全文获取类型
收费全文 | 17837篇 |
免费 | 432篇 |
国内免费 | 425篇 |
专业分类
化学 | 1755篇 |
晶体学 | 52篇 |
力学 | 178篇 |
综合类 | 17篇 |
数学 | 15213篇 |
物理学 | 1479篇 |
出版年
2023年 | 46篇 |
2022年 | 49篇 |
2021年 | 57篇 |
2020年 | 84篇 |
2019年 | 445篇 |
2018年 | 502篇 |
2017年 | 253篇 |
2016年 | 185篇 |
2015年 | 198篇 |
2014年 | 498篇 |
2013年 | 1181篇 |
2012年 | 609篇 |
2011年 | 1049篇 |
2010年 | 872篇 |
2009年 | 1256篇 |
2008年 | 1348篇 |
2007年 | 1332篇 |
2006年 | 1030篇 |
2005年 | 728篇 |
2004年 | 613篇 |
2003年 | 546篇 |
2002年 | 369篇 |
2001年 | 371篇 |
2000年 | 356篇 |
1999年 | 414篇 |
1998年 | 394篇 |
1997年 | 306篇 |
1996年 | 421篇 |
1995年 | 411篇 |
1994年 | 394篇 |
1993年 | 334篇 |
1992年 | 253篇 |
1991年 | 119篇 |
1990年 | 115篇 |
1989年 | 100篇 |
1988年 | 87篇 |
1987年 | 106篇 |
1986年 | 95篇 |
1985年 | 147篇 |
1984年 | 130篇 |
1983年 | 100篇 |
1982年 | 142篇 |
1981年 | 137篇 |
1980年 | 103篇 |
1979年 | 70篇 |
1978年 | 94篇 |
1977年 | 91篇 |
1976年 | 82篇 |
1975年 | 28篇 |
1974年 | 19篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
951.
We compare and contrast various length vs Laplace spectra of compact flat Riemannian manifolds. As a major consequence we
produce the first examples of pairs of closed manifolds that are isospectral on p-forms for some p ≠ 0, but have different
weak length spectrum. For instance, we give a pair of 4-dimensional manifolds that are isospectral on p-forms for p = 1, 3and we exhibit a length of a closed geodesic that occurs in one manifold but cannot occur in the other. We also exhibit examples
of this kind having different injectivity radius and different first eigenvalue of the Laplace spectrum on functions. These
results follow from a method that uses integral roots of the Krawtchouk polynomials.
We prove a Poisson summation formula relating the p-eigenvalue spectrum with the lengths of closed geodesics. As a consequence
we show that the Laplace spectrum on functions determines the lengths of closed geodesics and, by an example, that it does
not determine the complex lengths. Furthermore we show that orientability is an audible property for closed flat manifolds.
We give a variety of examples, for instance, a pair of manifolds isospectral on functions (resp. Sunada isospectral) with
different multiplicities of length of closed geodesies and a pair with the same multiplicities of complex lengths of closed
geodesies and not isospectral on p-forms for any p, or else isospectral on p-forms for only one value of p ≠ 0. 相似文献
952.
John?J.?BenedettoEmail author Wojciech?Czaja Przemystaw?Gadziński Alexander?M.?Powell 《Journal of Geometric Analysis》2003,13(2):239-254
For any positive real numbers A, B, and d satisfying the conditions
, d>2, we construct a Gabor orthonormal basis for L2(ℝ), such that the generating function g∈L2(ℝ) satisfies the condition:∫ℝ|g(x)|2(1+|x|
A
)/log
d
(2+|x|)dx < ∞ and
. 相似文献
953.
Nous ramenons l'existence d'estimations optimales pour la métrique de Kobayashi dans les domaines pseudoconvexes de type fini
deC
2 à un principe de Bloch asymptotique. Nous établissons ce principe en combinant la méthode de renormalisation utilisée par
Gromov dans le contexte des applications harmoniques aux techniques de dilatation des coordonnées. Cecifournit une preuve
totalement élémentaire d'un résultat de Catlin particulièrement utile dans l'étude des questions de prolongement et de rigidité
d'applications holomorphes.
相似文献
954.
Moxun Tang 《Journal of Differential Equations》2003,189(1):148-160
We prove uniqueness of positive radial solutions to the semilinear elliptic equation , subject to the Dirichlet boundary condition on an annulus in . As a by-product, our argument also provides a much simpler, if not the simplest, new proof for the uniqueness of positive solutions to the same problem in a finite ball or in the whole space . 相似文献
955.
Tai-Peng Tsai 《Journal of Differential Equations》2003,192(1):225-282
We consider a nonlinear Schrödinger equation with a bounded localized potential in . The linear Hamiltonian is assumed to have three or more bound states with the eigenvalues satisfying some resonance conditions. Suppose that the initial data is localized and small of order n in H1, and that its ground state component is larger than n3−ε with ε>0 small. We prove that the solution will converge locally to a nonlinear ground state as the time tends to infinity. 相似文献
956.
Michael Winkler 《Journal of Differential Equations》2003,192(2):445-474
We study nonglobal positive solutions to the Dirichlet problem for ut=up(Δu+u) in bounded domains, where 0<p<2. It is proved that the set of points at which u blows up has positive measure and the blow-up rate is exactly . If either the space dimension is one or p<1, the ω-limit set of consists of continuous functions solving . In one space dimension it is shown that actually as t→T, where w coincides with an element of a one-parameter family of functions inside each component of its positivity set; furthermore, we study the size of the components of {w>0} with the result that this size is uniquely determined by Ω in the case p<1, while for p>1, the positivity set can have the maximum possible size for certain initial data, but it may also be arbitrarily close to the minimal length π. 相似文献
957.
The aim of this paper is to study necessary conditions for existence of weak solutions of the inequality
958.
Julián López-Gómez 《Journal of Differential Equations》2003,195(1):25-45
In this paper we ascertain the blow-up rate of the large solutions of a class of sublinear elliptic boundary value problems with a weight function in front of the nonlinearity that vanishes on the boundary of the underlying domain, Ω, at different rates according to the point of the boundary, . All previous results in the literature assumed the decay rate of the underlying weight function to be the same at any point of ∂Ω. This hypothesis substantially simplified the mathematical analysis of the problem, as it allowed constructing global sub and supersolutions in an open neighborhood of ∂Ω. Obtaining general results requires localizing at each particular point of the boundary, making particularly involved the mathematical analysis of the problem. 相似文献
959.
E. Colorado 《Journal of Functional Analysis》2003,199(2):468-507
This work deals with the analysis of problems
960.
The context of much of the work in this paper is that of a backward-shift invariant subspace of the form , where B is some infinite Blaschke product. We address (but do not fully answer) the question: For which B can one find a (convergent) sequence in KB such that the sequence of real measures converges weak-star to some nontrivial singular measure on ? We show that, in order for this to hold, KB must contain functions with nontrivial singular inner factors. And in a rather special setting, we show that this is also sufficient. Much of the paper is devoted to finding conditions (on B) that guarantee that KB has no functions with nontrivial singular inner factors. Our primary result in this direction is based on the “geometry” of the zero set of B. 相似文献