全文获取类型
收费全文 | 443343篇 |
免费 | 5045篇 |
国内免费 | 1304篇 |
专业分类
化学 | 238911篇 |
晶体学 | 6515篇 |
力学 | 18947篇 |
综合类 | 13篇 |
数学 | 51140篇 |
物理学 | 134166篇 |
出版年
2021年 | 3856篇 |
2020年 | 4295篇 |
2019年 | 4638篇 |
2018年 | 5925篇 |
2017年 | 5805篇 |
2016年 | 9011篇 |
2015年 | 5704篇 |
2014年 | 8719篇 |
2013年 | 20588篇 |
2012年 | 16074篇 |
2011年 | 19775篇 |
2010年 | 13739篇 |
2009年 | 13539篇 |
2008年 | 18048篇 |
2007年 | 18015篇 |
2006年 | 16734篇 |
2005年 | 14950篇 |
2004年 | 13875篇 |
2003年 | 12190篇 |
2002年 | 12033篇 |
2001年 | 13548篇 |
2000年 | 10161篇 |
1999年 | 7991篇 |
1998年 | 6637篇 |
1997年 | 6402篇 |
1996年 | 6181篇 |
1995年 | 5545篇 |
1994年 | 5449篇 |
1993年 | 5264篇 |
1992年 | 5881篇 |
1991年 | 5969篇 |
1990年 | 5734篇 |
1989年 | 5511篇 |
1988年 | 5539篇 |
1987年 | 5424篇 |
1986年 | 5152篇 |
1985年 | 6648篇 |
1984年 | 6780篇 |
1983年 | 5361篇 |
1982年 | 5464篇 |
1981年 | 5452篇 |
1980年 | 5042篇 |
1979年 | 5409篇 |
1978年 | 5570篇 |
1977年 | 5439篇 |
1976年 | 5380篇 |
1975年 | 4961篇 |
1974年 | 4914篇 |
1973年 | 4936篇 |
1972年 | 3470篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
141.
In a recent paper to this journal (Whitman A M et al 2003 Waves Random Media 13 269-86) we derived a set of coupled equations that describe the intermodal scattering of acoustic radiation in a duct whose speed of sound varies randomly in space and time. In the paper we were mainly interested in modes that were not near cutoff. Here we study the solution of these equations in the vicinity of the cutoff. We find that near cutoff almost all the energy is reflected back independent of the other duct parameters. In addition to presenting these results, we analyse the mathematical structure of the equations in these regions in order to elucidate the reason for this behaviour. 相似文献
142.
We show that there are close relations between extremal problems in dual Brunn-Minkowski theory and isotropic-type properties for some Borel measures on the sphere. The methods we use allow us to obtain similar results in the context of Firey-Brunn-Minkowski theory. We also study reverse inequalities for dual mixed volumes which are related with classical positions, such as ?-position or isotropic position. 相似文献
143.
A homologous series of azomesogens, 2″-[4-(4′-n-alkoxybenzoyloxy)-2-chlorophenylazo] naphthalenes, with lateral chloro groups was synthesised. All the homologues synthesized
exhibit enantiotropic nematic mesophase. The mesomorphic properties of the present series are compared with other structurally
related series to evaluate the effect of lateral chloro group and its position on mesomorphism
This paper was presented at the 10th National Conference on Liquid Crystals held at Bangalore, India during 9–11 October 2003. 相似文献
144.
Yu. M. Dyukarev 《Mathematical Notes》2004,75(1-2):66-82
In this paper, we obtain criteria for the indeterminacy of the Stieltjes matrix moment problem. We obtain explicit formulas for Stieltjes parameters and study the multiplicative structure of the resolvent matrix. In the indeterminate case, we study the analytic properties of the resolvent matrix of the moment problem. We describe the set of all matrix functions associated with the indeterminate Stieltjes moment problem in terms of linear fractional transformations over Stieltjes pairs. 相似文献
145.
146.
147.
We show that, in dimensions equal or greater than three, classical strings do not join or split. This is part of a no-interaction theorem that is also proved. The quantum theory is considered. 相似文献
148.
Blood serum samples were irradiated by monochromatic synchrotron radiation (15 keV) and by 2.4-MeV protons to compare their performance for the detection of trace elements by x-ray fluorescence (XRF) spectrometry. Absolute concentration assignment was based on the addition of an internal standard and on a method which uses the incoherent and coherent radiation as a flux monitor of the incoming beam. Preliminary experiments with a synchrotron XRF microprobe are reported. 相似文献
149.
150.