全文获取类型
收费全文 | 80709篇 |
免费 | 4379篇 |
国内免费 | 93篇 |
专业分类
林业 | 3236篇 |
农学 | 2080篇 |
基础科学 | 470篇 |
8786篇 | |
综合类 | 15713篇 |
农作物 | 3180篇 |
水产渔业 | 3504篇 |
畜牧兽医 | 42786篇 |
园艺 | 874篇 |
植物保护 | 4552篇 |
出版年
2019年 | 761篇 |
2018年 | 1127篇 |
2017年 | 1253篇 |
2016年 | 1089篇 |
2015年 | 936篇 |
2014年 | 1236篇 |
2013年 | 2701篇 |
2012年 | 2186篇 |
2011年 | 2660篇 |
2010年 | 1673篇 |
2009年 | 1775篇 |
2008年 | 2665篇 |
2007年 | 2499篇 |
2006年 | 2357篇 |
2005年 | 2206篇 |
2004年 | 2146篇 |
2003年 | 2210篇 |
2002年 | 1998篇 |
2001年 | 2434篇 |
2000年 | 2491篇 |
1999年 | 1913篇 |
1998年 | 732篇 |
1997年 | 718篇 |
1996年 | 729篇 |
1995年 | 822篇 |
1993年 | 750篇 |
1992年 | 1581篇 |
1991年 | 1789篇 |
1990年 | 1669篇 |
1989年 | 1667篇 |
1988年 | 1495篇 |
1987年 | 1560篇 |
1986年 | 1622篇 |
1985年 | 1573篇 |
1984年 | 1200篇 |
1983年 | 1078篇 |
1982年 | 713篇 |
1979年 | 1174篇 |
1978年 | 907篇 |
1977年 | 768篇 |
1975年 | 780篇 |
1974年 | 1031篇 |
1973年 | 1038篇 |
1972年 | 1055篇 |
1971年 | 1016篇 |
1970年 | 1012篇 |
1969年 | 913篇 |
1968年 | 817篇 |
1967年 | 813篇 |
1966年 | 744篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
81.
82.
83.
84.
85.
86.
87.
Ariana M.P. Nap Yvonne W.E.A. Pollak Walter E. van den Brom Ad Rijnberk DVM PhD 《Journal of veterinary internal medicine / American College of Veterinary Internal Medicine》1994,8(4):302-303
Thyroidal 99m TcO4 (pertechnetate) uptake percentages were determined in unanesthetized euthyroid (n = 13) and hyperthyroid (n = 18) cats. Maximal uptakes were observed 60 minutes after IV injection of the radionuclide and ranged from 0.3 to 3.9% of the dose in euthyroid cats (median 2.23%) and from 5.2% to 23.9% of the dose in hyperthyroid cats (median 14.8%) ( P < .05). There were no overlaps in pertechnetate uptake percentages during any of the intervals evaluated. It is concluded that the optimal time for visualization of the thyroid by 99m TcO4 -scanning is 60 minutes after IV injection of the radionuclide. Calculation of the percentage uptake is of additional diagnostic value. 相似文献
88.
89.
J. Gonzalez-Soriano E. Rodriguez-Veiga P. Martinez-Sainz S. Mayayo-Vicente P. Marin-Garcia 《Anatomia, histologia, embryologia》1995,24(1):61-65
As in the number of mammals, the most prominent feature of the ganglion-cell layer in the retina of the German shepherd dog is the sharp increase in the density of ganglion cells in the central area. There is an area of maximum density and also a ‘cat-like’ visual streak, located dorsal to the optic disc. The isodensity lines of ganglion-cell distribution is roughly concentric. Their values vary from 5300-13 000 cells/mm2 in the central area, with the cells densely packed, to 1000 cells/mm2 or less in the periphery, where the cells are sparsely distributed. There were some individual differences amongst the animals studied, although all of them were pure-bred dogs. This suggests that the configuration of the retina in the canine species is not only dependent on the breed itself but also on some other parameters such as phylogenetic heritage, environment, aptitude, lifestyle, or even training. 相似文献
90.
P E Holt 《Research in veterinary science》1989,47(1):117-118
Pressure changes in the urinary bladder due to respiration were measured in 75 bitches. The changes fell within a narrow range (0.5 to 2.5 cm water) and were unaffected by size or whether the bitches were entire or spayed. Significant differences were found, however, between continent (mean +/- SD, 1.1 +/- 0.4 cm water) and incontinent (mean +/- SD, 1.4 +/- 0.5 cm water) animals (P less than 0.01). 相似文献