全文获取类型
收费全文 | 536966篇 |
免费 | 4045篇 |
国内免费 | 1194篇 |
专业分类
化学 | 256580篇 |
晶体学 | 8314篇 |
力学 | 28885篇 |
综合类 | 10篇 |
数学 | 73669篇 |
物理学 | 174747篇 |
出版年
2021年 | 5087篇 |
2020年 | 5406篇 |
2019年 | 6323篇 |
2018年 | 9015篇 |
2017年 | 9297篇 |
2016年 | 12323篇 |
2015年 | 6447篇 |
2014年 | 11454篇 |
2013年 | 24052篇 |
2012年 | 19122篇 |
2011年 | 22622篇 |
2010年 | 17584篇 |
2009年 | 17866篇 |
2008年 | 21020篇 |
2007年 | 20775篇 |
2006年 | 18958篇 |
2005年 | 16492篇 |
2004年 | 15617篇 |
2003年 | 14090篇 |
2002年 | 14210篇 |
2001年 | 15644篇 |
2000年 | 11935篇 |
1999年 | 9145篇 |
1998年 | 8040篇 |
1997年 | 7726篇 |
1996年 | 7162篇 |
1995年 | 6325篇 |
1994年 | 6298篇 |
1993年 | 6179篇 |
1992年 | 6519篇 |
1991年 | 7051篇 |
1990年 | 6761篇 |
1989年 | 6698篇 |
1988年 | 6325篇 |
1987年 | 6502篇 |
1986年 | 6074篇 |
1985年 | 7393篇 |
1984年 | 7671篇 |
1983年 | 6468篇 |
1982年 | 6639篇 |
1981年 | 6214篇 |
1980年 | 6001篇 |
1979年 | 6626篇 |
1978年 | 6662篇 |
1977年 | 6806篇 |
1976年 | 6819篇 |
1975年 | 6384篇 |
1974年 | 6199篇 |
1973年 | 6383篇 |
1972年 | 4988篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
941.
Bahraminasab A. Tabei S. M. A. Masoudi A. A. Shahbazi F. Reza Rahimi Tabar M. 《Journal of statistical physics》2004,116(5-6):1521-1544
The joint probability distribution function (PDF) of the height and its gradients is derived for a zero tension d + 1-dimensional Kardar-Parisi-Zhang (KPZ) equation. It is proved that the height's PDF of zero tension KPZ equation shows lack of positivity after a finite time t c . The properties of zero tension KPZ equation and its differences with the case that it possess an infinitesimal surface tension is discussed. Also potential relation between the time scale t c and the singularity time scale t c.v→0 of the KPZ equation with an infinitesimal surface tension is investigated. 相似文献
942.
943.
The results of optical study and quantum-chemical simulation of a conjugated organic system, 2-cyclooctylamino-5-nitropyridine (COANP)-fullerene, performed to determine its potential for application as a limiter of visible and near-IR laser radiation and as a material for diffraction elements in systems for reversible recording of optical information, are presented. Complexation between a COANP molecule and fullerene is considered as one of the main mechanisms responsible for the corresponding properties of this system. For the first time, nonlinear optical characteristics of COANP-C60 and COANP-C70 systems are comparatively studied and the intermolecular interaction between a COANP molecule and fullerene is analyzed on the quantum-chemical level. 相似文献
944.
A. V. Burenin 《Optics and Spectroscopy》2004,97(6):867-875
A noninvariant geometrical group characterizing the internal dynamics of the tetrahydrofuran molecule C4H8O with allowance for the clearly pronounced pseudorotation effect is constructed. On this basis, some qualitative features of the energy spectrum of the molecule following from the analysis of high-resolution spectroscopic data are explained. 相似文献
945.
The phenomenon of plasmon resonance in a nanosphere and a nanospheroid is considered. As is known, this phenomenon does not depend explicitly on the size of these nanoparticles. However, it is shown that, actually, the resonance conditions are determined by the diameter of the nanosphere and by the length of the major axis of the nanospheroid. 相似文献
946.
The Kα to Lα and Kβ to Lβ intensity ratios of seven elements have been measured following photoionization at 59.5 keV by using a Si (Li) detector
(FWHM=155 eV at 5.96 keV). The intensity ratios were determined by measuring K and L x-rays emitted from a standard target of a given element. The theoretical values of the Kα to Lα and Kβ to Lβ intensity ratios were calculated using theoretically tabulated values of shell/subshell photoionization cross sections,
fluorescence yields, Coster-Kronig transition probabilities, and radiative decay rates for ηKLi≠ and ηKLi=0. The measured values are in good agreement with theoretical results.
From Optika i Spektroskopiya, Vol. 97, No. 2, 2004, pp. 186–189.
Original English Text Copyright ? 2004 by A. Kü?ük?nder, S?ğüt, E. Kü?ük?nder, Büyükkasap.
This article was submitted by the authors in English. 相似文献
947.
The kinetics of decay of a phase hologram in a semiconductor CdF2 crystal with bistable In centers is studied. Kinetic constants of the hologram decay are found, and the potential relief of the bistable center is plotted. The resolving power of the crystal is evaluated and recording of a transparency is demonstrated. 相似文献
948.
Experimental dependences of the doubly charged ion yield N 2+ on the laser radiation intensity F are analyzed for the case of ion formation by the two-electron mechanism. It is shown that the region where the dependence N 2+(F) is characterized by the degree of nonlinearity K≈2.5 corresponds to the saturation of the process of doubly charged ion formation. This region is described well by theoretical calculations performed for Gaussian laser beams. 相似文献
949.
950.
The diffraction of a plane wave incident on a thick hologram at the first and second Bragg angles in the process of nonlinear recording is analyzed using the coupled-wave equations. It is shown that, in this case, the two-wave approximation with the use of effective modulation amplitudes of the refractive index, n 1ef and n 2ef, can be applied. Analytical dependences of n 1ef and n 2ef on the modulation amplitudes of the refractive index n 1 and n 2 at the fundamental and doubled spatial frequencies are obtained and the criteria of their applicability are determined. The dependences found are used to calculate the parameters of gratings recorded in a photopolymeric material. 相似文献