全文获取类型
收费全文 | 1966篇 |
免费 | 47篇 |
国内免费 | 20篇 |
专业分类
化学 | 1053篇 |
晶体学 | 5篇 |
力学 | 63篇 |
数学 | 374篇 |
物理学 | 538篇 |
出版年
2023年 | 12篇 |
2022年 | 10篇 |
2021年 | 15篇 |
2020年 | 31篇 |
2019年 | 32篇 |
2018年 | 23篇 |
2017年 | 15篇 |
2016年 | 34篇 |
2015年 | 33篇 |
2014年 | 40篇 |
2013年 | 84篇 |
2012年 | 74篇 |
2011年 | 107篇 |
2010年 | 61篇 |
2009年 | 56篇 |
2008年 | 86篇 |
2007年 | 92篇 |
2006年 | 86篇 |
2005年 | 94篇 |
2004年 | 84篇 |
2003年 | 85篇 |
2002年 | 51篇 |
2001年 | 26篇 |
2000年 | 15篇 |
1999年 | 17篇 |
1998年 | 13篇 |
1997年 | 10篇 |
1996年 | 14篇 |
1995年 | 10篇 |
1994年 | 25篇 |
1993年 | 19篇 |
1992年 | 22篇 |
1991年 | 22篇 |
1990年 | 20篇 |
1989年 | 14篇 |
1987年 | 14篇 |
1986年 | 14篇 |
1985年 | 41篇 |
1984年 | 33篇 |
1983年 | 27篇 |
1982年 | 43篇 |
1981年 | 41篇 |
1980年 | 23篇 |
1979年 | 14篇 |
1978年 | 21篇 |
1977年 | 12篇 |
1976年 | 19篇 |
1975年 | 21篇 |
1974年 | 17篇 |
1973年 | 14篇 |
排序方式: 共有2033条查询结果,搜索用时 31 毫秒
1.
2.
3.
Leo Iu Jos A. Fuentes Mesfin E. Janka Kevin J. Fontenot Matthew L. Clarke 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(7):2142-2146
The hydroformylation of propene to give predominantly iso‐butanal has been achieved; class‐leading selectivity is possible even at higher temperatures that deliver fast conversion. Racemic rhodium complexes of bidentate phospholane phosphites derived from tropos‐biphenols and unusual solvent systems are the key to the selectivity observed. 相似文献
4.
5.
Designs, Codes and Cryptography - In this article we generalize the concepts that were used in the PhD thesis of Drudge to classify Cameron–Liebler line classes in PG $$(n,q), n\ge 3$$ , to... 相似文献
6.
7.
8.
In this work crack formation and development is addressed and implemented in a planar layered reinforced-concrete beam element. The crack initiation and growth is described using the strength criterion in conjunction with exact kinematics of the interlayer connection. In this way a novel embedded-discontinuity beam finite element is derived in which the tensile stresses in concrete at the crack position reaching the tensile strength will trigger a crack to open. Since the element is multi-layered, in this way the crack is allowed to propagate through the depth of the beam. The cracked layer(s) will involve discontinuity in the cross-sectional rotation equal to the crack-profile angle, as well as a discontinuity in the position vector of the layer’s reference line. A bond–slip relationship is superimposed onto this model in a kinematically consistent manner with reinforcement being treated as an additional layer of zero thickness with its own material parameters and a constitutive law implemented in the multi-layered beam element. 相似文献
9.
Reut Levi Guy Moshkovitz Dana Ron Ronitt Rubinfeld Asaf Shapira 《Random Structures and Algorithms》2017,50(2):183-200
Constructing a spanning tree of a graph is one of the most basic tasks in graph theory. Motivated by several recent studies of local graph algorithms, we consider the following variant of this problem. Let G be a connected bounded‐degree graph. Given an edge e in G we would like to decide whether e belongs to a connected subgraph consisting of edges (for a prespecified constant ), where the decision for different edges should be consistent with the same subgraph . Can this task be performed by inspecting only a constant number of edges in G ? Our main results are:
- We show that if every t‐vertex subgraph of G has expansion then one can (deterministically) construct a sparse spanning subgraph of G using few inspections. To this end we analyze a “local” version of a famous minimum‐weight spanning tree algorithm.
- We show that the above expansion requirement is sharp even when allowing randomization. To this end we construct a family of 3‐regular graphs of high girth, in which every t‐vertex subgraph has expansion . We prove that for this family of graphs, any local algorithm for the sparse spanning graph problem requires inspecting a number of edges which is proportional to the girth.
10.
In this paper, we give a direct construction for a set of dice realizing any given tournament T. The construction for a tournament with n vertices requires dice with n sides if n is odd, sides if n is divisible by 4, and sides if mod 4. This appears to be the most efficient general construction to date. Our construction relies only on a standard construction from graph theory. 相似文献