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   21684篇
  免费   197篇
  国内免费   236篇
安全科学   555篇
废物处理   1078篇
环保管理   2549篇
综合类   2787篇
基础理论   5525篇
环境理论   6篇
污染及防治   6075篇
评价与监测   1870篇
社会与环境   1546篇
灾害及防治   126篇
  2023年   142篇
  2022年   379篇
  2021年   327篇
  2020年   162篇
  2019年   217篇
  2018年   399篇
  2017年   401篇
  2016年   616篇
  2015年   402篇
  2014年   635篇
  2013年   1890篇
  2012年   731篇
  2011年   929篇
  2010年   854篇
  2009年   833篇
  2008年   943篇
  2007年   1016篇
  2006年   919篇
  2005年   743篇
  2004年   738篇
  2003年   719篇
  2002年   692篇
  2001年   916篇
  2000年   635篇
  1999年   396篇
  1998年   277篇
  1997年   247篇
  1996年   295篇
  1995年   271篇
  1994年   252篇
  1993年   235篇
  1992年   242篇
  1991年   208篇
  1990年   214篇
  1989年   220篇
  1988年   198篇
  1987年   158篇
  1986年   126篇
  1985年   140篇
  1984年   171篇
  1983年   156篇
  1982年   197篇
  1981年   135篇
  1980年   119篇
  1979年   154篇
  1978年   119篇
  1977年   107篇
  1976年   100篇
  1975年   84篇
  1974年   89篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
12.
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   
13.
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   
14.
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   
15.
16.
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   
17.
18.
Journal of Material Cycles and Waste Management - The present research work focused on fabricating Biodegradable Plate (BD plate) composed of rice husk ash, bagasse and corn starch which is...  相似文献   
19.
20.
Quantitative methods have been applied to the study of floristic structure and diversity in Samarskaya Luka. The results show that Samarskaya Luka is a floristically heterogeneous area in which six elementary floras can be distinguished. This area has been assessed as a floristically autonomous formation, and its floristic representativeness was estimated.  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