全文获取类型
收费全文 | 448306篇 |
免费 | 2838篇 |
国内免费 | 1008篇 |
专业分类
化学 | 213216篇 |
晶体学 | 7008篇 |
力学 | 24206篇 |
综合类 | 15篇 |
数学 | 63398篇 |
物理学 | 144309篇 |
出版年
2021年 | 3228篇 |
2020年 | 3409篇 |
2019年 | 4092篇 |
2018年 | 12000篇 |
2017年 | 12528篇 |
2016年 | 10717篇 |
2015年 | 4796篇 |
2014年 | 7271篇 |
2013年 | 16430篇 |
2012年 | 16148篇 |
2011年 | 24700篇 |
2010年 | 16774篇 |
2009年 | 16911篇 |
2008年 | 22293篇 |
2007年 | 25030篇 |
2006年 | 13305篇 |
2005年 | 16588篇 |
2004年 | 13478篇 |
2003年 | 12574篇 |
2002年 | 10962篇 |
2001年 | 11120篇 |
2000年 | 8633篇 |
1999年 | 6408篇 |
1998年 | 5341篇 |
1997年 | 5376篇 |
1996年 | 5106篇 |
1995年 | 4597篇 |
1994年 | 4540篇 |
1993年 | 4337篇 |
1992年 | 4901篇 |
1991年 | 5016篇 |
1990年 | 4851篇 |
1989年 | 4737篇 |
1988年 | 4717篇 |
1987年 | 4704篇 |
1986年 | 4436篇 |
1985年 | 5659篇 |
1984年 | 6023篇 |
1983年 | 4978篇 |
1982年 | 5096篇 |
1981年 | 5053篇 |
1980年 | 4734篇 |
1979年 | 5140篇 |
1978年 | 5233篇 |
1977年 | 5319篇 |
1976年 | 5422篇 |
1975年 | 5029篇 |
1974年 | 4911篇 |
1973年 | 5178篇 |
1972年 | 3617篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
81.
82.
83.
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
84.
An overview of theoretical and experimental studies of the coherent type-B e
+
e-pair production by photons in aligned crystals performed at Nuclear Physics Institute at Tomsk Polytechnic University is given. 相似文献
85.
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
86.
Sanzharov N. A. Yarovoi A. T. Bekhtereva E. S. Ulenikov O. N. 《Russian Physics Journal》2002,45(10):1024-1031
Analytical formulas are derived that describe the dependences of the transition probabilities in vibrational-rotational spectra of XY3-type molecules with C
3v
symmetry on the rotational quantum numbers. 相似文献
87.
A. D. Smirnov 《Journal of Applied Spectroscopy》1991,54(1):33-38
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 54, No. 1, pp. 46–50, January, 1991. 相似文献
88.
In intonation research, prominence-lending pitch movements have either been described on a linear or on a logarithmic frequency scale. An experiment has been carried out to check whether pitch movements in speech intonation are perceived on one of these two scales or on a psychoacoustic scale representing the frequency selectivity of the auditory system. This last scale is intermediary between the other two scales. Subjects matched the excursion size of prominence-lending pitch movements in utterances resynthesized in different pitch registers. Their task was to adjust the excursion size in a comparison stimulus in such a way that it lent equal prominence to the corresponding syllable in a fixed test stimulus. The comparison stimulus and the test stimulus had pitches running parallel on either the logarithmic frequency scale, the psychoacoustic scale, or the linear frequency scale. In one-half of the experimental sessions, the test stimulus was presented in the low register, while the comparison stimulus was presented in the high register, and, conversely, for the other half of the sessions. The result is that, in all cases, stimuli are matched in such a way that the average excursion sizes in different registers are equal on the psychoacoustic scale. 相似文献
89.
It is proved that biorthogonal polynomials obey two different kinds of Christoffel-Darboux-type formulae, one linking polynomials with a different parameter and one combining polynomials with different degrees. This is used to produce a mixed recurrence relation, which is valid for all biorthogonal polynomials. This recurrence relation establishes several results on interlacing property of zeros of successive biorthogonal polynomials and leads to a new result on the interlace of zeros of orthogonal polynomials (of equal degrees) with respect to two distributionsdψ(x) andx p dψ(x), 0<p≤1, with support in either [0, 1] or [1, ∞). 相似文献
90.