全文获取类型
收费全文 | 151084篇 |
免费 | 16204篇 |
国内免费 | 8389篇 |
专业分类
化学 | 105904篇 |
晶体学 | 1846篇 |
力学 | 7425篇 |
综合类 | 472篇 |
数学 | 15987篇 |
物理学 | 44043篇 |
出版年
2023年 | 1176篇 |
2022年 | 2482篇 |
2021年 | 3010篇 |
2020年 | 4136篇 |
2019年 | 5490篇 |
2018年 | 4440篇 |
2017年 | 4099篇 |
2016年 | 7475篇 |
2015年 | 6509篇 |
2014年 | 7683篇 |
2013年 | 9951篇 |
2012年 | 9469篇 |
2011年 | 9105篇 |
2010年 | 8088篇 |
2009年 | 7930篇 |
2008年 | 7864篇 |
2007年 | 6911篇 |
2006年 | 6112篇 |
2005年 | 5698篇 |
2004年 | 4930篇 |
2003年 | 4473篇 |
2002年 | 5309篇 |
2001年 | 4301篇 |
2000年 | 3577篇 |
1999年 | 2347篇 |
1998年 | 1891篇 |
1997年 | 1642篇 |
1996年 | 1629篇 |
1995年 | 1401篇 |
1994年 | 1389篇 |
1993年 | 1264篇 |
1992年 | 1243篇 |
1991年 | 1297篇 |
1990年 | 1270篇 |
1989年 | 1154篇 |
1988年 | 1013篇 |
1987年 | 985篇 |
1986年 | 933篇 |
1985年 | 974篇 |
1984年 | 951篇 |
1983年 | 853篇 |
1982年 | 815篇 |
1979年 | 802篇 |
1978年 | 814篇 |
1977年 | 806篇 |
1976年 | 919篇 |
1975年 | 812篇 |
1974年 | 844篇 |
1973年 | 847篇 |
1972年 | 753篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
51.
The structural evolution in amorphous silicon and germanium thin films has been investigated by high-resolution transmission electron microscopy (HRTEM) in conjunction with autocorrelation function (ACF) analysis. The results established that the structure of as-deposited semiconductor films is of a high density of nanocrystallites embedded in the amorphous matrix. In addition, from ACF analysis, the structure of a-Ge is more ordered than that of a-Si. The density of embedded nanocrystallites in amorphous films was found to diminish with annealing temperature first, then to increase. The conclusions also corroborate well with the results of diminished medium-range order in annealed amorphous films determined previously by a variable coherence microscopy method. 相似文献
52.
53.
Guofen Yu Yuanci Gao Shenggang Liu Wenxiang Wang Jin Wu 《International Journal of Infrared and Millimeter Waves》2002,23(8):1261-1269
Analysis of the field distributions in a single biological cell under electromagnetic wave is given. With Debye approximation, the dielectric relaxation of each part of the cell, including the extracellular and cellular media, the cell membrane and the nuclear membrane, was taken into account. Making use of some typical parameters for a cell, the voltage across nuclear and cytoplasma membranes under electromagnetic waves are calculated up to millimeter wave frequency range. The calculated result indicates that it is unlikely to generate electroporation by present available millimeter wave sources. 相似文献
54.
A. I. Bril' V. P. Kabashnikov N. V. Kuz'mina Yu. V. Khodyko 《Journal of Applied Spectroscopy》1991,55(3):934-939
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 3, pp. 478–484, September, 1991. 相似文献
55.
In this paper, we consider a class of functional equations and prove three theorems which give the approximation properties
and error estimates of the optimal polynomial approximation of slution of those functional equations. 相似文献
56.
A. P. Prudnikov Yu. A. Brychkov O. I. Marichev 《Journal of Mathematical Sciences》1991,54(6):1239-1341
Translated from Itogi Nauki i Tekhniki, Seriya Matematicheskii Analiz, Vol. 27, pp. 3–146, 1989. 相似文献
57.
The stressed state of a thick three-layer plate with two circular holes is studied. Resolving functions are expressed in terms of Kolosov-Muskhelishvili integral potentials and modified Bessel functions. The problem is reduced to solving an infinite set of linear algebraic equations.Translated from Teoreticheskaya i Prikladnaya Mekhanika, No. 18, pp. 25–28, 1987. 相似文献
58.
D. Yu. Gladilov S. Yu. Nekhaevskii A. V. Ochkin 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2006,80(12):1934-1939
Various methods for describing the distribution of water in the H2O-tributyl phosphate (TBP) system were considered. An equation for describing the deviations from the Henry law was proposed. A three-parameter equation for calculating the distribution of water in H2O-TBP-solvent systems was derived. It is based on the additive solubility model and allows for the dependence of the activity coefficients on the TBP concentration. Based on the published data, the parameters of the equation for a number of systems were calculated. 相似文献
59.
Wen Zhang Hui Huang Yu Ding Margherita Gavagnin Ernesto Mollo Guido Cimino Yue‐Wei Guo 《Helvetica chimica acta》2006,89(4):813-820
Three new polyoxygenated steroids, muricesteroid ( 1 ), and menellsteroids A ( 2 ) and B ( 3 ), were isolated from two species of the South China Sea gorgonian Muricella flexuosa and Menella verrucosa Brundin , respectively. The structures of these new compounds were elucidated on the basis of extensive spectroscopic analysis, chemical methods and comparison with known related compounds. 相似文献
60.
It is proved that the variety of relevant disjunction lattices has the finite embeddability property. It follows that Avron's relevance logic RMI min has a strong form of the finite model property, so it has a solvable deducibility problem. This strengthens Avron's result that RMI min is decidable. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献