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   1537篇
  免费   55篇
  国内免费   75篇
林业   144篇
农学   237篇
基础科学   51篇
  354篇
综合类   253篇
农作物   90篇
水产渔业   52篇
畜牧兽医   357篇
园艺   42篇
植物保护   87篇
  2022年   38篇
  2021年   38篇
  2020年   32篇
  2019年   24篇
  2018年   18篇
  2017年   32篇
  2016年   33篇
  2015年   37篇
  2014年   26篇
  2013年   100篇
  2012年   71篇
  2011年   78篇
  2010年   70篇
  2009年   59篇
  2008年   73篇
  2007年   66篇
  2006年   70篇
  2005年   70篇
  2004年   27篇
  2003年   34篇
  2002年   37篇
  2001年   44篇
  2000年   39篇
  1999年   42篇
  1998年   27篇
  1997年   39篇
  1996年   31篇
  1995年   17篇
  1994年   17篇
  1993年   13篇
  1992年   16篇
  1991年   18篇
  1990年   21篇
  1989年   15篇
  1988年   18篇
  1987年   18篇
  1985年   13篇
  1983年   13篇
  1979年   23篇
  1978年   8篇
  1977年   9篇
  1976年   11篇
  1975年   8篇
  1971年   21篇
  1970年   14篇
  1969年   14篇
  1968年   8篇
  1967年   20篇
  1966年   21篇
  1965年   10篇
排序方式: 共有1667条查询结果,搜索用时 187 毫秒
41.
稻飞虱(Nilaparvata lugens Stal)是以稻属为食的单食性昆虫,刺吸稻株汁液危害水稻。建瓯全市水稻种植面积约3.5万hm2,稻飞虱年发生面积0.9万hm2,近几年来已成为建瓯市水稻的主要害虫之一。  相似文献   
42.
43.
44.
The pharmacokinetics of enrofloxacin and its active metabolite ciprofloxacin were investigated in goats after a single intramuscular administration of enrofloxacin at 2.5 mg/kg body weight. The plasma concentrations of enrofloxacin and ciprofloxacin were determined simultaneously by a HPLC method. The peak concentrations (C max) of enrofloxacin (1.13 g/ml) and ciprofloxacin (0.24 g/ml) were observed at 0.8 and 1.2 h, respectively. The elimination half-life (t 1/2), volume of distribution (V d(area)), total body clearance (ClB) and mean residence time (MRT) of enrofloxacin were 0.74 h, 1.42 L/kg, 1329 ml/h per kg and 1.54 h, respectively. The t 1/2, area under the plasma concentration–time curve (AUC) and the MRT of ciprofloxacin were 1.38 h, 0.74 g h/ml and 2.73 h, respectively. The metabolic conversion of enrofloxacin to ciprofloxacin was appreciable (36%) and the sum of the plasma concentrations of enrofloxacin and ciprofloxacin was maintained at or above 0.1 g/ml for up to 4 h. Enrofloxacin appears to be useful for the treatment of goat diseases associated with pathogens sensitive to this drug.  相似文献   
45.
Conditional expression of harpinPsscauses yeast cell death that shares features of cell death pathway with harpinPss-mediated plant hypersensitive response (HR).Pseudomonas syringae pv.syringae 61 hrp Z gene encodes harpinPss, a 34.7 kD extracellular protein that elicits a hypersensitive response (HR) in plants. Conditional expression of either full-length or truncated hrp Z sequences under the GAL1 promoter caused cell death in Saccharomyces cerevisiae Y187. Plating of pYEUT- hrp Z transformants on a medium containing galactose resulted in complete inhibition of colony formation, whereas their growth on a glucose-based medium was unaffected. Western blot analysis confirmed the expression of harpinPssin yeast cells transformed with pYEUT- hrp Z and grown in galactose-containing medium. A time-dependent decline in the percentage of trypan blue-excluding cells in cultures of pYEUT- hrp Z transformants was observed when cultured on galactose-containing medium. Similarly, the number of viable cells reduced to about 50% within 6 h. There were similarities in the harpinPss-mediated cell death in plants and yeast cell death (YCD). Galactose-induced cell death in pYEUT-hrp Z transformants of S. cerevisiae Y187 was suppressed by a protein kinase inhibitor K252a (10 μ M). The viability of pYEUT- hrp Z transformants was prolonged in the presence of 100 U ml−1catalase suggesting a role for the oxidative burst in YCD that was further supported by the flow cytometric patterns of propidium iodide uptake by yeast cells. Overall, it appears that yeast provides a useful model system to understand the molecular mechanism of harpinPss-mediated cell death.  相似文献   
46.
Urinary calculi from three bulls, six bullocks and one male buffalo from the Guntur district were investigated. By chemical analysis only CO32, Ca2+, Mg2+, and a trace of PO¾- were found. X-ray analysis showed that all samples consisted of magnesian calcite with an atomic percentage of magnesium between 14.5 and 21.9. The size of the crystallites varied approx. from 200 to 400 Å.  相似文献   
47.
48.
49.
50.
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