全文获取类型
收费全文 | 119360篇 |
免费 | 9354篇 |
国内免费 | 14010篇 |
专业分类
化学 | 77729篇 |
晶体学 | 1607篇 |
力学 | 5205篇 |
综合类 | 1418篇 |
数学 | 22376篇 |
物理学 | 34389篇 |
出版年
2024年 | 121篇 |
2023年 | 913篇 |
2022年 | 2081篇 |
2021年 | 2420篇 |
2020年 | 2878篇 |
2019年 | 2776篇 |
2018年 | 2500篇 |
2017年 | 3683篇 |
2016年 | 4004篇 |
2015年 | 3402篇 |
2014年 | 5151篇 |
2013年 | 8621篇 |
2012年 | 7788篇 |
2011年 | 7137篇 |
2010年 | 5972篇 |
2009年 | 7753篇 |
2008年 | 8024篇 |
2007年 | 8364篇 |
2006年 | 7385篇 |
2005年 | 6245篇 |
2004年 | 5811篇 |
2003年 | 4857篇 |
2002年 | 5989篇 |
2001年 | 3786篇 |
2000年 | 3387篇 |
1999年 | 3233篇 |
1998年 | 2789篇 |
1997年 | 2221篇 |
1996年 | 1926篇 |
1995年 | 1796篇 |
1994年 | 1481篇 |
1993年 | 1258篇 |
1992年 | 1143篇 |
1991年 | 860篇 |
1990年 | 695篇 |
1989年 | 620篇 |
1988年 | 501篇 |
1987年 | 403篇 |
1986年 | 346篇 |
1985年 | 302篇 |
1984年 | 297篇 |
1983年 | 177篇 |
1982年 | 249篇 |
1981年 | 219篇 |
1980年 | 228篇 |
1979年 | 210篇 |
1978年 | 189篇 |
1977年 | 137篇 |
1976年 | 115篇 |
1973年 | 79篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
101.
102.
Abstract
In this note, we consider a Frémond model of shape memory alloys. Let us imagine a piece of a shape memory alloy which is
fixed on one part of its boundary, and assume that forcing terms, e.g., heat sources and external stress on the remaining
part of its boundary, converge to some time-independent functions, in appropriate senses, as time goes to infinity. Under
the above assumption, we shall discuss the asymptotic stability for the dynamical system from the viewpoint of the global
attractor. More precisely, we generalize the paper [12] dealing with the one-dimensional case. First, we show the existence
of the global attractor for the limiting autonomous dynamical system; then we characterize the asymptotic stability for the
non-autonomous case by the limiting global attractor.
* Project supported by the MIUR-COFIN 2004 research program on “Mathematical Modelling and Analysis of Free Boundary Problems”. 相似文献
103.
M. V. Kartikeyan G. Singh E. Borie B. Piosczyk M. Thumm 《International Journal of Infrared and Millimeter Waves》2006,27(5):657-670
The feasibility of an 84 GHz, 500 kW, CW gyrotron for ECRH on an experimental tokamak will be presented in this paper. Mode
competition and mode selection procedures are carefully investigated by considering various candidate modes and the TE10,4 mode is chosen as the operating mode. A conventional cylindrical cavity resonator with weak input and output tapers and parabolic
roundings is considered for interaction studies. Self-consistent, both single mode and time-dependent, calculations are carried
out and power and efficiencies are computed for a typical set of beam parameters. The results show that an output power of
well over 500 kW, CW and efficiency around 40% can be reached without a depressed collector. 相似文献
104.
105.
Knut Smoczyk 《Mathematische Zeitschrift》2002,240(4):849-883
We prove that symplectic maps between Riemann surfaces L, M of constant, nonpositive and equal curvature converge to minimal symplectic maps, if the Lagrangian angle for the corresponding Lagrangian submanifold in the cross product space satisfies . If one considers a 4-dimensional K?hler-Einstein manifold of nonpositive scalar curvature that admits two complex structures J, K which commute and assumes that is a compact oriented Lagrangian submanifold w.r.t. J such that the K?hler form w.r.t.K restricted to L is positive and , then L converges under the mean curvature flow to a minimal Lagrangian submanifold which is calibrated w.r.t. .
Received: 11 April 2001 / Published online: 29 April 2002 相似文献
106.
WANG Libin 《数学年刊B辑(英文版)》2002,23(4):439-454
The author gets a blow-up result of C1 solution to the Cauchy problem for a first order quasilinear non-strictly hyperbolic system in one space dimension. 相似文献
107.
PANG Jin-qiao WU Ze-qing YAN Jun 《原子与分子物理学报》2006,23(Z1):37-40
The effects of highly doubly excited states on ionization balance are investigated. In the calculation, A Collisional-Radiative model in Detailed-Configuration-Accounting (DCA) is applied to population calculations for NLTE plasmas. Configuration-averaged rate coefficients that needed in the rate equations are obtained based on the first order perturbation theory. The Hatree-Fock-Slater self-consistent-field method is used to calculate the electron wave functions. The mean ionization stage of high-Z plasma Lu is presented. The comparison shows that the mean ionization stage increases more than 3 stages when doubly excited states 5l6l' and 5l5l' are not included in the population calculations. 相似文献
108.
在长距离无线光通信中,接收点光功率密度与光束发散角平方呈反比关系,为了获得小的发散角和大的功率耦合效率,要求准直系统有较大的数值孔径(NA),但数值孔径过大会增加像差,因此合理设计功率耦合效率与准直系统的数值孔径就非常重要。该文对半导体激光器光束准直系统中功率耦合效率进行了研究,给出了半导体激光器光束功率耦合效率与k(孔径半径与孔径处等效光束半径之比)的关系表达式,并结合激光器光束准直系统,给出了半导体激光器光束功率耦合效率与准直系统数值孔径的关系表达式。该研究结论对于半导体激光器光束准直系统设计具有参考作用。 相似文献
109.
110.