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   30639篇
  免费   197篇
  国内免费   245篇
安全科学   557篇
废物处理   1771篇
环保管理   3679篇
综合类   3670篇
基础理论   8424篇
环境理论   6篇
污染及防治   7686篇
评价与监测   2790篇
社会与环境   2372篇
灾害及防治   126篇
  2023年   143篇
  2022年   393篇
  2021年   332篇
  2020年   166篇
  2019年   222篇
  2018年   1723篇
  2017年   1650篇
  2016年   1699篇
  2015年   520篇
  2014年   654篇
  2013年   1905篇
  2012年   1152篇
  2011年   2183篇
  2010年   1482篇
  2009年   1386篇
  2008年   1770篇
  2007年   2160篇
  2006年   927篇
  2005年   765篇
  2004年   773篇
  2003年   777篇
  2002年   787篇
  2001年   930篇
  2000年   644篇
  1999年   398篇
  1998年   285篇
  1997年   247篇
  1996年   295篇
  1995年   272篇
  1994年   255篇
  1993年   235篇
  1992年   243篇
  1991年   209篇
  1990年   214篇
  1989年   221篇
  1988年   199篇
  1987年   158篇
  1986年   126篇
  1985年   140篇
  1984年   180篇
  1983年   164篇
  1982年   197篇
  1981年   135篇
  1980年   120篇
  1979年   158篇
  1978年   119篇
  1977年   107篇
  1976年   105篇
  1975年   85篇
  1974年   89篇
排序方式: 共有10000条查询结果,搜索用时 343 毫秒
11.
12.
13.
Research suggests that encouraging motivated residents to reach out to others in their social network is an effective strategy for increasing the scale and speed of conservation action adoption. However, little is known about how to effectively encourage large numbers of residents to reach out to others about conservation causes. We examined the influence of normative and efficacy-based messaging at motivating residents to engage in and to encourage others to participate in native plant gardening in their community. To do so, we conducted a field experiment with messages on mailings and tracked native plant vouchers used. Efficacy messages tended to be more effective than normative messages at increasing residents’ willingness to reach out to others to encourage conservation action, as indicated by a several percentage point increase in native plant voucher use by residents’ friends and neighbors. Messages sometimes had different impacts on residents based on past behaviors and perceptions related to native plant gardening. Among these subgroups, efficacy and combined efficacy and norm messages most effectively encouraged individual and collective actions, as indicated by increased voucher usage. Our findings suggest that interventions that build residents’ efficacy for engaging in a conservation behavior and for reaching out to others may be a promising path forward for outreach. However, given our results were significant at a false discovery rate cutoff of 0.25 but not 0.05, more experimental trials are needed to determine the robustness of these trends.  相似文献   
14.
15.
Environmental Science and Pollution Research - Seasonal distribution of phytoplankton community and size structure was assessed in three different tropical ecosystems of the western Bay of Bengal...  相似文献   
16.
Purpose. The current research was carried out to determine grip strength (GS) with change in posture and upper-limb muscle activity of manual workers and investigate the impacts of these changes. Methods. For the current research, 120 male and 80 female participants were selected and GS was assessed using a digital hand grip dynamometer in various conditions. Results. The outcomes showed that male participants had higher GS as compared to female participants. Maximum GS was found in a standing posture with the fixed forward shoulder at 45°, elbow at 90° and a neutral position of the wrist and forearm for all participants. Conclusions. Higher values of GS were attained in standing postures which may result in attainment of higher performance levels by the workers. The outcomes justify the importance of correct postures during manual work in industries employing traditional methods.  相似文献   
17.
Following the renewed effort at achieving a new green revolution for Africa, emphasis has been placed on modernizing smallholder agriculture through the deployment of improved inputs especially mechanized technologies. In Ghana, the government has in the last decade emphasized the provision of subsidized mechanized ploughing services to farmers alongside a rapidly growing private sector tractor service market. While mechanized technology adoption rates have increased rapidly, the deployment of these technologies has been without critical analysis of the impacts on production patterns and local agrarian systems. This paper examines the distributional impacts of agriculture mechanization on cropping patterns and farm sizes of smallholder farmers in northern Ghana using Geographic Information Systems (GIS) techniques, and semi-structured interviews with smallholder farmers (n=60). Specifically, comparative analysis of the field sizes and cropping patterns of participant farmers prior to and after the adoption of mechanized technologies was conducted. In-depth interviews were used to contextualize the experiences of smallholder farmers toward understanding how mechanization may be impacting traditional agriculture. Our findings reveal a mechanization paradox in which farm sizes are expanding, while cropping patterns are shifting away from traditional staple crops (pearl millet and sorghum bicolor) to market-oriented crops (maize, rice and groundnuts). This transition we argue, has adverse implications on the cultural dimension of food security, the organization of social life, and climate change adaptation. We recommend a retooling of the current agricultural policy focus to ensure context sensitivity for a more robust battle against food insecurity.  相似文献   
18.
19.
The purpose of the research is to identify the critical challenges that are impeding the adoption of e-mobility in India. It also aims to give a roadmap how to address these challenges while taking into considerations concerns of all the relevant stakeholders. Based on an in-depth literature review, an exploratory research design is employed to delve deep into various aspects of e-mobility. This is followed by a three-phase Delphi technique to identify and rate the e-mobility challenges in the Indian context. The study successfully identifies four different categories of challenges and proposes integrative framework for e-mobility. Further, the research goes on to lay out the future roadmap for mass adoption of electric vehicles (EVs) in India. The research is novel in terms of presenting a holistic viewpoint on e-mobility in India. Its originality lies in identifying the major inhibitors obstructing EVs adoption in India and then suggesting the roadmap how to overcome these impediments for mass adoption of e-mobility.  相似文献   
20.
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