全文获取类型
收费全文 | 401595篇 |
免费 | 2271篇 |
国内免费 | 768篇 |
专业分类
化学 | 187942篇 |
晶体学 | 6104篇 |
力学 | 21624篇 |
综合类 | 10篇 |
数学 | 60323篇 |
物理学 | 128631篇 |
出版年
2020年 | 3003篇 |
2019年 | 3530篇 |
2018年 | 11643篇 |
2017年 | 12341篇 |
2016年 | 9957篇 |
2015年 | 4116篇 |
2014年 | 6287篇 |
2013年 | 13838篇 |
2012年 | 13853篇 |
2011年 | 22249篇 |
2010年 | 15246篇 |
2009年 | 15519篇 |
2008年 | 20193篇 |
2007年 | 22949篇 |
2006年 | 10991篇 |
2005年 | 14431篇 |
2004年 | 11597篇 |
2003年 | 11013篇 |
2002年 | 9445篇 |
2001年 | 9540篇 |
2000年 | 7293篇 |
1999年 | 5402篇 |
1998年 | 4744篇 |
1997年 | 4520篇 |
1996年 | 4371篇 |
1995年 | 4014篇 |
1994年 | 3930篇 |
1993年 | 3856篇 |
1992年 | 4126篇 |
1991年 | 4377篇 |
1990年 | 4240篇 |
1989年 | 4215篇 |
1988年 | 4121篇 |
1987年 | 4169篇 |
1986年 | 3906篇 |
1985年 | 5012篇 |
1984年 | 5069篇 |
1983年 | 4431篇 |
1982年 | 4594篇 |
1981年 | 4368篇 |
1980年 | 4135篇 |
1979年 | 4591篇 |
1978年 | 4769篇 |
1977年 | 4681篇 |
1976年 | 4870篇 |
1975年 | 4614篇 |
1974年 | 4485篇 |
1973年 | 4854篇 |
1972年 | 3552篇 |
1971年 | 3104篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
Q. Sun Q. Wang X.G. Gong V. Kumar Y. Kawazoe 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(1):77-81
We report results of the atomic and electronic structures of Al7C cluster using ab initio molecular dynamics with ultrasoft pseudopotentials and generalized gradient approximation. The lowest energy structure is
found to be the one in which carbon atom occupies an interstitial position in Al7 cluster. The electronic structure shows that the recent observation [Chem. Phys. Lett. 316, 31 (2000)] of magic behavior of Al7C- cluster is due to a large highest occupied and lowest unoccupied molecular orbital (HOMO-LUMO) gap which makes Al7C- chemically inert. These results have further led us to the finding of a new neutral magic cluster Al7N which has the same number of valence electrons as in Al7C- and a large HOMO-LUMO gap of 1.99 eV. Further, calculations have been carried out on (Al7N)2 to study interaction between magic clusters.
Received 28 July 2001 相似文献
62.
The present paper analyzes the properties of structural phase transitions under the extremal conditions of high pressures. In the context of the theory of density functional (TDF), the pressures of the B1–B2 transitions are calculated for small alkali-halide crystals as functions of the crystal size. The size effect of the B1–B2 transition – an increase in the transition pressure with the decreasing crystal grain radius – has been established for all investigated halides except lithium fluoride for which the dependence is reverse. 相似文献
63.
B. Dubrulle F. Hersant 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(3):379-386
We generalize an analogy between rotating and stratified shear flows. This analogy is summarized in Table 1. We use this analogy
in the unstable case (centrifugally unstable flow vs. convection) to compute the torque in Taylor-Couette configuration, as a function of the Reynolds number. At low Reynolds
numbers, when most of the dissipation comes from the mean flow, we predict that the non-dimensional torque G = T/ν2
L, where L is the cylinder length, scales with Reynolds number R and gap width η, G = 1.46η3/2(1 - η)-7/4
R
3/2. At larger Reynolds number, velocity fluctuations become non-negligible in the dissipation. In these regimes, there is no
exact power law dependence the torque versus Reynolds. Instead, we obtain logarithmic corrections to the classical ultra-hard (exponent 2) regimes: G = 0.50
. These predictions are found to be in excellent agreement with avail-able experimental data. Predictions for scaling of velocity
fluctuations are also provided.
Received 7 June 2001 and Received in final form 7 December 2001 相似文献
64.
65.
Electrical resistivity of U3Tein4, U2Te3 (cubic) and UTe3 has been measured over temperature range 4.2–300 K. The two former compounds appear to be semimetallic conductors while the last one has semiconducting character. The results are discussed in the terms of available magnetic data. 相似文献
66.
67.
68.
69.
Results of an experiment on investigating the fluctuations of a sound signal with a frequency of 295 Hz on a stationary 32-km-long acoustic path in a shallow sea are presented. Hydrological conditions on the path were characterized by the presence of a weak thermocline and a frequent occurrence of intense internal wave trains. The space-time characteristics of these internal waves were measured in detail. Experimental evidence of the repetition of the forms of internal solitons in the variations of the amplitude and phase of an acoustic signal was obtained. 相似文献
70.
Possibilities for the control of the parameters of free-polarization decay (FPD), optical nutation, and photon echo (PE) using the dressing field are studied. Coherent transients are generated with the Stark switching technique and are detected in the radiation of the probe field polarized orthogonally to the dressing field. The evolution-operator technique is employed in the calculations. The experiments are performed at the R(4, 3) transition of the 0 ? 1 v3 13CH3F vibrational band with the radiation of a cw CO2 laser. It is theoretically and experimentally demonstrated that FPD and PE are suppressed upon an increase in the intensity of the dressing field. The observed shapes of the transient FPD and PE signals and their variations with the dressing field intensity are in qualitative agreement with the results of the calculations. 相似文献