全文获取类型
收费全文 | 14334篇 |
免费 | 1327篇 |
国内免费 | 1633篇 |
专业分类
化学 | 1003篇 |
晶体学 | 33篇 |
力学 | 1019篇 |
综合类 | 350篇 |
数学 | 12233篇 |
物理学 | 2656篇 |
出版年
2024年 | 17篇 |
2023年 | 155篇 |
2022年 | 179篇 |
2021年 | 216篇 |
2020年 | 288篇 |
2019年 | 336篇 |
2018年 | 315篇 |
2017年 | 369篇 |
2016年 | 401篇 |
2015年 | 314篇 |
2014年 | 608篇 |
2013年 | 978篇 |
2012年 | 583篇 |
2011年 | 785篇 |
2010年 | 773篇 |
2009年 | 1013篇 |
2008年 | 1068篇 |
2007年 | 1146篇 |
2006年 | 939篇 |
2005年 | 880篇 |
2004年 | 679篇 |
2003年 | 735篇 |
2002年 | 669篇 |
2001年 | 529篇 |
2000年 | 588篇 |
1999年 | 499篇 |
1998年 | 478篇 |
1997年 | 394篇 |
1996年 | 295篇 |
1995年 | 171篇 |
1994年 | 175篇 |
1993年 | 100篇 |
1992年 | 87篇 |
1991年 | 72篇 |
1990年 | 60篇 |
1989年 | 34篇 |
1988年 | 36篇 |
1987年 | 27篇 |
1986年 | 16篇 |
1985年 | 42篇 |
1984年 | 50篇 |
1983年 | 16篇 |
1982年 | 35篇 |
1981年 | 21篇 |
1980年 | 30篇 |
1979年 | 26篇 |
1978年 | 15篇 |
1977年 | 13篇 |
1976年 | 10篇 |
1936年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
Bernardo Lafuerza-Guillén Donal O’regan Reza Saadati 《Proceedings Mathematical Sciences》2007,117(1):61-70
We introduce the concept of quotient in PN spaces and give some examples. We prove some theorems with regard to the completeness
of a quotient. 相似文献
102.
We prove equivalence of the definitions by the author and by Korevaar and Schoen of the Sobolev classes of mappings of a domain of an arithmetic n-dimensional space to a metric space. 相似文献
103.
T. Domínguez Benavides 《Journal of Mathematical Analysis and Applications》2004,291(1):100-108
Let X be a Banach space whose characteristic of noncompact convexity is less than 1 and satisfies the nonstrict Opial condition. Let C be a bounded closed convex subset of X, KC(X) the family of all compact convex subsets of X and T a nonexpansive mapping from C into KC(X) with bounded range. We prove that T has a fixed point. The nonstrict Opial condition can be removed if, in addition, T is an 1-χ-contractive mapping. 相似文献
104.
Stability and bifurcation in a delayed predator-prey system with Beddington-DeAngelis functional response 总被引:1,自引:0,他引:1
Zhihua Liu 《Journal of Mathematical Analysis and Applications》2004,296(2):521-537
We consider a delayed predator-prey system with Beddington-DeAngelis functional response. The stability of the interior equilibrium will be studied by analyzing the associated characteristic transcendental equation. By choosing the delay τ as a bifurcation parameter, we show that Hopf bifurcation can occur as the delay τ crosses some critical values. The direction and stability of the Hopf bifurcation are investigated by following the procedure of deriving normal form given by Faria and Magalhães. An example is given and numerical simulations are performed to illustrate the obtained results. 相似文献
105.
Gabriela Jeronimo Teresa Krick Juan Sabia Martín Sombra 《Foundations of Computational Mathematics》2004,4(1):41-117
We present a bounded probability algorithm for the computation of the
Chowforms of the equidimensional components of an algebraic variety. In particular,
this gives an alternative procedure for the effective equidimensional decomposition
of the variety, since each equidimensional component is characterized by its Chow
form.
The expected complexity of the algorithm is polynomial in the size and the geometric
degree of the input equation system defining the variety. Hence it improves (or
meets in some special cases) the complexity of all previous algorithms for computing Chow forms. In addition to this, we clarify the probability and uniformity aspects,
which constitutes a further contribution of the paper.
The algorithm is based on elimination theory techniques, in line with the geometric
resolution algorithm due to M. Giusti, J. Heintz, L. M. Pardo, and their collaborators.
In fact, ours can be considered as an extension of their algorithm for zero-dimensional
systems to the case of positive-dimensional varieties. The key element for dealing
with positive-dimensional varieties is a new Poisson-type product formula. This
formula allows us to compute the Chow form of an equidimensional variety from a
suitable zero-dimensional fiber.
As an application, we obtain an algorithm to compute a subclass of sparse resultants,
whose complexity is polynomial in the dimension and the volume of the input
set of exponents. As another application, we derive an algorithm for the computation
of the (unique) solution of a generic overdetermined polynomial equation system. 相似文献
106.
Spiros Cotsakis 《General Relativity and Gravitation》2004,36(5):1183-1188
We show that for generic sliced spacetimes global hyperbolicity is equivalent to space completeness under the assumption that the lapse, shift and spatial metric are uniformly bounded. This leads us to the conclusion that simple sliced spaces are timelike and null geodesically complete if and only if space is a complete Riemannian manifold. 相似文献
107.
On Covariant Phase Space and the Variational Bicomplex 总被引:1,自引:0,他引:1
Enrique G. Reyes 《International Journal of Theoretical Physics》2004,43(5):1267-1286
The notion of a phase space in classical mechanics is well known. The extension of this concept to field theory however, is a challenging endeavor, and over the years numerous proposals for such a generalization have appeared in the literature. In this paper We review a Hamiltonian formulation of Lagrangian field theory based on an extension to infinite dimensions of J.-M. Souriau's symplectic approach to mechanics. Following G. Zuckerman, we state our results in terms of the modern geometric theory of differential equations and the variational bicomplex. As an elementary example, we construct a phase space for the Monge–Ampere equation. 相似文献
108.
The authors give the necessary and sufficient conditions for a generalized circle in a Weyl hypersurface to be generalized circle in the enveloping Weyl space. They then obtain the neccessary and sufficient conditions under which a generalized concircular transformation of one Weyl space onto another induces a generalized transformation oil its subspaces. Finally, it is shown that any totally geodesic or totally umbilical hypersurface of a generalized concircularly flat Weyl space is also generalized concircularly flat. 相似文献
109.
Ghulam Mustafa 《数学研究及应用》2003,23(3):413-421
本文引入了一种满足更一般的收缩不等式的多重函数类,并证明了属于该类的可测多重函数对的一些随机重合点定理。 相似文献
110.
We prove that all invariant distances on the universal Teichmuller space agree and are determined by the Grunsky coefficients of the naturally related conformal maps. This fact yields various important consequences; in particular, we obtain solutions of certain well-known geometric problems in complex analysis and related fields. 相似文献