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   4502篇
  免费   231篇
  国内免费   133篇
林业   2478篇
农学   87篇
基础科学   140篇
  175篇
综合类   1711篇
农作物   22篇
水产渔业   50篇
畜牧兽医   61篇
园艺   93篇
植物保护   49篇
  2024年   5篇
  2023年   39篇
  2022年   47篇
  2021年   56篇
  2020年   90篇
  2019年   141篇
  2018年   58篇
  2017年   72篇
  2016年   126篇
  2015年   88篇
  2014年   240篇
  2013年   247篇
  2012年   420篇
  2011年   360篇
  2010年   246篇
  2009年   308篇
  2008年   251篇
  2007年   311篇
  2006年   308篇
  2005年   335篇
  2004年   253篇
  2003年   209篇
  2002年   114篇
  2001年   135篇
  2000年   65篇
  1999年   62篇
  1998年   42篇
  1997年   40篇
  1996年   44篇
  1995年   29篇
  1994年   20篇
  1993年   29篇
  1992年   15篇
  1991年   19篇
  1990年   12篇
  1989年   17篇
  1988年   8篇
  1987年   3篇
  1986年   1篇
  1985年   1篇
排序方式: 共有4866条查询结果,搜索用时 15 毫秒
41.
以文献研究、逻辑分析为主要研究方法,分析了当前我国体育经纪组织发展所面临的困境,指出了我国体育经纪组织品牌化发展的必要性。从五个方面提出了我国体育经纪组织品牌化发展的思路:增强体育经纪组织品牌意识、实施体育经纪组织品牌战略、设计体育经纪组织品牌要素、塑造体育经纪组织品牌文化、打造体育经纪组织知名品牌。  相似文献   
42.
家庭林场经营模式的优点,除了创新经营管理体制,解放农村生产力,调动广大林农的生产经营积极性,促进林农脱贫致富外,还在于该模式内涵丰富的生态文明价值理念,能够将生态文明价值观在代际间传递延续,指导生产实践,保护生态环境,实现永续发展,这对促进生态文明建设、构建美丽中国具有重大的现实作用和深远的影响意义。本研究在阐明家庭林场内涵丰富的生态文明价值理念的基础上,阐释了发展家庭林场的经济、社会和生态效益,并针对目前家庭林场发展存在的问题提出对策建议。  相似文献   
43.
本文结合吉林省实际,重点阐述了碳汇林业发展的必要性和重要性,指出了科技、人才对碳汇林业发展的支撑作用,强调了科技研发环节前移和发挥学术组织作用的战略选择。  相似文献   
44.
In this paper the results of the first comprehensive study on perception of and satisfaction with urban forests and green space in seven Southeast European cities are presented. The aims of the paper are to analyse 1) citizen perceptions of the current state of urban forests and green space in their cities, 2) to what extent current urban forests and green space meet their needs and how this can be improved. A cross-sectional study was conducted by using a common face-to-face survey questionnaire. Respondents were selected based on census data though a stratified sampling procedure by taking into account age, gender and city district (n = 384 in each city). The results showed that citizens genuinely care for urban forests and green space in their cities, but are not satisfied with their current state. The respondents found issues related to misbehaviour of other users, the presence and quality of facilities, as well as the presence and quality of management or maintenance the most pressing. There were more statistically significant differences than similarities between cities. Socioeconomic variables explained perceptions only to some extent. Citizens were very supportive of educational campaigns about the importance of urban forests and green space as well as of better enforcement of the existing regulations though having more community wardens that were expected to tackle current unsatisfactory situations. Urban planning and urban forest and green space management in these cities are facing many problems characteristic for post-socialist countries. Study findings are expected to contribute to decision making in urban planning and natural resource management.  相似文献   
45.
