全文获取类型
收费全文 | 143588篇 |
免费 | 7370篇 |
国内免费 | 85篇 |
专业分类
林业 | 6520篇 |
农学 | 4248篇 |
基础科学 | 896篇 |
16098篇 | |
综合类 | 28565篇 |
农作物 | 5729篇 |
水产渔业 | 6440篇 |
畜牧兽医 | 72426篇 |
园艺 | 1662篇 |
植物保护 | 8459篇 |
出版年
2018年 | 1731篇 |
2017年 | 1897篇 |
2016年 | 1768篇 |
2015年 | 1558篇 |
2014年 | 1859篇 |
2013年 | 5215篇 |
2012年 | 3643篇 |
2011年 | 4421篇 |
2010年 | 2890篇 |
2009年 | 2916篇 |
2008年 | 4381篇 |
2007年 | 4149篇 |
2006年 | 3954篇 |
2005年 | 3722篇 |
2004年 | 3767篇 |
2003年 | 3714篇 |
2002年 | 3584篇 |
2001年 | 4340篇 |
2000年 | 4316篇 |
1999年 | 3314篇 |
1998年 | 1413篇 |
1997年 | 1428篇 |
1995年 | 1614篇 |
1994年 | 1504篇 |
1993年 | 1469篇 |
1992年 | 2994篇 |
1991年 | 3164篇 |
1990年 | 3068篇 |
1989年 | 3134篇 |
1988年 | 2856篇 |
1987年 | 2985篇 |
1986年 | 3113篇 |
1985年 | 3033篇 |
1984年 | 2440篇 |
1983年 | 2244篇 |
1982年 | 1488篇 |
1981年 | 1401篇 |
1979年 | 2224篇 |
1978年 | 1825篇 |
1977年 | 1506篇 |
1976年 | 1478篇 |
1975年 | 1555篇 |
1974年 | 2028篇 |
1973年 | 2045篇 |
1972年 | 2056篇 |
1971年 | 1995篇 |
1970年 | 1840篇 |
1969年 | 1717篇 |
1968年 | 1363篇 |
1967年 | 1493篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
101.
R J Slappendel 《The Veterinary quarterly》1986,8(4):329-333
Based upon a survey of the pathophysiology of haemostasis, the causes of epistaxis in the dog are discussed, and guidelines for a diagnostic and therapeutic approach are given. 相似文献
102.
Two-year field trials with winter wheat cultivars Batis and Toronto were conducted in Southern Bavaria, Germany, to investigate the possible causes of cultivar differences in response to N supply varying in total amount and time of application. Cultivar-related differences in grain yields were observed in treatments with low and medium N supply. High doses of N supply resulted in grain yield adjustment or grain yield advantage for cv. Toronto. The results of this study revealed a consistent, genotypic pattern in response to N fertilization in spite of strong seasonal effects. Systematic modifications in canopy growth rates in response to N supply were of particular relevance and a main factor for differences in tillering intensity resulting in modified stand densities. In the present study, cultivar differences in spike development and interactions with N supply related more to abortion than to initiation processes for number of spikelets and number of flowers per spikelet. High grain density (grains per m2) of cv. Toronto was evident during reproduction stages even under conditions of medium N supply. However, decreased growth rates during the later part of grain filling in combination with low 1000 grain weight, which was barely modified by N fertilization, allowed only partial utilization of this potential. It is assumed that sink limitations were of particular relevance for grain yield development in cv. Toronto, while cv. Batis combined a less intense response to N supply with more stability in the development of grain yield components. 相似文献
103.
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
104.
The accumulation of soluble carbohydrates in vegetative parts of sweet sorghum ( Sorghum bicolor (L.) Moench.) represents an intermediate reserve pool for grain filling as well as an irreversible storage up to maturity. In order to study the effect of Sterility on soluble sugar accumulation in vegetative parts, two cytoplasmic male sterile (CMS) lines of sweet sorghum were compared with their corresponding fertile mamtainers for non-structural carbohydrate concentrations in shoots. Plants were harvested at four different physiological stages. The lines showed significant differences in the yield of non-structural carbohydrates. At maturity, the yields of soluble carbohydrates from vegetative parts of the two sterile lines were 93 % and 43 % higher than the yield of the two corresponding fertile lines. At that stage, sucrose represented about 80 % of total soluble carbohydrates and the higher yield of soluble carbohydrates of sterile lines was mainly due to the higher yield of sucrose. This indicates that the yield of extractable carbohydrates, especially sucrose, in vegetative parts of sweet sorghum could be considerably improved by using sterile lines which are utilized in hybrid production. 相似文献
105.
106.
107.
108.
109.
110.