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 218 毫秒
811.
基于被引率统计的中文茶学论文价值分析   总被引:2,自引:1,他引:1  
朱永兴 《茶叶科学》2007,27(2):172-178
搜集整理了最近20多年来中文茶科技文献的引文数据,统计分析了文献被引数据的各项指标,主要包括被引用频次和篇均被引率,以及它们在各期刊、机构、作者间的分布特征。据此,还对我国茶科技文献及其相关机构、期刊和作者的学术水平评价等问题进行了讨论。  相似文献   
812.
[目的/意义]循证方法已成为管理、教育、经济和法律等社会领域的重要研究范式。在数字人文研究中,如何从原始文献资料中获取和加工证据,以便有效地解决研究问题,这是一个具有重要的理论和现实意义的研究议题。[方法/过程]本文以社会认识层次论作为循证数字人文证据综合的理论基础,解析了循证数字人文证据生态系统的层次结构,并以原始文献和二手文献中的原始证据与二手证据的综合过程为例,演示了多元互证的具体流程。[结果/结论]本文提出了循证数字人文的证据层级结构,并在此基础上从效度和认知两个方面探讨了循证效度协同问题。基于前序研究,本文还对循证数字人文的多元互证模式与途径进行了归纳梳理。本文所提出的循证数字人文研究中证据整合的范式,有助于为构建具有中国特色循证数字人文自主知识体系提供参考。  相似文献   
813.
中央"一号文件"连续多年提出要推进农业绿色发展。绿色食品不仅具有安全优质的特点,还有着保护生态环境的社会价值,其产业发展状况一直备受关注。现有文献主要从绿色食品产业的发展历程、发展现状、制约因素、发展问题和发展建议五个角度进行相关研究,还存在三个方面不足:一是实证类的相关文献偏少;二是文献研究的区域比较集中;三是研究层次较为宏观。  相似文献   
814.
为系统分析植物免疫诱抗剂(plant immune inducer)当前的研究概况及应用前景。本研究从Web of Science、CNKI中国知网下载相关数据,利用CiteSpace软件和excel等分析工具,采用文献计量学方法对1985—2021年在国内外期刊上发表的关于植物免疫诱抗剂的文献进行可视化分析。结果表明,当前植物免疫诱抗剂相关研究文献处于波动上升的趋势;根据WOS数据库,在外文文献中,植物免疫诱抗剂相关文献主要出自美国、中国、日本等国家。通过高频次关键词分布,研究热点为水杨酸类植物免疫诱抗剂、氨基寡糖素类、青枯雷尔氏菌,以及秸秆反应堆技术、作物增产技术等方面;在高共被引文章中,以植物免疫诱抗剂机制阐述为主。本研究计量分析结果可为中国植物免疫诱抗剂的研究及技术应用提供思路和方法。  相似文献   
815.
The global intensification of urbanization is driving a disconnect between humans and nature. Communicating ecosystem services (ES) and disservices (EDS) to city residents offers an opportunity to help reassociate people with ecological processes of the urban forest, benefiting support for urban forest management. It has been theorized that the complexity of ES and EDS may dissuade their coverage by journalists in print media. Further, the complexity of the interrelationship of ES and EDS could represent a challenge for communication. To examine communication of ES and EDS, we conducted a literature review of newspaper articles published in two prominent newspapers in Winnipeg, Manitoba between January 2010 and May 2021. During the study period, 114 urban forestry articles mentioned ES and/or EDS. Cultural services were the most frequently discussed, followed by regulating services. Provisioning services were discussed least which may reflect their reduced importance in urban forestry discourse/management. Twenty-three articles mentioned EDS, only eight of which also mentioned ES. Only six articles referenced the related ES to the EDS, all of which were in articles focused on tree planting. Despite the complexity of many ES discussed in the articles, the interrelatedness of some ES and EDS were not well described. Counter to previous newspaper reviews, we found that ES were discussed more than EDS. However, the communication of EDS remains an important component of urban forest discourse. While navigating communication on the intersection of ES and EDS may prove challenging in print journalism, we argue restructuring EDS communication such that it is framed in ES discourse could mitigate public concerns surrounding urban forestry, while creating equitable coverage of urban forest affairs. We identify the need for further research on the impact of social media and television as alternative venues for urban forestry discourse.  相似文献   
816.
通过介绍GoPubMed、h指数和F1000因子,拓展文献检索课的教学内容,提高文献资源的利用效率。  相似文献   
817.
