全文获取类型
收费全文 | 451350篇 |
免费 | 3133篇 |
国内免费 | 1045篇 |
专业分类
化学 | 222145篇 |
晶体学 | 6774篇 |
力学 | 23366篇 |
综合类 | 16篇 |
数学 | 64014篇 |
物理学 | 139213篇 |
出版年
2020年 | 3497篇 |
2019年 | 4180篇 |
2018年 | 11992篇 |
2017年 | 12497篇 |
2016年 | 10892篇 |
2015年 | 4779篇 |
2014年 | 7278篇 |
2013年 | 16314篇 |
2012年 | 15599篇 |
2011年 | 24058篇 |
2010年 | 16310篇 |
2009年 | 16550篇 |
2008年 | 22106篇 |
2007年 | 24705篇 |
2006年 | 13019篇 |
2005年 | 16092篇 |
2004年 | 12993篇 |
2003年 | 12373篇 |
2002年 | 10710篇 |
2001年 | 10544篇 |
2000年 | 8344篇 |
1999年 | 6115篇 |
1998年 | 5253篇 |
1997年 | 5346篇 |
1996年 | 5085篇 |
1995年 | 4302篇 |
1994年 | 4473篇 |
1993年 | 4421篇 |
1992年 | 4830篇 |
1991年 | 4961篇 |
1990年 | 4752篇 |
1989年 | 4813篇 |
1988年 | 4686篇 |
1987年 | 4660篇 |
1986年 | 4450篇 |
1985年 | 5724篇 |
1984年 | 5924篇 |
1983年 | 4851篇 |
1982年 | 5109篇 |
1981年 | 4969篇 |
1980年 | 4576篇 |
1979年 | 5144篇 |
1978年 | 5256篇 |
1977年 | 5323篇 |
1976年 | 5368篇 |
1975年 | 5019篇 |
1974年 | 4933篇 |
1973年 | 5197篇 |
1972年 | 3702篇 |
1971年 | 3363篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
V. N. Likhachev 《Journal of Applied Mathematics and Mechanics》1989,53(6):750-756
The method of combined asymptotic expansions is used to solve the problem of the focusing of a shock wave (in a weakly compressible medium of high viscosity. Asymptotic forms of the solution are constructed in a number of spatial zones. The focusing zone is described by its asymptotic form obtained by combining it with the solution corresponding to viscous geometrical acoustics. The reflection of a shock wave formed as a result of velocity jump near one of the foci of the ellipsoid of revolution is discussed as an example. Analytical relationships descrbing the focusing zone around the second focus are obtained. It is shown that at the focus itself the wave profile has an antisymmetric form, and the compression wave is followed by a rarefaction wave of the same form. 相似文献
992.
993.
A new singular integral equation is obtained that describes the elastic equilibrium of a strip with both an inner and an edge slit (crack) and has a considerable advantage over existing equations /1–9/, etc.) from the viewpoint of a numerical realization and clarification of the analytical relationship with an analogous equation for a half-plane. Numerical results are given of a computation of the stress intensity coefficients at the tips of the inner and edge cracks that refine data in the literature. 相似文献
994.
N. V. Krasnikov 《Theoretical and Mathematical Physics》1987,73(2):1184-1190
995.
Under a one-sided dissipative Lipschitz condition on its drift, a stochastic evolution equation with additive noise of the
reaction-diffusion type is shown to have a unique stochastic stationary solution which pathwise attracts all other solutions.
A similar situation holds for each Galerkin approximation and each implicit Euler scheme applied to these Galerkin approximations.
Moreover, the stationary solution of the Euler scheme converges pathwise to that of the Galerkin system as the stepsize tends
to zero and the stationary solutions of the Galerkin systems converge pathwise to that of the evolution equation as the dimension
increases. The analysis is carried out on random partial and ordinary differential equations obtained from their stochastic
counterparts by subtraction of appropriate Ornstein-Uhlenbeck stationary solutions. 相似文献
996.
N. S. Maslova A. I. Oreshkin S. I. Oreshkin V. I. Panov I. V. Radchenko S. V. Savinov 《JETP Letters》2006,84(6):320-323
We report the results of STM investigation of the initial stage of Ag adsorption on an Si(110) surface. At 0.21 ML Ag coverage,
the size and orientation of the unit cell correspond to the parameters of a 16 × 2 unit cell of clean Si(110) surface. With
increasing of the Ag coverage up to 0.42 ML, the type of surface reconstruction changes to a 4 × 1-Si(110)-Ag structure.
The text was submitted by the authors in English. 相似文献
997.
Given a1,a2,...,an ∈ ℤ^d$, we examine the set, G, of all non-negative integer combinations of these ai. In particular, we examine the generating function f(z) = ∑b ∈ Gzb. We prove that one can write this generating function as a rational function using the neighborhood complex (sometimes called
the complex of maximal lattice-free bodies or the Scarf complex) on a particular lattice in ℤn. In the generic case, this follows from algebraic results of Bayer and Sturmfels. Here we prove it geometrically in all
cases, and we examine a generalization involving the neighborhood complex on an arbitrary lattice. 相似文献
998.
Characterizations of the containment of a convex set either in an arbitrary convex set or in the complement of a finite union
of convex sets (i.e., the set, described by reverse-convex inequalities) are given. These characterizations provide ways of
verifying the containments either by comparing their corresponding dual cones or by checking the consistency of suitable associated
systems. The convex sets considered in this paper are the solution sets of an arbitrary number of convex inequalities, which
can be either weak or strict inequalities. Particular cases of dual characterizations of set containments have played key
roles in solving large scale knowledge-based data classification problems where they are used to describe the containments
as inequality constraints in optimization problems. The idea of evenly convex set (intersection of open half spaces), which
was introduced by W. Fenchel in 1952, is used to derive the dual conditions, characterizing the set containments. 相似文献
999.
The theory of dielectric space-charge polarization losses describes well both the model of an inhomogeneous dielectric [1]
and the polarization resulting from mosaic blocks of alkali-halide crystals [2]. The Debye frequency dependences ε*(ω) and
tan δ(ω) with non-Arrhenius relaxation time are calculated in the first approximation of perturbation theory [3, 4] with the
use of a nonlinear system of the Fokker-Planck and Poisson equations for the interlayer polarization with allowance for tunnel
transitions of relaxation oscillators. For the Maxwell mechanism of space-charge relaxation, tan δ(ω) also has the Debye form
[5]. It should be noted that in studies cited above the electric field was considered uniform, and the nonlinearity of the
initial system of equations was not investigated. This paper removes these restrictions and elaborates a theory of relaxation
mechanism.
__________
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 28–34, November, 2006. 相似文献
1000.
A. P. Avdeenko S. A. Konovalova O. N. Ludchenko 《Russian Journal of Organic Chemistry》2006,42(5):683-688
Reactions of halogens with N-arylsulfonyl-1,4-benzoquinone monoimines occur with the formation of a halogenonium ion that either transforms into a carbocation where the first halogen atom adds to the carbon in the ortho-position relative to the carbonyl carbon, or the halogenonium ion adds directly the second halogen atom. 相似文献