全文获取类型
收费全文 | 1530篇 |
免费 | 26篇 |
国内免费 | 2篇 |
专业分类
化学 | 1150篇 |
晶体学 | 3篇 |
力学 | 17篇 |
数学 | 197篇 |
物理学 | 191篇 |
出版年
2021年 | 11篇 |
2020年 | 18篇 |
2019年 | 9篇 |
2016年 | 30篇 |
2015年 | 22篇 |
2014年 | 20篇 |
2013年 | 39篇 |
2012年 | 62篇 |
2011年 | 67篇 |
2010年 | 39篇 |
2009年 | 39篇 |
2008年 | 49篇 |
2007年 | 61篇 |
2006年 | 47篇 |
2005年 | 60篇 |
2004年 | 56篇 |
2003年 | 42篇 |
2002年 | 45篇 |
2001年 | 32篇 |
2000年 | 39篇 |
1999年 | 27篇 |
1998年 | 27篇 |
1997年 | 25篇 |
1996年 | 30篇 |
1995年 | 27篇 |
1994年 | 48篇 |
1993年 | 21篇 |
1992年 | 24篇 |
1991年 | 28篇 |
1990年 | 9篇 |
1989年 | 30篇 |
1988年 | 15篇 |
1987年 | 12篇 |
1986年 | 20篇 |
1985年 | 32篇 |
1984年 | 35篇 |
1983年 | 11篇 |
1982年 | 33篇 |
1981年 | 32篇 |
1980年 | 32篇 |
1979年 | 32篇 |
1978年 | 29篇 |
1977年 | 19篇 |
1976年 | 23篇 |
1975年 | 17篇 |
1974年 | 17篇 |
1973年 | 18篇 |
1972年 | 11篇 |
1971年 | 12篇 |
1970年 | 8篇 |
排序方式: 共有1558条查询结果,搜索用时 0 毫秒
81.
82.
83.
84.
We consider the question whether, given a countable family of lattices in a locally compact abelian group G, there exist functions such that the resulting generalized shift-invariant system is a tight frame of . This paper develops a new approach to the study of generalized shift-invariant system via almost periodic functions, based on a novel unconditional convergence property. From this theory, we derive characterizing relations for tight and dual frame generators, we introduce the system bandwidth as a measure of the total bandwidth a generalized shift-invariant system can carry, and we show that the so-called Calderón sum is uniformly bounded from below for generalized shift-invariant frames. Without the unconditional convergence property, we show, counter intuitively, that even orthonormal bases can have arbitrary small system bandwidth. Our results show that the question of existence of frame generators for a general lattice system is rather subtle and depends on analytical and algebraic properties of the lattice system. 相似文献
85.
Chun-Chi Lin Hartmut R. Schwetlick 《Calculus of Variations and Partial Differential Equations》2010,39(3-4):621-647
In this paper we present a method to untangle smooth knots by a gradient flow for a suitable energy. We show that the flow of smooth initial knots remains smooth for all time and approaches asymptotically an “optimal embedding” in its isotopy type. The method is to set up a gradient flow for the total energy of knots, which consists of bending energy and the Möbius energy of knots. 相似文献
86.
87.
This paper discusses stationary rotordynamics of synchronous electric machinery, considering different load cases. The model comprises the electrical operation in a rigid network and in an isolated condition. The mechanical part is modelled as a Laval Rotor (Jeffcott Rotor) with a noncircular shaft, accounting for both static- and dynamic rotor eccentricities. The results show, that the machine's electrical operation may influence the occurence of mechanical vibrations significantly and therefore demonstrate the importance of analysing the electromechanical interaction. (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
88.
Hartmut Schwetlick Daniel C. Sutton Johannes Zimmer 《Journal of Nonlinear Science》2012,22(6):917-934
The nonexistence of heteroclinic travelling waves in an atomistic model for martensitic phase transitions is the focus of this study. The elastic energy is assumed to be piecewise quadratic, with two wells representing two stable phases. We demonstrate that there is no travelling wave joining bounded strains in the different wells of this potential for a range of wave speeds significantly lower than the speed of sound. We achieve this using a profile-corrector method previously used to show existence of travelling waves for the same model at higher subsonic velocities. 相似文献
89.
90.