全文获取类型
收费全文 | 887616篇 |
免费 | 9304篇 |
国内免费 | 2874篇 |
专业分类
化学 | 449973篇 |
晶体学 | 12370篇 |
力学 | 44688篇 |
综合类 | 28篇 |
数学 | 135419篇 |
物理学 | 257316篇 |
出版年
2021年 | 6560篇 |
2020年 | 7283篇 |
2019年 | 7984篇 |
2018年 | 19552篇 |
2017年 | 19323篇 |
2016年 | 20486篇 |
2015年 | 9880篇 |
2014年 | 14667篇 |
2013年 | 36568篇 |
2012年 | 30759篇 |
2011年 | 42442篇 |
2010年 | 28582篇 |
2009年 | 28657篇 |
2008年 | 36777篇 |
2007年 | 38637篇 |
2006年 | 29267篇 |
2005年 | 27312篇 |
2004年 | 25431篇 |
2003年 | 23363篇 |
2002年 | 22260篇 |
2001年 | 22919篇 |
2000年 | 17944篇 |
1999年 | 14035篇 |
1998年 | 12040篇 |
1997年 | 11765篇 |
1996年 | 11423篇 |
1995年 | 10362篇 |
1994年 | 10057篇 |
1993年 | 9729篇 |
1992年 | 10507篇 |
1991年 | 10874篇 |
1990年 | 10296篇 |
1989年 | 10158篇 |
1988年 | 10178篇 |
1987年 | 9827篇 |
1986年 | 9395篇 |
1985年 | 12515篇 |
1984年 | 12932篇 |
1983年 | 10852篇 |
1982年 | 11661篇 |
1981年 | 11108篇 |
1980年 | 10687篇 |
1979年 | 11209篇 |
1978年 | 11618篇 |
1977年 | 11456篇 |
1976年 | 11381篇 |
1975年 | 10852篇 |
1974年 | 10527篇 |
1973年 | 11056篇 |
1972年 | 7530篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The variational approach based on the covariant quantization method for the curved Einstein space is applied. 相似文献
992.
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
993.
The precision of intensity modulated fiber optic sensor systems mainly is restricted by the attenuation characteristics of the analog fiber optical data link. Special encoding and referencing schemes are used to overcome this data link dependence. In this paper encoding and referencing principles for optical sensors are outlined and compared. Especially the two wavelengths referencing and the optical delay line processing techniques are discussed in more detail and results are presented. 相似文献
994.
995.
996.
R. J. Saykally K. M. Evenson D. A. Jennings L. R. Zink A. Scalabrin 《International Journal of Infrared and Millimeter Waves》1987,8(6):653-662
Twenty new cw FIR laser lines in CD3OH, optically pumped by a CO2 laser, are reported. The frequencies of 39 of the stronger laser lines were measured relative to stabilized CO2 lasers with a fractional uncertainty, as determined by the reproducibility of the FIR frequency itself, of 2 parts in 107.Contribution of the U.S. Government, not subject to copyright. 相似文献
997.
T.S. Khlebnicova V.G. Isakova A.V. Baranovsky E.V. Borisov F.A. Lakhvich 《Journal of fluorine chemistry》2006,127(12):1564-1569
A one-pot synthesis of 2-perfluoroalkanoylcyclohexane-1,3-diones via C-acylation of cyclohexane-1,3-diones with N-perfluoroacylimidazole as an acylating agent is reported. A reaction was examined with isolated N-trifluoroacetylimidazole and with N-perfluoroacylimidazoles generated in situ from perfluorocarboxylic acid anhydrides or perfluorocarboxylic acids. 相似文献
998.
An analytical solution of a linearized problem of the emission of periodic internal waves by part of a plane which oscillates with a small amplitude in an arbitrary direction in a viscous exponentially stratified fluid is constructed. Solutions of the dispersion equation are given for all positions of the emitting surface (arbitrary, vertical, horizontal, and critical when one of the beam propagation directions is collinear with the emitting surface). The possibility of transition to the case of a uniform fluid, which is important for applications, is analyzed. 相似文献
999.
D. N. Karimov E. A. Krivandina Z. I. Zhmurova B. P. Sobolev V. A. Bezhanov S. P. Chernov G. M. Shapochkin 《Crystallography Reports》2006,51(6):1009-1015
Crystalline materials that are transparent in the vacuum UV spectral region and currently used have been reviewed. Transmission of crystals of solid solutions with the fluorite structure Ca1?x R xF2+x (R = Sc, Y, La, Yb, Lu) in the UV and vacuum UV spectral regions has been investigated. It is shown that application of different methods of purification of fluorides from some impurities can significantly improve the optical quality of fluoride multicomponent crystals in the short-wavelength spectral region. 相似文献
1000.
P.A. Grillet 《Acta Mathematica Hungarica》2005,106(4):301-315
Summary Three weak variants of compactness which lie strictly between compactness and quasicompactness, are introduced. Their basic properties are studied. The interplay with mapping and their direct and inverse preservation under mappings are investigated. In the process three decompositions of compactness are observed. 相似文献