全文获取类型
收费全文 | 5805篇 |
免费 | 692篇 |
国内免费 | 531篇 |
专业分类
化学 | 456篇 |
晶体学 | 36篇 |
力学 | 545篇 |
综合类 | 136篇 |
数学 | 4472篇 |
物理学 | 1383篇 |
出版年
2024年 | 9篇 |
2023年 | 57篇 |
2022年 | 62篇 |
2021年 | 111篇 |
2020年 | 119篇 |
2019年 | 171篇 |
2018年 | 185篇 |
2017年 | 171篇 |
2016年 | 178篇 |
2015年 | 146篇 |
2014年 | 275篇 |
2013年 | 541篇 |
2012年 | 236篇 |
2011年 | 318篇 |
2010年 | 294篇 |
2009年 | 354篇 |
2008年 | 388篇 |
2007年 | 400篇 |
2006年 | 353篇 |
2005年 | 336篇 |
2004年 | 276篇 |
2003年 | 304篇 |
2002年 | 289篇 |
2001年 | 221篇 |
2000年 | 201篇 |
1999年 | 198篇 |
1998年 | 172篇 |
1997年 | 149篇 |
1996年 | 107篇 |
1995年 | 61篇 |
1994年 | 59篇 |
1993年 | 35篇 |
1992年 | 41篇 |
1991年 | 28篇 |
1990年 | 21篇 |
1989年 | 15篇 |
1988年 | 21篇 |
1987年 | 16篇 |
1986年 | 14篇 |
1985年 | 19篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 4篇 |
1979年 | 15篇 |
1978年 | 9篇 |
1977年 | 4篇 |
1976年 | 5篇 |
1974年 | 3篇 |
排序方式: 共有7028条查询结果,搜索用时 15 毫秒
11.
Keye Martin 《Applied Categorical Structures》2003,11(1):27-40
We introduce the triangle inequality for measurement. This is a property that when satisfied by a measurement enables one to construct a metric on the set of elements with measure zero that yields the relative Scott topology. The naturality of this construction permits a categorical solution to the model problem in domain theory for locally compact metric spaces. The first time such a solution has been achieved. 相似文献
12.
Substructuring preconditioners for saddle-point problems arising from Maxwell's equations in three dimensions 总被引:1,自引:0,他引:1
This paper is concerned with the saddle-point problems arising from edge element discretizations of Maxwell's equations in a general three dimensional nonconvex polyhedral domain. A new augmented technique is first introduced to transform the problems into equivalent augmented saddle-point systems so that they can be solved by some existing preconditioned iterative methods. Then some substructuring preconditioners are proposed, with very simple coarse solvers, for the augmented saddle-point systems. With the preconditioners, the condition numbers of the preconditioned systems are nearly optimal; namely, they grow only as the logarithm of the ratio between the subdomain diameter and the finite element mesh size.
13.
14.
Tae Young Kim Dong Myung Kim Won Jung Kim Tae Hee Lee Kwang S. Suh 《Journal of Polymer Science.Polymer Physics》2004,42(15):2813-2820
The effect of the triblock copolymer poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] (SEBS) on the formation of the space charge of immiscible low‐density polyethylene (LDPE)/polystyrene (PS) blends was investigated. Blends of 70/30 (wt %) LDPE/PS were prepared through melt blending in an internal mixer at a blend temperature of 220 °C. The amount of charge that accumulated in the 70% LDPE/30% PS blends decreased when the SEBS content increased up to 10 wt %. For compatibilized and uncompatibilized blends, no significant change in the degree of crystallinity of LDPE in the blends was observed, and so the effect of crystallization on the space charge distribution could be excluded. Morphological observations showed that the addition of SEBS resulted in a domain size reduction of the dispersed PS phase and better interfacial adhesion between the LDPE and PS phases. The location of SEBS at a domain interface enabled charges to migrate from one phase to the other via the domain interface and, therefore, resulted in a significant decrease in the amount of space charge for the LDPE/PS blends with SEBS. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 2813–2820, 2004 相似文献
15.
16.
We construct the polynomial quantization on the space G/H where G=SL(n,R),H=GL(n–1,R). It is a variant of quantization in the spirit of Berezin. In our case covariant and contravariant symbols are polynomials on G/H. We introduce a multiplication of covariant symbols, establish the correspondence principle, study transformations of symbols (the Berezin transform) and of operators. We write a full asymptotic decomposition of the Berezin transform. 相似文献
17.
Riemannian manifolds for which a natural curvature operator has constant eigenvalues on circles are studied. A local classification in dimensions two and three is given. In the 3-dimensional case one gets all locally symmetric spaces and all Riemannian manifolds with the constant principal Ricci curvatures r
1 = r
2 = 0, r
3= 0 , which are not locally homogeneous, in general. 相似文献
18.
In this paper, we consider questions related to the structure of inverse matrices of linear bounded operators acting in infinite-dimensional complex Banach spaces. We obtain specific estimates of elements of inverse matrices for bounded operators whose matrices have a special structure. Matrices are introduced as special operator-valued functions on an index set. The matrix structure is described by the behavior of the given function on elements of a special partition of the index set. The method used for deriving the estimates is based on an analysis of Fourier series of strongly continuous periodic functions. 相似文献
19.
本文对近20年来多复变函数的一个发展迅速的数学热门分支-逆紧映照作了一个回顾和整理。这是作者继续从事此方向研究的先声,也希望本文能为有志于此的研究者提供一些便利。本文从经典的结果开始,通过对逆紧映照在边界上的开拓及分支点的分布的讨论,详细地阐述了这些年来关于逆紧映照何时成为双全纯映照的若干结果。最后,对近年来关于逆紧映照另外的一些工作进行了简单的介绍。 相似文献
20.
A. M. Chebotarev 《Mathematical Notes》2002,71(3-4):408-427
We prove that a quantum stochastic differential equation is the interaction representation of the Cauchy problem for the Schrödinger equation with Hamiltonian given by a certain operator restricted by a boundary condition. If the deficiency index of the boundary-value problem is trivial, then the corresponding quantum stochastic differential equation has a unique unitary solution. Therefore, by the deficiency index of a quantum stochastic differential equation we mean the deficiency index of the related symmetric boundary-value problem.In this paper, conditions sufficient for the essential self-adjointness of the symmetric boundary-value problem are obtained. These conditions are closely related to nonexplosion conditions for the pair of master Markov equations that we canonically assign to the quantum stochastic differential equation. 相似文献