全文获取类型
收费全文 | 443673篇 |
免费 | 3349篇 |
国内免费 | 1227篇 |
专业分类
化学 | 207746篇 |
晶体学 | 5990篇 |
力学 | 23994篇 |
综合类 | 10篇 |
数学 | 83552篇 |
物理学 | 126957篇 |
出版年
2020年 | 2594篇 |
2019年 | 2838篇 |
2018年 | 19211篇 |
2017年 | 19716篇 |
2016年 | 13535篇 |
2015年 | 4814篇 |
2014年 | 5561篇 |
2013年 | 12600篇 |
2012年 | 16545篇 |
2011年 | 30468篇 |
2010年 | 18703篇 |
2009年 | 18824篇 |
2008年 | 25392篇 |
2007年 | 29981篇 |
2006年 | 11142篇 |
2005年 | 16598篇 |
2004年 | 13086篇 |
2003年 | 12597篇 |
2002年 | 9948篇 |
2001年 | 8114篇 |
2000年 | 6627篇 |
1999年 | 4893篇 |
1998年 | 4440篇 |
1997年 | 4364篇 |
1996年 | 4286篇 |
1995年 | 3809篇 |
1994年 | 3974篇 |
1993年 | 3653篇 |
1992年 | 4051篇 |
1991年 | 4045篇 |
1990年 | 3941篇 |
1989年 | 3779篇 |
1988年 | 3895篇 |
1987年 | 3792篇 |
1986年 | 3571篇 |
1985年 | 4822篇 |
1984年 | 5060篇 |
1983年 | 4255篇 |
1982年 | 4449篇 |
1981年 | 4312篇 |
1980年 | 4296篇 |
1979年 | 4232篇 |
1978年 | 4531篇 |
1977年 | 4360篇 |
1976年 | 4427篇 |
1975年 | 4089篇 |
1974年 | 4098篇 |
1973年 | 4261篇 |
1972年 | 2976篇 |
1971年 | 2461篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
In this Note, we study a 2×2 system of evolution equations with some codimension 3 crossing. We derive two conditions of non-degeneracy. We focus on one of them and reduce our system to some Landau–Zener's type system. Using this reduction, we describe the energy transfer at the crossing by Landau–Zener formula for 2-scales semi-classical measures. To cite this article: C. Fermanian Kammerer, P. Gérard, C. R. Acad. Sci. Paris, Ser. I 335 (2002) 915–920. 相似文献
63.
Julio Castellanos 《Mathematische Zeitschrift》2002,239(4):777-802
We consider complete ideals supported on finite sequences of infinitely near points, in regular local rings with dimensions
greater than two. We study properties of factorizations in Lipman special *-simple complete ideals. We relate it to a type
of proximity, linear proximity, of the points, and give conditions in order to have unique factorization. Several examples
are presented.
Received: 2 February 2000 / in final form: 14 March 2001 / Published online: 18 January 2002 相似文献
64.
We investigate the linear stability of the Bickley jet in the framework of the beta-plane approximation. Because singular inviscid neutral modes exist in the retrograde case , it is necessary to add viscosity to interpret them. One of these modes was found in closed form by Howard and Drazin [1] . However, its critical point is at the center of the jet and it was therefore not possible for these authors to ascertain the relationship of this mode to the stability problem or to discuss how to continue the eigenfunction across the singularity.
The viscous critical layer problem associated with this singularity is considerably more difficult than the usual one (which leads to integrals of the Airy function) because and, consequently, a second-order turning point is involved. Our analysis shows that the Howard–Drazin mode is degenerate in the domain where it is valid as a limit of the viscous problem (wavenumber α2 ≤ 9/2 ), that is, it corresponds to both an odd and an even mode. This conclusion is confirmed by direct numerical solution of the Orr–Sommerfeld equation which shows, in addition, that viscosity is destabilizing along portions of the stability boundary. For a retrograde jet, instability is found to occur beyond the inviscid critical value of β, that is, in the region where the flow would be stable according to the Rayleigh–Kuo condition. 相似文献
The viscous critical layer problem associated with this singularity is considerably more difficult than the usual one (which leads to integrals of the Airy function) because and, consequently, a second-order turning point is involved. Our analysis shows that the Howard–Drazin mode is degenerate in the domain where it is valid as a limit of the viscous problem (wavenumber α
65.
66.
Michael K. Kinyon Kenneth Kunen J. D. Phillips 《Proceedings of the American Mathematical Society》2002,130(3):619-624
An A-loop is a loop in which every inner mapping is an automorphism. A problem which had been open since 1956 is settled by showing that every diassociative A-loop is Moufang.
67.
Claudia-Elisabeth Wulz 《Czechoslovak Journal of Physics》2002,52(3):C155-C170
The principal physics goals of the Compact Muon Solenoid experiment under construction at the Large Hadron Collider at CERN in Geneva are reviewed. Procedures to search for the Standard Model Higgs boson, supersymmetric Higgses and other supersymmetric particles are described. 相似文献
68.
A fast-frequency modulated (FM) diode laser has been optically narrowed using the technique of resonant optical feedback, to provide linewidths in each FM mode of ≈ 200 kHz peak-to-peak. With a drive frequency of 50 MHz and modulation index of 0.2, the FM laser has been used for the first time to obtain Doppler-free FM spectra of the Rb D1 line at 795 nm. The potential use of this system for laser frequency stabilisation is discussed. 相似文献
69.
Under idealized conditions, electroconvection in a nematic liquid crystal sets in at a well-defined threshold of the driving ac voltage. Fluctuating convection rolls of a small amplitude below that threshold have been observed recently. The measurement of the amplitude of these fluctuations is described in detail in this paper. It is based on averaging the light intensity signals using the structure function and a quantitative analysis of the light deflection. 相似文献
70.
Robert M. O'Keefe 《The Journal of the Operational Research Society》1989,40(5):415-422
Cognitive style refers to differences that can be perceived in individuals due to differing cognitive structures. There has been a large amount of research on how cognitive style affects managerial decision-making, particularly in the context of management information systems, but little or no attempt to relate these findings to operational research. This paper reviews the findings of cognitive-style research from the perspective of operational research, and draws a number of useful inferences concerning the matching of OR aids to managers, the presentation of information and recommendations, the use and acceptance of OR, and the structure of OR groups. Further, it is argued that cognitive-style findings help to give a justification to the move towards ‘soft’ approaches to analysis. 相似文献