年 | 60篇 |
1988年 | 62篇 |
1987年 | 44篇 |
1986年 | 30篇 |
1985年 | 38篇 |
1984年 | 37篇 |
1983年 | 14篇 |
1982年 | 29篇 |
1981年 | 14篇 |
1980年 | 7篇 |
1979年 | 8篇 |
1978年 | 12篇 |
1977年 | 8篇 |
1976年 | 6篇 |
1957年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
921.
922.
本文研究三维热传导型半导体器件瞬态模拟问题的数值方法.针对数学模型中各方程不同的特点,分别提出不同的有限元格式.特别针对浓度方程组是对流为主扩散问题的特点,使用Crank-Nicolson差分-流线扩散计算格式,提高了数值解的稳定性.得到的L2误差估计关于空间剖分步长是拟最优的,关于时间步长具有二阶精度. 相似文献
923.
Initial-boundary value problems with Dirichlet and Neumann conditions arising in the theory of bending of plates with transverse
shear deformation are reduced to time-dependent boundary integral equations by means of layer potentials. The solvability
of these equations is then investigated in Sobolev-type spaces.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
924.
925.
926.
Ming‐Chih Lai 《Numerical Methods for Partial Differential Equations》2004,20(1):72-81
In this article, we extend our previous work 3 for developing some fast Poisson solvers on 2D polar and spherical geometries to an elliptical domain. Instead of solving the equation in an irregular Cartesian geometry, we formulate the equation in elliptical coordinates. The solver relies on representing the solution as a truncated Fourier series, then solving the differential equations of Fourier coefficients by finite difference discretizations. Using a grid by shifting half mesh away from the pole and incorporating the derived numerical boundary value, the difficulty of coordinate singularity can be elevated easily. Unlike the case of 2D disk domain, the present difference equation for each Fourier mode is coupled with its conjugate mode through the numerical boundary value near the pole; thus, those two modes are solved simultaneously. Both second‐ and fourth‐order accurate schemes for Dirichlet and Neumann problems are presented. In particular, the fourth‐order accuracy can be achieved by a three‐point compact stencil which is in contrast to a five‐point long stencil for the disk case. © 2003 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 20: 72–81, 2004 相似文献
927.
Ronald E. Mickens P. M. Jordan 《Numerical Methods for Partial Differential Equations》2004,20(5):639-649
A positivity‐preserving nonstandard finite difference scheme is constructed to solve an initial‐boundary value problem involving heat transfer described by the Maxwell‐Cattaneo thermal conduction law, i.e., a modified form of the classical Fourier flux relation. The resulting heat transport equation is the damped wave equation, a PDE of hyperbolic type. In addition, exact analytical solutions are given, special cases are mentioned, and it is noted that the positivity condition is equivalent to the usual linear stability criteria. Finally, solution profiles are plotted and possible extensions to a delayed diffusion equation and nonlinear reaction‐diffusion systems are discussed. © 2004 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2004. 相似文献
928.
Using the constructions of the preceding two papers, we construct a natural transformation (after inverting 2) from the Browder-Novikov-Sullivan-Wall
surgery exact sequence of a compact manifold to a certain exact sequence of C
*-algebra K-theory groups.
Mathematics Subject Classification (1991): 19J25, 19K99 相似文献
929.
We develop the theory of analytically controlled Poincaré complexes over C
*-algebras. We associate a signature in C
*-algebra K-theory to such a complex, and we show that it is invariant under bordism and homotopy.
The authors were supported in part by NSF Grant DMS-0100464. 相似文献
930.
We consider propositional dynamic logic for agents. For this logic, we present a sequent calculus with a restricted cut rule and prove the soundness and completeness for the calculus. 相似文献