全文获取类型
收费全文 | 101345篇 |
免费 | 5479篇 |
国内免费 | 4646篇 |
专业分类
化学 | 57607篇 |
晶体学 | 1341篇 |
力学 | 5616篇 |
综合类 | 322篇 |
数学 | 12255篇 |
物理学 | 34329篇 |
出版年
2023年 | 765篇 |
2022年 | 1755篇 |
2021年 | 2174篇 |
2020年 | 2355篇 |
2019年 | 2567篇 |
2018年 | 2952篇 |
2017年 | 2876篇 |
2016年 | 3559篇 |
2015年 | 2495篇 |
2014年 | 3551篇 |
2013年 | 5072篇 |
2012年 | 5188篇 |
2011年 | 5505篇 |
2010年 | 4354篇 |
2009年 | 4360篇 |
2008年 | 4614篇 |
2007年 | 4308篇 |
2006年 | 3972篇 |
2005年 | 3508篇 |
2004年 | 3127篇 |
2003年 | 2793篇 |
2002年 | 2915篇 |
2001年 | 2582篇 |
2000年 | 2014篇 |
1999年 | 1631篇 |
1998年 | 1559篇 |
1997年 | 1352篇 |
1996年 | 1327篇 |
1995年 | 1093篇 |
1994年 | 1169篇 |
1993年 | 1108篇 |
1992年 | 1072篇 |
1991年 | 1132篇 |
1990年 | 1120篇 |
1989年 | 1044篇 |
1988年 | 921篇 |
1987年 | 915篇 |
1986年 | 881篇 |
1985年 | 925篇 |
1984年 | 919篇 |
1983年 | 822篇 |
1982年 | 801篇 |
1979年 | 803篇 |
1978年 | 814篇 |
1977年 | 806篇 |
1976年 | 920篇 |
1975年 | 814篇 |
1974年 | 846篇 |
1973年 | 848篇 |
1972年 | 753篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
42.
43.
Analytical expressions are obtained that describe the changes in the degree of coherence and in the thickness of the coherence layers occurring upon propagation of a dispersed broadband laser beam. It is found that the greater the tilting of the coherence layers with respect to the phase fronts, the more rapidly the spatial coherence is violated with increasing distance. A comparison with the case of an undispersed beam is performed. It is shown that, as the beam propagates, the decrease in the degree of coherence is accompanied by the appearance of spatial fluctuations of this parameter. The degree of mutual coherence of intersecting dispersed beams with parallel correlated coherence layers, which determines the efficiency of their coherent interaction, is investigated. The existence of spatial fluctuations of the degree of mutual coherence is established. 相似文献
44.
Yu. V. Brezhnev 《Theoretical and Mathematical Physics》2002,133(3):1657-1662
We construct Dubrovin equations and trace formulas for finite-band operators with trigonal curves and present some examples. 相似文献
45.
46.
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
47.
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
48.
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
49.
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
50.
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