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   68篇
  免费   2篇
林业   1篇
农学   3篇
基础科学   4篇
  4篇
综合类   6篇
农作物   2篇
水产渔业   2篇
畜牧兽医   44篇
园艺   1篇
植物保护   3篇
  2019年   2篇
  2018年   2篇
  2017年   1篇
  2016年   1篇
  2013年   1篇
  2012年   4篇
  2011年   4篇
  2009年   2篇
  2008年   14篇
  2007年   11篇
  2006年   10篇
  2005年   2篇
  2004年   2篇
  2003年   2篇
  2002年   3篇
  2001年   1篇
  2000年   2篇
  1999年   2篇
  1995年   1篇
  1981年   3篇
排序方式: 共有70条查询结果,搜索用时 15 毫秒
1.
2.
Economic growth in China’s agricultural sector lags behind growth in industry and services, creating an ever widening rural–urban income gap. Development of the non-agricultural sectors offers new opportunities for farmers in China’s more advanced provinces such as Zhejiang. Increased income in the urban sector creates markets for new products, and migrating farmers rent their land to those staying. Until now, the prevailing rice-based systems have been managed mainly using manual labour and animal traction, but the larger farms resulting from migration may facilitate, or even require mechanization. In this study, we use a simulation model of the farm household to analyse the effects of increasing farm size and the transition from rice to vegetable production, while also studying the effects of mechanization.  相似文献   
3.
4.
Ex situ collections offer the potential to reduce extinction risks, affording option to society in maintaining future breeding opportunities for productivity and heritage traits. However, how much should we be seeking to collect and conserve in gene banks, and where? We developed a mathematical model to optimize logistical decisions of breed conservation choices and to evaluate alternative scenarios for efficiently re‐allocating genetic materials currently stored in different European gene banks, allowing for cross‐country collections, cost and cryogenic capacity differentials. We show how alternative allocations for the breeds that are currently stored in 11 European gene banks could reduce overall conservation costs by around 20% by selecting cryogenic banks that have relatively lower combination of fixed and collection costs, and are geographically closer to collection regions. Our results show that centralizing collections in one gene bank would double the costs, relative to collective European collections approaches. We also calculate marginal costs of collections and show that increasing diversity within the gene banks implies in higher costs per conserved breed.  相似文献   
5.
6.
7.
On 26th of july 2007 a new case of bluetongue was notified in the Netherlands and on 2nd of august 2007 foot-and-mouth disease was diagnosed in Surrey, England, which raised the threat of having both infections simultaniously in one area. Bluetongue and foot-and-mouth disease have a different pathogenesis, but symptoms may resemble each other at a later stage of infection. The pathogenesis and possible clinical symptoms of both infections are discussed and illustrated with pictures.  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