全文获取类型
收费全文 | 13305篇 |
免费 | 2371篇 |
国内免费 | 2022篇 |
专业分类
化学 | 5105篇 |
晶体学 | 99篇 |
力学 | 749篇 |
综合类 | 213篇 |
数学 | 4579篇 |
物理学 | 6953篇 |
出版年
2024年 | 17篇 |
2023年 | 146篇 |
2022年 | 234篇 |
2021年 | 292篇 |
2020年 | 397篇 |
2019年 | 308篇 |
2018年 | 325篇 |
2017年 | 362篇 |
2016年 | 431篇 |
2015年 | 456篇 |
2014年 | 672篇 |
2013年 | 1083篇 |
2012年 | 706篇 |
2011年 | 914篇 |
2010年 | 818篇 |
2009年 | 949篇 |
2008年 | 1006篇 |
2007年 | 1048篇 |
2006年 | 943篇 |
2005年 | 861篇 |
2004年 | 649篇 |
2003年 | 687篇 |
2002年 | 644篇 |
2001年 | 524篇 |
2000年 | 491篇 |
1999年 | 472篇 |
1998年 | 367篇 |
1997年 | 299篇 |
1996年 | 272篇 |
1995年 | 201篇 |
1994年 | 201篇 |
1993年 | 132篇 |
1992年 | 131篇 |
1991年 | 105篇 |
1990年 | 65篇 |
1989年 | 76篇 |
1988年 | 51篇 |
1987年 | 51篇 |
1986年 | 38篇 |
1985年 | 67篇 |
1984年 | 33篇 |
1983年 | 25篇 |
1982年 | 42篇 |
1981年 | 22篇 |
1980年 | 11篇 |
1979年 | 15篇 |
1978年 | 8篇 |
1977年 | 7篇 |
1976年 | 11篇 |
1973年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 839 毫秒
131.
We have studied the temperature dependence of the radiative deactivation of the Pd-porphine triplet states in Shpol’skii matrices
in the temperature range 1.2–210 K. A substantial transformation of the phosphorescence spectra is observed as the temperature
increases and is due to the inclusion of thermally activated Pd-porphine states in the radiative deactivation processes. The
activation energy Ea of these Pd-porphine states is measured in matrices of n-octane and n-nonane. The splitting of the lowest quasidegenerate
triplet state ΔE(T2−T1) is determined for planar and distorted conformations of the Pd-porphine macrocycle in the n-octane matrix as 40 and 57 cm−1, respectively. The ability to use the temperature dependence of the phosphorescence properties of Pd-porphine to fabricate
molecular thermometers for the low-temperature range is analyzed.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 4, pp. 460–464, July–August, 2007. 相似文献
132.
广义酉矩阵与广义Hermite矩阵 总被引:22,自引:3,他引:19
给出了广义酉矩阵与广义(斜)Hermite矩阵的概念,研究了它们的性质及其与酉阵、共轭辛阵、Hermite阵、Hamilton及广义逆矩阵之间的联系;取得了许多新的结果;推广了酉矩阵、Hermite阵与斜Hermite阵间的相应结果,特别将正交阵的广义Cayley分解推广到了广义酉矩阵上;将各类酉矩阵、Hermite矩阵及广义逆矩阵统一了起来. 相似文献
133.
In this work we show that the energy associated to the linear three-dimensional magneto-elastic system decays polynomially to zero as time goes to infinity, provided the initial data is smooth enough. 相似文献
134.
LIANG Liang 《原子与分子物理学报》2003,20(4):575-578
By using the multichannel quantum defect theory(MQDT),we have evaluated the energy levels and lifetimes of 2sns ^3 S1,2snd ^3D(n=3-25)of BeI and 1 sns ^3s1,1snd ^3D(n=3-25)of BeⅢ,These energies and lifetimes that we have calculated not only agree with the recent measurements and theoretical calculation of Ref.4 and Ref.3, but also predict the lifetimes of 66 other highly excited states. 相似文献
135.
