全文获取类型
收费全文 | 576897篇 |
免费 | 70617篇 |
国内免费 | 214篇 |
专业分类
647728篇 |
出版年
2018年 | 5334篇 |
2016年 | 7205篇 |
2015年 | 10187篇 |
2014年 | 11750篇 |
2013年 | 16131篇 |
2012年 | 18137篇 |
2011年 | 17917篇 |
2010年 | 11671篇 |
2009年 | 11084篇 |
2008年 | 15420篇 |
2007年 | 16174篇 |
2006年 | 14955篇 |
2005年 | 14880篇 |
2004年 | 14723篇 |
2003年 | 13967篇 |
2002年 | 13142篇 |
2001年 | 23786篇 |
2000年 | 24267篇 |
1999年 | 19530篇 |
1998年 | 7148篇 |
1997年 | 7505篇 |
1996年 | 7341篇 |
1995年 | 6952篇 |
1994年 | 6941篇 |
1993年 | 6839篇 |
1992年 | 16931篇 |
1991年 | 16716篇 |
1990年 | 16383篇 |
1989年 | 15955篇 |
1988年 | 14969篇 |
1987年 | 14362篇 |
1986年 | 13447篇 |
1985年 | 13576篇 |
1984年 | 11441篇 |
1983年 | 10037篇 |
1982年 | 7762篇 |
1981年 | 7271篇 |
1980年 | 6825篇 |
1979年 | 11326篇 |
1978年 | 8809篇 |
1977年 | 8076篇 |
1976年 | 7662篇 |
1975年 | 8509篇 |
1974年 | 8803篇 |
1973年 | 8667篇 |
1972年 | 8129篇 |
1971年 | 7076篇 |
1970年 | 6182篇 |
1969年 | 5847篇 |
1968年 | 5343篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
941.
942.
W J Koopman M H Gillis J R David 《Journal of immunology (Baltimore, Md. : 1950)》1973,110(6):1609-1614
943.
Isolation of mucin from human submaxillary secretions 总被引:2,自引:0,他引:2
M M Baig R J Winzler W M Rennert 《Journal of immunology (Baltimore, Md. : 1950)》1973,111(6):1826-1833
944.
Pressure-flow relationships in the isolated canine trachea 总被引:1,自引:0,他引:1
945.
946.
The copigment present in the crystalline blue pigment isolated from Blue Boy cornflowers (Centaurea cyanus L.) was identified as apigenin 4′-O-β-glucoside 7-O-β-d-glucuronide. The NMR spectra of aryl glucuronides are discussed. 相似文献
947.
The presence of prostaglandins (PGs) was determined in gastric juice obtained from 3 conscious dogs, provided with a chronic gastric fistula. Outputs of acid (mequiv min?1) and PGs (pg min?1) were measured in gastric secretions stimulated by pentagastrin (100 or 200 ng kg?1min?1). Prostaglandin activity was estimated, after extraction and thin layer chromatography, by radioimmuno-assay of the PGB formed by treatment with alkali. Tritiated PGs were added to gastric juice for the purpose of correcting for PGs recovery. Using this method, the minimum mass of PGB which could be satisfactorily distinguished from zero was 25 pg. Prostaglandins A2 and E2 were present in pentagastrin-activated gastric secretions and averaged (mean ± SE, n = 8) 200.7 ± 18.1 and 260.1 ± 18.0 pg min?1 respectively. The identity of PGA2 and PGE2 was confirmed by gas liquid chromatography combined with mass spectrometry. The amount of PGE2 converted to PGA2 during extraction, separation and conversion procedures was estimated from the amount of [3H] PGA2 found when only [3H] PGE2 had been added to a sample of gastric juice and averaged 14.5% ± 2.0. Our preliminary results support the possibility that PGE2 and PGA2 may be of physiological importance in the regulation of canine gastric secretions. 相似文献
948.
R B Reisberg 《Life sciences》1974,14(10):1965-1973
Choline acetyltransferase activity in homogenates, or in partially purified extracts of rat brain cerebra, was increased by 11–37% in the presence of ethanol when incubated at 38°C with [14C] acetyl-CoA, choline chloride and alcohol concentrations of 0.17M to 1.02M. In preincubation experiments with enzyme preparations and ethanol, inactivation of the enzyme by the alcohol, which occurs at incubation times longer than 20 minutes, could be at least partially prevented by the addition of certain components of the incubation mixture to the preincubation mixture. 相似文献
949.
950.