全文获取类型
收费全文 | 657633篇 |
免费 | 5309篇 |
国内免费 | 1491篇 |
专业分类
化学 | 319817篇 |
晶体学 | 9250篇 |
力学 | 35762篇 |
综合类 | 24篇 |
数学 | 97155篇 |
物理学 | 202425篇 |
出版年
2021年 | 5618篇 |
2020年 | 6101篇 |
2019年 | 6969篇 |
2018年 | 13427篇 |
2017年 | 13726篇 |
2016年 | 15052篇 |
2015年 | 7274篇 |
2014年 | 11844篇 |
2013年 | 26655篇 |
2012年 | 22871篇 |
2011年 | 31031篇 |
2010年 | 22139篇 |
2009年 | 22319篇 |
2008年 | 28643篇 |
2007年 | 30437篇 |
2006年 | 21161篇 |
2005年 | 21503篇 |
2004年 | 18976篇 |
2003年 | 17765篇 |
2002年 | 16743篇 |
2001年 | 17194篇 |
2000年 | 13369篇 |
1999年 | 10177篇 |
1998年 | 8865篇 |
1997年 | 8675篇 |
1996年 | 8208篇 |
1995年 | 7381篇 |
1994年 | 7326篇 |
1993年 | 7125篇 |
1992年 | 7496篇 |
1991年 | 8093篇 |
1990年 | 7715篇 |
1989年 | 7698篇 |
1988年 | 7475篇 |
1987年 | 7276篇 |
1986年 | 6960篇 |
1985年 | 8880篇 |
1984年 | 9201篇 |
1983年 | 7794篇 |
1982年 | 8081篇 |
1981年 | 7586篇 |
1980年 | 7155篇 |
1979年 | 7831篇 |
1978年 | 8136篇 |
1977年 | 7994篇 |
1976年 | 8011篇 |
1975年 | 7685篇 |
1974年 | 7471篇 |
1973年 | 7866篇 |
1972年 | 5838篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
881.
I. Morgenstern 《Zeitschrift für Physik B Condensed Matter》1987,67(2):265-270
I present an abstraction of the Hopfield-model for neural networks which is suitable for physical chip design using commerically available two-dimensional gate arrays. It can be shown that ±1-bonds combined with a dilution of about 80–90% of the original Hopfield-connections still lead to a comparable performance of the network. Furthermore the learning capability of the chips is discussed. Future extensions concerning programmable designs are outlined. The impact on aspects of brain research is discussed. 相似文献
882.
883.
884.
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
885.
Conclusions When formamide was reacted with phosphorous acid and phosphorus trichloride, the formation of iminobis(methylenediphosphonic) acid was detected.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 865–868, April, 1987.The authors wish to express their graditude to Yu. P. Tsentalovich for helping with the NMR spectral analysis. 相似文献
886.
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
887.
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
888.
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
889.
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
890.