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   803篇
  免费   24篇
  国内免费   3篇
林业   83篇
农学   24篇
基础科学   7篇
  52篇
综合类   607篇
农作物   10篇
水产渔业   8篇
畜牧兽医   30篇
园艺   4篇
植物保护   5篇
  2024年   1篇
  2023年   9篇
  2022年   10篇
  2021年   17篇
  2020年   18篇
  2019年   12篇
  2018年   11篇
  2017年   10篇
  2016年   17篇
  2015年   21篇
  2014年   33篇
  2013年   39篇
  2012年   58篇
  2011年   82篇
  2010年   87篇
  2009年   75篇
  2008年   67篇
  2007年   59篇
  2006年   40篇
  2005年   45篇
  2004年   27篇
  2003年   29篇
  2002年   10篇
  2001年   8篇
  2000年   7篇
  1999年   2篇
  1998年   1篇
  1997年   9篇
  1996年   6篇
  1995年   5篇
  1994年   5篇
  1993年   4篇
  1992年   1篇
  1991年   4篇
  1989年   1篇
排序方式: 共有830条查询结果,搜索用时 15 毫秒
101.
In recent decades agroforestry has undergone significant development in Latin America. South America generates the most scientific research on the topic in the region. We conducted a comprehensive review and analysis of knowledge production for South American agroforestry that includes livestock grazing, known as agrosilvopastoralism (AS), examining how different sociopolitical factors such as sources of funding, institutional priorities, and international cooperation can bias the direction and objectives of scientific research. We assessed the major attributes of scientific publications on the topic (25 articles per country; overall n = 210) and the potential factors underlying the processes of research and development in the region. The tree component was the most studied, while the livestock component received less attention. Studies were mainly focused on the production of goods and services (monetary or nonmonetary approaches), except in Brazil, where conservation was the major study objective. Stakeholders were involved in more than half of the studies (60%), and they were mostly ranchers and local producers. More than half (70%) of the studies offered recommendations based on their results, and such recommendations were mostly concerned with the management of agrosilvopastoral system components. In general, studies were led just as often by local as foreign first authors and coauthored by more than three people as part of interinstitutional working groups. Brazil, Argentina, Colombia, and Chile had more frequent cooperation among institutions and countries but mainly used their own funding. In contrast, Bolivia, Ecuador, and Peru had almost 100% of their studies supported by foreign countries (North America and Europe). Countries with greater internal funding of research generated more long-term studies. Besides this, two clear trends were detected: 1) conservation and social aspects were mainly supported by sources from external countries led by foreign principal investigators, and 2) production issues were supported from sources within countries and supported high levels of cooperation among institutions.  相似文献   
102.
面向21世纪,培养高素质的创新人才,需要强化个性教育。盲生因其视觉的缺陷,在接受教育时个性发展受到限制。在语文学习中,我们可以从以下四方面来尝试,以便更好地发展盲生的个性。1.丰富内容,使盲生在语文学习时具有选择性。2。留出空间,让盲生在语文学习中独立感悟。3.合理引导,使盲生思维能力自由独特。4.走进生活,让盲生在实践中锻炼个性。  相似文献   
103.
本文阐述了开展幼儿民间文学、民间音乐、民问美术等民间艺术教育研究的目的、教学实验方法步骤和实验结果,并运用统计学原理对实验班与对照班幼儿进行了效果测评比较、差异显著性检验及其结果分析与探讨,得出在3-6岁幼儿中开展系统科学的民间艺术教育对于促进幼儿身心发展、增强幼儿艺术素质具有显著效果。  相似文献   
104.
辛弃疾是南宋词人中的大家 ,其词作对后世影响深远 ,业已成为一种文学范型 ,而宋元之际的刘辰翁对这种范型归纳得最为详尽具体 ,共有四个方面 :1)以诗文为词 ;2 )用经用史 ;3)牵雅颂 ;4)入郑卫。而这四个特点也始终贯彻在辰翁自己的词作中 ,并为其所发展 ,形成了独具面目的须溪风格  相似文献   
105.
专业化生物学文献检索系统的设计与开发   总被引:2,自引:1,他引:1  
以国际互联网的文献资料为主要信息资源,建立了一个易于维护和更新的大规模的专业化生物学文献数据库,同时,以PowerBuilder为开发工具、以Sybase为数据库引擎,基于Windows操作工发了相应的文献检索系统软件,经1年的使用,该数据及检索系统运行稳定、正常。  相似文献   
106.
通过对《中国林业文摘》及其前身《中文科技资料目录(林业)》1983~1993年文献量的统计分析,较系统地揭示了我国林业科学各学科及分支学科研究的动态规律,为合理调整与平衡我国林业科学研究的全面发展提供科学依据。  相似文献   
107.
重点探讨了绿洲乡土聚落形态在水资源约束下所呈现的各种特征。界定了乡土聚落、聚落形态的概念;从历史维度和空间维度进行了绿洲聚落变迁与分布的水资源约束分析;以新疆吐鲁番麻扎古村落为例,从聚落选址形态、聚落水平形态、聚落垂直形态、聚落要素形态4个方面,探讨了基于水资源约束下的绿洲乡土聚落形态特征,总结归纳出"缘水而居"、"川...  相似文献   
108.
为了了解中国马铃薯渣发明专利申请的情况,促进我国马铃薯渣处理与利用技术水平的提高,为我国马铃薯渣专利申请的研究提供决策依据,用《中国专利数据库(知网版)》检索1988~2013年间所申请的马铃薯渣发明专利,并按照申请发明专利进行数据分析,按照专利公开的时间、专利数量、专利申请人类型和专利申请状况等项目进行数据统计与分析.结果表明,从2007年开始,马铃薯渣发明专利取得较大的发展,按各个研究进行统计,主要集中饲料、生化制品、膳食纤维、机械等方面的利用较多,且国内发明专利最多的省份是甘肃.  相似文献   
109.
ABSTRACT

A brief overview is provided of the policies, responsibilities, procedures and current projects of the Gift and Exchange Unit of the National Agricultural Library (NAL). Exchange operations which formed a part of the earliest library traditions of the U.S. Department of Agriculture now aid NAL in meeting the challenges of acquisitions operations which must adapt continually during an era of rapid technological change and stringent funding.  相似文献   
110.
Global interest in studying biochar stems from its ability to sequester carbon in soil and render nutrients and moisture more readily available to root systems. Therefore, a bibliometric analysis was conducted to investigate global scientific publications related to biochar research, providing insight into the number of articles published, journal platforms, subjects, citations, and overall trends. The primary databases employed were the Web of Science and Science Citation Index. A total of 1,697 articles published between 2000 and 2015 were evaluated. This systematic bibliometric analysis will assist research groups and individuals to understand global biochar research trends and focus future research. The influence of biochar on soil, plants, and the environment continues to require greater attention.  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