全文获取类型
收费全文 | 203545篇 |
免费 | 2273篇 |
国内免费 | 506篇 |
专业分类
化学 | 111616篇 |
晶体学 | 3661篇 |
力学 | 8014篇 |
综合类 | 11篇 |
数学 | 19288篇 |
物理学 | 63734篇 |
出版年
2020年 | 1746篇 |
2019年 | 1942篇 |
2018年 | 2249篇 |
2017年 | 2371篇 |
2016年 | 3544篇 |
2015年 | 2218篇 |
2014年 | 3589篇 |
2013年 | 9169篇 |
2012年 | 6574篇 |
2011年 | 8086篇 |
2010年 | 5745篇 |
2009年 | 5704篇 |
2008年 | 7226篇 |
2007年 | 7144篇 |
2006年 | 6756篇 |
2005年 | 6124篇 |
2004年 | 5595篇 |
2003年 | 5154篇 |
2002年 | 4920篇 |
2001年 | 6175篇 |
2000年 | 4659篇 |
1999年 | 3530篇 |
1998年 | 2770篇 |
1997年 | 2724篇 |
1996年 | 2629篇 |
1995年 | 2489篇 |
1994年 | 2371篇 |
1993年 | 2203篇 |
1992年 | 2863篇 |
1991年 | 2756篇 |
1990年 | 2704篇 |
1989年 | 2713篇 |
1988年 | 2727篇 |
1987年 | 2736篇 |
1986年 | 2603篇 |
1985年 | 3314篇 |
1984年 | 3327篇 |
1983年 | 2604篇 |
1982年 | 2720篇 |
1981年 | 2773篇 |
1980年 | 2543篇 |
1979年 | 2887篇 |
1978年 | 2870篇 |
1977年 | 2984篇 |
1976年 | 2824篇 |
1975年 | 2561篇 |
1974年 | 2519篇 |
1973年 | 2479篇 |
1972年 | 1704篇 |
1968年 | 1706篇 |
排序方式: 共有10000条查询结果,搜索用时 8 毫秒
81.
Kasper K. Berthelsen Jesper Møller 《Bulletin of the Brazilian Mathematical Society》2002,33(3):351-367
This primer provides a self-contained exposition of the case where spatial birth-and-death processes are used for perfect
simulation of locally stable point processes. Particularly, a simple dominating coupling from the past (CFTP) algorithm and
the CFTP algorithms introduced in [13], [14], and [5] are studied. Some empirical results for the algorithms are discussed.
Received: 30 June 2002 相似文献
82.
The structural evolution in amorphous silicon and germanium thin films has been investigated by high-resolution transmission electron microscopy (HRTEM) in conjunction with autocorrelation function (ACF) analysis. The results established that the structure of as-deposited semiconductor films is of a high density of nanocrystallites embedded in the amorphous matrix. In addition, from ACF analysis, the structure of a-Ge is more ordered than that of a-Si. The density of embedded nanocrystallites in amorphous films was found to diminish with annealing temperature first, then to increase. The conclusions also corroborate well with the results of diminished medium-range order in annealed amorphous films determined previously by a variable coherence microscopy method. 相似文献
83.
Michael K. Kinyon Kenneth Kunen J. D. Phillips 《Proceedings of the American Mathematical Society》2002,130(3):619-624
An A-loop is a loop in which every inner mapping is an automorphism. A problem which had been open since 1956 is settled by showing that every diassociative A-loop is Moufang.
84.
K. Batra V. Prasad M. Mohan 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(2):191-198
The scattering of heavy ion with a multilevel Rydberg atom in the presence of an electromagnetic field is studied. The interaction
of Rydberg atom and the e.m field is explored using non-perturbative quasi-energy technique. Although the results are presented
for selected excitations but in actual calculations we have included many levels of the atom. The effect of various parameters
are shown on collisional excitation process. As an illustration detailed calculations are performed for the inelastic proton-Na
Rydberg atom collision accompanied by the transfer of photons and the effects of dressing due to the field are considered.
The emphasis of the present work is on collision induced transitions especially the case that involves change of orbital as
well as principal quantum number.
Received 26 December 2001 / Received in final form 8 April 2002 Published online 19 July 2002 相似文献
85.
Purification and some properties of squalene-2,3-epoxide: lanosterol cyclase from rat liver 总被引:1,自引:0,他引:1
Squalene-2,3-epoxide: lanosterol cyclase was purified from rat liver in five steps as a soluble and homogeneous protein. The purified enzyme showed a single band on SDS-polyacrylamide gel electrophoresis with a molecular weight of 75 kD. In its native state it behaved as a homo-dimer. The isoelectric point of 5.5 and the apparent Km value for (3S)-squalene-epoxide of 55 microM were estimated for the cyclase. 相似文献
86.
V. K. Malyutenko A. I. Liptuga V. A. Botte V. I. Chernyakhovskii 《Journal of Applied Spectroscopy》1991,55(4):1024-1028
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 4, pp. 624–629, October, 1991. 相似文献
87.
88.
Partially supported by the general research fund at the University of Kansas 相似文献
89.
90.
Ludmila C. Fidale Sarah Köhler Martin H.G. Prechtl Thomas Heinze Omar A. El Seoud 《Cellulose (London, England)》2006,13(5):581-592
The concentrations of water, W, and electrolytes present in solutions of LiCl in N,N-dimethylacetamide, LiCl/DMAc, and of tetrabutylammonium fluoride. x-hydrate in DMSO, TBAF.xW/DMSO can be accurately and expediently determined by three independent methods, UV–vis, FTIR and EMF measurement. The first relies on the use of solvatochromic probes whose spectra are sensitive to solution composition. It is applicable to W/LiCl/DMAc solutions but not to TBAF.xW/DMSO, because the charge-transfer complex bands of the probes are suppressed by strong interactions with the latter electrolyte. Integration of νOH band of water may be employed in order to determine [W], hence [electrolyte] by weight difference. EMF measurement uses ion-selective electrodes in order to determine [electrolyte], hence [W] by weight difference. Results of the latter method were in excellent agreement with those of FTIR. The reason for the failure of Karl Fischer titration is addressed, and the relevance of the results obtained to functionalization of cellulose under homogenous solution conditions is briefly commented on. 相似文献