全文获取类型
收费全文 | 264624篇 |
免费 | 4410篇 |
国内免费 | 1368篇 |
专业分类
化学 | 149360篇 |
晶体学 | 3516篇 |
力学 | 9683篇 |
综合类 | 62篇 |
数学 | 33082篇 |
物理学 | 74699篇 |
出版年
2021年 | 1987篇 |
2020年 | 2434篇 |
2019年 | 2515篇 |
2018年 | 3435篇 |
2017年 | 3385篇 |
2016年 | 5284篇 |
2015年 | 3761篇 |
2014年 | 4874篇 |
2013年 | 11731篇 |
2012年 | 10426篇 |
2011年 | 12003篇 |
2010年 | 8409篇 |
2009年 | 7906篇 |
2008年 | 11090篇 |
2007年 | 10972篇 |
2006年 | 10260篇 |
2005年 | 9593篇 |
2004年 | 8476篇 |
2003年 | 7361篇 |
2002年 | 7141篇 |
2001年 | 7490篇 |
2000年 | 5857篇 |
1999年 | 4256篇 |
1998年 | 3534篇 |
1997年 | 3402篇 |
1996年 | 3536篇 |
1995年 | 2993篇 |
1994年 | 3156篇 |
1993年 | 2983篇 |
1992年 | 3286篇 |
1991年 | 3265篇 |
1990年 | 3107篇 |
1989年 | 2961篇 |
1988年 | 2879篇 |
1987年 | 2792篇 |
1986年 | 2807篇 |
1985年 | 3683篇 |
1984年 | 3723篇 |
1983年 | 3096篇 |
1982年 | 3321篇 |
1981年 | 3116篇 |
1980年 | 2840篇 |
1979年 | 3043篇 |
1978年 | 3243篇 |
1977年 | 3271篇 |
1976年 | 3323篇 |
1975年 | 3005篇 |
1974年 | 3144篇 |
1973年 | 3197篇 |
1972年 | 2445篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
911.
V. Vittoria R. Russo F. De Candia P. L. Magagnini B. Bresci 《Journal of Polymer Science.Polymer Physics》1991,29(9):1163-1168
The transport properties of a side-chain liquid-crystalline polymer forming a smectic A phase have been investigated using dichloromethane as a permeant. Samples differing in the isotropization enthaoly were analyzed. A. Correlation between this thermal parameter and sorption has been found, while the diffusion coefficient is substantially the same in all samples. The results obtained can be explained in terms of a biphasis model in which a disordered permeable phase is present within the liquid-crystalline phase, which is impermeable to the diffusant molecules. 相似文献
912.
A mean-field model of nonlinearly coupled oscillators with randomly distributed frequencies and subject to independent external white noises is analyzed in the thermodynamic limit. When the frequency distribution isbimodal, new results include subcritical spontaneous stationary synchronization of the oscillators, supercritical time-periodic synchronization, bistability, and hysteretic phenomena. Bifurcating synchronized states are asymptotically constructed near bifurcation values of the coupling strength, and theirnonlinear stability properties ascertained. 相似文献
913.
Song B. Merlino R.L. D'Angelo N. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1992,20(4):476-479
Measurements of the perpendicular (to B) double-layer widths of ionization-produced (anode) double layers are presented. These widths were determined from measurements of the double-layer charge separations. The variations of the transverse-to-B widths with plasma density and magnetic field strength are given 相似文献
914.
It is shown that in a poroacoustic Biot layer placed inside an elastic medium, for any parameters of the model an interference slow wave exists. For low frequencies, the wave has very weak attenuation and the polarization of it coincides with the direction of the layer. This is evidence for the possibility of mapping subtle collectors inside an elastic medium in crosshole measurements. Bibliography: 7 titles. 相似文献
915.
In this paper we define the vertex-cover polynomial Ψ(G,τ) for a graph G. The coefficient of τr in this polynomial is the number of vertex covers V′ of G with |V′|=r. We develop a method to calculate Ψ(G,τ). Motivated by a problem in biological systematics, we also consider the mappings f from {1, 2,…,m} into the vertex set V(G) of a graph G, subject to f−1(x)f−1(y)≠ for every edge xy in G. Let F(G,m) be the number of such mappings f. We show that F(G,m) can be determined from Ψ(G,τ). 相似文献
916.
Institute of Mathematics and Cybernetics, Lithuanian Academy of Sciences. Vilnius University. Translated from Litovskii Matematicheskii Sbornik (Lietuvos Matematikos Rinkinys), Vol. 31, No. 2, pp. 337–350, April–June, 1991. 相似文献
917.
Il Nuovo Cimento D - The applicability of the Kosterlitz-Thouless theory to HTSC is examined. The model initially presented in its general lines for bidimensional systems is then applied to... 相似文献
918.
Raskulova T. V. Volkova L. I. Danilevich Yu. S. Shainyan B. A. Khaliullin A. K. 《Russian Journal of Organic Chemistry》2002,38(5):754-755
Russian Journal of Organic Chemistry - 相似文献
919.
A pair of coupled classical oscillators with a general potential and general form of coupling is investigated. For general
potentials, the single-frequency solution is shown to be stable for small excitations. For special potentials, such system
remains stable for an arbitrary excitation. In both cases, the stability does not depend on the form of coupling. Transition
to the instability regime follows from the way how nonlinear potential entrains the energy transfer between the oscillators.
Relation between the existence of multi-frequency quasi-periodic or periodic solutions and the instability of single-frequency
ones is discussed. 相似文献
920.
We obtain estimates for errors of interpolation on a nonuniform grid for a parabolic nonperiodic spline of defect 1. 相似文献