全文获取类型
收费全文 | 3404篇 |
免费 | 139篇 |
国内免费 | 3篇 |
专业分类
林业 | 211篇 |
农学 | 86篇 |
基础科学 | 21篇 |
618篇 | |
综合类 | 490篇 |
农作物 | 172篇 |
水产渔业 | 286篇 |
畜牧兽医 | 1351篇 |
园艺 | 104篇 |
植物保护 | 207篇 |
出版年
2023年 | 20篇 |
2022年 | 15篇 |
2021年 | 61篇 |
2020年 | 64篇 |
2019年 | 69篇 |
2018年 | 62篇 |
2017年 | 68篇 |
2016年 | 84篇 |
2015年 | 48篇 |
2014年 | 86篇 |
2013年 | 127篇 |
2012年 | 147篇 |
2011年 | 235篇 |
2010年 | 108篇 |
2009年 | 98篇 |
2008年 | 188篇 |
2007年 | 210篇 |
2006年 | 222篇 |
2005年 | 204篇 |
2004年 | 209篇 |
2003年 | 196篇 |
2002年 | 191篇 |
2001年 | 41篇 |
2000年 | 39篇 |
1999年 | 40篇 |
1998年 | 51篇 |
1997年 | 50篇 |
1996年 | 44篇 |
1995年 | 37篇 |
1994年 | 35篇 |
1993年 | 29篇 |
1992年 | 32篇 |
1991年 | 29篇 |
1990年 | 33篇 |
1989年 | 29篇 |
1988年 | 21篇 |
1987年 | 20篇 |
1986年 | 16篇 |
1985年 | 27篇 |
1984年 | 19篇 |
1983年 | 25篇 |
1982年 | 23篇 |
1981年 | 21篇 |
1980年 | 19篇 |
1978年 | 18篇 |
1977年 | 10篇 |
1975年 | 16篇 |
1974年 | 16篇 |
1967年 | 8篇 |
1966年 | 7篇 |
排序方式: 共有3546条查询结果,搜索用时 15 毫秒
11.
12.
William F. Krise Michael A. Hendrix Wayne A. Bonney Susan E. Baker-Gordon 《Journal of the World Aquaculture Society》1995,26(4):384-389
The use of saline solutions was tested to determine their efficacy as replacements for ovarian fluid as sperm activators and to eliminate variability encountered with the use of Ovarian fluid. We tested fertilization rate of semen from eight males on Atlantic salmon Salmo salar eggs after five sperm-activating solutions and a non-activating saline were substituted for ovarian fluid. We used solutions shown acceptable for use with other salmonid species. The six solutions tested were a non sperm-activating phosphate-buffered saline (PBS, 7.2 g/L NaCl, 1.48 g/L Na2 HPO4 , 0.43 g/L K H2 PO4 ), a Tris buffer (6.99 g/L NaCl, 3.63 g/L Tris and 2.42 g/L glycine), a Borax buffer (12.2 g boric acid/L in solution 1, 76 g disodium tetraborate/L combined 100:118, then 1 L combined with 3.7 L water and 18 g NaCl), and three solutions of 9.25 g/L (125 mM) NaCl buffered to pH 6.0, 7.5, and 8.9. The latter five solutions activated sperm immediately on contact, while PBS required additional water to activate sperm. The PBS solution was the least effective (mean percent eyed eggs 37.6%) for egg fertilization. The mean percent eyed eggs for the other five saline solutions (range 78% to 86%) were not significantly different. Sperm from one male provided significantly lower egg fertilization (39.6%) when compared with the other seven males (67.2–87.4% egg fertilization). Percent egg fertilization was not related to number of live sperm cells per egg. Our results show that osmotically-balanced sperm-activation solutions, even those with a pH range from 6.0 to 8.9 provide adequate media for fertilization of Atlantic salmon eggs. Fertilization in a deactivation saline and water reactivation of sperm resulted in low egg fertilization. 相似文献
13.
14.
A review of models of landscape change 总被引:23,自引:1,他引:22
William L. Baker 《Landscape Ecology》1989,2(2):111-133
Models of landscape change may serve a variety of purposes, from exploring the interaction of natural processes to evaluating proposed management treatments. These models can be categorized as either whole landscape models, distributional landscape models, or spatial landscape models, depending on the amount of detail included in the models. Distributional models, while widely used, exclude spatial detail important for most landscape ecological research. Spatial models require substantial data, now more readily available, via remote sensing, and more easily manipulated, in geographical information systems. In spite of these technical advances, spatial modelling is poorly developed, largely because landscape change itself is poorly understood.To facilitate further development of landscape models I suggest (1) empirical multivariate studies of landscape change, (2) modelling of individual landscape processes, (3) explicit study of the effect of model scale on model behavior, and (4) scaling-up results of studies, on smaller land areas, that have landscape relevance. 相似文献
15.
16.
17.
18.
19.
Single and multiple dose pharmacokinetics of a novel mirtazapine transdermal ointment in cats 下载免费PDF全文
William Buhles Jessica M. Quimby Daizie Labelle Valentine S. Williams 《Journal of veterinary pharmacology and therapeutics》2018,41(5):644-651
Single and multiple dose pharmacokinetics (PK) of mirtazapine transdermal ointment applied to the inner ear pinna of cats were assessed. Study 1 was a randomized, cross‐over single dose study (n = 8). Cats were treated once with 0.5 mg/kg of mirtazapine transdermal ointment applied topically to the inner ear pinna (treatment) or administered orally (control) and then crossed over after washout. Plasma was collected predose and at specified intervals over 96 hr following dosing. Study 2 was a multiple dose study (n = 8). Cats were treated daily for 14 days with 0.5 mg/kg of mirtazapine transdermal ointment applied topically to the inner pinna. Plasma was collected on Day 13 predose and at specified intervals over 96 hr following the final dose. In Study 1, single transdermal administration of mirtazapine resulted in mean Tmax = 15.9 hr, Cmax = 21.5 ng/mL, AUC0‐24 = 100 ng*hr/mL, AUC0‐∞ = 260 ng*hr/mL and calculated half‐life = 26.8 hr. Single oral administration of mirtazapine resulted in mean Tmax = 1.1 hr, Cmax = 83.1 ng/mL, AUC0‐24 = 377 ng*hr/mL, AUC0‐∞ = 434 ng*hr/mL and calculated half‐life = 10.1 hr. Mean relative bioavailability (F) of transdermal to oral dosing was 64.9%. In Study 2, daily application of mirtazapine for 14 days resulted in mean Tmax = 2.1 hr, Cmax = 39.6 ng/mL, AUC0‐24 = 400 ng*hr/mL, AUC0‐∞ = 647 ng*hr/mL and calculated half‐life = 20.7 hr. Single and repeat topical doses of a novel mirtazapine transdermal ointment achieve measurable plasma concentrations in cats. 相似文献
20.