全文获取类型
收费全文 | 28520篇 |
免费 | 688篇 |
国内免费 | 524篇 |
专业分类
化学 | 4393篇 |
晶体学 | 945篇 |
力学 | 530篇 |
综合类 | 51篇 |
数学 | 19571篇 |
物理学 | 4242篇 |
出版年
2023年 | 75篇 |
2022年 | 211篇 |
2021年 | 175篇 |
2020年 | 211篇 |
2019年 | 623篇 |
2018年 | 678篇 |
2017年 | 420篇 |
2016年 | 457篇 |
2015年 | 427篇 |
2014年 | 826篇 |
2013年 | 1831篇 |
2012年 | 755篇 |
2011年 | 2095篇 |
2010年 | 1820篇 |
2009年 | 1911篇 |
2008年 | 2072篇 |
2007年 | 2044篇 |
2006年 | 1524篇 |
2005年 | 1221篇 |
2004年 | 1086篇 |
2003年 | 880篇 |
2002年 | 824篇 |
2001年 | 565篇 |
2000年 | 534篇 |
1999年 | 577篇 |
1998年 | 563篇 |
1997年 | 414篇 |
1996年 | 525篇 |
1995年 | 504篇 |
1994年 | 486篇 |
1993年 | 374篇 |
1992年 | 331篇 |
1991年 | 242篇 |
1990年 | 242篇 |
1989年 | 238篇 |
1988年 | 146篇 |
1987年 | 169篇 |
1986年 | 142篇 |
1985年 | 220篇 |
1984年 | 156篇 |
1983年 | 102篇 |
1982年 | 133篇 |
1981年 | 163篇 |
1980年 | 142篇 |
1979年 | 92篇 |
1978年 | 135篇 |
1977年 | 115篇 |
1976年 | 108篇 |
1975年 | 46篇 |
1974年 | 49篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
In this paper we generalize to coisotropic actions of compact Lie groups a theorem of Guillemin on deformations of Hamiltonian
structures on compact symplectic manifolds. We show how one can reconstruct from the moment polytope the symplectic form on
the manifold.
Received: 21 March 2006 相似文献
102.
Let Λ be a smooth Lagrangian submanifold of a complex symplectic manifold X. We construct twisted simple holonomic modules along Λ in the stack of deformation-quantization modules on X. 相似文献
103.
Helly and Hadwiger type theorems for transversal m-flats to families of flats and, respectively, convex sets of dimension n are proved in the case of general position. The proofs rely on Helly type theorems for “linear partitions” and “convex partitions,” so that a general theory of Helly numbers is also developed. 相似文献
104.
Lévy processes in matrix Lie groups are studied. Subordination (random time change) is used to show that quasi-invariance of the Brownian motion in a Lie group induces absolute continuity of the laws of the corresponding pure jump processes. These results are applied to several examples which are discussed in detail. 相似文献
105.
Roberto E. Madariaga-Garcia 《Topology and its Applications》2007,154(7):1470-1480
Tkachenko showed in 1990 the existence of a countably compact group topology on the free Abelian group of size c using CH. Koszmider, Tomita and Watson showed in 2000 the existence of a countably compact group topology on the free Abelian group of size c2 using a forcing model in which CH holds.Wallace's question from 1955, asks whether every both-sided cancellative countably compact semigroup is a topological group. A counterexample to Wallace's question has been called a Wallace semigroup. In 1996, Robbie and Svetlichny constructed a Wallace semigroup under CH. In the same year, Tomita constructed a Wallace semigroup from MAcountable.In this note, we show that the examples of Tkachenko, Robbie and Svetlichny, and Koszmider, Tomita and Watson can be obtained using a family of selective ultrafilters. As a corollary, the constructions presented here are compatible with the total failure of Martin's Axiom. 相似文献
106.
We construct cellular homotopy theories for categories of simplicial presheaves on small Grothendieck sites and discuss applications to the motivic homotopy category of Morel and Voevodsky. 相似文献
107.
The main results of the paper are as follows: covering characterizations of wQN-spaces, covering characterizations of QN-spaces and a theorem saying that Cp(X) has the Arkhangel'ski?ˇ property (α1) provided that X is a QN-space. The latter statement solves a problem posed by M. Scheepers [M. Scheepers, Cp(X) and Arhangel'ski?ˇ's αi-spaces, Topology Appl. 89 (1998) 265-275] and for Tychonoff spaces was independently proved by M. Sakai [M. Sakai, The sequence selection properties of Cp(X), Preprint, April 25, 2006]. As the most interesting result we consider the equivalence that a normal topological space X is a wQN-space if and only if X has the property S1(Γshr,Γ). Moreover we show that X is a QN-space if and only if Cp(X) has the property (α0), and for perfectly normal spaces, if and only if X has the covering property (β3). 相似文献
108.
We classify all the global phase portraits of the quadratic polynomial vector fields having a rational first integral of degree 2. In other words we characterize all the global phase portraits of the quadratic polynomial vector fields having all their orbits contained in conics. For such a vector field there are exactly 25 different global phase portraits in the Poincaré disc, up to a reversal of sense. 相似文献
109.
Q. Gong R. N tzel P.J. van Veldhoven T.J. Eijkemans J.H. Wolter 《Journal of Crystal Growth》2005,280(3-4):413-418
We report on the shape transition from InAs quantum dashes to quantum dots (QDs) on lattice-matched GaInAsP on InP(3 1 1)A substrates. InAs quantum dashes develop during chemical-beam epitaxy of 3.2 monolayers InAs, which transform into round InAs QDs by introducing a growth interruption without arsenic flux after InAs deposition. The shape transition is solely attributed to surface properties, i.e., increase of the surface energy and symmetry under arsenic deficient conditions. The round QD shape is maintained during subsequent GaInAsP overgrowth because the reversed shape transition from dot to dash is kinetically hindered by the decreased ad-atom diffusion under arsenic flux. 相似文献
110.