长期以来,围绕着政治立场问题展开的探讨,为理解阮籍《为郑冲劝晋王笺》提供了诸多启示,但也带来了视角单一的障蔽。将该文返置于中古文章学发展的脉络,能够在客观认识其文本属性、贴切归纳其文本特质的基础上,探知其进入文学史脉络的机缘,体会阮籍的一系列公牍书写对于两晋南朝文士提升"笔"体内涵,进而改善自身社会地位和文化生态的启示意义。  相似文献   
818.
[目的/意义]雨花英烈精神是中国共产党新民主主义革命精神的重要组成和代表,雨花英烈的原始革命文献是记录雨花英烈精神的重要来源与载体,利用内容标注、特征构建等文本处理技术对文献内容进行深度挖掘,既有助于弘扬革命文化,赓续红色血脉,也有益于开拓技术应用对象,促进技术水平提升。[方法/过程]本文以雨花英烈相关原始文献为数据来源,以雨花英烈为对象构建雨花英烈轻量级本体,以此作为雨花英烈群体特征描述框架,基于领域词表及触发词特征从雨花英烈革命文献中抽取本体中相关实例,实现对雨花英烈多维属性的形式化特征构建。雨花英烈轻量级本体的类别及属性描述了雨花英烈群体特征框架,通过对抽取的本体实例的数据分析,则可实现对雨花英烈群体特征的数据分析。[结果/结论]通过对雨花英烈基本信息、革命活动及狱中斗争的有关文本内容的统计分析,从数据角度进一步揭示了雨花英烈的群体特征,包括受教育程度高、牺牲年龄小,长期在国民党统治中心坚持斗争,坚守信仰,对党忠诚,满怀修齐治平的家国情怀,自觉践行对高尚的道德追求等。运用轻量级本体等本文量化分析方法有助于具象化地呈现雨花英烈的崇高理想信念、高尚道德情操以及为民牺牲的大无畏精神内涵。本文对于创新雨花英烈精神的呈现方式与传播效果有一定参考价值。  相似文献   
819.
Improved rice varieties (IRVs) play a significant role in establishing food security and improving livelihood in the Global South since its introduction in the 1960s. However, the adoption of new IRVs has remained relatively low. This low adoption poses a challenge to rice-producing and consuming countries as they are increasingly threatened by production shortages, malnutrition, and poor rice quality. Many empirical studies have attempted to identify the determinants influencing the adoption of IRVs by distinguishing the characteristics between adopters and non-adopters. This review showed a consensus on the important determinants influencing the adoption of IRVs in the Global South. Findings synthesized from 99 studies suggested that variables (farm size, education, information access and farm location) examined extensively are not necessarily the most important determinants of adoption when undertaking a weighted analysis. Terrain, source of seed and technology-related attributes (perceived yield, maturity, ease of use, marketability and technical efficiency) are more important determinants of adoption, with determinants changing according to adoption type (probability or intensity of adoption), variety type and region. The recommendations for future adoption studies include: incorporating more technology-specific variables, increasing research for overlooked regions and variety types, shifting away from predominant static analysis by capturing the dynamics of the adoption process, and considering the potential biases in analyses. This review will facilitate the development of targeted interventions and policies that promote IRV adoption in the Global South.  相似文献   
820.
Edible landscapes provide a series of benefits for the sustainable development of a city, and therefore, in recent years, their development has become a fashion which has stimulated research. However, there is a need for a comprehensive, integrated, literature review, to increase people's knowledge of edible landscapes for a sustainable future. Therefore, this paper conducts a systematic review through the Preferred Reporting Initiative for Systematic Evaluation and Meta-Analysis (PRISMA). This study was conducted using Web of Science and Google Scholar, and 41 eligible articles were selected from the 2004 articles originally identified from the years 1975–2022. These articles were related to the topics of (1) ecology, (2) food safety, (3) social, economic and healing benefits, (4) construction, and (5) understanding, motivation, and evaluation. The findings suggest that, first, the creation of edible landscapes in different urban areas of the world can have different effects, with most studies showing that the creation of edible landscapes in urban areas can increase ecological diversity. Despite this, some individual studies draw different conclusions. Secondly, most studies show that the development of edible landscapes in urban areas is beneficial for increasing food production and thus improving urban food security, provided that the land is not contaminated. Again, some studies have found that developing edible landscapes in urban areas has social and economic benefits. However, without a reasonable management mechanism, this process is prone to contradictions and thus unproductive. Therefore, urban land policies, land contamination, and management issues in different countries have limited the further development of urban edible landscapes. This study suggests that future research on edible landscapes can be conducted in the areas of land policy, land pollution control, and management mechanisms to solve these problems and promote further development.  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