全文获取类型
收费全文 | 44039篇 |
免费 | 1255篇 |
国内免费 | 752篇 |
专业分类
化学 | 7962篇 |
晶体学 | 318篇 |
力学 | 907篇 |
综合类 | 75篇 |
数学 | 27088篇 |
物理学 | 9696篇 |
出版年
2023年 | 148篇 |
2022年 | 254篇 |
2021年 | 174篇 |
2020年 | 254篇 |
2019年 | 1033篇 |
2018年 | 946篇 |
2017年 | 596篇 |
2016年 | 408篇 |
2015年 | 417篇 |
2014年 | 856篇 |
2013年 | 2090篇 |
2012年 | 1130篇 |
2011年 | 2154篇 |
2010年 | 1730篇 |
2009年 | 2466篇 |
2008年 | 2671篇 |
2007年 | 2680篇 |
2006年 | 2229篇 |
2005年 | 1494篇 |
2004年 | 1753篇 |
2003年 | 1749篇 |
2002年 | 2021篇 |
2001年 | 1996篇 |
2000年 | 1861篇 |
1999年 | 2054篇 |
1998年 | 1781篇 |
1997年 | 1172篇 |
1996年 | 892篇 |
1995年 | 748篇 |
1994年 | 694篇 |
1993年 | 482篇 |
1992年 | 407篇 |
1991年 | 273篇 |
1990年 | 334篇 |
1989年 | 333篇 |
1988年 | 235篇 |
1987年 | 223篇 |
1986年 | 252篇 |
1985年 | 394篇 |
1984年 | 327篇 |
1983年 | 174篇 |
1982年 | 305篇 |
1981年 | 388篇 |
1980年 | 332篇 |
1979年 | 180篇 |
1978年 | 260篇 |
1977年 | 191篇 |
1976年 | 160篇 |
1975年 | 113篇 |
1974年 | 100篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
221.
We consider the support problem of Erdös in the context of l-adic representations of the absolute Galois group of a number field. Main applications of the results of the paper concern Galois cohomology of the Tate module of abelian varieties with real and complex multiplications, the algebraic K-theory groups of number fields and the integral homology of the general linear group of rings of integers. We answer the question of Corrales-Rodrigáñez and Schoof concerning the support problem for higher dimensional abelian varieties. 相似文献
222.
223.
Eckhard Steffen 《Discrete Mathematics》2004,280(1-3):191-214
Cubic bridgeless graphs with chromatic index four are called uncolorable. We introduce parameters measuring the uncolorability of those graphs and relate them to each other. For k=2,3, let ck be the maximum size of a k-colorable subgraph of a cubic graph G=(V,E). We consider r3=|E|−c3 and
. We show that on one side r3 and r2 bound each other, but on the other side that the difference between them can be arbitrarily large. We also compare them to the oddness ω of G, the smallest possible number of odd circuits in a 2-factor of G. We construct cyclically 5-edge connected cubic graphs where r3 and ω are arbitrarily far apart, and show that for each 1c<2 there is a cubic graph such that ωcr3. For k=2,3, let ζk denote the largest fraction of edges that can be k-colored. We give best possible bounds for these parameters, and relate them to each other. 相似文献
224.
In [7] point-reflection geometries were studied which can be derived from commutative kinematic
spaces without involutory elements. But the class of point-reflection geometries is larger. For example, elliptic
planes with their reflections cannot be derived from commutative kinematic spaces. Here we investigate a larger
class of reflection geometries.This paper was sponsored by Vigoni Program 1999. 相似文献
225.
Hongrui Zhang Mingju Chao Mingyi Gao Liwen Zhang Jianquan Yao 《Optics & Laser Technology》2003,35(6):573-449
A fiber-coupled diode-single-end-pumped Nd:YVO4 laser with an Nd:YVO4 crystal of 0.3 at% doping concentration and 3×3×10 mm3 dimensions was reported. 14.850 W of continuous-wave output power in an M2 factor of 1.12 was obtained under pump power of 27.365 W, with an optical conversion efficiency of 60.49%, and a slope efficiency of 64.5%. 相似文献
226.
It can be conjectured that the colored Jones function of a knot can be computed in terms of counting paths on the graph of
a planar projection of a knot. On the combinatorial level, the colored Jones function can be replaced by its weight system.
We give two curious formulas for the weight system of a colored Jones function: one in terms of the permanent of a matrix
associated to a chord diagram, and another in terms of counting paths of intersecting chords.
Electronic supplementary material to this article is available at and is accessible to authorized users.
* S. G. was partially supported by an NSF and by an Israel-US BSF grant.
† M. L. was partly supported by GAUK 158 grant and by the Project LN00A056 of the Czech Ministry of Education. 相似文献
227.
Luc Miller 《Bulletin des Sciences Mathématiques》2005,129(2):175-185
We make two remarks about the null-controllability of the heat equation with Dirichlet condition in unbounded domains. Firstly, we give a geometric necessary condition (for interior null-controllability in the Euclidean setting) which implies that one cannot go infinitely far away from the control region without tending to the boundary (if any), but also applies when the distance to the control region is bounded. The proof builds on heat kernel estimates. Secondly, we describe a class of null-controllable heat equations on unbounded product domains. Elementary examples include an infinite strip in the plane controlled from one boundary and an infinite rod controlled from an internal infinite rod. The proof combines earlier results on compact manifolds with a new lemma saying that the null-controllability of an abstract control system and its null-controllability cost are not changed by taking its tensor product with a system generated by a non-positive self-adjoint operator. 相似文献
228.
In this paper the neo-classical economic Solow-Swan model (1956) has been improved replacing its Malthusian manpower law with
the Verhulst (logistic) one. The relevant ordinary differential equation for the ratio capital/work has been then integrated
in closed form via the Hypergeometric function2
F
1. The logistic growth injection for the manpower is detected to induce a more slow dynamics onto the Solow-Swan system, which
keeps its stability. Increasing developments are displayed as the technologic progress rises. Further sceneries are tested
and the congruence of the new solution with the classical one is shown switching to zero the selflimitation coefficent in
the logistic law.
Research supported by MURST grant:Metodi matematici in economia 相似文献
229.
Annalisa Baldi Bruno Franchi 《Calculus of Variations and Partial Differential Equations》2003,16(3):283-298
Abstract. In this paper we study the notion of perimeter associated with doubling metric measures or strongly weights. We prove that the metric perimeter in the sense of L. Ambrosio and M. Miranda jr. coincides with the metric Minkowski
content and can be obtained also as a -limit of Modica-Mortola type degenerate integral functionals.
Received: 27 August 2001 / Accepted: 29 November 2001 / Published online: 10 June 2002
Investigation supported by University of Bologna, funds for selected research topics and by GNAMPA of INdAM, Italy. The authors
are very grateful to Luigi Ambrosio and Francesco Serra Cassano for making their preprints available to them, for listening
with patience and for many unvaluable suggestions. 相似文献
230.
Huazhong Tang Tao Tang Kun Xu 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2004,55(3):365-382
In this paper, the Kinetic Flux Vector Splitting (KFVS)
scheme is extended to solving the shallow water equations with
source terms. To develop a well-balanced scheme between the source
term and the flow convection, the source term effect is accounted
in the flux evaluation across cell interfaces. This leads to a
modified gas-kinetic scheme with particular application to the
shallow water equations with bottom topography. Numerical
experiments show better resolution of the unsteady solution than
conventional finite difference method and KFVS method with little
additional cost. Moreover, some positivity properties of the
gas-kinetic scheme is established. 相似文献