全文获取类型
收费全文 | 15763篇 |
免费 | 490篇 |
国内免费 | 385篇 |
专业分类
化学 | 2312篇 |
晶体学 | 79篇 |
力学 | 246篇 |
综合类 | 57篇 |
数学 | 12380篇 |
物理学 | 1564篇 |
出版年
2023年 | 44篇 |
2022年 | 135篇 |
2021年 | 134篇 |
2020年 | 127篇 |
2019年 | 435篇 |
2018年 | 468篇 |
2017年 | 199篇 |
2016年 | 203篇 |
2015年 | 257篇 |
2014年 | 523篇 |
2013年 | 946篇 |
2012年 | 551篇 |
2011年 | 1130篇 |
2010年 | 889篇 |
2009年 | 1109篇 |
2008年 | 1187篇 |
2007年 | 1280篇 |
2006年 | 978篇 |
2005年 | 665篇 |
2004年 | 569篇 |
2003年 | 539篇 |
2002年 | 370篇 |
2001年 | 297篇 |
2000年 | 300篇 |
1999年 | 351篇 |
1998年 | 327篇 |
1997年 | 225篇 |
1996年 | 298篇 |
1995年 | 286篇 |
1994年 | 286篇 |
1993年 | 233篇 |
1992年 | 186篇 |
1991年 | 112篇 |
1990年 | 113篇 |
1989年 | 105篇 |
1988年 | 77篇 |
1987年 | 80篇 |
1986年 | 53篇 |
1985年 | 107篇 |
1984年 | 89篇 |
1983年 | 53篇 |
1982年 | 76篇 |
1981年 | 64篇 |
1980年 | 39篇 |
1979年 | 21篇 |
1978年 | 35篇 |
1977年 | 30篇 |
1976年 | 21篇 |
1975年 | 12篇 |
1974年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 296 毫秒
21.
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
22.
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
23.
Using Brown's construction (J. Algebra 15 (1970) 103) of an exact 6-term sequence for a fibration of groupoids we show how an exact 9-term sequence can be associated to a fibration of bigroupoids. Applications to topology and algebra are given. 相似文献
24.
Parallel to Cox's [JRSS B34 (1972) 187-230] proportional hazards model, generalized logistic models have been discussed by Anderson [Bull. Int. Statist. Inst. 48 (1979) 35-53] and others. The essential assumption is that the two densities ratio has a known parametric form. A nice property of this model is that it naturally relates to the logistic regression model for categorical data. In astronomic, demographic, epidemiological, and other studies the variable of interest is often truncated by an associated variable. This paper studies generalized logistic models for the two-sample truncated data problem, where the two lifetime densities ratio is assumed to have the form exp{α+φ(x;β)}. Here φ is a known function of x and β, and the baseline density is unspecified. We develop a semiparametric maximum likelihood method for the case where the two samples have a common truncation distribution. It is shown that inferences for β do not depend the nonparametric components. We also derive an iterative algorithm to maximize the semiparametric likelihood for the general case where different truncation distributions are allowed. We further discuss how to check goodness of fit of the generalized logistic model. The developed methods are illustrated and evaluated using both simulated and real data. 相似文献
25.
F. Balibrea 《Topology and its Applications》2006,153(12):2092-2095
Recently, Forti, Paganoni and Smítal constructed an example of a triangular map of the unite square, F(x,y)=(f(x),g(x,y)), possessing periodic orbits of all periods and such that no infinite ω-limit set of F contains a periodic point. In this note we show that the above quoted map F has a homoclinic orbit. As a consequence, we answer in the negative the problem presented by A.N. Sharkovsky in the eighties whether, for a triangular map of the square, existence of a homoclinic orbit implies the existence of an infinite ω-limit set containing a periodic point. It is well known that, for a continuous map of the interval, the answer is positive. 相似文献
26.
27.
Using the theory of noncommutative symmetric functions, we introduce the higher order peak algebras (Sym(N))N≥1, a sequence of graded Hopf algebras which contain the descent algebra and the usual peak algebra as initial cases (N=1 and N=2). We compute their Hilbert series, introduce and study several combinatorial bases, and establish various algebraic identities
related to the multisection of formal power series with noncommutative coefficients.
Received November 19, 2004 相似文献
28.
29.
Paulo D. Cordaro 《Advances in Mathematics》2004,184(1):89-118
Taking as a start point the recent article of Meziani [7], we present several results concerning the normalization of a class of complex vector fields in the plane which degenerate along a real curve. We mainly deal with operators with finite regularity and analyze both the local situation as well as the case of normalization near a circle. Some related questions (e.g., on semi-global solvability and on the normalization of a class of generalized Mizohata operators) are also discussed. 相似文献
30.
富勒烯 (C60 /C70 )与N ,N ,N′ ,N′ 四 (对甲苯基 ) 4,4′ 二胺 1,1′ 二苯硒醚 (TPDASe)间在激光光诱导条件下 ,发生了分子间的电子转移过程 .在可见 -近红外区 ( 60 0~ 12 0 0nm) ,观测到了TPDASe阳离子自由基、富勒烯 (C60 /C70 )激发三线态和阴离子自由基 ,在苯腈溶液中 ,观测瞬态谱测定了电子从TPDASe转移到富勒烯 (C60 /C70 )激发三线态的量子转化产率(ΦTet)和电子转移常数 (Ket) . 相似文献