全文获取类型
收费全文 | 199821篇 |
免费 | 2381篇 |
国内免费 | 653篇 |
专业分类
化学 | 111371篇 |
晶体学 | 3327篇 |
力学 | 7947篇 |
综合类 | 4篇 |
数学 | 19382篇 |
物理学 | 60824篇 |
出版年
2016年 | 2448篇 |
2015年 | 1850篇 |
2014年 | 2587篇 |
2013年 | 8157篇 |
2012年 | 5626篇 |
2011年 | 7026篇 |
2010年 | 4693篇 |
2009年 | 4630篇 |
2008年 | 6325篇 |
2007年 | 6504篇 |
2006年 | 6235篇 |
2005年 | 5722篇 |
2004年 | 5171篇 |
2003年 | 4594篇 |
2002年 | 4470篇 |
2001年 | 5841篇 |
2000年 | 4445篇 |
1999年 | 3561篇 |
1998年 | 2781篇 |
1997年 | 2822篇 |
1996年 | 2792篇 |
1995年 | 2555篇 |
1994年 | 2427篇 |
1993年 | 2320篇 |
1992年 | 2823篇 |
1991年 | 2693篇 |
1990年 | 2630篇 |
1989年 | 2665篇 |
1988年 | 2599篇 |
1987年 | 2603篇 |
1986年 | 2421篇 |
1985年 | 3300篇 |
1984年 | 3304篇 |
1983年 | 2734篇 |
1982年 | 2935篇 |
1981年 | 2859篇 |
1980年 | 2772篇 |
1979年 | 2908篇 |
1978年 | 3148篇 |
1977年 | 2965篇 |
1976年 | 2897篇 |
1975年 | 2761篇 |
1974年 | 2707篇 |
1973年 | 2719篇 |
1972年 | 1761篇 |
1971年 | 1472篇 |
1968年 | 1934篇 |
1967年 | 2132篇 |
1966年 | 1922篇 |
1965年 | 1499篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
921.
922.
H. Leutwyler 《Czechoslovak Journal of Physics》2002,52(2):B9-B27
The lectures review some of the basic concepts relevant for an understanding of the low energy properties of the strong interactions: chiral symmetry, spontaneous symmetry breakdown, Goldstone bosons, quark condensate. The effective field theory used to analyze the low energy structure is briefly sketched. As an illustration, I discuss the implications of the recent data on the decay K→ππeν for the magnitude of the quark condensate. 相似文献
923.
Y. Masuda K. Asahi J. Kura Y. Mori H. Sato H. M. Shimizu 《Hyperfine Interactions》1992,74(1-4):149-157
An experimental scheme of the spin detailed balance in polarized neutron transmission through a polarized nuclear target is
discussed for the T-violation test. The value of the spin detailed balance is estimated by using the data of the scattering
amplitudes. The nuclear polarizations of proton,3He and139La are discussed for the T-violation experiment. 相似文献
924.
Computer-generated holograms from 3D-objects written on twisted-nematic liquid crystal displays 总被引:1,自引:0,他引:1
In order to optimize computer-generated holograms (CGHs) for three-dimensional objects, an extension of the well known Gerchberg-Saxton algorithm is used. Optical reconstructions using an electrically addressed twisted-nematic liquid crystal display are presented. For arbitrary CGHs, reconstructing 3D-objects, we will discuss the problems and solutions associated with periodic replication of holograms. 相似文献
925.
A series of hematites with up to 15 mol% Al substitution was converted to maghemites by reduction in the presence of organic matter, followed by slow oxidation. The maghemites formed were studied by Mössbauer spectroscopy in an external field of 60 kOe at 4 K. This technique allows the determination of site occupancy as well as the canting angle. The spectra are in agreement with a model having both vacancies and Al only in the octahedral sites and small canting angles for both sites. A small dipolar field at the tetrahedral sites was required to fit the line shape. The data indicate that about 10 mol% Al may be a solubility limit in maghemite. 相似文献
926.
We show that it is a NP-complete problem to decide whether a finite poset arises as the (Birkhoff) dual of the Frattini sublattice of some finite distributive lattice.This work was supported in part by Swiss NSF grant 20-32644.91. 相似文献
927.
Summary The RHF and geometry optimization sections of the ab initio quantum chemistry code, GAMESS, have been optimized for a network of parallel microprocessors, Inmos T800-20 transputers, using both indirect and direct SCF techniques. The results indicate great scope for implementation of such codes on small parallel computer systems, very high efficiencies having been achieved, particularly in the cases of direct SCF and geometry optimization with large basis sets.The work, although performed upon one particular parallel system, the Meiko Computing Surface, is applicable to a wide range of parallel systems with both shared and distributed memory. 相似文献
928.
K. Ishikawa H. Nakano H. Masuda C. Kusano Y. Takahashi T. Hamagishi N. Endo 《Fiber and Integrated Optics》1992,11(4):385-394
A 10-Gbit/s optical receiver is developed using low-capacitance HBT IC technology. The HBT allows a cutoff frequency of 45 GHz and a maximum oscillation frequency of 70 GHz. The receiver contains an automatic gain-control amplifier IC with a gain of 16 dB, a bandwidth of 10.7 GHz, and a decision-circuit IC with an ambiguity of 66 mVp-p at a data rate of 10 Gbit/s. The sensitivity of this receiver is -26.5 dBm at a bit error rate of 10-9. Transmission over a 140-km fiber was achieved successfully. 相似文献
929.
Summary. In this paper we are interested in two phase flow problems in porous media. We use a Dual Mesh Method to discretize this
problem with finite volume schemes. In a simplified case (elliptic - hyperbolic system) we prove the convergence of approximate
solutions to the exact solutions. We use the Dual Mesh Method in physically complex problems (heterogeneous cases with non
constant total mobility). We validate numerically the Dual Mesh Method on practical examples by computing error estimates
for different test-cases.
Received March 21, 1997 / Revised version received October 13, 1997 相似文献
930.
L. S. de C. Oliveira M. T. X. Silva A. Vasquez J. A. H. da Jornada 《Hyperfine Interactions》1991,66(1-4):267-270
An exploratory Mössbauer spectroscopy study of the Fe-C system in the C rich region, prepared by high pressure-high temperature treatment near the graphite-diamond stability line, was made. The results obtained for the different processing conditions give no evidence of Fe intercalation in graphite. The presence of some water in the cell produced hydrated Fe complexes, which can explain the deleterious effect of water or hydrogen in the high pressure diamond synthesis. 相似文献