全文获取类型
收费全文 | 137878篇 |
免费 | 7509篇 |
国内免费 | 124篇 |
专业分类
林业 | 5949篇 |
农学 | 4075篇 |
基础科学 | 859篇 |
15789篇 | |
综合类 | 25133篇 |
农作物 | 5357篇 |
水产渔业 | 6357篇 |
畜牧兽医 | 71852篇 |
园艺 | 1581篇 |
植物保护 | 8559篇 |
出版年
2018年 | 1835篇 |
2017年 | 2031篇 |
2016年 | 1854篇 |
2015年 | 1586篇 |
2014年 | 2004篇 |
2013年 | 4927篇 |
2012年 | 3653篇 |
2011年 | 4359篇 |
2010年 | 2864篇 |
2009年 | 2950篇 |
2008年 | 4433篇 |
2007年 | 4164篇 |
2006年 | 3898篇 |
2005年 | 3678篇 |
2004年 | 3539篇 |
2003年 | 3698篇 |
2002年 | 3364篇 |
2001年 | 4103篇 |
2000年 | 4114篇 |
1999年 | 3197篇 |
1998年 | 1293篇 |
1997年 | 1354篇 |
1995年 | 1504篇 |
1994年 | 1293篇 |
1993年 | 1344篇 |
1992年 | 2726篇 |
1991年 | 3013篇 |
1990年 | 2875篇 |
1989年 | 2901篇 |
1988年 | 2675篇 |
1987年 | 2687篇 |
1986年 | 2781篇 |
1985年 | 2693篇 |
1984年 | 2193篇 |
1983年 | 1935篇 |
1982年 | 1333篇 |
1979年 | 2099篇 |
1978年 | 1616篇 |
1977年 | 1462篇 |
1976年 | 1331篇 |
1975年 | 1452篇 |
1974年 | 1875篇 |
1973年 | 1894篇 |
1972年 | 1887篇 |
1971年 | 1779篇 |
1970年 | 1754篇 |
1969年 | 1626篇 |
1968年 | 1433篇 |
1967年 | 1516篇 |
1966年 | 1314篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
Reduced levels of total iron binding capacity and unsaturated iron binding capacity were observed in the blood of trichinous and iron-injected trichinous pigs. No change was observed in their serum iron and saturation concentration levels. Also, reduced iron concentration levels were observed in the livers of trichinous pigs, while increased iron concentration levels were observed in the spleens of trichinous pigs and the livers and spleens of iron-injected pigs. No difference was found with regard to weight gains, number of larvae per gram of tissues, or histologic characteristics of 'nurse cells'. 相似文献
92.
93.
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
94.
95.
96.
97.
Fifty six dogs of mixed age and sex were acquired from farms in the Otago/Southland region, and maintained at the Hydatid Research Unit, Taieri, where 43 were each fed two Tueniu ovis cysts. All were bled fortnightly for six or 12 weeks. Coded sera were sent to Wallaceville Animal Research Centre for testing using ELISA, with antigen from T. ovis scoleces. Dog treatments were identified after all tests were complete. A discriminant level was derived from the mean absorbance value plus three standard deviations of 56 sera taken at time zero and 78 sera from serially bled uninfected dogs. None of these 134 sera registered as a false positive using this discriminant level. The data showed no significant deviation from normality, and the expected frequency of the occurrence of false positives is therefore less than 0.14%. Four weeks after infection 63% of dogs proved to be infected were serologically positive, rising to 78% after 6 weeks. When worms were removed by anthelmintic treatment, ELISA absorbance levels decreased. Four weeks after removal 70% of previously infected dogs remained positive, decreasing to 30% after 6 weeks. Six weeks after infection the sensitivity of the test was 78%, and the specificity 63%. However, if dogs with positive ELISA absorbance levels, but which did not purge worms, were regarded as having had worms, the respective figures would be 82% and 100%. The latter figures are similar to our previously published laboratory results. The test is of comparable efficiency to arecoline purgation for surveillance, and has the additional advantage of detecting infection in the majority of those dogs that have been infected for three weeks or more but fail to pass worms on purgation, and a substantial proportion of those infected dogs that were treated by their owners prior to presenting them for purgation in order to avoid detection of infection. 相似文献
98.
99.
Harasen GL 《The Canadian veterinary journal. La revue veterinaire canadienne》1985,26(6):193-194
Two cases of noninfectious, nonerosive arthritis are presented. The diagnostic features, clinical course and treatment are reviewed. Potential etiologies are discussed in the light of relatively little current material on this subject in the veterinary literature. 相似文献
100.
Ten out of eleven subcutaneous abscesses in cats harboured anaerobic bacteria. Seven of the ten abscesses contained a mixture of obligate anaerobes and facultative anaerobes or microaerophilic bacteria. All of the anaerobic isolates were sensitive to the antibiotic metronidazole, but were resistant to streptomycin. Three isolates from one abscess were resistant to penicillin and ampicillin. Clinical resolution of subcutaneous abscesses was poor when procaine penicillin was used alone as treatment. 相似文献