全文获取类型
收费全文 | 2178篇 |
免费 | 71篇 |
国内免费 | 21篇 |
专业分类
化学 | 1447篇 |
晶体学 | 16篇 |
力学 | 43篇 |
数学 | 383篇 |
物理学 | 381篇 |
出版年
2023年 | 17篇 |
2022年 | 9篇 |
2021年 | 17篇 |
2020年 | 36篇 |
2019年 | 33篇 |
2018年 | 32篇 |
2017年 | 31篇 |
2016年 | 63篇 |
2015年 | 59篇 |
2014年 | 52篇 |
2013年 | 123篇 |
2012年 | 134篇 |
2011年 | 138篇 |
2010年 | 69篇 |
2009年 | 77篇 |
2008年 | 136篇 |
2007年 | 150篇 |
2006年 | 152篇 |
2005年 | 105篇 |
2004年 | 100篇 |
2003年 | 75篇 |
2002年 | 93篇 |
2001年 | 50篇 |
2000年 | 53篇 |
1999年 | 31篇 |
1998年 | 27篇 |
1997年 | 33篇 |
1996年 | 37篇 |
1995年 | 28篇 |
1994年 | 34篇 |
1993年 | 20篇 |
1992年 | 21篇 |
1991年 | 23篇 |
1990年 | 26篇 |
1989年 | 10篇 |
1988年 | 17篇 |
1987年 | 13篇 |
1986年 | 11篇 |
1985年 | 23篇 |
1984年 | 13篇 |
1982年 | 7篇 |
1980年 | 6篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1975年 | 5篇 |
1974年 | 11篇 |
1973年 | 9篇 |
1971年 | 8篇 |
排序方式: 共有2270条查询结果,搜索用时 15 毫秒
1.
Maria Chudnovsky Jim Geelen Bert Gerards Luis Goddyn Michael Lohman Paul Seymour 《Combinatorica》2006,26(5):521-532
Let G=(V,E) be an oriented graph whose edges are labelled by the elements of a group Γ and let A⊂V. An A-path is a path whose ends are both in A. The weight of a path P in G is the sum of the group values on forward oriented arcs minus the sum of the backward oriented arcs in P. (If Γ is not abelian, we sum the labels in their order along the path.) We are interested in the maximum number of vertex-disjoint
A-paths each of non-zero weight. When A = V this problem is equivalent to the maximum matching problem. The general case also includes Mader's S-paths problem. We prove that for any positive integer k, either there are k vertex-disjoint A-paths each of non-zero weight, or there is a set of at most 2k −2 vertices that meets each of the non-zero A-paths. This result is obtained as a consequence of an exact min-max theorem.
These results were obtained at a workshop on Structural Graph Theory at the PIMS Institute in Vancouver, Canada. This research
was partially conducted during the period the first author served as a Clay Mathematics Institute Long-Term Prize Fellow. 相似文献
2.
It is shown that the condition υ > υp (ω), which is necessary in order to trigger the Vavilov-Cherenkov effect, determines the interval of radiated frequencies
and it alone cannot establish a strong restriction to the velocity of the particle. It is exhibited that it is possible to
define a general lower bound for the velocity of the particle, which does not depend on the frequency when both, a specific
response of the medium is taken into account and the mentioned condition is considered. The minimum value of the phase velocity
of light in the medium determines the existence of such general lower bound. 相似文献
3.
Phil Diamond Peter Kloeden Victor Kozyakin Alexei Pokrovskii 《Mathematische Nachrichten》1998,191(1):59-81
The finiteness of computer arithmetic can lead to some dramatic differences between the behaviour of a continuous dynamical system and a computer simulation. A thorough rigorous theoretical analysis of what may or what does happen is usually extremely difficult and to date little has been done even in relatively simple contexts. The comparative behaviour of a rotation mapping in the plane and on a uniform lattice in the plane is one such example. Simulations show that the rounding operator applied to a planar rotation mapping more or less preserves the qualitative behaviour of the original mapping, whereas the application of the truncation operator to a planar rotation can lead to quite different dynamical features. In this paper a theoretical justification of the properties of the planar rotation mappings under truncation to a, uniform integer lattice is provided, in particular properties of boundedness and dissipativity are investigated. 相似文献
4.
5.
6.
7.
8.
Jim Bashkin Clive E. Briant D. Michael P. Mingos Robert W. M. Wardle 《Transition Metal Chemistry》1985,10(3):113-114
Summary [(Ph3P)AuCo(CO)3(PPh3)] has been synthesised from [(Ph3P)AuCo(CO)4], PPh3v and Me3NO in acetonitrile. Its molecular structure, determined by single-crystal x-ray crystallography, consists of an almost linear
P-Au-Co-P arrangement in which the Co atom is in a slightly distorted trigonalbipyramidal geometry, with the Au and P atoms
occupying the apical sites. The Au-Co bond length of 2.450(1) ? is shorter than that reported for [(Ph3P)AuCo(CO)4]. The carbonyl ligands are bent towards the Au atom and the mean Au-Co-C angle is 81(1)°. 相似文献
9.
10.
Transition metal complexes that reversibly bind to DNA have been studied for almost 30 years. In the last few years a variety of new systems have been developed, employing a range of metal ions and ligand architectures. In many cases, high affinity binding and specific selectivities have been observed. These complexes display properties that make them attractive as probes of DNA structure and function, suggesting that they may find a r?le as prototypical tools for a spectrum of applications, from basic molecular biology to medicine. This review presents an overview of some of the structures and properties of such complexes. 相似文献