全文获取类型
收费全文 | 87334篇 |
免费 | 5780篇 |
国内免费 | 13篇 |
专业分类
93127篇 |
出版年
2023年 | 634篇 |
2022年 | 652篇 |
2021年 | 1362篇 |
2020年 | 1206篇 |
2019年 | 1241篇 |
2018年 | 2700篇 |
2017年 | 2474篇 |
2016年 | 3226篇 |
2015年 | 4233篇 |
2014年 | 4284篇 |
2013年 | 5727篇 |
2012年 | 6882篇 |
2011年 | 6349篇 |
2010年 | 3982篇 |
2009年 | 3123篇 |
2008年 | 5004篇 |
2007年 | 4684篇 |
2006年 | 4384篇 |
2005年 | 3758篇 |
2004年 | 3669篇 |
2003年 | 3326篇 |
2002年 | 3051篇 |
2001年 | 1902篇 |
2000年 | 1926篇 |
1999年 | 1431篇 |
1998年 | 708篇 |
1997年 | 532篇 |
1996年 | 524篇 |
1995年 | 487篇 |
1994年 | 406篇 |
1993年 | 366篇 |
1992年 | 693篇 |
1991年 | 609篇 |
1990年 | 538篇 |
1989年 | 487篇 |
1988年 | 499篇 |
1987年 | 432篇 |
1986年 | 390篇 |
1985年 | 447篇 |
1984年 | 425篇 |
1983年 | 288篇 |
1982年 | 278篇 |
1981年 | 215篇 |
1980年 | 227篇 |
1979年 | 266篇 |
1978年 | 252篇 |
1975年 | 235篇 |
1974年 | 246篇 |
1973年 | 250篇 |
1972年 | 206篇 |
排序方式: 共有10000条查询结果,搜索用时 10 毫秒
1.
The influence of fruit ingestion by the bat, Sturnira lilium, on germination of the seeds of the tree Solanum riparium was studied in a secondary rain forest in northwestern Argentina. Bat frequencies in disturbed areas were analyzed by mist net captures. Germination rates were determined for seeds collected from trees and bat feces. S. lilium was the most abundant fruit bat in the study area. Fruit digestion and the passage of seeds through the intestine did not significantly affect germination in S. riparium. In this case the fruit bats, therefore, probably provide only seed dispersal. 相似文献
2.
3.
4.
Four new species ofCayaponia are described and illustrated: three from Brazil (C. cogniauxiana, C. nitida andC. rugosa) and one from Brazil and Bolivia (C. ferruginea). 相似文献
5.
Sebastián Moran Miguel Vizoso Anna Martinez-Cardús Antonio Gomez Xavier Matías-Guiu Sebastián M Chiavenna Andrés G Fernandez Manel Esteller 《Epigenetics》2014,9(6):829-833
A formalin-fixed paraffin-embedded (FFPE) sample usually yields highly degraded DNA, which limits the use of techniques requiring high-quality DNA, such as Infinium Methylation microarrays. To overcome this restriction, we have applied an FFPE restoration procedure consisting of DNA repair and ligation processes in a set of paired fresh-frozen (FF) and FFPE samples. We validated the FFPE results in comparison with matched FF samples, enabling us to use FFPE samples on the Infinium HumanMethylation450 Methylation array. 相似文献
6.
7.
8.
"Pertussis toxin induces tachycardia and impairs the increase in blood pressure produced by alpha 2-adrenergic agonists" 总被引:4,自引:0,他引:4
Administration of purified pertussis toxin to rats induced persistent tachycardia, (observed in conscious rats but not after pithing); as little as 0.05 microgram/100 g produced a significant effect. Pertussis toxin-treatment did not affected the pressor response produced in the pithed rats by the alpha 2-adrenergic agonist methoxamine but markedly diminished the pressor effect of the alpha 2-adrenergic agonists clonidine and azepexole. A role of adenylate cyclase inhibition in the action of postsynaptic vascular alpha 2-adrenergic receptors is suggested. 相似文献
9.
R. Borges-Argez L. Balnbury A. Flowers A. Gimnez-Turba G. Ruiz P.G. Waterman L.M. Pea-Rodríguez 《Phytomedicine》2007,14(7-8):530-533
A number of flavonoids isolated from Lonchocarpus spp. were evaluated for their antiprotozoal and cytotoxic activity. Flavone 6 and chalcone 7 were found to be the most active against Leishmania parasites and against cell cultures of Leukemia P388DI and adenocarcinoma prostate PC-3. 相似文献
10.