全文获取类型
收费全文 | 247767篇 |
免费 | 3443篇 |
国内免费 | 1453篇 |
专业分类
化学 | 122657篇 |
晶体学 | 3230篇 |
力学 | 8886篇 |
综合类 | 61篇 |
数学 | 24407篇 |
物理学 | 65648篇 |
无线电 | 27774篇 |
出版年
2020年 | 1890篇 |
2019年 | 2079篇 |
2018年 | 2669篇 |
2017年 | 2723篇 |
2016年 | 3934篇 |
2015年 | 2591篇 |
2014年 | 3889篇 |
2013年 | 9421篇 |
2012年 | 8133篇 |
2011年 | 9964篇 |
2010年 | 7222篇 |
2009年 | 7297篇 |
2008年 | 9872篇 |
2007年 | 10234篇 |
2006年 | 9722篇 |
2005年 | 8907篇 |
2004年 | 8041篇 |
2003年 | 7143篇 |
2002年 | 7006篇 |
2001年 | 7812篇 |
2000年 | 6101篇 |
1999年 | 4571篇 |
1998年 | 3891篇 |
1997年 | 3892篇 |
1996年 | 3758篇 |
1995年 | 3375篇 |
1994年 | 3504篇 |
1993年 | 3361篇 |
1992年 | 3510篇 |
1991年 | 3582篇 |
1990年 | 3397篇 |
1989年 | 3284篇 |
1988年 | 3098篇 |
1987年 | 2788篇 |
1986年 | 2792篇 |
1985年 | 3619篇 |
1984年 | 3648篇 |
1983年 | 3026篇 |
1982年 | 3263篇 |
1981年 | 3024篇 |
1980年 | 2793篇 |
1979年 | 2952篇 |
1978年 | 3177篇 |
1977年 | 3180篇 |
1976年 | 3197篇 |
1975年 | 2955篇 |
1974年 | 3043篇 |
1973年 | 3086篇 |
1972年 | 2412篇 |
1971年 | 1941篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
971.
972.
Zupac D. Baum K.W. Kosier S.L. Schrimpf R.D. Galloway K.F. 《Electron Device Letters, IEEE》1991,12(10):546-549
The effect of noncatastrophic positive human body model (HBM) electrostatic discharge (ESD) stress on n-channel power MOSFETs is radically different from that on p-channel MOSFETs. In n-channel transistors, the stress causes negative shifts of the current-voltage characteristics indicative of positive charge trapping in the gate oxide. In p-channel transistors, the stress increases the drain-to-source leakage current, probably due to localized avalanche electron injection from the p-doped drain 相似文献
973.
974.
Partially supported by NSF Grant DMS-9004123 and ARO through MSI Cornell (DAAG 29-85-C-0018) 相似文献
975.
976.
Zboril R. Mashlan M. Machala L. Walla J. Barcova K. Martinec P. 《Hyperfine Interactions》2004,156(1-4):403-410
Hyperfine Interactions - The natural garnets from almandine (Fe3Al2Si3O12)–pyrope (Mg3Al2Si3O12) series with the iron to magnesium atomic ratio ranging from 0.2 to 1 were characterised and... 相似文献
977.
This paper delineates the first steps in a systematic quantitative study of the spacetime fluctuations induced by quantum
fields in an evaporating black hole. We explain how the stochastic gravity formalism can be a useful tool for that purpose
within a low-energy effective field theory approach to quantum gravity. As an explicit example we apply it to the study of
the spherically-symmetric sector of metric perturbations around an evaporating black hole background geometry. For macroscopic
black holes we find that those fluctuations grow and eventually become important when considering sufficiently long periods
of time (of the order of the evaporation time), but well before the Planckian regime is reached. In addition, the assumption
of a simple correlation between the fluctuations of the energy flux crossing the horizon and far from it, which was made in
earlier work on spherically-symmetric induced fluctuations, is carefully analyzed and found to be invalid. Our analysis suggests
the existence of an infinite amplitude for the fluctuations of the horizon as a three-dimensional hypersurface. We emphasize
the need for understanding and designing operational ways of probing quantum metric fluctuations near the horizon and extracting
physically meaningful information.
Dedicated to Rafael Sorkin on the occasion of his 60th birthday. 相似文献
978.
A novel soft-switching full-bridge DC/DC converter: analysis,design considerations, and experimental results at 1.5 kW, 100 kHz 总被引:1,自引:0,他引:1
The addition of an external commutating inductor and two clamp diodes to the phase-shifted PWM (pulsewidth modulated) full-bridge DC/DC converter substantially reduces the switching losses of the transistors and the rectifier diodes, under all loading conditions. The authors give analyses, practical design considerations, and experimental results for a 1.5 kW converter with 60 V, 25 A output, operating at 100 kHz clock frequency and 95% efficiency 相似文献
979.
L Dalla Libera M Fasolo P Cavallini E Ratti G Gaviraghi 《Journal of chromatography. A》1991,566(2):427-434
Avian myosin light-chain kinase from smooth muscle of the gizzard and its catalytic domain, derived from the intact enzyme by trypsin digestion, was purified within 30-40 min by both analytical and preparative anion-exchange high-performance liquid chromatography. The proteins obtained were more than 95% pure and retained their biological activity. The high-performance anion-exchange chromatography protocols represent a significant decrease in purification time when compared with conventional ion-exchange chromatography. 相似文献
980.