全文获取类型
收费全文 | 473307篇 |
免费 | 3520篇 |
国内免费 | 1092篇 |
专业分类
化学 | 225821篇 |
晶体学 | 7545篇 |
力学 | 25231篇 |
综合类 | 3篇 |
数学 | 63476篇 |
物理学 | 155843篇 |
出版年
2020年 | 4568篇 |
2019年 | 5432篇 |
2018年 | 7717篇 |
2017年 | 7826篇 |
2016年 | 10325篇 |
2015年 | 5265篇 |
2014年 | 9514篇 |
2013年 | 20014篇 |
2012年 | 15758篇 |
2011年 | 18879篇 |
2010年 | 14688篇 |
2009年 | 14836篇 |
2008年 | 17814篇 |
2007年 | 17703篇 |
2006年 | 16236篇 |
2005年 | 14349篇 |
2004年 | 13562篇 |
2003年 | 12367篇 |
2002年 | 12519篇 |
2001年 | 13150篇 |
2000年 | 10268篇 |
1999年 | 7780篇 |
1998年 | 6995篇 |
1997年 | 6814篇 |
1996年 | 6353篇 |
1995年 | 5685篇 |
1994年 | 5670篇 |
1993年 | 5778篇 |
1992年 | 5956篇 |
1991年 | 6388篇 |
1990年 | 6179篇 |
1989年 | 6137篇 |
1988年 | 5897篇 |
1987年 | 5868篇 |
1986年 | 5462篇 |
1985年 | 6873篇 |
1984年 | 7320篇 |
1983年 | 6019篇 |
1982年 | 6414篇 |
1981年 | 6068篇 |
1980年 | 5775篇 |
1979年 | 6238篇 |
1978年 | 6418篇 |
1977年 | 6435篇 |
1976年 | 6563篇 |
1975年 | 6074篇 |
1974年 | 5948篇 |
1973年 | 6157篇 |
1972年 | 4790篇 |
1971年 | 4192篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
971.
The Fokker–Planck-type kinetic equation is constructed with the help of the evolution equation for the transverse energy of channelized particles, which in its turn is derived beyond the framework of perturbation theory proceeding from the condition of nonconcervation of the adiabatic invariant. 相似文献
972.
The maximum likely and optimal (Bayesian) algorithms for detecting an arbitrary-shaped signal observed against the background of Gaussian white noise and for measuring the duration are synthesized. Exact expressions for the characteristics of the maximum likely algorithms are found. The characteristics of the Bayesian algorithms are obtained using computer simulations. 相似文献
973.
Atomic-force microscopy was used to study the surface topography of SiGe structures grown by epitaxial deposition of Ge on profiled Si(111) substrates under electromigration conditions. Systems of highly ordered germanium nanosized islands with dimensions of 10–20 nm and a density of 6×1010 cm?2 were obtained. It is shown that the geometrical parameters of self-organizing nanoislands can be controlled by a proper choice of the growth and postgrowth annealing conditions for these structures. 相似文献
974.
Eremenko L. T. Oreshko G. V. Nesterenko D. A. Lagodzinskaya G. V. Eremenko I. L. 《Russian Chemical Bulletin》2002,51(1):157-159
The reactions of ethylene glycol mononitrate and glycerol 1,3-dinitrate with methylphosphonic dichloride afforded new nitroxyalkyl methylphosphonates. 相似文献
975.
976.
The literature on the synthesis of N-substituted xanthines by cyclization, recyclization, and N-substitution is reviewed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 3–27, January, 1991. 相似文献
977.
V. P. Nosko 《Journal of Mathematical Sciences》1991,56(3):2489-2492
We study the asymptotics of some regression functions which occur in the study of high rejections of homogeneous Gaussian random fields.Translated from Statisticheskie Metody Otsenivaniya i Proverki Gipotez, pp. 143–148, 1988. 相似文献
978.
979.
Barotropic FRW cosmologies are presented from the standpoint of nonrelativistic supersymmetry. First, we reduce the barotropic FRW system of differential equations to simple harmonic oscillator differential equations. Employing the factorization procedure, the solutions of the latter equations are divided into the two classes of bosonic (nonsingular) and fermionic (singular) cosmological solutions. We next introduce a coupling parameter denoted by K between the two classes of solutions and obtain barotropic cosmologies with dissipative features acting on the scale factors and spatial curvature of the universe. The K-extended FRW equations in comoving time are presented in explicit form in the low coupling regime. The standard barotropic FRW cosmologies correspond to the dissipationless limit K = 0. 相似文献
980.
A Hamiltonian version has been formulated for the model of axisymmetric equally rotating jet streams with a free boundary. In the framework of this approach, dominant structures, i.e., structure elements appearing in strongly disturbed jet streams at the preturbulent stage of their decay, are studied. It has been shown that compactons, i.e., solution with a compact support, can be such dominant structures. Analysis of the mechanism of the instability of compactons shows the possibility of collapse, which occurs almost without deformation of their shape but leads to the intensification of the vortex sheet at the boundary according to the law (t 0 ? t)?1, where t 0 is the collapse time. 相似文献