全文获取类型
收费全文 | 365220篇 |
免费 | 4013篇 |
国内免费 | 1090篇 |
专业分类
化学 | 187619篇 |
晶体学 | 5639篇 |
力学 | 16126篇 |
综合类 | 11篇 |
数学 | 45074篇 |
物理学 | 115854篇 |
出版年
2022年 | 2779篇 |
2021年 | 3697篇 |
2020年 | 3868篇 |
2019年 | 4365篇 |
2018年 | 5881篇 |
2017年 | 6046篇 |
2016年 | 8590篇 |
2015年 | 5140篇 |
2014年 | 8044篇 |
2013年 | 18027篇 |
2012年 | 14486篇 |
2011年 | 17098篇 |
2010年 | 12443篇 |
2009年 | 12289篇 |
2008年 | 15236篇 |
2007年 | 15149篇 |
2006年 | 13962篇 |
2005年 | 12211篇 |
2004年 | 11246篇 |
2003年 | 9829篇 |
2002年 | 9671篇 |
2001年 | 11113篇 |
2000年 | 8304篇 |
1999年 | 6485篇 |
1998年 | 5360篇 |
1997年 | 5174篇 |
1996年 | 4960篇 |
1995年 | 4227篇 |
1994年 | 4205篇 |
1993年 | 4040篇 |
1992年 | 4430篇 |
1991年 | 4601篇 |
1990年 | 4370篇 |
1989年 | 4238篇 |
1988年 | 3997篇 |
1987年 | 4127篇 |
1986年 | 3893篇 |
1985年 | 4894篇 |
1984年 | 4964篇 |
1983年 | 4077篇 |
1982年 | 4185篇 |
1981年 | 3914篇 |
1980年 | 3859篇 |
1979年 | 4070篇 |
1978年 | 4033篇 |
1977年 | 4051篇 |
1976年 | 3999篇 |
1975年 | 3785篇 |
1974年 | 3697篇 |
1973年 | 3759篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
992.
S. Yu. Pilyugin 《Journal of Mathematical Sciences》1987,37(3):1149-1153
A compact set K in a smooth closed manifold M is said to be attractive, if on M there exists a system of differential equations, for which K is an asymptotically stable invariant set. It is proved that the set of attractive compacta is dense and its complement contains a dense set of type G in the space of all compacta of the manifold M endowed with two natural topologies.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 143, pp. 170–175, 1985. 相似文献
993.
S. G. Mikhlin 《Journal of Mathematical Sciences》1987,36(2):240-251
Error estimates are derived for the following methods: the sweepout method for tridiagonal systems, the method of square roots, the bordering method, and the method of reflection matrices. The book of S. K. Godunov is devoted to the last method; he altered the method so that it takes any matrix into a bidiagonal matrix; a considerable part of that book is devoted to the error of this alteration. In the present paper the method of reflection matrices is studied in the form in which it is expounded in the familiar book of D. K. Faddeev and V. N. Faddeeva. Recurrent formulas are obtained for the sweepout method which make it possible to successively estimate errors of the components of the solution vector. In the method of square roots the error of the solution vector is estimated by the quantity
Here i and are small quantities; the first characterizes the accuracy of small arithmetics effects, and the second the round-off error in the reverse step. Further, A is the matrix of the system, m, is its order, f is the vector of free terms, and C and are constants with 0 <1. We shall not present here the rather involved estimates for the bordering method. The error of the solution vector obtained by the method of reflection matrices is estimated by the quantity (pA is the conditioning number of the matrix A)
All estimates are obtained up to terms of higher order of smallness than and 1. The estimates themselves are related to the classification of errors of computing processes proposed by the author in recent years.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 139, pp. 94–110, 1984. 相似文献
994.
A hybrid method for measuring the electron distribution function in the low temperature plasma is described. The time resolution of the measurement is of the order of several sec. 相似文献
995.
A quasi-linear Si2O molecule model (QLMM) is suggested from an analysis of the configuration and the interactions of an isolated oxygen atom with its neighbor silicon atoms. The vibrational modes are assigned and the infrared absorption spectra are calculated in detail with the model. The theoretical results are in reasonably good agreement with reported experimental values. This agreement shows that for the analysis of the vibrational modes of the interstitial oxygen atom in silicon crystals it is not necessary to consider the coupling of the molecule with the rest of the lattice. The interaction of the oxygen atom with its six second-nearest silicon atoms only causes the level separation of the
2 mode and the formation of the fine structure. 相似文献
996.
M. S. Ermakov 《Journal of Mathematical Sciences》1986,34(1):1413-1427
We study the asymptotic behavior of Bayesian and maximum likelihood estimators of the parameter when the density function f(x, ) for each fixed x has discontinuities in on some surface.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 74, pp. 83–107, 1977. 相似文献
997.
998.
In this paper we prove that there exists an elliptic semiplaneS(v, k, m) withk –m 2 if and only if there exists a group divisible design GDD
k
((k –m)(k – 1);k –m; 0, 1) withm pairwise orthogonal resolutions. As an example of this theorem, we construct an elliptic semiplaneW(45, 7, 3) and show thatW is isomorphic to the elliptic semiplaneS(45, 7, 3) given by R. D. Baker. 相似文献
999.
We study the ultraviolet behavior of two dimensional supersymmetric non-linear -models with target space an arbitrary Kähler manifoldM, so that the models areN=2 supersymmetric. We point out that these models have an additional fermionic axial symmetry if and only if the metric onM is Ricci flat. We show that the preservation of this symmetry in perturbation theory implies that both bare and renormalized metrics onM are Ricci flat. Combining this result with the constraint ofN=2 supersymmetry requiring that all counter-terms to the metric beyond one-loop order be cohomologically trivial, we argue thatN=2 models defined on Ricci flat Kähler manifolds are on-shell ultraviolet finite to all orders of perturbation theory. 相似文献
1000.