全文获取类型
收费全文 | 477545篇 |
免费 | 4146篇 |
国内免费 | 1770篇 |
专业分类
化学 | 234561篇 |
晶体学 | 7006篇 |
力学 | 24056篇 |
综合类 | 7篇 |
数学 | 77217篇 |
物理学 | 140614篇 |
出版年
2021年 | 2956篇 |
2020年 | 3268篇 |
2019年 | 3759篇 |
2018年 | 14584篇 |
2017年 | 14285篇 |
2016年 | 12752篇 |
2015年 | 5279篇 |
2014年 | 7154篇 |
2013年 | 18849篇 |
2012年 | 17359篇 |
2011年 | 26687篇 |
2010年 | 16698篇 |
2009年 | 16936篇 |
2008年 | 21351篇 |
2007年 | 23507篇 |
2006年 | 14692篇 |
2005年 | 14366篇 |
2004年 | 13502篇 |
2003年 | 12533篇 |
2002年 | 11406篇 |
2001年 | 12262篇 |
2000年 | 9410篇 |
1999年 | 7296篇 |
1998年 | 6042篇 |
1997年 | 6086篇 |
1996年 | 5694篇 |
1995年 | 5258篇 |
1994年 | 4982篇 |
1993年 | 4942篇 |
1992年 | 5408篇 |
1991年 | 5452篇 |
1990年 | 5187篇 |
1989年 | 5036篇 |
1988年 | 5110篇 |
1987年 | 5007篇 |
1986年 | 4790篇 |
1985年 | 6328篇 |
1984年 | 6674篇 |
1983年 | 5511篇 |
1982年 | 5933篇 |
1981年 | 5812篇 |
1980年 | 5631篇 |
1979年 | 5703篇 |
1978年 | 6010篇 |
1977年 | 5819篇 |
1976年 | 6070篇 |
1975年 | 5524篇 |
1974年 | 5603篇 |
1973年 | 5957篇 |
1972年 | 3776篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
Ph. Laurent M. Abgrall Ch. Jentsch P. Lemonde G. Santarelli A. Clairon I. Maksimovic S. Bize Ch. Salomon D. Blonde J.F. Vega O. Grosjean F. Picard M. Saccoccio M. Chaubet N. Ladiette L. Guillet I. Zenone Ch. Delaroche Ch. Sirmain 《Applied physics. B, Lasers and optics》2006,84(4):683-690
In this paper we describe the cold atom clock PHARAO, designed for microgravity operation. All elements of the PHARAO engineering model have been manufactured and delivered to CNES, the French space agency. We present the clock design, its main characteristics, and initial science operation. PHARAO is one of the main components of the Atomic Clock Ensemble in Space payload that is scheduled to fly on board the International Space Station in 2010. PACS 07.87.+v; 06.30.Ft; 95.55.Sh; 32.80.Pj 相似文献
992.
R. Knizikevi?ius 《Applied Surface Science》2006,253(3):1581-1583
The ion-beam-assisted etching of silicon in Cl2 environment is considered. The theoretically calculated dependences of silicon etching rate on the flux of Cl2 molecules at different ion current densities are compared with experimentally measured. The composition of the adsorbed layer is determined. It is found that SiCl2 molecules prevail in the adsorbed layer. The reciprocal of relative concentration of SiCl2 molecules in the adsorbed layer linearly depends on the ion-to-neutral flux ratio. 相似文献
993.
T. Rietmann S. Sohn M. Schröder D. Lipinsky H.F. Arlinghaus 《Applied Surface Science》2006,252(19):6640-6643
In order to improve quantification of high mass ions, the influence of cluster composition on detection efficiencies has been studied using a TOF-SIMS IV with the extended capability of postaccelerating ions up to 20 keV. In this experimental study, we focus on the comparison of detection efficiencies for three types of negatively charged secondary cluster ions: gold-alkanethiolate-clusters (AuxMy), gold-sulfur-clusters (AuxSy) and gold-clusters (Aux). The clusters were sputtered from self-assembled monolayers of hexadecanethiols on gold substrates using 10 keV Ar+ primary ions. The detection efficiencies were derived on the basis of a function for the secondary electron yield and a fourth-order approximated Poisson probability distribution for electron propagation and amplification within the microchannel plate.In addition to the well-known dependence of detection efficiencies on ion mass and energy, which has already been studied for positively charged ions, we were able to show a similar behaviour for the investigated negatively charged secondary ions. We have observed major variations among the three types of clusters at similar mass and energy as predicted in a theoretical approach. The observed differences are due to the different composition of the investigated clusters which has a major influence on the kinetic ion induced electron emission within the microchannel plate. For the first time it was possible to experimentally verify these predictions for detection efficiencies. 相似文献
994.
Highly ordered composite nanowires with multilayer Ni/Cu and NiFe/Cu have been fabricated by pulsed electrodeposition into
nanoporous alumina membrane. The diameter of wires can be easily varied by pore size of alumina, ranging from 30 to 100 nm.
The applied potential and the duration of each potential square pulse determine the thickness of the metal layers. The nanowires
have been characterized by transmission electron microscopy (TEM), magnetic force microscopy (MFM), and vibrating sample magnetometer
(VSM) measurements. The MFM images indicate that every ferromagnetic layer separated by Cu layer was present as single isolated
domain-like magnet. This technique has potential use in the measurement and application of magnetic nanodevices. 相似文献
995.
This paper considers the general synchronization dynamics of coupled Van der Pol–Duffing oscillators. The linear and nonlinear stability analysis on the synchronization process is derived through the Whittaker method and the Floquet theory in addition to the multiple time scales method. A stability map displaying different dynamical states of the system is performed. Numerical simulation is carried out to support and to complement the accuracy of the analytical treatment. 相似文献
996.
997.
De Ming ZHU Ying SUN 《数学学报(英文版)》2007,23(8):1495-1504
In this paper, we study the dynamical behavior for a 4-dimensional reversible system near its heteroclinic loop connecting a saddle-focus and a saddle. The existence of infinitely many reversible 1-homoclinic orbits to the saddle and 2-homoclinic orbits to the saddle-focus is shown. And it is also proved that, corresponding to each 1-homoclinic (resp. 2-homoclinic) orbit F, there is a spiral segment such that the associated orbits starting from the segment are all reversible 1-periodic (resp. 2-periodic) and accumulate onto F. Moreover, each 2-homoclinic orbit may be also accumulated by a sequence of reversible 4-homoclinic orbits. 相似文献
998.
I. A. Begishev R. A. Ganeev V. V. Gorbushin A. A. Gulamov Sh. R. Kamalov T. Usmanov 《Journal of Applied Spectroscopy》1989,51(5):1218-1221
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 51, No. 5, pp. 867–870, November, 1989. 相似文献
999.
1000.
Microemulsions (dispersions of water droplets, typical radius about 10 nm, in oil) show a particular percolation pattern, a so-called dynamical percolation. Predictions of scaling theory and Monte Carlo simulations were compared with experimental static and frequency dependent conductivity data. The latter gives evidence of two different time scales of charge transport.Dedicated to Professor Harry Thomas on the occasion of his 60th birthday 相似文献