In order to study the tolerance dose of Kunming mice to montmorillonite as a mycotoxin adsorbent in diets,the experiment selected 60 healthy male Kunming mice with initial average body weight of (17±0.12)g,randomly divided them into 5 treatments with two replicates per group and 6 mice per replicate.Five experimental diets were added to 0 (control group),0.5%,1%,2% and 5% montmorillonite,respectively.After 30 days,the growth performance,nutrients apparent digestibility,serum biochemical indices and internal organization were tested to determine the tolerance dose of montmorillonite for Kunming mice.The results showed that the ADFI was significantly increased in 0.5% group (P< 0.05),while there were no significant differences in ADFI and ADG between 1% group and control group (P> 0.05),then the ADFI was significantly decreased with the increasing of montmorillonite supplemental level (P< 0.05).The ADG in 2% group had no significant difference when compared with the control group (P> 0.05),while significantly lower than that in 0.5% and 1% groups (P< 0.05).The apparent digestibility of DM,CP and EE showed no significant effect at any level of montmorillonite (P> 0.05).Serum ALT,AST activities and MDA content were gradually increased with the montmorillonite supplemental level increasing,and that in 1%,2% and 5% groups were significantly higher than that in control group (P< 0.05),but there were no significant differences between 0.5% group and control group (P> 0.05).Tissue sections showed that mice livers were damaged in varying degrees when the montmorillonite supplemental level was 5%.In conclusion,based on a comprehensive consideration of all indexes,it could be seen that the tolerance dose of the tested montmorillonite for Kunming mice was between 0.5% and 2% when mycotoxin contents in diets were in security range.  相似文献   
46.
王俊雁 《湖南农机》2015,(3):126-127
可持续发展是一种新的科学发展观,已经深入到林业领域。要使森林资源满足当代人的建设需要,又为后代人储备资源,就要实施科技兴林,不断提高林业建设的科技含量,不断促进林业的可持续发展。  相似文献   
47.
总结了林业应用系统本体构建的基本方法,介绍了本体知识模型的构建思路,以期为本体技术的推广应用提供参考。  相似文献   
48.
Interest in planting urban food trees (UFTs) in public spaces is growing in popularity as a form of urban greening and a potential food source. Currently there is minimal research on the governance and policy aspects of integrating food trees into cities. To fill this gap, we investigated the characteristics of UFT site governance and how it compares to current urban forest governance. Semi-structured interviews were conducted with relevant municipal officials in Calgary, Edmonton, Toronto and Victoria about their perspectives and involvement with UFT sites in their city. A scan of policy documents was completed to supplement the interviews. The interviews were analyzed using a deductive coding framework based on the Policy Arrangement Approach. We found that key actors at the UFT sites were local organizations and site champions, with minimal municipal engagement. Most site resources provided by municipalities were in-kind. There are also basic knowledge gaps about how to care for UFTs. Currently municipal by-laws prohibit the harvesting and removal of plant material, and are at odds with the purpose of UFT sites, with few municipalities fully integrating UFTs in policies. The primary discussion around UFTs centre concerns for public health and safety, management, and use of public space with limited discussions of benefits. This research demonstrates the value of co-governance models to support UFTs, while a shift in focus from risks to benefits could encourage additional resources and policy integration. Further, including UFTs into policy would also support foraging and food tree maintenance in public spaces, and more fully reflect the plurality of urban forest engagement.  相似文献   
49.
为全面掌握全省各级林业站管理机构、各县(市、区)基层林业工作站的基本情况,基于云南省基层林业工作站情况调查的要求,结合乡镇林业工作站工程建设标准需要,以林业工作站调查信息数据为基础,利用VBA语言在Access 2007下开发具有形象直观的统计图功能、智能查询功能、数据导出至电子表格模板等功能特点的云南省基层林业工作站信息管理系统,文中阐述了系统开发方案、开发环境及系统主要功能。  相似文献   
50.
进行样地调查与树干解析,以研究米槠生长过程。采用米槠容器苗和裸根苗造林,比较造林保存率、胸径、树高、冠幅、变异系数等指标,以了解两种苗木的幼林生长效应,并比较天然林与人工林米槠的早期生长。研究表明,米槠在10-20 a,树高、胸径生长较快;14-30 a,材积生长较快;树龄33 a时,尚未达到数量成熟阶段。米槠容器苗造林的保存率、胸径、树高值均大于裸根苗,其中保存率比裸根苗高9.5%,胸径值大11.3%,树高值大4.6%。比较人工林和天然林的早期生长,人工林树高和胸径值均大于天然林。米槠容器苗造林,可以促进米槠生长,取得较好的造林效果。  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