全文获取类型
收费全文 | 855970篇 |
免费 | 100826篇 |
国内免费 | 336篇 |
专业分类
957132篇 |
出版年
2016年 | 9833篇 |
2015年 | 13328篇 |
2014年 | 15848篇 |
2013年 | 22317篇 |
2012年 | 24934篇 |
2011年 | 25524篇 |
2010年 | 17228篇 |
2009年 | 16085篇 |
2008年 | 23003篇 |
2007年 | 24175篇 |
2006年 | 22576篇 |
2005年 | 21741篇 |
2004年 | 21721篇 |
2003年 | 20716篇 |
2002年 | 20202篇 |
2001年 | 35118篇 |
2000年 | 35486篇 |
1999年 | 28522篇 |
1998年 | 10468篇 |
1997年 | 10962篇 |
1996年 | 10485篇 |
1995年 | 10032篇 |
1994年 | 9855篇 |
1993年 | 9810篇 |
1992年 | 24530篇 |
1991年 | 24369篇 |
1990年 | 23927篇 |
1989年 | 23247篇 |
1988年 | 21864篇 |
1987年 | 21062篇 |
1986年 | 19785篇 |
1985年 | 19791篇 |
1984年 | 16712篇 |
1983年 | 14663篇 |
1982年 | 11393篇 |
1981年 | 10441篇 |
1980年 | 9964篇 |
1979年 | 16388篇 |
1978年 | 12949篇 |
1977年 | 11936篇 |
1976年 | 11388篇 |
1975年 | 12467篇 |
1974年 | 13451篇 |
1973年 | 13186篇 |
1972年 | 12434篇 |
1971年 | 10982篇 |
1970年 | 9714篇 |
1969年 | 9321篇 |
1968年 | 8673篇 |
1967年 | 7511篇 |
排序方式: 共有10000条查询结果,搜索用时 6 毫秒
251.
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
252.
253.
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
254.
255.
J. E. D. Fox 《Economic botany》1971,25(3):221-233
256.
257.
258.
259.
260.