全文获取类型
收费全文 | 3361篇 |
免费 | 248篇 |
国内免费 | 340篇 |
专业分类
化学 | 226篇 |
晶体学 | 2篇 |
力学 | 102篇 |
综合类 | 76篇 |
数学 | 2752篇 |
物理学 | 791篇 |
出版年
2024年 | 4篇 |
2023年 | 31篇 |
2022年 | 60篇 |
2021年 | 70篇 |
2020年 | 82篇 |
2019年 | 87篇 |
2018年 | 100篇 |
2017年 | 95篇 |
2016年 | 89篇 |
2015年 | 64篇 |
2014年 | 130篇 |
2013年 | 279篇 |
2012年 | 108篇 |
2011年 | 134篇 |
2010年 | 136篇 |
2009年 | 192篇 |
2008年 | 234篇 |
2007年 | 218篇 |
2006年 | 194篇 |
2005年 | 208篇 |
2004年 | 136篇 |
2003年 | 174篇 |
2002年 | 165篇 |
2001年 | 145篇 |
2000年 | 140篇 |
1999年 | 100篇 |
1998年 | 102篇 |
1997年 | 93篇 |
1996年 | 71篇 |
1995年 | 47篇 |
1994年 | 39篇 |
1993年 | 25篇 |
1992年 | 26篇 |
1991年 | 17篇 |
1990年 | 16篇 |
1989年 | 11篇 |
1988年 | 16篇 |
1987年 | 11篇 |
1986年 | 8篇 |
1985年 | 10篇 |
1984年 | 8篇 |
1983年 | 9篇 |
1982年 | 15篇 |
1981年 | 4篇 |
1980年 | 10篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 8篇 |
1976年 | 4篇 |
1974年 | 3篇 |
排序方式: 共有3949条查询结果,搜索用时 15 毫秒
61.
We find a minimal system of generators and a homogeneous system of parameters for the algebra of invariants of three matrices of third order over a field of an arbitrary characteristic. 相似文献
62.
The wreath product of finite association schemes is a natural generalization of the notion of the wreath product of finite permutation groups. We determine all irreducible representations (the Jacobson radical) of a wreath product of two finite association schemes over an algebraically closed field in terms of the irreducible representations (Jacobson radicals) of the two factors involved. 相似文献
63.
A computably enumerable (c.e.) degree a is called nonbounding, if it bounds no minimal pair, and plus cupping, if every nonzero c.e. degree x below a is cuppable. Let NB and PC be the sets of all nonbounding and plus cupping c.e. degrees, respectively. Both NB and PC are well understood, but it has not been possible so far to distinguish between the two classes. In the present paper, we investigate the relationship between the classes NB and PC , and show that there exists a minimal pair which join to a plus cupping degree, so that PC ? NB . This gives a first known difference between NB and PC . (© 2003 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
64.
E. Puppo 《Computational Geometry》1998,11(3-4):219-238
A comprehensive study of multiresolution decompositions of planar domains into triangles is given. A general model is introduced, called a Multi-Triangulation (MT), which is based on a collection of fragments of triangulations arranged into a directed acyclic graph. Different decompositions of a domain can be obtained by combining different fragments of the model. Theoretical results on the expressive power of the MT are given. An efficient algorithm is proposed that can extract a triangulation from the MT, whose level of detail is variable over the domain according to a given threshold function. The algorithm works in linear time, and the extracted representation has minimum size among all possible triangulations that can be built from triangles in the MT, and that satisfy the given level of detail. Major applications of these results are in real-time rendering of complex surfaces, such as topographic surfaces in flight simulation. 相似文献
65.
66.
M. Brazil 《Discrete Applied Mathematics》2006,154(18):2545-2564
The Steiner problem in a λ-plane is the problem of constructing a minimum length network interconnecting a given set of nodes (called terminals), with the constraint that all line segments in the network have slopes chosen from λ uniform orientations in the plane. This network is referred to as a minimum λ-tree. The problem is a generalization of the classical Euclidean and rectilinear Steiner tree problems, with important applications to VLSI wiring design.A λ-tree is said to be locally minimal if its length cannot be reduced by small perturbations of its Steiner points. In this paper we prove that a λ-tree is locally minimal if and only if the length of each path in the tree cannot be reduced under a special parallel perturbation on paths known as a shift. This proves a conjecture on necessary and sufficient conditions for locally minimal λ-trees raised in [M. Brazil, D.A. Thomas, J.F. Weng, Forbidden subpaths for Steiner minimum networks in uniform orientation metrics, Networks 39 (2002) 186-222]. For any path P in a λ-tree T, we then find a simple condition, based on the sum of all angles on one side of P, to determine whether a shift on P reduces, preserves, or increases the length of T. This result improves on our previous forbidden paths results in [M. Brazil, D.A. Thomas, J.F. Weng, Forbidden subpaths for Steiner minimum networks in uniform orientation metrics, Networks 39 (2002) 186-222]. 相似文献
67.
研究全稳定广义生灭最小Q过程的可配称性,获得广义生灭最小Q过程是可配称的充分必要条件,以及最小Q过程是唯一的可配称Q过程的充分必要条件. 相似文献
68.
Minoru Murata 《Journal of Functional Analysis》2007,245(1):177-212
We consider nonnegative solutions of a parabolic equation in a cylinder D×(0,T), where D is a noncompact domain of a Riemannian manifold. Under the assumption [IU] (i.e., the associated heat kernel is intrinsically ultracontractive), we establish an integral representation theorem: any nonnegative solution is represented uniquely by an integral on (D×{0})∪(M∂D×[0,T)), where M∂D is the Martin boundary of D for the associated elliptic operator. We apply it in a unified way to several concrete examples to explicitly represent nonnegative solutions. We also show that [IU] implies the condition [SP] (i.e., the constant function 1 is a small perturbation of the elliptic operator on D). 相似文献
69.
Our purpose is to characterize the multiparameter Gaussian processes, that is Gaussian sheets, that are equivalent in law
to the Brownian sheet and to the fractional Brownian sheet. We survey multiparameter analogues of the Hitsuda, Girsanov and
Shepp representations. As an application, we study a special type of stochastic equation with linear noise.
相似文献
70.
V. N. Dubinin 《Mathematical Notes》2006,80(1-2):31-35
It is shown that if P(z) = z n + ? is a polynomial with connected lemniscate E(P) = {z: ¦P(z)¦ ≤ 1} and m critical points, then, for any n? m+1 points on the lemniscate E(P), there exists a continuum γ ? E(P) of logarithmic capacity cap γ ≤ 2?1/n which contains these points and all zeros and critical points of the polynomial. As corollaries, estimates for continua of minimum capacity containing given points are obtained. 相似文献