首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   142篇
  免费   4篇
林业   15篇
农学   1篇
  7篇
综合类   22篇
农作物   3篇
水产渔业   2篇
畜牧兽医   86篇
植物保护   10篇
  2019年   1篇
  2017年   1篇
  2016年   2篇
  2013年   18篇
  2012年   2篇
  2011年   4篇
  2009年   6篇
  2008年   5篇
  2007年   4篇
  2006年   4篇
  2005年   6篇
  2004年   2篇
  2003年   4篇
  2002年   4篇
  2001年   1篇
  2000年   1篇
  1999年   2篇
  1997年   2篇
  1996年   1篇
  1995年   4篇
  1994年   1篇
  1993年   2篇
  1992年   3篇
  1991年   2篇
  1990年   6篇
  1989年   4篇
  1988年   2篇
  1987年   3篇
  1986年   1篇
  1985年   6篇
  1984年   5篇
  1983年   2篇
  1982年   2篇
  1979年   4篇
  1977年   4篇
  1976年   2篇
  1975年   1篇
  1974年   2篇
  1973年   3篇
  1972年   1篇
  1971年   2篇
  1969年   5篇
  1968年   1篇
  1967年   1篇
  1960年   1篇
  1948年   1篇
  1943年   1篇
  1941年   1篇
  1892年   2篇
  1891年   1篇
排序方式: 共有146条查询结果,搜索用时 15 毫秒
131.
132.
133.
We performed a clinical trial to study whether cows with palpable corpora lutea treated with cloprostenol by the farmer on the morning following examination (median time 0630 hours) were seen in heat and conceived more frequently than cows treated by the veterinarian immediately following the reproductive examination (median time 1210 hours).

There were no significant differences between the two groups in the proportions of cows seen in estrus or fertility at the induced estrus.

The proportions of animals that had the time of onset of estrus recorded and were seen in estrus during working hours (0800-1600 hours) were also not significantly different between the veterinary-treated and farmer-treated groups.

Under the conditions of this study, there was no reason to prefer prescribing early morning administration of cloprostenol by farmers over immediate administration of the drug by the clinician.

  相似文献   
134.
Fifty-one calves were divided into six trial groups of seven to eleven animals and vaccinated with a commercial leptospiral vaccine containing serovars pomona and hardjo. Vaccinations were given at 6,7,14 or 21 months of age and animals in various groups were vaccinated on one to four occasions. Antibody responses were determined by the microscopic agglutination test (MAT) and the complement fixation test (CFT) at one to four weeks intervals until 66 weeks after the start of the trial. Fifty percent or greater agglutination in serum diluted 1:100 or more and 50% or greater fixation of complement in serum diluted 1:20 or more were considered positive titres in the MAT or CFI respectively. Positive titres were still present in some animals six weeks after vaccination at 21 months of age. In other cases MAT titres (range 1:100-1:3000) persisted for 7-23 weeks and CFI titres (range 1:20-1540) persisted for 1-14 weeks. Marked individual variation in serological findings occurred using either test. In general the number of animals producing a positive titre, and the magnitude and persistence of titres was related to the number of doses of vaccine given. It was concluded that for diagnostic purposes neither the CFT nor the MAT could reliably differentiate titres due to vaccination from those following natural infections.  相似文献   
135.
136.
Nineteen isolates of Actinobacillus suis were recovered from horses during the period October 1978-December 1980. Animals varied in age from a full term foetus to 12 years. One isolate was obtained from the nose of an apparently healthy horse, the remainder were obtained from still-born foetuses (2), foals dying within a week of birth (5), older animals with respiratory (6) or genital infections (3) or abscesses in the jaw (1). One isolate was obtained from the lung of a 2-week-old foal which had shown diarrhoea. The bacteriological characteristics of the isolates and the pathological lesions present in eight cases are described. The organism has a wide geographical distribution in New Zealand, and in the northern part of the North Island appears to be more common than A. equuli.  相似文献   
137.
138.
Heterobasidion annosum. Biology, Ecology, Impact and Control   总被引:1,自引:0,他引:1  
  相似文献   
139.
140.
Index methods can be valuable for monitoring forest-dwelling vertebrates over broad spatial or temporal scales. Fecal pellet counts are often used as an index of density or habitat use of snowshoe hares, Lepus americanus, but previous surveys have used different plot types and sample sizes, leading to problems comparing results from different studies and questions about the inferential power of each study. In this paper, we use field data and simulations to examine how the precision, bias, and efficiency of four commonly used plot types vary with plot type, pellet density, and sample size. Although no one plot type was consistently superior, we recommend thin rectangles (5.08 cm × 305 cm (2 in. × 10 ft), 0.155 m2) or 1 m2 circles over 0.155 m2 circles or 10 cm × 10 m (1 m2) rectangles. We recommend that researchers explicitly address the power of their survey design to detect different pellet densities, because much larger sample sizes are needed at low pellet densities than at high pellet densities to obtain similar precision. Small sample sizes are also much more likely to be biased, which could lead to incorrect inferences about management of snowshoe hare populations. Both uncleared and cleared plots performed well and will have value in different research contexts.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号