全文获取类型
收费全文 | 402929篇 |
免费 | 3360篇 |
国内免费 | 1306篇 |
专业分类
化学 | 186964篇 |
晶体学 | 6082篇 |
力学 | 21950篇 |
综合类 | 7篇 |
数学 | 68988篇 |
物理学 | 123604篇 |
出版年
2021年 | 3132篇 |
2020年 | 3330篇 |
2019年 | 3760篇 |
2018年 | 15114篇 |
2017年 | 15147篇 |
2016年 | 13120篇 |
2015年 | 4934篇 |
2014年 | 7285篇 |
2013年 | 16142篇 |
2012年 | 15848篇 |
2011年 | 24619篇 |
2010年 | 16283篇 |
2009年 | 16637篇 |
2008年 | 19412篇 |
2007年 | 21407篇 |
2006年 | 12300篇 |
2005年 | 11706篇 |
2004年 | 11243篇 |
2003年 | 10512篇 |
2002年 | 9598篇 |
2001年 | 10598篇 |
2000年 | 7903篇 |
1999年 | 6090篇 |
1998年 | 5130篇 |
1997年 | 4928篇 |
1996年 | 4665篇 |
1995年 | 3973篇 |
1994年 | 3892篇 |
1993年 | 3790篇 |
1992年 | 4144篇 |
1991年 | 4365篇 |
1990年 | 4143篇 |
1989年 | 4065篇 |
1988年 | 3835篇 |
1987年 | 3970篇 |
1986年 | 3739篇 |
1985年 | 4673篇 |
1984年 | 4720篇 |
1983年 | 3920篇 |
1982年 | 4013篇 |
1981年 | 3734篇 |
1980年 | 3691篇 |
1979年 | 3955篇 |
1978年 | 3935篇 |
1977年 | 3924篇 |
1976年 | 3894篇 |
1975年 | 3690篇 |
1974年 | 3626篇 |
1973年 | 3672篇 |
1972年 | 2620篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
21.
22.
D. N. Karimov E. A. Krivandina Z. I. Zhmurova B. P. Sobolev V. A. Bezhanov S. P. Chernov G. M. Shapochkin 《Crystallography Reports》2006,51(6):1009-1015
Crystalline materials that are transparent in the vacuum UV spectral region and currently used have been reviewed. Transmission of crystals of solid solutions with the fluorite structure Ca1?x R xF2+x (R = Sc, Y, La, Yb, Lu) in the UV and vacuum UV spectral regions has been investigated. It is shown that application of different methods of purification of fluorides from some impurities can significantly improve the optical quality of fluoride multicomponent crystals in the short-wavelength spectral region. 相似文献
23.
24.
25.
S. Szegedi P. Raics M. Fayez-Hassan 《Journal of Radioanalytical and Nuclear Chemistry》2004,260(2):429-433
Considering the importance of the X-ray production cross sections for the determination of the element concentrations in a
given material, we have measured them experimentally for Al Si, Sc, Ti, V, Fe, Co, Ni and Cu bombarded by protons with energies
ranging from 40 to 180 keV.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
26.
We consider the optimal service control of a multiclass M/G/1 queueing system in which customers are served nonpreemptively and the system cost rate is additive across classes and increasing convex in the numbers present in each class. Following Whittle's approach to a class of restless bandit problems, we develop a Langrangian relaxation of the service control problem which serves to motivate the development of a class of index heuristics. The index for a particular customer class is characterised as a fair charge for service of that class. The paper develops these indices and reports an extensive numerical investigation which exhibits strong performance of the index heuristics for both discounted and average costs. 相似文献
27.
Andrew Barton 《The Journal of the Operational Research Society》1987,38(10):965-974
This paper describes some work carried out in the Scientific Research and Development Branch (SRDB) of the Home Office, intended to contribute to an overall aim of building up internal expertise in the field of expert systems. This was done by carrying out a number of pilot and demonstrator projects, two of which are described in some detail. The plan, which proved successful, was to build as far as possible on the relevant skills already possessed by an OR group in the branch. The lessons learned from these are summarized in the hope that they will be of use to other groups who wish to become involved in this important area. 相似文献
28.
29.
30.
We present all-atom molecular dynamics simulations ofn-hexane on the basal plane of graphite at monolayer and multilayer coverages. In keeping with experimental data, we find the
presence of ordered adsorbed layers both at single monolayer coverage and when the adsorbed layer coexists with excess liquid
adsorbate. Using a simulation method that does not impose any particular periodicity on the adsorbed layer, we quantitatively
compare our results to the results of neutron diffraction experiments and find a structural transition from a uniaxially incommensurate
lattice to a fully commensurate structure on increasing the coverage from a monolayer to a multilayer. The zig-zag backbone
planes of all the alkane molecules lie parallel to the graphite surface at the multilayer coverage, while a few molecules
are observed to attain the perpendicular orientation at monolayer coverage.
Dedicated to Professor C N R Rao on his 70th birthday 相似文献