全文获取类型
收费全文 | 656篇 |
免费 | 58篇 |
出版年
2023年 | 5篇 |
2021年 | 21篇 |
2020年 | 12篇 |
2019年 | 8篇 |
2018年 | 18篇 |
2017年 | 9篇 |
2016年 | 17篇 |
2015年 | 28篇 |
2014年 | 28篇 |
2013年 | 24篇 |
2012年 | 37篇 |
2011年 | 42篇 |
2010年 | 17篇 |
2009年 | 20篇 |
2008年 | 30篇 |
2007年 | 35篇 |
2006年 | 29篇 |
2005年 | 22篇 |
2004年 | 25篇 |
2003年 | 17篇 |
2002年 | 20篇 |
2001年 | 16篇 |
2000年 | 14篇 |
1999年 | 15篇 |
1998年 | 10篇 |
1997年 | 8篇 |
1996年 | 6篇 |
1995年 | 8篇 |
1992年 | 12篇 |
1991年 | 7篇 |
1990年 | 12篇 |
1989年 | 11篇 |
1988年 | 10篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 4篇 |
1981年 | 4篇 |
1979年 | 6篇 |
1978年 | 4篇 |
1977年 | 4篇 |
1975年 | 7篇 |
1974年 | 5篇 |
1972年 | 3篇 |
1969年 | 3篇 |
1968年 | 5篇 |
1966年 | 9篇 |
1962年 | 3篇 |
排序方式: 共有714条查询结果,搜索用时 15 毫秒
641.
642.
643.
Ryosuke Shirasaki Geoffrey M. Matthews Sara Gandolfi Ricardo de Matos Simoes Dennis L. Buckley Joseline Raja Vora Quinlan L. Sievers Johanna B. Brüggenthies Olga Dashevsky Haley Poarch Huihui Tang Megan A. Bariteau Michal Sheffer Yiguo Hu Sondra L. Downey-Kopyscinski Paul J. Hengeveld Brian J. Glassner Eugen Dhimolea Constantine S. Mitsiades 《Cell reports》2021,34(1):108532
644.
645.
646.
D W Sepkovic N J Haley C M Axelrad E J LaVoie 《Proceedings of the Society for Experimental Biology and Medicine. Society for Experimental Biology and Medicine (New York, N.Y.)》1984,177(3):412-416
In an attempt to evaluate the observed relationship of chronic cigarette smoking and reduced thyroid hormone activity, the major urinary metabolites of nicotine were administered to rats for 78 weeks. The animals were divided equally into one control (n = 33) and three treatment groups. Treatment group 1 received 0.1% (w/v continine, group 2 received 0.02% pure trans-nicotine-N'-oxide, and group 3 received 0.02% of a trans/cis mixture (64/36%) of nicotine-N'-oxide. Plasma and urinary nicotine and cotinine concentrations were determined as well as a variety of thyroid hormone parameters. Pure trans-nicotine-N'-oxide was more extensively metabolized to its cotinine end product, relative to the diasteromeric N'-oxides, mixture. Serum triiodothyronine (T3) was markedly reduced in animals receiving nicotine-N'-oxides, but was not different in the cotinine treatment group when compared to control values. A reduction in serum thyroxine (T4) values was noted only among those rats receiving the pure trans-nicotine-N'-oxide. The T3/T4 ratio, free T3 index, T3 uptake, and rT3 were altered in animals receiving nicotine-N'-oxides. These findings indicate that specific nicotine metabolites alter thyroid hormone concentrations after chronic low-dose administration and possibly do so through back conversion to the parent compound, nicotine. 相似文献
647.
648.
649.
Genetic differentiation among Hereford populations from Britain, Ireland, Sweden, Canada and New Zealand together with six other beef breeds was assessed using blood type polymorphisms. Changes in the genetic structure of the British Hereford population over time were also examined. Loci surveyed were seven red cell antigen systems (A, B, C, F, L, S, Z), and two serum protein loci (transferrin and albumin). Within group variation was measured by the average expected heterozygosity, and between group relationships by genetic distance. There was significant genetic differentiation among Hereford populations from different countries. Differences between Hereford groups, however, were not as large as differences between breeds. There were also significance differences among British herds. The proportion of Canadian genes in the British 'hybrid' population was estimated to have increased from 0·42 (±0·34) in the 1970s to 0·98 (±0·11) in the 1990s. Canadian Hereford groups were found to be less heterozygous than other groups, and replacement of the British population with Canadian animals may lead to loss of variation. Breeding strategies that preserve original native genes in British Hereford populations should be considered by commercial breeders, in order to prevent the long-term loss of genetic variation within the breed. 相似文献
650.