全文获取类型
收费全文 | 547165篇 |
免费 | 53372篇 |
国内免费 | 472篇 |
专业分类
601009篇 |
出版年
2018年 | 9730篇 |
2017年 | 9431篇 |
2016年 | 9442篇 |
2015年 | 7478篇 |
2014年 | 8940篇 |
2013年 | 12552篇 |
2012年 | 15854篇 |
2011年 | 20680篇 |
2010年 | 14670篇 |
2009年 | 13879篇 |
2008年 | 17878篇 |
2007年 | 19571篇 |
2006年 | 12955篇 |
2005年 | 13143篇 |
2004年 | 12725篇 |
2003年 | 12661篇 |
2002年 | 12319篇 |
2001年 | 26439篇 |
2000年 | 26721篇 |
1999年 | 20345篇 |
1998年 | 6139篇 |
1997年 | 6447篇 |
1996年 | 6122篇 |
1995年 | 5567篇 |
1994年 | 5506篇 |
1993年 | 5519篇 |
1992年 | 16151篇 |
1991年 | 15975篇 |
1990年 | 15518篇 |
1989年 | 15230篇 |
1988年 | 14220篇 |
1987年 | 13341篇 |
1986年 | 12016篇 |
1985年 | 12142篇 |
1984年 | 9610篇 |
1983年 | 8402篇 |
1982年 | 5960篇 |
1981年 | 5372篇 |
1980年 | 5066篇 |
1979年 | 8869篇 |
1978年 | 6857篇 |
1977年 | 6288篇 |
1976年 | 5827篇 |
1975年 | 6670篇 |
1974年 | 7107篇 |
1973年 | 7031篇 |
1972年 | 6691篇 |
1971年 | 6223篇 |
1970年 | 5126篇 |
1969年 | 4812篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
991.
A. V. Timofeev 《Plasma Physics Reports》2003,29(8):683-687
The conditions under which the energy of the electron Langmuir oscillations can escape from the plasma into vacuum are determined in the simplest model of a plane slab of an inhomogeneous cold magnetized plasma in a uniform magnetic field. 相似文献
992.
993.
994.
N W Cornell J J Stegeman M J Kerich B R Woodin 《Comparative biochemistry and physiology. B, Comparative biochemistry》1986,85(3):669-674
Hepatic metabolites and enzymes in the marine fish, scup or porgy (Stenotomus chrysops), were determined in freeze-clamped tissue taken either within a day of removing fish from their natural habitat or after scup were held in captivity for 6-8 months. The same determinations were made for liver from fed or 48 hr-starved rats (Mus norvegicus albinus). Compared with rat liver, both groups of fish had, per gram of liver, higher contents of AMP, inorganic phosphate, glucose, glucose-6-phosphate, malate, glutamate and NH4+. ATP was lower in fish liver, and ADP, lactate and pyruvate contents were similar in rats and fish. Fish held in captivity had significantly lower pyruvate, alpha-ketoglutarate, and cytosolic free NAD+/NADH and higher cytosolic free NADPH/NADP+. These decreases were similar to those seen when starved rats were compared with fed ones. In scup liver, glucose-6-phosphate dehydrogenase was 3-8 times, malic enzyme about 2 times, and alanine aminotransferase 2-4 times higher than those activities in rat liver. Those results and a higher cytosolic free NADPH/NADP+ are consistent with the liver being the major site of lipogenesis in fish. 相似文献
995.
T L Marshak M Sh Avrushchenko 《Biulleten' eksperimental'no? biologii i meditsiny》1986,102(10):477-479
The changes in the size of Purkinje cell (PC) nucleolus in the lateral and medial cerebellum zones were studied in dogs with different degree of neurologic status recovery after clinical death of various etiology and duration. PC always possess one nucleolus in the control and experimental groups. In the case of complete neurologic status recovery of animals the area of PC nucleolus increases in both zones studied, irrespective of the cause of clinical death. In the case of neurologic disorders the increase in PC nucleolus area is clearly expressed only in the medial zone of the cerebellum, being insignificant in the lateral zone. It is suggested that adaptive characteristics of PC are distinct in the two compared zones, which leads to greater PC vulnerability in the lateral zone during deep hypoxia. 相似文献
996.
J. T. Mogoll’on 《Mycopathologia》1982,80(2):65-72
The ninth Colombian case of Lobomycosis is presented, along with a review of the Colombian literature. The clinical, histopathological, and mycological aspects are summarized emphasizing the peculiar birefringent appearance of Lobomyces when examined under polarized light. 相似文献
997.
U. Behrens N. Fedoroff A. Laird M. Müller-Neumann P. Starlinger J. Yoder 《Molecular & general genetics : MGG》1984,194(1-2):346-347
Summary The cloning of the controlling element Ac from the wx-m7 allele of Zea mays is described. The cloned fragment carries a 4.3 kb insertion that by restriction analysis is indistinguishable from the Ac insertion in Ac wx-m9. It is located approximately 2.5 kb upstream of the Ac wx-m9 insertion.
Offprint requests to: P. Starlinger 相似文献
998.
999.
Effects of mutation on the downfield proton nuclear magnetic resonance spectrum of the 5S RNA of Escherichia coli 总被引:4,自引:0,他引:4
The imino proton spectra of several mutants of the 5S RNA of Escherichia coli are compared with that of the wild type. Three of the variants discussed are point mutations, and the fourth is a deletion mutant lacking bases 11-69 of the parent sequence, all obtained by site-directed mutagenesis techniques. The spectroscopic effects of mutation are limited in all cases, and the differences between normal and mutant spectra can be used to make or confirm the assignments of resonances. Several new assignments in the 5S spectrum are reported. Spectroscopic differences due to sequence differences permit the products of single genes within the 5S gene family to be distinguished and their fates followed by NMR. 相似文献
1000.
D. Y. Sorokin E. N. Detkova G. Muyzer 《Extremophiles : life under extreme conditions》2010,14(1):71-77
Evidence on the utilization of simple fatty acids by sulfate-reducing bacteria (SRB) at extremely haloalkaline conditions are practically absent, except for a single case of syntrophy by Desulfonatronum on acetate. Our experiments with sediments from soda lakes of Kulunda Steppe (Altai, Russia) showed sulfide production with sulfate as electron acceptor and propionate and butyrate (but not acetate) as an electron donor at a pH 10–10.5 and a salinity 70–180 g l?1. With propionate as substrate, a highly enriched sulfidogenic culture was obtained in which the main component was identified as a novel representative of the family Syntrophobacteraceae. With butyrate as substrate, a pure SRB culture was isolated which oxidized butyrate and some higher fatty acids incompletely to acetate. The strain represents the first haloalkaliphilic representative of the family Desulfobacteraceae and is described as Desulfobotulus alkaliphilus sp. nov. 相似文献