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   363篇
  免费   44篇
林业   12篇
农学   1篇
基础科学   1篇
  20篇
综合类   41篇
农作物   10篇
水产渔业   3篇
畜牧兽医   305篇
园艺   2篇
植物保护   12篇
  2022年   3篇
  2021年   4篇
  2020年   10篇
  2019年   8篇
  2018年   18篇
  2017年   15篇
  2016年   15篇
  2015年   6篇
  2014年   13篇
  2013年   20篇
  2012年   16篇
  2011年   12篇
  2010年   22篇
  2009年   27篇
  2008年   15篇
  2007年   18篇
  2006年   13篇
  2005年   5篇
  2004年   10篇
  2003年   8篇
  2002年   2篇
  2001年   9篇
  2000年   3篇
  1999年   10篇
  1998年   17篇
  1997年   8篇
  1996年   16篇
  1995年   6篇
  1994年   2篇
  1993年   4篇
  1992年   6篇
  1991年   6篇
  1990年   6篇
  1989年   4篇
  1988年   6篇
  1987年   2篇
  1985年   2篇
  1984年   3篇
  1982年   2篇
  1978年   2篇
  1977年   2篇
  1976年   2篇
  1975年   2篇
  1974年   3篇
  1973年   5篇
  1971年   7篇
  1970年   1篇
  1969年   3篇
  1967年   2篇
  1966年   1篇
排序方式: 共有407条查询结果,搜索用时 0 毫秒
71.
SUMMARY The clinical, pathological and biochemical manifestations of maple syrup urine disease (MSUD) are similar in Poll Hereford and Poll Shorthorn X Poll Hereford calves. No significant differences were observed in branched-chain amino acid concentrations in plasma, or of branched-chain keto acid dehydrogenase activity in fibroblasts, between Poll Herefords homozygous normal and heterozygous for the mutation responsible for MSUD. Haemopoietic chimerism resulted in incorrect diagnosis of the MSUD genotype in 30% of non-identical twins when blood DNA was analysed using allele-specific amplification. Hair roots are shown to be a suitable source of target DNA for genotyping Poll Hereford cattle for the MSUD mutation. Twelve of 203 (5.8%) aged Poll Hereford bulls, sampled at saleyards during the last 4 months of 1993, were found to be heterozygous for the mutation. In contrast, the mutant sequence was detected in only 1 of 150 (0.7%) 2- and 3-year-old Poll Hereford bulls offered for sale at 2 stud sales held during 1993, suggesting that the prevalence of the disease may decline over the next few years.  相似文献   
72.
73.
Progressive ethmoidal haematoma was diagnosed in 12 Thoroughbreds, 1 part- Arab and 1 stock horse. Ages ranged from 3 to 18 years and both males and females were affected. Diagnosis was based on history, clinical signs, endoscopic and radiographic findings, and was confirmed histologically in 10 cases. Eleven (78%) of the lesions were unilateral and 3 (22%) were bilateral. Two horses were euthanased on diagnosis, 4 were treated conservatively. Of the latter, 3 were euthanased 6 to 24 months after diagnosis, due to progression of the lesions, while 1 case resolved completely within 13 months. Eight horses were treated by surgical excision of the lesion. Three died in the post-operative period, 3 were euthanased within 48 months after recurrence of the condition, and 2 had no recurrence within 60 and 72 months, respectively.  相似文献   
74.
75.
76.
77.
Cutaneous pythiosis in beef calves   总被引:3,自引:0,他引:3  
Six Brahman and Brahman-cross calves less than or equal to 9 months old were examined because of ulcerative swellings of the fetlocks (5 calves) or numerous focal ulcerated cutaneous lesions (1 calf). Biopsies revealed focal cutaneous granulomas around regular, thick-walled branching hyphae, 4 to 9 micron in diameter. In all cases, portions of the hyphae were surrounded by granular encrustations, which ultrastructurally were composed of amorphous material comparable to antigen-antibody complexes. The protist Pythium sp was isolated from 2 calves.  相似文献   
78.
Changes in management of the surgical colic patient over the last 30 years have resulted in considerable improvement in post operative survival rates. However, post operative complications remain common and these impact negatively on horse welfare, probability of survival, return to previous use and the costs of treatment. Multiple studies have investigated risk factors for post operative complications following surgical management of colic and interventions that might be effective in reducing the likelihood of these occurring. The findings from these studies are frequently contradictory and the evidence for many interventions is lacking or inconclusive. This review discusses the current available evidence and identifies areas where further studies are necessary and factors that should be taken into consideration in study design.  相似文献   
79.
Global Oscillation Network Group data reveal that the internal structure of the sun can be well represented by a calibrated standard model. However, immediately beneath the convection zone and at the edge of the energy-generating core, the sound-speed variation is somewhat smoother in the sun than it is in the model. This could be a consequence of chemical inhomogeneity that is too severe in the model, perhaps owing to inaccurate modeling of gravitational settling or to neglected macroscopic motion that may be present in the sun. Accurate knowledge of the sun's structure enables inferences to be made about the physics that controls the sun; for example, through the opacity, the equation of state, or wave motion. Those inferences can then be used elsewhere in astrophysics.  相似文献   
80.
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