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   240篇
  免费   10篇
林业   77篇
农学   9篇
  38篇
综合类   29篇
农作物   5篇
水产渔业   5篇
畜牧兽医   73篇
园艺   4篇
植物保护   10篇
  2020年   3篇
  2019年   2篇
  2018年   6篇
  2016年   3篇
  2015年   4篇
  2014年   6篇
  2013年   10篇
  2012年   8篇
  2011年   5篇
  2010年   9篇
  2009年   5篇
  2008年   9篇
  2007年   6篇
  2006年   10篇
  2005年   13篇
  2004年   8篇
  2003年   5篇
  2002年   5篇
  2001年   2篇
  2000年   3篇
  1999年   3篇
  1992年   2篇
  1988年   2篇
  1987年   4篇
  1986年   2篇
  1984年   4篇
  1982年   5篇
  1981年   3篇
  1980年   6篇
  1979年   8篇
  1978年   7篇
  1977年   2篇
  1976年   4篇
  1975年   3篇
  1974年   2篇
  1973年   3篇
  1972年   4篇
  1971年   4篇
  1970年   5篇
  1969年   2篇
  1967年   5篇
  1966年   3篇
  1962年   2篇
  1961年   6篇
  1960年   2篇
  1958年   2篇
  1948年   2篇
  1933年   2篇
  1930年   2篇
  1896年   2篇
排序方式: 共有250条查询结果,搜索用时 179 毫秒
81.
82.
83.
Ohne Zusammenfassung  相似文献   
84.
85.
Information about disease management in winter wheat (Triticum aestiva) in eight European countries was collated and analysed by scientists and extension workers within the European Network for the Durable Exploitation of Crop Protection Strategies (ENDURE). This included information about specific disease thresholds, decision support systems, host varieties, disease prevalence and pathogen virulence. Major differences in disease prevalence and economic importance were observed. Septoria tritici blotch (Mycosphaerella graminicola) was recognized as the most yield reducing disease in countries with intensive wheat production, but also rust diseases (Puccinia striiformis and Puccinia triticina), powdery mildew (Blumeria graminis) and Fusarium head blight (Fusarium spp.) were seen as serious disease problems. Examples of current integrated pest management (IPM) strategies in different countries have been reported. Disease management and fungicide use patterns showed major differences, with an average input equivalent to 2.3 full dose rates (TFI) in the UK and a TFI of 0.6 in Denmark. These differences are most likely due to a combination of different cropping systems, climatic differences, disease prevalence, and socio-economic factors. The web based information platform www.eurowheat.org was used for dissemination of information and results including information on control thresholds, cultural practices which can influence disease attack, fungicide efficacy, fungicide resistance, and pathogen virulence, which are all elements supporting 1PM for disease control in wheat. The platform is open to all users. The target groups of EuroWheat information are researchers, advisors, breeders, and similar partners dealing with disease management in wheat.  相似文献   
86.
87.
88.
The prediction of the structures and interactions of biological macromolecules at the atomic level and the design of new structures and interactions are critical tests of our understanding of the interatomic interactions that underlie molecular biology. Equally important, the capability to accurately predict and design macromolecular structures and interactions would streamline the interpretation of genome sequence information and allow the creation of macromolecules with new and useful functions. This review summarizes recent progress in modeling that suggests that we are entering an era in which high-resolution prediction and design will make increasingly important contributions to biology and medicine.  相似文献   
89.
90.
The Podzol has been elected “Soil of the year 2007” in Germany. This article reviews the present knowledge on the development, functions, and threats of Podzols. The main theories on mobilization and transport of organic matter, Fe, Al, and Si are (1) metal‐organic migration, (2) metal reduction, and (3) inorganic sol migration. Immobilization theories include precipitation or polymerization due to increasing pH/abundance of base cations with depth, mechanical filtering in soil pores, oxidation of metal‐organic complexes, biodegradation of the organic part, decreasing C‐to‐metal ratios during translocation, adsorption to soil particles, and flocculation at the point of zero charge. Podzolization is discussed also on the catena scale, where vertical and lateral translocation processes (across pedon boundaries) need to be considered to understand Podzol patterns in landscapes. Chronosequence studies show that incipient podzolization usually becomes visible between 100 and 500 y and mature Podzols develop in 1,000–6,000 y. The occurrence of Podzols worldwide is concentrated mainly on the boreal zone and mountain regions within the humid temperate zone. Smaller Podzol areas are found in some perhumid tropical and subtropical regions. In Germany, Podzols occur in the Alps, in the glaciofluvial valleys and heathlands of N Germany, and in the mountain ranges. They fulfil several ecological functions, especially for groundwater recharge. Main threats for these mostly sandy soils are wind erosion and surface mining of sand. Two pedons which were chosen to represent the “Soil of the year 2007” are presented. Finally, some conclusions about podzolization processes are drawn, which may explain the diverse observations reported in the literature.  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