全文获取类型
收费全文 | 46919篇 |
免费 | 10896篇 |
国内免费 | 2281篇 |
专业分类
化学 | 48901篇 |
晶体学 | 498篇 |
力学 | 1010篇 |
综合类 | 74篇 |
数学 | 3156篇 |
物理学 | 6457篇 |
出版年
2024年 | 26篇 |
2023年 | 219篇 |
2022年 | 264篇 |
2021年 | 574篇 |
2020年 | 1652篇 |
2019年 | 2907篇 |
2018年 | 1339篇 |
2017年 | 945篇 |
2016年 | 3830篇 |
2015年 | 3917篇 |
2014年 | 3966篇 |
2013年 | 4858篇 |
2012年 | 4011篇 |
2011年 | 3286篇 |
2010年 | 3450篇 |
2009年 | 3437篇 |
2008年 | 3158篇 |
2007年 | 2491篇 |
2006年 | 2083篇 |
2005年 | 2214篇 |
2004年 | 1826篇 |
2003年 | 1626篇 |
2002年 | 2319篇 |
2001年 | 1617篇 |
2000年 | 1523篇 |
1999年 | 586篇 |
1998年 | 244篇 |
1997年 | 181篇 |
1996年 | 176篇 |
1995年 | 192篇 |
1994年 | 175篇 |
1993年 | 139篇 |
1992年 | 114篇 |
1991年 | 97篇 |
1990年 | 100篇 |
1989年 | 56篇 |
1988年 | 51篇 |
1987年 | 52篇 |
1986年 | 54篇 |
1985年 | 49篇 |
1984年 | 35篇 |
1983年 | 25篇 |
1982年 | 37篇 |
1981年 | 21篇 |
1980年 | 18篇 |
1979年 | 14篇 |
1978年 | 21篇 |
1976年 | 16篇 |
1975年 | 15篇 |
1974年 | 18篇 |
排序方式: 共有10000条查询结果,搜索用时 218 毫秒
141.
Mari Grobbelaar‐Van Dalsen 《Mathematical Methods in the Applied Sciences》2004,27(11):1301-1315
This paper is concerned with well‐posedness results for a mathematical model for the transversal vibrations of a two‐dimensional hybrid elastic structure consisting of a rectangular Reissner–Mindlin plate with a Timoshenko beam attached to its free edge. The model incorporates linear dynamic feedback controls along the interface between the plate and the beam. Classical semigroup methods are employed to show the unique solvability of the coupled initial‐boundary‐value problem. We also show that the energy associated with the system exhibits the property of strong stability. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
142.
Sergue A. Nazarov Maria Specovius‐Neugebauer 《Mathematical Methods in the Applied Sciences》2004,27(13):1507-1544
The approximation of solutions to boundary value problems on unbounded domains by those on bounded domains is one of the main applications for artificial boundary conditions. Based on asymptotic analysis, here a new method is presented to construct local artificial boundary conditions for a very general class of elliptic problems where the main asymptotic term is not known explicitly. Existence and uniqueness of approximating solutions are proved together with asymptotically precise error estimates. One class of important examples includes boundary value problems for anisotropic elasticity and piezoelectricity. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
143.
144.
Let f be a smooth map between unit spheres of possibly different dimensions. We prove the global existence and convergence of the mean curvature flow of the graph of f under various conditions. A corollary is that any area‐decreasing map between unit spheres (of possibly different dimensions) is isotopic to a constant map. © 2004 Wiley Periodicals, Inc. 相似文献
145.
Jensen and Toft 8 conjectured that every 2‐edge‐connected graph without a K5‐minor has a nowhere zero 4‐flow. Walton and Welsh 19 proved that if a coloopless regular matroid M does not have a minor in {M(K3,3), M*(K5)}, then M admits a nowhere zero 4‐flow. In this note, we prove that if a coloopless regular matroid M does not have a minor in {M(K5), M*(K5)}, then M admits a nowhere zero 4‐flow. Our result implies the Jensen and Toft conjecture. © 2005 Wiley Periodicals, Inc. J Graph Theory 相似文献
146.
147.
1978年,D,Quillen证明了:若群G有非平凡的正规p-子群,则由p-子群组成的半序集是可缩的。同时,他还猜想逆定理也成立。1993年,M.Aschbacher和S.D.Smith证明了若群G不包含某种酉分支的话,则Quillen猜想的确成立,在他们的证明中,Quillen所证明的下述定理起着很重要的作用:由基本阿贝耳P-子群组成的半序集到所有P-子群组成的半序集的包含映射导出对应下同调的同构。以Buchsbaum条件为重要的工具,本文将重新叙述此定理的证明。 相似文献
148.
149.
谐振子薛定谔方程的简单解法 总被引:2,自引:0,他引:2
物质的许多物理与化学性质都可以用线性谐振子模型解释,本文用简单的数学运算求解线性谐振子的薛定谔方程,避免了特殊函数等复杂的数学运算,得出了量子力学教材完全相同的结果。 相似文献
150.
To incorporate an acceptor type polythiophene segment onto a supramolecular block copolymer for potential light harvesting applications, effective synthetic routes for the end‐functionalized and acceptor‐substituted polythiophenes are critical. The Ullmann coupling reaction can be utilized to obtain electron‐deficient polythiophenes and to attach terminal thiophene units that carry functional groups. In this article, the reactions involving a 2,5‐dibromothiophene monomer containing an electron‐withdrawing fluorinated ester and 5‐bromo‐2‐thiophenecarboxaldehyde (the end‐capper) were studied in detail. It was found that the Ullmann coupling reaction of the dibromide is very fast (completed in a few minutes) and the terminal bromine group does not survive long under the reaction condition. These findings lead to the development of an effective procedure for aldehyde end‐capping of electron‐deficient polythiophenes. Polymers with molecular weights around 4000 Da are routinely obtained. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 41–47, 2007 相似文献