We consider the problem of a self-consistent determination of an essentially inhomogeneous equilibrium state of classical plasma. The solutions of the stationary Vlasov–Poisson equations are constructed in the form of a localized transition layer that separates the domains of homogeneous plasmas with different equilibrium parameters. The layer can also transform into a local perturbation inside a homogeneous plasma. In both cases, the solution contains neither mass currents nor electric currents, and all electrodynamic and hydrodynamic quantities and their derivatives are continuous. The parameters of the adjacent domains uniquely determine the transition layer structure. 相似文献
136.
Norman Biggs 《Journal of Combinatorial Theory, Series B》2004,92(2):359
An explicit formula for the chromatic polynomials of certain families of graphs, called bracelets', is obtained. The terms correspond to irreducible representations of symmetric groups. The theory is developed using the standard bases for the Specht modules of representation theory, and leads to an effective means of calculation. 相似文献
137.
Kung-Yu Chen 《Journal of Mathematical Analysis and Applications》2004,298(2):411-417
In his recent investigations involving differential operators for some generalizations of the classical Laguerre polynomials, H. Bavinck [J. Phys. A Math. Gen. 29 (1996) L277-L279] encountered and proved a certain summation identity for the classical Laguerre polynomials. The main object of this sequel to Bavinck's work is to prove a generalization of this summation identity for the Srivastava-Singhal polynomials. The demonstration, which is presented here in the general case, differs markedly from the earlier proof given for the known special case. It is also indicated how the general summation identity can be applied to derive the corresponding result for one class of the Konhauser biorthogonal polynomials. 相似文献
138.
Richard Arratia Bla Bollobs Gregory B. Sorkin 《Journal of Combinatorial Theory, Series B》2004,92(2):199-233
Motivated by circle graphs, and the enumeration of Euler circuits, we define a one-variable “interlace polynomial” for any graph. The polynomial satisfies a beautiful and unexpected reduction relation, quite different from the cut and fuse reduction characterizing the Tutte polynomial.It emerges that the interlace graph polynomial may be viewed as a special case of the Martin polynomial of an isotropic system, which underlies its connections with the circuit partition polynomial and the Kauffman brackets of a link diagram. The graph polynomial, in addition to being perhaps more broadly accessible than the Martin polynomial for isotropic systems, also has a two-variable generalization that is unknown for the Martin polynomial. We consider extremal properties of the interlace polynomial, its values for various special graphs, and evaluations which relate to basic graph properties such as the component and independence numbers. 相似文献
139.
Ya.G. Groda P. Argyrakis G.S. Bokun V.S. Vikhrenko 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,32(4):527-535
The selfconsistent diagram approximation (SCDA) is generalized for three-dimensional lattice gases with nearest neighbor repulsive
interactions. The free energy is represented in a closed form through elementary functions. Thermodynamical (phase diagrams,
chemical potential and mean square fluctuations), structural (order parameter, distribution functions) as well as diffusional
characteristics are investigated. The calculation results are compared with the Monte Carlo simulation data to demonstrate
high precision of the SCDA in reproducing the equilibrium lattice gas characteristics. It is shown that similarly to two-dimensional
systems the specific statistical memory effects strongly influence the lattice gas diffusion in the ordered states.
Received 7 August 2002 / Received in final form 22 January 2003 Published online 24 April 2003 相似文献
140.
激发对相干态的等阶Y压缩效应 总被引:16,自引:0,他引:16
用数值计算法研究了激发对相干态|ζ;m〉=a+mb+m|ζ〉的等阶Y压缩效应.结果表明:对于态a+mb+m|ζ〉,光场存在着等阶K(=2,3,4,5,…)次方Y压缩效应,但是随着场模上光子增加数m的增大,等阶K次方Y压缩效应减弱. 相似文献