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   829篇
  免费   20篇
  国内免费   28篇
林业   57篇
农学   43篇
基础科学   78篇
  113篇
综合类   527篇
农作物   13篇
水产渔业   2篇
畜牧兽医   31篇
园艺   4篇
植物保护   9篇
  2024年   4篇
  2023年   14篇
  2022年   11篇
  2021年   20篇
  2020年   15篇
  2019年   18篇
  2018年   14篇
  2017年   13篇
  2016年   18篇
  2015年   17篇
  2014年   31篇
  2013年   38篇
  2012年   55篇
  2011年   85篇
  2010年   97篇
  2009年   85篇
  2008年   78篇
  2007年   68篇
  2006年   55篇
  2005年   47篇
  2004年   30篇
  2003年   24篇
  2002年   15篇
  2001年   9篇
  2000年   7篇
  1999年   2篇
  1998年   1篇
  1997年   4篇
  1995年   2篇
排序方式: 共有877条查询结果,搜索用时 15 毫秒
101.
We examine the development of irrigation management in northern China using data from village and household panels. During the past decade, reform-oriented institutions, such as water user associations and contracting, have largely replaced the traditional institution of collective management in village-level irrigation systems. A feature unique to China is that water user associations and contractors are provided with monetary incentives to save water. Water user associations have not yet achieved the broad-based participation of farmers that some advocates consider as a primary goal for forming the associations. Many village leaders serve also as the leaders of water user associations, thus possibly reducing opportunities for receiving operational input and policy direction from farmers. However, we observe improved performance of irrigation systems managed by water user associations, relative to collective management, in terms of maintenance expenditures, the timeliness of water deliveries, and the rates of fee collection. Performance has improved also in systems managed by contractors, although not as substantially as in the case of water user associations.  相似文献   
102.
Use of varieties bred under organic conditions is essential in order to minimize the yield gap between organic and conventional agriculture. The aim of this study was to analyse research publications related to the topic ‘organic plant breeding’ from the Web of Science database using bibliometric science mapping and visualization tools. The number of analysed documents in the bibliographic dataset was 204 from the 53 sources. The overall trend in the organic plant breeding literature showed that the number of publications increased during the observed time-span. We found that in total, 65 countries and 337 institutions are active in the field of organic plant breeding with a high degree of international collaboration. The top five countries according to the number of publications were the United States, Italy, Germany, France, and Canada, while the most active institutions were Wageningen University, Iowa State University, University of Alberta, University of Copenhagen, and University of Hohenheim. All keywords from the organic plant breeding research in the agronomy category were separated into seven clusters for different research topics. Although there is evident progress viewed through the increased trend in the number of publications, organic plant breeding needs further expansion and development. This is especially through the implementation of novel plant breeding techniques and methods aiming to improve traits that are highly specific to organic conditions.  相似文献   
103.
论"国家农业科学数据共享平台"的内容与服务   总被引:7,自引:0,他引:7  
本文简述了国内在线数据库现状 ,对“国家农业科学数据共享平台”的内容、地位和优势 ,以及服务机制和模式等问题进行了较为详尽的论述  相似文献   
104.
Micronutrient deficiencies in diets, including iron (Fe) and zinc (Zn), are an important public health problem across population in Ethiopia. Potato is a modest source of dietary nutrients. The purpose of this study was to assess the mineral (Fe & Zn) composition of potato germplasm in Ethiopia and grower's willingness to try new potato types. The Fe and Zn contents were assessed in peeled tubers of popular farmer varieties, and newly introduced Andean diploid group Phureja accessions and improved tetraploid clones grown in multi-location trials. Grower's preferences for the new potato types was assessed using a participatory approach. Significant variations in mineral and tuber yield traits exist among the germplasm assessed and broad-sense heritability appears to be high for most traits measured, suggesting that progress through breeding can be made among these materials. However, the slightly negative correlation of tuber yield with Fe and Zn content and user appreciation traits found in this study suggests that progress in improving crops for yield and enhanced Fe and Zn concentrations with end-user acceptable quality will be challenging. The results from this study provide baseline information on Fe and Zn composition of many popular farmer varieties in Ethiopia and end-user preference criteria for evaluating new potato varieties that would help to orient the biofortification breeding to the conditions and preference of farmers.  相似文献   
105.
黄武  胡新文  毛帅  闵义 《热带作物学报》2018,39(7):1452-1461
为了探究热带作物木薯的研究热点和趋势,本文对近年来木薯研究成果进行了分析,数据检索时间是 1999—2017 年,各项数据分析和可视化分析的时间范围是 2009—2017 年。基于 Web of Science 数据库,利用网页检索功能分析了木薯研究的年发文量、基金资助机构及国家地区分布、研究方向及研究机构状况;利用 CiteSpace 对 2009—2017年木薯研究关键词进行共现性和可视化图谱聚类分析。中国地区发文量、基金资助分布及研究机构排名位于前列;农业研究、食品科学技术领域占比较大;以 3 a 为时间轴对数据的关键词聚类分析,绘制可视化信息图谱并分析聚类下的信息,得出木薯研究的趋势和热点问题。木薯淀粉-壳聚糖、燃料乙醇研究引发新的研究热点。从发文量来看,中国在木薯研究科研投入和成果数量产出方面都位居前列;分子育种成为品质改良的重要手段,木薯病毒、燃料乙醇、光暗发酵制氢、甲烷和单细胞油脂生产、延缓块根变质、耐受性基因选择持续成为关注热点;最近 3 a,木薯淀粉在新型材料加工方面有了新的应用,在可再生能源方面出现了新的研究领域。  相似文献   
106.
采用EJB3技术及Web服务技术,设计并建立了基于J2EE的桉树模型库服务系统。该系统由参数数据库、模型库、模型引擎和模型服务模块组成,实现了桉树生长模型库的管理和远程在线调用等功能,方便用户进行模型的更新和添加。除了可进行本地调用桉树模型外,还提供了桉树模型的跨语言和跨平台Web服务功能,使得用户可以远程以任何支持Web服务的语言在线调用桉树模型,最大化地实现了模型算法的共享。  相似文献   
107.
陈绯  刘兵兵 《安徽农业科学》2009,37(34):17230-17231
在分析了研究背景的基础上,提出了构建基于Web的农业支持系统的设想。结合已有的研究成果,对基于Web的农业支持系统进行了深入阐述,设计了该系统的开发框架,并对开发过程中的一些重要问题进行了探讨。  相似文献   
108.
利用Web2.0设计人性化的图书馆网站   总被引:1,自引:0,他引:1  
首先概述了图书馆网站建设情况及其人性化设计的趋势,接着从5个方面论述了Web2.0在图书馆网站中的应用。最后总结出图书馆网站的人性化设计能更好的为读者提供服务。  相似文献   
109.
图书馆2.0的问世对图书馆的存在和发展产生了巨大的影响。论述了图书馆2.0的起源及概念.对图书馆2.0与Web2.0进行了比较;介绍了图书馆2.O的五原则和技术环境,也对图书馆2.0环境下的图书馆员提出了新的要求。  相似文献   
110.
基于ASP.NET2.0技术的系统设计实现了由地面气象测报软件生成的数据库B文件的定时自动传输;编制Web应用程序,实现了气象站监测信息在Web页面的交互式动态实时查询。在IIS服务器上建立Web站点,实现了气象站监测信息的发布与共享。对这一系统的设计思路、设计方案进行了介绍,以期促进气象工作的开展。  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