全文获取类型
收费全文 | 28187篇 |
免费 | 3353篇 |
国内免费 | 3582篇 |
专业分类
化学 | 10969篇 |
晶体学 | 144篇 |
力学 | 3252篇 |
综合类 | 229篇 |
数学 | 8316篇 |
物理学 | 12212篇 |
出版年
2024年 | 94篇 |
2023年 | 312篇 |
2022年 | 731篇 |
2021年 | 764篇 |
2020年 | 949篇 |
2019年 | 851篇 |
2018年 | 839篇 |
2017年 | 936篇 |
2016年 | 1138篇 |
2015年 | 978篇 |
2014年 | 1435篇 |
2013年 | 2324篇 |
2012年 | 1515篇 |
2011年 | 1814篇 |
2010年 | 1410篇 |
2009年 | 1800篇 |
2008年 | 1796篇 |
2007年 | 1853篇 |
2006年 | 1579篇 |
2005年 | 1353篇 |
2004年 | 1101篇 |
2003年 | 1116篇 |
2002年 | 1007篇 |
2001年 | 798篇 |
2000年 | 835篇 |
1999年 | 702篇 |
1998年 | 637篇 |
1997年 | 506篇 |
1996年 | 346篇 |
1995年 | 343篇 |
1994年 | 290篇 |
1993年 | 288篇 |
1992年 | 266篇 |
1991年 | 209篇 |
1990年 | 231篇 |
1989年 | 207篇 |
1988年 | 181篇 |
1987年 | 179篇 |
1986年 | 146篇 |
1985年 | 152篇 |
1984年 | 144篇 |
1983年 | 85篇 |
1982年 | 120篇 |
1981年 | 108篇 |
1980年 | 96篇 |
1979年 | 102篇 |
1978年 | 79篇 |
1977年 | 76篇 |
1976年 | 71篇 |
1973年 | 62篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
142.
动态模糊随机信息处理的数学方法 总被引:1,自引:1,他引:0
本文系统地概述了我们近年来提出的动态模糊随机信息处理的数学方法,内容包括模糊随机变量、模糊随机过程和模糊随机微分方程的基本解法等方面的基本概念、基本定义和某些重要的定理,以及动态系统的模糊随机响应与可靠性分析的方法等。这些方法是为我们研究工程实际问题的需要逐步发展起来的,对于处理某些类型的问题简便实用。 相似文献
143.
The projector formalism of Zwanzig-Mori type is extended to obtain generalized Fokker-Planck and generalized nonlinear Langevin equations for coarse-grained variables when the underlying microscopic dynamics is dissipative and noisy (stochastic). 相似文献
144.
145.
Matthew Fayers 《Algebras and Representation Theory》2005,8(3):415-426
In Fayers and Martin [J. Algebra 240 (2001), 859–873], the author and Martin constructed embeddings of Schur algebras S(2,r)↪S(2,R). Here, we generalise to the q-Schur algebras Sq(2,r).
Presented by A. Verschoren
Mathematics Subject Classifications (2000) 20G05, 20C33. 相似文献
146.
This paper presents a generalized Adadorov theory for anisotropic thin—walled beams. The theory takes account of the shear strain of the middle surface, which exerts a significant influence on the anisotropic thin-walled beams. A new approach is established to solve the governing equations, which have the same form for both open and closed section beams. The numerical examples show that the effects of the shear strain cannot be neglected for this class of beams.This work was part of research project supported by the National Natural Science Foundation of China 相似文献
147.
Stephan H. Irsen Peter Kroll Richard Dronskowski Thomas E. Weirich Matthias Epple 《无机化学与普通化学杂志》2003,629(10):1751-1759
Tetrasulfur tetranitride, S4N4, reacts with elemental Cu within inert solvents to a black‐blue material of approximate composition Cu7S4N4 which is totally amorphous to X‐rays and which cannot be made crystalline by either thermal treatment or electron radiation. Cu7S4N4 explodes if heated above 234 °C or when subjected to mechanical shock to eventually yield copper(I) sulfide; this together with the characteristic infrared spectrum of Cu7S4N4 indicates the presence of molecular S4N4 units inside the amorphous phase. The metastable nature of Cu7S4N4 is also mirrored by electron microscopy which furthermore allows the structural characterization of its degradation products. Based on experimental EXAFS data offering characteristic Cu—N and Cu—S distances, a theoretical crystalline approximant of Cu7S4N4 was suggested and structurally optimized by density‐functional total‐energy calculations including periodic boundary conditions. This model incorporates a central S4N4 unit bonded to three shells of Cu atoms of different functionalities; in addition, a partial rupture of the S4N4 unit is likely to allow for a lowering of the total energy of the metastable phase. The latter observation supports the impossibility to make Cu7S4N4 crystallize using 4N4 crystallize using whatever kind of measures. 相似文献
148.
Wilfried B. Kr tzig Jian-Wu Zhang 《Journal of Computational and Applied Mathematics》1994,50(1-3):361-373
A simple and accurate four-node quadrilateral finite element based on the Mindlin plate theory and Kirchhoff constraints is presented for general thin plate bending applications. The derivation of the element stiffness properties is straightforward, starting with a specified eight-node interpolation; usual discrete Kirchhoff (DK) constraints are employed to constrain out the four midside nodes of the element. The present resulting DK element passes patch tests with elements of arbitrary and even highly distorted mesh types. Numerical studies of the element convergence behaviours are undertaken for various plate bending problems so far investigated. It is indicated from comparative examples that fairly good convergence characteristics have been achieved. 相似文献
149.
150.
A method is developed for performing a local reduction of the governing physics for fluid problems with domains that contain a combination of narrow and non‐narrow regions, and the computational accuracy and performance of the method are measured. In the narrow regions of the domain, where the fluid is assumed to have no inertia and the domain height and curvature are assumed small, lubrication, or Reynolds, theory is used locally to reduce the two‐dimensional Navier–Stokes equations to the one‐dimensional Reynolds equation while retaining a high degree of accuracy in the overall solution. The Reynolds equation is coupled to the governing momentum and mass equations of the non‐narrow region with boundary conditions on the mass and momentum flux. The localized reduction technique, termed ‘stitching,’ is demonstrated on Stokes flow for various geometries of the hydrodynamic journal bearing—a non‐trivial test problem for which a known analytical solution is available. The computational advantage of the coupled Stokes–Reynolds method is illustrated on an industrially applicable fully‐flooded deformable‐roll coating example. The examples in this paper are limited to two‐dimensional Stokes flow, but extension to three‐dimensional and Navier–Stokes flow is possible. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献