全文获取类型
收费全文 | 558415篇 |
免费 | 69176篇 |
国内免费 | 189篇 |
专业分类
627780篇 |
出版年
2018年 | 4931篇 |
2016年 | 6673篇 |
2015年 | 9531篇 |
2014年 | 11247篇 |
2013年 | 15554篇 |
2012年 | 17476篇 |
2011年 | 17451篇 |
2010年 | 11482篇 |
2009年 | 10689篇 |
2008年 | 15240篇 |
2007年 | 15823篇 |
2006年 | 14664篇 |
2005年 | 14151篇 |
2004年 | 14013篇 |
2003年 | 13450篇 |
2002年 | 12791篇 |
2001年 | 22999篇 |
2000年 | 23468篇 |
1999年 | 18891篇 |
1998年 | 6874篇 |
1997年 | 7248篇 |
1996年 | 6999篇 |
1995年 | 6733篇 |
1994年 | 6724篇 |
1993年 | 6622篇 |
1992年 | 16394篇 |
1991年 | 16292篇 |
1990年 | 15962篇 |
1989年 | 15516篇 |
1988年 | 14509篇 |
1987年 | 13925篇 |
1986年 | 13047篇 |
1985年 | 13196篇 |
1984年 | 11071篇 |
1983年 | 9787篇 |
1982年 | 7565篇 |
1981年 | 7117篇 |
1980年 | 6665篇 |
1979年 | 11058篇 |
1978年 | 8617篇 |
1977年 | 7921篇 |
1976年 | 7542篇 |
1975年 | 8347篇 |
1974年 | 8640篇 |
1973年 | 8472篇 |
1972年 | 8011篇 |
1971年 | 6962篇 |
1970年 | 6105篇 |
1969年 | 5765篇 |
1968年 | 5247篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
161.
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
162.
163.
Establishment of pregnancy in cattle has been proposed to depend on production of a conceptus protein, bovine trophoblast protein-1 (bTP-1), which has a high degree of sequence homology with bovine interferon-alpha (bIFN-alpha), especially the alpha II subfamily. A preparation of bovine conceptus secretory proteins enriched for bTP-1 has antiviral and physico-chemical properties similar to other bIFN-alpha. Antiviral activity is initially detectable in uterine flushings on Day 14 of pregnancy, when the conceptus measures 4-5 mm in length, and increases as the conceptus elongates through Day 18. Day 17 conceptuses produce more than 10(6) U antiviral activity during 24 h of culture. All IFNs induce the enzyme 2',5'-oligoadenylate synthetase, which catalyzes production of 2',5'-oligo(A), which in turn is involved in antiviral and growth inhibitory effects of IFNs. This enzyme activity is induced in Madin-Darby bovine kidney cells by the partially purified bTP-1 preparation similarly to IFN-alpha, -beta, and -gamma. Likewise, the partially purified bTP-1 and bIFN-alpha 1 induce 2',5'-oligo(A) synthetase activity in monolayers of endometrial epithelial and stromal cells. Compared to epithelial cells, stromal cells have higher baseline activity of 2'-5'-oligo(A) synthetase activity (p less than 0.01) and show a greater degree of induction in the presence of either the partially purified bTP-1 or bIFN-alpha 1 (p less than 0.01). Also, 2',5'-oligo(A) synthetase of endometrial stromal cells is induced to a greater degree by our enriched bTP-1 preparation than by bIFN-alpha 1 (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
164.
165.
166.
167.
168.
169.
170.