全文获取类型
收费全文 | 7171篇 |
免费 | 186篇 |
国内免费 | 156篇 |
专业分类
化学 | 1234篇 |
晶体学 | 64篇 |
力学 | 39篇 |
综合类 | 17篇 |
数学 | 5444篇 |
物理学 | 715篇 |
出版年
2024年 | 5篇 |
2023年 | 32篇 |
2022年 | 38篇 |
2021年 | 51篇 |
2020年 | 66篇 |
2019年 | 159篇 |
2018年 | 142篇 |
2017年 | 85篇 |
2016年 | 79篇 |
2015年 | 105篇 |
2014年 | 199篇 |
2013年 | 334篇 |
2012年 | 230篇 |
2011年 | 453篇 |
2010年 | 365篇 |
2009年 | 423篇 |
2008年 | 436篇 |
2007年 | 494篇 |
2006年 | 373篇 |
2005年 | 245篇 |
2004年 | 195篇 |
2003年 | 207篇 |
2002年 | 192篇 |
2001年 | 141篇 |
2000年 | 135篇 |
1999年 | 178篇 |
1998年 | 195篇 |
1997年 | 167篇 |
1996年 | 162篇 |
1995年 | 208篇 |
1994年 | 157篇 |
1993年 | 163篇 |
1992年 | 154篇 |
1991年 | 92篇 |
1990年 | 92篇 |
1989年 | 112篇 |
1988年 | 63篇 |
1987年 | 49篇 |
1986年 | 53篇 |
1985年 | 76篇 |
1984年 | 72篇 |
1983年 | 55篇 |
1982年 | 66篇 |
1981年 | 43篇 |
1980年 | 40篇 |
1979年 | 42篇 |
1978年 | 42篇 |
1977年 | 17篇 |
1976年 | 17篇 |
1974年 | 4篇 |
排序方式: 共有7513条查询结果,搜索用时 484 毫秒
31.
Piet Borst 《Topology and its Applications》2007,154(3):665-674
We comment on the definition of C-spaces in [D.F. Addis, J.H. Gresham, A class of infinite-dimensional spaces. Part I: Dimension theory and Alexandroff's Problem, Fund. Math. 101 (1978) 195-205] and [W.E. Haver, A covering property for metric spaces, in: Topology Conference at Virginia Polytechnic Institute 1973, in: Lecture Notes in Math., vol. 375, 1974, pp. 108-113]. Furthermore we introduce two types of ‘finite’ C-spaces one of which gives an internal characterization of all spaces having a metrizable compactification satisfying property C. We also introduce a transfinite dimension function for those finite C-spaces. Several questions arise that are related to Alexandrov's problem. 相似文献
32.
In a structural measurement error model the structural quasi-score (SQS) estimator is based on the distribution of the latent regressor variable. If this distribution is misspecified, the SQS estimator is (asymptotically) biased. Two types of misspecification are considered. Both assume that the statistician erroneously adopts a normal distribution as his model for the regressor distribution. In the first type of misspecification, the true model consists of a mixture of normal distributions which cluster around a single normal distribution, in the second type, the true distribution is a normal distribution admixed with a second normal distribution of low weight. In both cases of misspecification, the bias, of course, tends to zero when the size of misspecification tends to zero. However, in the first case the bias goes to zero in a flat way so that small deviations from the true model lead to a negligible bias, whereas in the second case the bias is noticeable even for small deviations from the true model. 相似文献
33.
The large deviation theorems, exponential inequalities and a non-uniform estimate of the Berry–Esséen theorem in a discounted version are proved.Dedicated to Professor Vytautas Statulevičius on the occasion of his 75th birthday. 相似文献
34.
Zhijun Yi Tingyu LiuQiren Zhang Yuanyuan Sun 《Journal of Electron Spectroscopy and Related Phenomena》2006
The electronic structures of PbWO4 crystals containing F type color centers with the lattice structure optimized are studied within the framework of the fully relativistic self-consistent Direc–Slater theory, using a numerically discrete variational (DV-Xα) method. The calculated results show that F and F+ centers have donor energy level in forbidden band. Their optical transition energy are 1.84 eV, 2.21 eV, respectively, which corresponds to the 680 nm, 550 nm absorption bands. It predicts that the 680 nm, 550 nm absorption bands originate form the F and F+ centers in PbWO4 crystals. 相似文献
35.
Teruhisa Tsuda 《Letters in Mathematical Physics》2006,77(1):21-30
Starting from certain point sets in the projective plane, we construct a tropical (or subtraction-free birational) representation of Weyl groups over the field of τ-functions. In particular, our construction includes E
8
(1)
, E
7
(1)
, E
6
(1)
and D
5
(1)
as affine cases; each of them gives rise to the q-difference Painlevé equation. 相似文献
36.
Jan P. Boroński 《Topology and its Applications》2007,154(18):3156-3166
A set (or a collection of sets) contained in the Euclidean space Rm is symmetric if it is invariant under the antipodal map. Given a symmetric unicoherent polyhedron X (like an n-dimensional cube or a sphere) and an odd real function f defined on vertices of a certain symmetric triangulation of X, we algorithmically construct a connected symmetric separator of X by choosing a subcollection of the triangulation. Each element of the subcollection contains the vertices v and u such that f(v)f(u)?0. 相似文献
37.
We investigate separability questions for the mapping class group of a surface. While this group is not subgroup separable in general, we prove a large family of interesting subgroups are separable. This includes many classically studied subgroups such as solvable subgroups, Heegaard and Handlebody groups, geometric subgroups, and all the terms in the Johnson filtration. 相似文献
38.
39.
Inna Bumagina 《Geometriae Dedicata》2004,106(1):211-230
A group is said to be Hopfian if every surjective endomorphism of the group is injective. We show that finitely generated subgroups of torsion-free hyperbolic groups are Hopfian. Our proof generalizes a theorem of Sela (Topology
35 (2) 1999, 301–321). 相似文献
40.
Systems that involve N identical interacting particles under quantum confinement appear throughout many areas of physics, including chemical, condensed matter, and atomic physics. In this paper, we present the methods of dimensional perturbation theory, a powerful set of tools that uses symmetry to yield simple results for studying such many-body systems. We present a detailed discussion of the dimensional continuation of the N-particle Schrödinger equation, the spatial dimension D→∞ equilibrium (D0) structure, and the normal-mode (D−1) structure. We use the FG matrix method to derive general, analytical expressions for the many-body normal-mode vibrational frequencies, and we give specific analytical results for three confined N-body quantum systems: the N-electron atom, N-electron quantum dot, and N-atom inhomogeneous Bose-Einstein condensate with a repulsive hard-core potential. 相似文献