全文获取类型
收费全文 | 3304篇 |
免费 | 159篇 |
国内免费 | 13篇 |
专业分类
化学 | 2435篇 |
晶体学 | 17篇 |
力学 | 95篇 |
数学 | 417篇 |
物理学 | 512篇 |
出版年
2023年 | 32篇 |
2022年 | 47篇 |
2021年 | 73篇 |
2020年 | 93篇 |
2019年 | 94篇 |
2018年 | 80篇 |
2017年 | 48篇 |
2016年 | 131篇 |
2015年 | 110篇 |
2014年 | 116篇 |
2013年 | 201篇 |
2012年 | 242篇 |
2011年 | 276篇 |
2010年 | 156篇 |
2009年 | 121篇 |
2008年 | 226篇 |
2007年 | 201篇 |
2006年 | 167篇 |
2005年 | 155篇 |
2004年 | 159篇 |
2003年 | 111篇 |
2002年 | 129篇 |
2001年 | 44篇 |
2000年 | 45篇 |
1999年 | 24篇 |
1998年 | 33篇 |
1997年 | 25篇 |
1996年 | 22篇 |
1995年 | 27篇 |
1994年 | 12篇 |
1993年 | 17篇 |
1992年 | 12篇 |
1991年 | 20篇 |
1990年 | 9篇 |
1989年 | 13篇 |
1988年 | 7篇 |
1986年 | 7篇 |
1985年 | 14篇 |
1984年 | 18篇 |
1983年 | 8篇 |
1982年 | 15篇 |
1981年 | 16篇 |
1980年 | 15篇 |
1979年 | 18篇 |
1978年 | 21篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1974年 | 9篇 |
1973年 | 8篇 |
1912年 | 3篇 |
排序方式: 共有3476条查询结果,搜索用时 15 毫秒
11.
12.
We consider an M/G/1 queue with symmetric service discipline. The class of symmetric service disciplines contains, in particular, the preemptive
last-come-first-served discipline and the processor-sharing discipline. It has been conjectured in Kella et al. [1] that the
marginal distribution of the queue length at any time is identical for all symmetric disciplines if the queue starts empty.
In this paper we show that this conjecture is true if service requirements have an Erlang distribution. We also show by a
counterexample, involving the hyperexponential distribution, that the conjecture is generally not true.
AMS Subject Classifications Primary—60K25; Secondary—90B22 相似文献
13.
Denis V. Osin 《Archiv der Mathematik》2007,88(5):403-412
The aim of this paper is to show that free Burnside groups of sufficiently large odd exponent are non-amenable in a certain
strong sense. More precisely their left regular representations are isolated from the trivial representation uniformly on
finite generating sets. It follows that free Burnside groups are of uniform exponential growth. This answers a question of
de la Harpe.
This work has been partially supported by the NSF grant DMS-0605093 and by the RFBR Grant # 05-01-00892.
Received: 25 April 2006 相似文献
14.
15.
Using ab initio calculations, we have studied Sc2AC with A=Al, Ga, In and Tl. We show that C 2p and Sc 3d as well as A p and Sc 3d states are hybridized, but the antibonding states in the vicinity of the Fermi level weaken the overall bonding. In terms of the chemical bonding, the influence of the size of the A element is minute. Furthermore, the bulk modulus of the corresponding binary transition metal carbide is not conserved in these phases. Therefore, Sc2AC can be classified as weakly coupled MAX phases according to Sun and co-workers [Z. Sun, D. Music, R. Ahuja, S. Li, J.M. Schneider, Phys. Rev. B 70 (2004) 092102]. It is our ambition that these calculations will stimulate experimental research on these compounds. 相似文献
16.
Denis Prat Françoise Benedetti Lahlou Nait Bouda Gilles Franc Girard 《Tetrahedron letters》2004,45(4):765-768
An industrial synthesis of 11β-aryl-estrone derivatives is described, based on the 1,4-addition of the aryl side-chain, as a cuprate, on to a mixture of allylic 5(10) alpha and beta epoxides, followed by hydrolysis and subsequent aromatization. 相似文献
17.
18.
Juray De Wilde Denis Constales Geraldine J. Heynderickx Guy B. Marin 《International Journal of Multiphase Flow》2007
The propagation speeds of linear waves in gas–solid suspensions depend strongly on the solids volume fraction and the wave frequency. The latter is due to gas–solid momentum transfer and allows a simple test on filtered gas–solid momentum transfer models. Such models may predict linear wave propagation speeds different from those obtained with the non-filtered model at wave frequencies higher than the filter frequency, but not at wave frequencies lower than the filter frequency. 相似文献
19.
20.
Abstract— Ultraviolet irradiation of photosensitive molecules like phenothiazine derivatives leads to the formation of short lived free radicals which are able to reduce stable nitroxide free radicals generally used as spin labels. The measurement of the electron spin resonance signal decay of nitroxides offers a tool for studying the photochemical reaction of phenothiazine derivatives in solution at room temperature, in a 10-5 to 10-2 M concentration range. Analysis of the reaction mechanism shows that the paramagnetic nitroxide is an efficient quencher of the phenothiazine triplet state; this reaction was used to demonstrate the influence of the solvent, quenching by oxygen and the role of the chemical structure of six phenothiazine derivatives on their photoreactivity in solution. 相似文献