全文获取类型
收费全文 | 45956篇 |
免费 | 7454篇 |
国内免费 | 5442篇 |
专业分类
化学 | 32552篇 |
晶体学 | 575篇 |
力学 | 2829篇 |
综合类 | 384篇 |
数学 | 5309篇 |
物理学 | 17203篇 |
出版年
2024年 | 85篇 |
2023年 | 893篇 |
2022年 | 1146篇 |
2021年 | 1578篇 |
2020年 | 1823篇 |
2019年 | 1667篇 |
2018年 | 1469篇 |
2017年 | 1390篇 |
2016年 | 2060篇 |
2015年 | 2068篇 |
2014年 | 2561篇 |
2013年 | 3283篇 |
2012年 | 4187篇 |
2011年 | 4283篇 |
2010年 | 2946篇 |
2009年 | 2822篇 |
2008年 | 2972篇 |
2007年 | 2663篇 |
2006年 | 2523篇 |
2005年 | 2121篇 |
2004年 | 1724篇 |
2003年 | 1274篇 |
2002年 | 1212篇 |
2001年 | 1011篇 |
2000年 | 906篇 |
1999年 | 1003篇 |
1998年 | 839篇 |
1997年 | 750篇 |
1996年 | 789篇 |
1995年 | 671篇 |
1994年 | 613篇 |
1993年 | 525篇 |
1992年 | 503篇 |
1991年 | 405篇 |
1990年 | 355篇 |
1989年 | 252篇 |
1988年 | 228篇 |
1987年 | 204篇 |
1986年 | 149篇 |
1985年 | 167篇 |
1984年 | 146篇 |
1983年 | 120篇 |
1982年 | 83篇 |
1981年 | 63篇 |
1980年 | 52篇 |
1979年 | 36篇 |
1978年 | 27篇 |
1976年 | 27篇 |
1975年 | 31篇 |
1974年 | 23篇 |
排序方式: 共有10000条查询结果,搜索用时 875 毫秒
911.
We make a high-precision Monte Carlo study of two- and three-dimensional self-avoiding walks (SAWs) of length up to 80,000 steps, using the pivot algorithm and the Karp-Luby algorithm. We study the critical exponentsv and 2
4 – as well as several universal amplitude ratios; in particular, we make an extremely sensitive test of the hyperscaling relationdv = 2
4 –. In two dimensions, we confirm the predicted exponentv=3/4 and the hyperscaling relation; we estimate the universal ratios <R
g
2
>/<R
e
2
>=0.14026±0.00007, <R
m
2
>/<R
e
2
>=0.43961±0.00034, and *=0.66296±0.00043 (68% confidence limits). In three dimensions, we estimatev=0.5877±0.0006 with a correctionto-scaling exponent
1=0.56±0.03 (subjective 68% confidence limits). This value forv agrees excellently with the field-theoretic renormalization-group prediction, but there is some discrepancy for
1. Earlier Monte Carlo estimates ofv, which were 0.592, are now seen to be biased by corrections to scaling. We estimate the universal ratios <R
g
2
>/<R
e
2
>=0.1599±0.0002 and *=0.2471±0.0003; since *>0, hyperscaling holds. The approach to * is from above, contrary to the prediction of the two-parameter renormalization-group theory. We critically reexamine this theory, and explain where the error lies. In an appendix, we prove rigorously (modulo some standard scaling assumptions) the hyperscaling relationdv = 2
4 – for two-dimensional SAWs. 相似文献
912.
913.
914.
915.
916.
917.
918.
Fission fluctuation-dissipation dynamics of heavy nuclei has been studied using Langevin Monte Carlo simulations. The covariant form of the fission transport equation and the coefficients related to it are investigated. To learn about the influence of the dynamics from the ground state to the saddle point on the kinetic energy distributions we have studied various systems and compared the calculations both starting from the ground state and from the saddle point. Both the mean total kinetic energy of the fission fragments and its variances can fit with the experimental values in terms of a finite neck radius as scission condition.This work was supported by the National Natural Science Foundation of China. 相似文献
919.
J. N. Spencer Jarusha DeGarmo I. M. Paul Qing He Xiaoming Ke Zhenqing Wu C. H. Yoder Shuyun Chen J. E. Mihalick 《Journal of solution chemistry》1995,24(6):601-609
Calorimetric studies of the inclusion complexes of straight and branched alcohols and of diols with alpha-cyclodextrin (-CD) have been carried out in water solvent. The data suggest that straight and branched chain alcohols enter the cavity of -CD alkyl end first. The hydroxyl group hydrogen bonds to the outer oxygen ring of the cyclodextrin. For branched chain alcohols the longer alkyl part of the molecule penetrates the -CD cavity up to the hydroxyl group. Diols form two hydrogen bonds to the outer oxygen ring of the cyclodextrin with some penetration into its interior. 相似文献
920.
This paper deals with the GI x /G/c queueing system in a steady state. We refine a diffusion approximation method incorporating the constraint of traffic conservation for general queueing systems. An approximate expression for the distribution of the number of customers is obtained. Numerical results are presented to show that the refined model provides improved performance. 相似文献