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   332篇
  免费   18篇
  国内免费   3篇
林业   21篇
农学   4篇
基础科学   3篇
  58篇
综合类   41篇
农作物   9篇
水产渔业   15篇
畜牧兽医   188篇
园艺   5篇
植物保护   9篇
  2021年   4篇
  2020年   6篇
  2019年   5篇
  2018年   7篇
  2017年   6篇
  2016年   4篇
  2015年   6篇
  2014年   6篇
  2013年   24篇
  2012年   16篇
  2011年   10篇
  2010年   7篇
  2009年   15篇
  2008年   14篇
  2007年   18篇
  2006年   8篇
  2005年   13篇
  2004年   8篇
  2003年   8篇
  2002年   12篇
  2001年   8篇
  2000年   11篇
  1999年   9篇
  1998年   5篇
  1996年   10篇
  1994年   4篇
  1993年   4篇
  1992年   2篇
  1991年   4篇
  1990年   2篇
  1989年   7篇
  1988年   2篇
  1987年   6篇
  1986年   4篇
  1985年   3篇
  1984年   7篇
  1983年   3篇
  1982年   3篇
  1981年   5篇
  1980年   4篇
  1979年   5篇
  1978年   4篇
  1977年   4篇
  1976年   2篇
  1975年   4篇
  1974年   5篇
  1973年   7篇
  1972年   5篇
  1971年   5篇
  1970年   3篇
排序方式: 共有353条查询结果,搜索用时 15 毫秒
1.
In a nine-year-old female cat, the diagnostic procedure, therapy and differential diagnoses of a rare, primary, malignant, epibulbar melanoma are presented. Post-operatively no recidivation or metastases occurred within 18 months.  相似文献   
2.
3.
As plants mature it has been observed that some become more resistant to normally virulent pathogens. The ability to manifest the Age-Related Resistance (ARR) response in Arabidopsis to Pseudomonas syringae pathovars tomato (Pst) coincided with the transition to flowering in plants both delayed and accelerated in the transition to flowering. ARR was also associated with a change in PR-1 gene expression, such that young plants expressed PR-1 abundantly at 3 days post inoculation (dpi) while mature plants expressed much less. The Arabidopsis ARR response requires SA accumulation via isochorismate synthase (ICS1) [24]. ICS1 was expressed one dpi with virulent and avirulent Pst in both young and mature plants. The ARR response was also effective versus avirulent Pst providing an additional 4-fold limitation in bacterial growth. Arabidopsis ARR was found to be ineffective against two necrotrophs, Erwinia carotovora subspecies carotovora (bacterium) and Botrytis cinerea (fungus) and one obligate biotroph, Erysiphe cichoracearum (fungus). However, mature wild type, SA-deficient sid2 and NahG plants supported little growth of the obligate biotrophic oomycete, Peronospora parasitica. Therefore ARR to P. parasitica appears to be SA-independent, however the level of ARR resistance was somewhat reduced in these mutants in some experiments. Thus, there may be numerous defence pathways that contribute to adult plant resistance in Arabidopsis.  相似文献   
4.
This study describes the age-related variation in boar taint compounds, skatole and androstenone, and testosterone, oestradiol-17 beta (E17 beta), oestrone sulphate (ES), dehydroepiandrosterone sulphate (DHEAS), triiodothyronine (T(3)) and insulin-like growth factor-1 (IGF-1) in six boars. Three pairs of littermates of crossbred entire male pigs (from three Yorkshire x Duroc dams and one Hampshire sire) were included. Blood samples were taken at the age of 9-15 weeks and thereafter at weekly intervals from the age of 20-32 weeks. Plasma concentrations of skatole, androstenone, testosterone, E17 beta, ES, DHEAS, T(3) and IGF-1 were measured. We found that skatole levels in boars increased at the age around puberty after an increase in the levels of testicular steroids. Levels of skatole were not associated with the levels of sex steroids, T(3) and IGF-1. However, the increased level of testicular steroids is probably the underlying factor needed for high skatole levels to occur although the specific mechanism leading to increased skatole levels remains unknown.  相似文献   
5.
Landscape Ecology - Maintaining biodiversity in multifunction landscapes is a significant challenge. Planning for the impacts of change requires knowledge of how species respond to landscape...  相似文献   
6.
7.
The two insecticidal benzoylurea compounds, diflubenzuron and chlorfluazuron, show large differences in their toxicity against the larvae of insects like the tobacco budworm, Heliothis virescens, or the Egyptian cotton leafworm, Spodoptera littoralis, chlorfluazuron being about 100 times more toxic. This difference is due mainly to a much faster metabolism of diflubenzuron. Its half-life within the larvae is about 5 h, compared to about 50 h for chlorfluazuron. Chlorfluazuron is also the much better ovicide of the two, following injection of the compounds into the females of H. virescens. Again the difference in the rate of metabolism is the main cause. The rate of excretion of the parent benzoylureas is relatively low, but their metabolites are excreted very quickly.  相似文献   
8.
9.
10.
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