全文获取类型
收费全文 | 130083篇 |
免费 | 2639篇 |
国内免费 | 403篇 |
专业分类
化学 | 59218篇 |
晶体学 | 1053篇 |
力学 | 8199篇 |
数学 | 39386篇 |
物理学 | 25269篇 |
出版年
2023年 | 434篇 |
2022年 | 364篇 |
2021年 | 587篇 |
2020年 | 789篇 |
2019年 | 782篇 |
2018年 | 11105篇 |
2017年 | 10782篇 |
2016年 | 7609篇 |
2015年 | 2480篇 |
2014年 | 1975篇 |
2013年 | 3720篇 |
2012年 | 7549篇 |
2011年 | 13958篇 |
2010年 | 7769篇 |
2009年 | 7733篇 |
2008年 | 9724篇 |
2007年 | 11754篇 |
2006年 | 3234篇 |
2005年 | 4147篇 |
2004年 | 3974篇 |
2003年 | 3925篇 |
2002年 | 2729篇 |
2001年 | 1209篇 |
2000年 | 1104篇 |
1999年 | 762篇 |
1998年 | 638篇 |
1997年 | 562篇 |
1996年 | 719篇 |
1995年 | 452篇 |
1994年 | 451篇 |
1993年 | 484篇 |
1992年 | 459篇 |
1991年 | 420篇 |
1990年 | 390篇 |
1989年 | 391篇 |
1988年 | 337篇 |
1987年 | 332篇 |
1986年 | 310篇 |
1985年 | 467篇 |
1984年 | 430篇 |
1983年 | 307篇 |
1982年 | 401篇 |
1981年 | 389篇 |
1980年 | 339篇 |
1979年 | 327篇 |
1978年 | 296篇 |
1976年 | 290篇 |
1975年 | 268篇 |
1974年 | 265篇 |
1973年 | 270篇 |
排序方式: 共有10000条查询结果,搜索用时 26 毫秒
991.
992.
993.
994.
995.
In this paper we prove results in resonance scattering for the Schrödinger operatorP
v=–h
2+V, V being a smooth, short range potential onR
n
. More precisely, for energy near a trapping energy level 0 for the classical system defined by the Hamiltonianp(x,)=
2+V(x), we prove that the scattering phase and the scattering cross sections associated to (P
v, P0) have the Breit-Wigner form (Lorentzian line shape) in the limith0. 相似文献
996.
V. Candelier V. Giordano A. Hamel G. Théobald P. Cérez C. Audoin 《Applied physics. B, Lasers and optics》1989,49(4):365-370
Results obtained in an experimental optically pumped cesium beam frequency standard in which a single semiconductor laser is used for the state selection and the atom detection are reported. The separation between the two interaction regions is equal to 21 cm. This gives a 500 Hz linewidth which is observed with a signal to noise ratio equal to 10,000 in a 1 Hz noise bandwidth. A quartz crystal oscillator is frequency controlled by the atomic transition. The measured short term frequency stability is given by y()=2×10–12–1/2 for 1 s<500 s. Prospects for improvement of this frequency stability are discussed. 相似文献
997.
998.
999.
Gutiérrez de Dios FJ Gómez R Feliu JM 《Langmuir : the ACS journal of surfaces and colloids》2005,21(16):7439-7448
Rhodium adlayers on Pt(100) substrates have been prepared by electrodeposition from dilute Rh(III) acidic solutions. The initially disordered layer is electrochemically annealed by applying a polarization program consisting of high-sweep-rate multicycle sequences between 0.05 and 0.78 V(RHE) in 0.1 M H(2)SO(4). In this way, a pseudomorphic Rh monolayer can be prepared on Pt(100) substrates. The degree of order of the electrochemically annealed layer has been evidenced not only through voltammetric experiments but also by means of scanning tunneling microscopy with atomic resolution for iodine-protected adlayers, which show a c(2 x 2) structure. The electrochemically induced ordering of the Rh adlayer appears to be a consequence of the repeated cycles of adsorption/desorption of H and, especially, oxygenated species. Voltammetry in sulfuric acid solutions permits examination of the energetics of H/anions and OH/O adsorption as a function of the Rh coverage. The first monolayer adsorbs both hydrogen and oxygenated species more strongly than the second one. This can be explained through an electronic effect caused by the underlying Pt(100) substrate. 相似文献
1000.
Strong, low-energy two-photon absorption in extended amine-terminated cyano-substituted phenylenevinylene oligomers 总被引:8,自引:0,他引:8
Chung SJ Rumi M Alain V Barlow S Perry JW Marder SR 《Journal of the American Chemical Society》2005,127(31):10844-10845
Three quadrupolar oligophenylenevinylenes with five rings in the conjugated backbone, terminal donor groups, and various acceptors and/or donors along the backbone were synthesized and their two-photon spectroscopic properties investigated. These chromophores exhibit large two-photon absorption cross sections over a wide wavelength range and two distinct peaks, the strongest of which (deltamax > 3600 GM) is observed at 960-970 nm, a wavelength close to twice the value of the linear absorption maximum (2lambda(1)max). The findings on these chromophores are compared with those for analogous molecules with shorter conjugation length, for which the main two-photon band is at significantly shorter wavelength than 2lambda(1)max. 相似文献