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   234篇
  免费   12篇
林业   28篇
农学   7篇
  19篇
综合类   34篇
农作物   5篇
水产渔业   9篇
畜牧兽医   132篇
园艺   1篇
植物保护   11篇
  2023年   5篇
  2022年   1篇
  2021年   3篇
  2020年   3篇
  2019年   4篇
  2018年   5篇
  2017年   6篇
  2016年   1篇
  2015年   4篇
  2014年   7篇
  2013年   11篇
  2012年   9篇
  2011年   5篇
  2010年   9篇
  2009年   9篇
  2008年   5篇
  2007年   14篇
  2006年   16篇
  2005年   9篇
  2004年   4篇
  2003年   10篇
  2002年   6篇
  2001年   5篇
  2000年   2篇
  1999年   7篇
  1998年   5篇
  1997年   16篇
  1996年   2篇
  1995年   6篇
  1994年   7篇
  1993年   4篇
  1992年   6篇
  1991年   2篇
  1990年   4篇
  1989年   3篇
  1988年   3篇
  1987年   1篇
  1986年   2篇
  1976年   1篇
  1975年   9篇
  1972年   1篇
  1971年   3篇
  1969年   1篇
  1968年   1篇
  1965年   1篇
  1955年   1篇
  1911年   4篇
  1867年   1篇
  1864年   1篇
  1862年   1篇
排序方式: 共有246条查询结果,搜索用时 15 毫秒
1.
SUMMARY Twenty-four of 57 calves fed a diet containing 33% cotton seed meal (CSM) died between 7 and 15 weeks of age. Initial deaths were not accompanied by premonitory signs, but after CSM withdrawal most calves developed rough coats, anorexia, weakness, ascites and subcutaneous oedema. Those that died had large volumes of serous fluid in the body cavities, hard livers of ‘nutmeg’ appearance, and pulmonary congestion. Histopathologically the livers showed periacinar necrosis in acute cases and periacinar fibrosis in chronic cases. Lungs from several calves had oedema, haemosiderosis and fibrosis in some pulmonary vessels. Atrophy of myocardial fibres was present in most cases. The concentration of free gossypol in the diet was 100 to 220 mg/kg. Ante-mortem and post-mortem findings supported a diagnosis of gossypol poisoning. The deaths continued for 4 weeks after withdrawal of CSM from the diet.  相似文献   
2.
The objective was to study the use of ultrasound as a complementary test in the breeding soundness evaluation in male pigs and study the pattern of echogenicity of the testicular parenchyma in boars of different racial groups. Twenty‐six adult boars from four different racial groups were used, 10 from the Piau breed (group 1), four from the commercial and finishing group (group 2), six Pietrain breed (group 3) and six from the Duroc breed (group 4). All animals were evaluated for breeding soundness evaluation and the ultrasound examination of the testicles. The groups of animals that were evaluated showed no difference in the main semen parameters that were evaluated, except for the sperm volume, concentration of the ejaculated sperm and the supravital staining; the lowest figures were for the animals from the Piau breed (group 1). In relation to the testicular biometrics, Duroc animals (group 4) had a greater scrotal width compared to the other groups. But when we assessed the intensity of pixels of the testicles, there was a difference between groups. The groups 2 (finishing animals), 3 (Pietrain) and 4 had no difference between themselves. Group 3 had greater pixel intensity in relation to group 1. Of the 26 animals studied, five showed an abnormality during ultrasound evaluation, like hydrocele, hyperechoic mass in the testicular parenchyma, cyst in the head of the epididymis and the presence of fluid in the head and tail of the epididymis. The various animal groups studied did not differ in the principal reproductive parameters evaluated, showing that despite the great variability of reproductive traits between breeds and within the same breed, the breeding soundness evaluation, the more complete it is, is essential for the selection of breeders and the ultrasonography of the reproductive system becomes an important addition in this examination.  相似文献   
3.
Journal of Plant Diseases and Protection - Psyllids are small, phloem-feeding insects. Several species are vectors of economically important pathogens, such as ‘Candidatus Liberibacter...  相似文献   
4.
5.
6.
7.
We evaluated whether new information could be drawn from additional data collection and unconventional statistical analyses of an on-farm trial. First, we compared a conventional sampling method using a biomass estimate of weed abundance to repeated visual assessment of the percentage ground cover of weeds. The biomass was sampled once after the treatment, whereas the ground cover was repeatedly sampled once before weed control plus several occasions after weed control. Second, we contrasted the outcomes from analysis of variance ( anova ), taking samples from a single point in time with repeated measures (rm) anova and a multivariate method. As the outcomes and conclusions drawn were relatively similar, we conclude that the ground cover estimate of weed abundance was as reliable as the biomass estimate. The rm anova enabled us to follow the temporal trend in response to treatments in the most abundant species, including possible initial differences. Multivariate analysis went even further, by clearly displaying species-wise responses and treatment selectivity.  相似文献   
8.
9.
Reference values for Cortisol, T4 and T-Uptake, determined with the Fluorescence-Polarization-Immunoassays (FPIAs) in blood-plasma of different horse groups were established. The highest Cortisol values were measured in blood samples from thoroughbred racehorses and riding horses taken between 7 and 8 a.m. (181 +/- 37 and 268 +/- 43 nmol/l), the lowest gained between 5 and 6 p.m. (69 +/- 45 and 85 +/- 32 nmol/l respectively). Peak values for T4 in riding horses were found in blood samples collected between 1 and 2 p.m. (28.2 +/- 5.7 nmol/l) followed by the samples taken at 5-6 p.m. and 7-8 a.m. T-Uptake values did not show a diurnal variation. Values of thoroughbred racehorses were much lower than in thoroughbred broodmares and riding horses (0.11 +/- 0.03, 0.18 +/- 0.03 and 0.24 +/- 0.05 units). The blood samples collected on 5 successive days showed significant variations for Cortisol. T4-values were stable whilst T-Uptake had small variations.  相似文献   
10.
Morphological structures of the bovine Papilla mammae can be differentiated with portable ultrasound units and 5 MHz linear arrays. For practical use it is possible to scan the teat in a water-filled plastic cup as a kind of water delay system. The visualization of pathological findings shows a possibility to evaluate this method as a diagnostic tool for the bovine teat.  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