全文获取类型
收费全文 | 497650篇 |
免费 | 3238篇 |
国内免费 | 911篇 |
专业分类
化学 | 243271篇 |
晶体学 | 7693篇 |
力学 | 25949篇 |
综合类 | 11篇 |
数学 | 67095篇 |
物理学 | 157780篇 |
出版年
2020年 | 4708篇 |
2019年 | 5493篇 |
2018年 | 7867篇 |
2017年 | 8082篇 |
2016年 | 10684篇 |
2015年 | 5444篇 |
2014年 | 9730篇 |
2013年 | 20342篇 |
2012年 | 16081篇 |
2011年 | 19118篇 |
2010年 | 14956篇 |
2009年 | 14872篇 |
2008年 | 18232篇 |
2007年 | 18121篇 |
2006年 | 16619篇 |
2005年 | 14678篇 |
2004年 | 13815篇 |
2003年 | 12689篇 |
2002年 | 12858篇 |
2001年 | 13102篇 |
2000年 | 10369篇 |
1999年 | 7855篇 |
1998年 | 7190篇 |
1997年 | 7068篇 |
1996年 | 6559篇 |
1995年 | 5929篇 |
1994年 | 6098篇 |
1993年 | 5831篇 |
1992年 | 6250篇 |
1991年 | 6563篇 |
1990年 | 6433篇 |
1989年 | 6334篇 |
1988年 | 6208篇 |
1987年 | 6182篇 |
1986年 | 5730篇 |
1985年 | 7259篇 |
1984年 | 7672篇 |
1983年 | 6508篇 |
1982年 | 6747篇 |
1981年 | 6445篇 |
1980年 | 6245篇 |
1979年 | 6589篇 |
1978年 | 6948篇 |
1977年 | 6944篇 |
1976年 | 7144篇 |
1975年 | 6619篇 |
1974年 | 6521篇 |
1973年 | 6797篇 |
1972年 | 5251篇 |
1971年 | 4564篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
102.
103.
Birational equivalence in the symplectic category 总被引:7,自引:0,他引:7
104.
The diffraction of plane surface gravitational waves by the edge of an ice cover lying on the surface of an incompressible fluid of infinitely great depth is considered. The ice cover is simulated by a thin elastic plate. The wave reflection and transmission coefficients are determined when it interacts with the ice cover. A wave field is constructed in the fluid under the conditions that a periodic lumped force and a lumped moment act on the edge of the ice cover. It is shown that as the incident wavelength increases the reflection coefficient tends to zero and the transmission coefficient tends to unity. 相似文献
105.
Results of an experiment on investigating the fluctuations of a sound signal with a frequency of 295 Hz on a stationary 32-km-long acoustic path in a shallow sea are presented. Hydrological conditions on the path were characterized by the presence of a weak thermocline and a frequent occurrence of intense internal wave trains. The space-time characteristics of these internal waves were measured in detail. Experimental evidence of the repetition of the forms of internal solitons in the variations of the amplitude and phase of an acoustic signal was obtained. 相似文献
106.
Possibilities for the control of the parameters of free-polarization decay (FPD), optical nutation, and photon echo (PE) using the dressing field are studied. Coherent transients are generated with the Stark switching technique and are detected in the radiation of the probe field polarized orthogonally to the dressing field. The evolution-operator technique is employed in the calculations. The experiments are performed at the R(4, 3) transition of the 0 ? 1 v3 13CH3F vibrational band with the radiation of a cw CO2 laser. It is theoretically and experimentally demonstrated that FPD and PE are suppressed upon an increase in the intensity of the dressing field. The observed shapes of the transient FPD and PE signals and their variations with the dressing field intensity are in qualitative agreement with the results of the calculations. 相似文献
107.
108.
A. G. Bratsos 《Numerical Algorithms》2006,43(4):295-308
A three-time level finite-difference scheme based on a fourth order in time and second order in space approximation has been
proposed for the numerical solution of the nonlinear two-dimensional sine-Gordon equation. The method, which is analysed for
local truncation error and stability, leads to the solution of a nonlinear system. To avoid solving it, a predictor–corrector
scheme using as predictor a second-order explicit scheme is proposed. The procedure of the corrector has been modified by
considering as known the already evaluated corrected values instead of the predictor ones. This modified scheme has been tested
on the line and circular ring soliton and the numerical experiments have proved that there is an improvement in the accuracy
over the standard predictor–corrector implementation.
This research was co-funded by E.U. (75%) and by the Greek Government (25%). 相似文献
109.
G. Giorgadze 《Journal of Mathematical Sciences》2006,132(6):716-738
We discuss a number of topics concerned with certain boundary-value problems in the context of generalized analytic functions.
Solution of the classical Riemann-Hilbert problem and the linear conjugation problem for analytic functions is described in
appropriate function classes and the same scheme is applied to generalized analytic functions and vectors. In particular,
we describe solution of the Riemann-Hilbert problem for generalized analytic functions and obtain an explicit analytic presentation
of monodromy matrices in the case of generalized analytic vectors.
__________
Translated from Sovremennaya Matematika i Ee Prilozheniya (Contemporary Mathematics and Its Applications), Vol. 15, Theory
of Functions, 2004. 相似文献
110.
A. V. Bobylev 《Journal of statistical physics》2006,124(2-4):371-399
It is well-known that the classical Chapman-Enskog procedure does not work at the level of Burnett equations (the next step after the Navier-Stokes equations). Roughly speaking, the reason is that the solutions of higher equations of hydrodynamics (Burnett's, etc.) become unstable with respect to short-wave perturbations. This problem was recently attacked by several authors who proposed different ways to deal with it. We present in this paper one of possible alternatives. First we deduce a criterion for hyperbolicity of Burnett equations for the general molecular model and show that this criterion is not fulfilled in most typical cases. Then we discuss in more detail the problem of truncation of the Chapman-Enskog expansion and show that the way of truncation is not unique. The general idea of changes of coordinates (based on analogy with the theory of dynamical systems) leads finally to nonlinear Hyperbolic Burnett Equations (HBEs) without using any information beyond the classical Burnett equations. It is proved that HBEs satisfy the linearized H-theorem. The linear version of the problem is studied in more detail, the complete Chapman-Enskog expansion is given for the linear case. A simplified proof of the Slemrod identity for Burnett coefficients is also given. 相似文献