全文获取类型
收费全文 | 15048篇 |
免费 | 395篇 |
国内免费 | 239篇 |
专业分类
化学 | 947篇 |
晶体学 | 23篇 |
力学 | 199篇 |
综合类 | 25篇 |
数学 | 13439篇 |
物理学 | 1049篇 |
出版年
2023年 | 28篇 |
2022年 | 42篇 |
2021年 | 46篇 |
2020年 | 63篇 |
2019年 | 404篇 |
2018年 | 483篇 |
2017年 | 251篇 |
2016年 | 165篇 |
2015年 | 193篇 |
2014年 | 486篇 |
2013年 | 918篇 |
2012年 | 541篇 |
2011年 | 905篇 |
2010年 | 818篇 |
2009年 | 1151篇 |
2008年 | 1207篇 |
2007年 | 1179篇 |
2006年 | 927篇 |
2005年 | 564篇 |
2004年 | 497篇 |
2003年 | 466篇 |
2002年 | 359篇 |
2001年 | 316篇 |
2000年 | 307篇 |
1999年 | 374篇 |
1998年 | 321篇 |
1997年 | 245篇 |
1996年 | 321篇 |
1995年 | 330篇 |
1994年 | 329篇 |
1993年 | 224篇 |
1992年 | 162篇 |
1991年 | 103篇 |
1990年 | 87篇 |
1989年 | 104篇 |
1988年 | 63篇 |
1987年 | 55篇 |
1986年 | 53篇 |
1985年 | 86篇 |
1984年 | 88篇 |
1983年 | 45篇 |
1982年 | 91篇 |
1981年 | 80篇 |
1980年 | 50篇 |
1979年 | 26篇 |
1978年 | 34篇 |
1977年 | 27篇 |
1976年 | 29篇 |
1974年 | 14篇 |
1973年 | 11篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
In this paper, the influence functions and limiting distributions of the canonical correlations and coefficients based on affine equivariant scatter matrices are developed for elliptically symmetric distributions. General formulas for limiting variances and covariances of the canonical correlations and canonical vectors based on scatter matrices are obtained. Also the use of the so-called shape matrices in canonical analysis is investigated. The scatter and shape matrices based on the affine equivariant Sign Covariance Matrix as well as the Tyler's shape matrix serve as examples. Their finite sample and limiting efficiencies are compared to those of the Minimum Covariance Determinant estimators and S-estimator through theoretical and simulation studies. The theory is illustrated by an example. 相似文献
12.
In this paper we give a realization of some symmetric space G/K as a closed submanifold P of G. We also give several equivalent representations of the submanifold P. Some properties of the set gK∩P are also discussed, where gK is a coset space in G. 相似文献
13.
A. M. Vinogradov 《Acta Appl Math》1989,15(1-2):3-21
The main notions and results which are necessary for finding higher symmetries and conservation laws for general systems of partial differential equations are given. These constitute the starting point for the subsequent papers of this volume. Some problems are also discussed. 相似文献
14.
Summary In 1980 Dahmen-DeVore-Scherer introduced a modulus of continuity which turns out to reflect invariance properties of compound cubature rules effectively. Accordingly, sharp error bounds are derived, the existence of relevant counterexamples being a consequence of a quantitative resonance principle, established previously. 相似文献
15.
Camillo Costantini 《Topology and its Applications》2006,153(7):1056-1078
For X a metrizable space and (Y,ρ) a metric space, with Y pathwise connected, we compute the density of (C(X,(Y,ρ)),σ)—the space of all continuous functions from X to (Y,ρ), endowed with the supremum metric σ. Also, for (X,d) a metric space and (Y,‖⋅‖) a normed space, we compute the density of (UC((X,d),(Y,ρ)),σ) (the space of all uniformly continuous functions from (X,d) to (Y,ρ), where ρ is the metric induced on Y by ‖⋅‖). We also prove that the latter result extends only partially to the case where (Y,ρ) is an arbitrary pathwise connected metric space.To carry such an investigation out, the notions of generalized compact and generalized totally bounded metric space, introduced by the author and A. Barbati in a former paper, turn out to play a crucial rôle. Moreover, we show that the first-mentioned concept provides a precise characterization of those metrizable spaces which attain their extent. 相似文献
16.
Yevhen Zelenyuk 《Topology and its Applications》2006,153(14):2382-2385
We introduce the notion of a partially selective ultrafilter and prove that (a) if G is an extremally disconnected topological group and p is a converging nonprincipal ultrafilter on G containing a countable discrete subset, then p is partially selective, and (b) the existence of a nonprincipal partially selective ultrafilter on a countable set implies the existence of a P-point in ω∗. Thus it is consistent with ZFC that there is no extremally disconnected topological group containing a countable discrete nonclosed subset. 相似文献
17.
Saida Sultanic 《Integral Equations and Operator Theory》2006,55(4):573-595
The central question of this paper is the one of finding the right analogue of the Commutant Lifting Theorem for the Bergman
space La2. We also analyze the analogous problem for weighted Bergman spaces La,α2, − 1 < α < ∞. 相似文献
18.
Michel Hébert 《Archive for Mathematical Logic》1991,31(2):133-143
Summary We give a syntactic characterization of (finitary) theories whose categories of models are closed under the formation of connected limits (respectively the formation of pullbacks and substructures) in the category of all structures. They are also those theories whose consistent extensions by new atomic facts admit in each component an initial structure (respectively an initial term structure), and also thoseT for whichM(T) is locally finitely multi-presentable in a canonical way. We also show that these two properties of theories are nonuniform. 相似文献
19.
J. Kalliongis 《Mathematische Zeitschrift》2002,241(4):801-828
For compact irreducible sufficiently large 3-manifolds containing 2-sided projective planes, we consider the following Realization
Problem: Given a finite subgroup of the outer automorphism group of the fundamental group, is there a finite group of homeomorphisms,
which induces this subgroup?
Received: 16 November 1999; in final form: 18 January 2001 / Published online: 8 November 2002 相似文献
20.