全文获取类型
收费全文 | 1376篇 |
免费 | 15篇 |
国内免费 | 1篇 |
专业分类
化学 | 817篇 |
晶体学 | 9篇 |
力学 | 51篇 |
数学 | 138篇 |
物理学 | 377篇 |
出版年
2021年 | 10篇 |
2020年 | 10篇 |
2019年 | 12篇 |
2016年 | 10篇 |
2015年 | 15篇 |
2014年 | 16篇 |
2013年 | 48篇 |
2012年 | 53篇 |
2011年 | 69篇 |
2010年 | 41篇 |
2009年 | 51篇 |
2008年 | 65篇 |
2007年 | 76篇 |
2006年 | 65篇 |
2005年 | 65篇 |
2004年 | 52篇 |
2003年 | 46篇 |
2002年 | 34篇 |
2001年 | 30篇 |
2000年 | 30篇 |
1999年 | 18篇 |
1998年 | 10篇 |
1997年 | 14篇 |
1996年 | 32篇 |
1995年 | 32篇 |
1994年 | 31篇 |
1993年 | 24篇 |
1992年 | 24篇 |
1991年 | 17篇 |
1990年 | 17篇 |
1989年 | 20篇 |
1988年 | 16篇 |
1987年 | 16篇 |
1986年 | 27篇 |
1985年 | 13篇 |
1984年 | 21篇 |
1983年 | 16篇 |
1982年 | 9篇 |
1981年 | 19篇 |
1980年 | 15篇 |
1979年 | 12篇 |
1978年 | 13篇 |
1977年 | 18篇 |
1976年 | 12篇 |
1975年 | 22篇 |
1974年 | 13篇 |
1973年 | 13篇 |
1972年 | 10篇 |
1971年 | 7篇 |
1969年 | 7篇 |
排序方式: 共有1392条查询结果,搜索用时 46 毫秒
991.
Tatarakis M Beg FN Clark EL Dangor AE Edwards RD Evans RG Goldsack TJ Ledingham KW Norreys PA Sinclair MA Wei MS Zepf M Krushelnick K 《Physical review letters》2003,90(17):175001
Measurements of energetic electron beams generated from ultrahigh intensity laser interactions (I>10(19) W/cm(2)) with dense plasmas are discussed. These interactions have been shown to produce very directional beams, although with a broad energy spectrum. In the regime where the beam density approaches the density of the background plasma, we show that these beams are unstable to filamentation and "hosing" instabilities. Particle-in-cell simulations also indicate the development of such instabilities. This is a regime of particular interest for inertial confinement fusion applications of these beams (i.e., "fast ignition"). 相似文献
992.
Onagi H Carrozzini B Cascarano GL Easton CJ Edwards AJ Lincoln SF Rae AD 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(24):5971-5977
The conformations of two [2]rotaxanes, each comprising alpha-cyclodextrin as the rotor, a stilbene as the axle and 2,4,6-trinitrophenyl substituents as the capping groups, have been examined in solution and in the solid state, using (1)H NMR spectroscopy and X-ray crystallography, respectively. In solution, introducing substituents onto the stilbene prevents the cyclodextrin from being localized over one end of the axle. Instead the cyclodextrin moves back and forth along the substituted stilbene. In the solid state, the axles of the rotaxanes form extended molecular fibres that are separated from each other and aligned along a single axis. The molecular fibres are strikingly similar to those formed by the axle component of one of the rotaxanes in the absence of the cyclodextrin, but in the latter case they are neither separated nor all aligned. 相似文献
993.
Starting from ethylbutyrate, an efficient synthesis of the right hand half of the antibiotic X-14547A has been achieved in which the desired five relative chiral centres were created by an intramolecular Diels-Alder reaction. 相似文献
994.
995.
John T. Edwards Neville J. Ford 《Journal of Computational and Applied Mathematics》2002,140(1-2):275-289
This paper is concerned with the qualitative behaviour of solutions to difference equations. We focus on boundedness and stability of solutions and we present a unified theory that applies both to autonomous and nonautonomous equations and to nonlinear equations as well as linear equations. Our presentation brings together new, established, and hard-to-find results from the literature and provides a theory that is both memorable and easy to apply. We show how the theoretical results given here relate to some of those in the established literature and by means of simple examples we indicate how the use of Lipschitz constants in this way can provide useful insights into the qualitative behaviour of solutions to some nonlinear problems including those arising in numerical analysis. 相似文献
996.
G. D. Wignall L. Mandelkern C. Edwards M. Glotin 《Journal of Polymer Science.Polymer Physics》1982,20(2):245-258
Wide-angle neutron scattering studies have been made of a series of mixed crystal blends of polyethylene and deuterated polyethylene in the range 0.68 ≤ K = 4πλ?1 sinθ ≤ 2.02 Å?1. Recent calculations by Stamm have shown that regularly folded subunits of small numbers (two to ten) of stems should produce an observable modulation of the diffuse scattering pattern of such mixtures in this K range. For both melt- and solution-crystallized blends, no extra signal was observed above the background scattering level. The data are used to place an upper limit (of about four) on the number of stems that could be regularly folded in the (100) and (010) planes for these materials. 相似文献
997.
The intermolecular potentials for the X 2σ and A2Π states of Li… Ar were studied by a variety of multiconfiguration, single-configuration, and perturbation methods (CASPT 2). The A 2Π excited state was calculated to have a well depth of 811 cm?1 at an internuclear separation of 2.59 Å, in excellent agreement with the 810 cm?1 derived from experimental data. A smaller well of 77 cm?1 was found for the X 2σ ground state at an intermolecular separation of 4.8 Å. These results are in better agreement with experimental results than were the previously reported pseudopotential calculations. The comparison of CI calculation with the CAPST 2 results shows that the latter is able to give good results for interacting metal–rare gas systems. © 1995 John Wiley & Sons, Inc. 相似文献
998.
999.
P.J. Bussey C. Raine J.G. Rutherglen P.S.L. Booth L.J. Carroll P.R. Daniel A.W. Edwards C.J. Hardwick J.R. Holt J.N. Jackson J. Norem W.H. Range W. Galbraith V.H. Rajaratnam C. Sutton M.C. Thorne P. Waller 《Physics letters. [Part B]》1976,61(5):479-482
Measurements of the polarised beam asymmetry parameter Σ for eta photoproduction from protons, have been carried out at incident energies of 2.5 GeV and 3.0 GeV, and for various t-values between ?0.2 (GeV/c)2 and ?1.2 (GeV/c)2. The values of Σ are close to +1 for values of |t| less than 0.7 (GeV/c)2, showing that there can be little contribution from unnatural parity exchange in any Regge exchange model of the process, in disagreement with present theories. Differential cross sections for the process werre also measured, and are consistent with those from other experiments. 相似文献
1000.