全文获取类型
收费全文 | 105842篇 |
免费 | 6141篇 |
国内免费 | 13篇 |
专业分类
111996篇 |
出版年
2023年 | 595篇 |
2021年 | 1180篇 |
2020年 | 1098篇 |
2019年 | 1067篇 |
2018年 | 2856篇 |
2017年 | 2518篇 |
2016年 | 3429篇 |
2015年 | 4521篇 |
2014年 | 4618篇 |
2013年 | 6168篇 |
2012年 | 7192篇 |
2011年 | 6311篇 |
2010年 | 4145篇 |
2009年 | 3055篇 |
2008年 | 5048篇 |
2007年 | 4840篇 |
2006年 | 4841篇 |
2005年 | 4017篇 |
2004年 | 4020篇 |
2003年 | 3609篇 |
2002年 | 3335篇 |
2001年 | 2710篇 |
2000年 | 2597篇 |
1999年 | 1994篇 |
1998年 | 842篇 |
1997年 | 601篇 |
1996年 | 639篇 |
1995年 | 601篇 |
1992年 | 1242篇 |
1991年 | 1143篇 |
1990年 | 1073篇 |
1989年 | 1143篇 |
1988年 | 976篇 |
1987年 | 980篇 |
1986年 | 892篇 |
1985年 | 950篇 |
1984年 | 787篇 |
1983年 | 690篇 |
1982年 | 571篇 |
1979年 | 858篇 |
1978年 | 600篇 |
1977年 | 591篇 |
1975年 | 698篇 |
1974年 | 759篇 |
1973年 | 725篇 |
1972年 | 670篇 |
1971年 | 604篇 |
1970年 | 658篇 |
1969年 | 725篇 |
1968年 | 681篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
62.
63.
Effect of precursors on biosynthesis of monensins A and B 总被引:1,自引:0,他引:1
Precursors of monensins (acetate, propionate, butyrate, isobutyrate) affect the total production and the relative proportion of monensins A and B. Addition of propionate into the fermentation medium causes a prevalence of monensin B whereas butyrate and isobutyrate stimulate the production of monensin A and suppress the production of monensin B. 相似文献
64.
M Lebl E E Sugg G van Binst P Vander Elst D Tourwé J Slaninová V J Hruby 《International journal of peptide and protein research》1987,30(3):318-322
Analogs of deamino-oxytocin and deamino-oxypressin containing a CH2-NH group instead of an amide bond between positions 8 and 9 were synthesized. All tested compounds exhibit significantly lowered biological activities. 相似文献
65.
H. Štorchová 《Biologia Plantarum》1994,36(3):358-358
66.
M Górska 《Polski tygodnik lekarski (Warsaw, Poland : 1960)》1992,47(46-48):1069-1071
67.
68.
Caitlin M. Cossaboom Laura Córdoba Dianjun Cao Yan-Yan Ni Xiang-Jin Meng 《Journal of virology》2012,86(23):13124-13125
Hepatitis E virus (HEV) is a single-strand positive-sense RNA virus in the family Hepeviridae. The disease caused by HEV, hepatitis E, is an important public health problem in developing countries of Asia and Africa and is also endemic in many industrialized countries, including the United States. HEV has been identified from several other animal species in addition to humans, including the pig, chicken, mongoose, deer, rabbit, ferret, bat, and fish. Here we report the complete genome sequence of the first strain of HEV from rabbits in the United States. Sequence and phylogenetic analyses revealed that the U.S. rabbit HEV is a distant member of the zoonotic genotype 3 HEV, thus raising a concern for potential zoonotic human infection. A unique 90-nucleotide insertion within the X domain of the ORF1 was identified in the rabbit HEV, and this insertion may play a role in the species tropism of HEV. 相似文献
69.
Effect of pharmacological agents on the activity of the circular and longitudinal smooth muscle layers of human fallopian tube ampullar segments 总被引:1,自引:0,他引:1
The in vitro determination of the effects of some pharmacological agents on the outer diameter and axial tension of human Fallopian tube ampullar segments showed that some drugs may act on the circular and longitudinal smooth muscle layers relatively separately. PGF2 alpha elicited an excitatory response in both muscle layers while norepinephrine and isoproterenol decreased the activity. Oxytocin and indomethacin had relatively limited effects on the spontaneous motility of the ampullar segments. The calcium antagonist verapamil inhibited the spontaneous periodic activity. 相似文献
70.