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   53318篇
  免费   513篇
  国内免费   548篇
安全科学   1358篇
废物处理   2713篇
环保管理   6809篇
综合类   8399篇
基础理论   14671篇
环境理论   28篇
污染及防治   13185篇
评价与监测   3821篇
社会与环境   3105篇
灾害及防治   290篇
  2022年   417篇
  2021年   410篇
  2020年   312篇
  2019年   384篇
  2018年   1924篇
  2017年   1880篇
  2016年   2078篇
  2015年   877篇
  2014年   1199篇
  2013年   3576篇
  2012年   1841篇
  2011年   3130篇
  2010年   2225篇
  2009年   2103篇
  2008年   2721篇
  2007年   3065篇
  2006年   1808篇
  2005年   1547篇
  2004年   1457篇
  2003年   1551篇
  2002年   1436篇
  2001年   1742篇
  2000年   1225篇
  1999年   746篇
  1998年   545篇
  1997年   558篇
  1996年   563篇
  1995年   659篇
  1994年   648篇
  1993年   553篇
  1992年   572篇
  1991年   546篇
  1990年   593篇
  1989年   550篇
  1988年   474篇
  1987年   450篇
  1986年   399篇
  1985年   407篇
  1984年   481篇
  1983年   420篇
  1982年   447篇
  1981年   387篇
  1980年   321篇
  1979年   343篇
  1978年   318篇
  1977年   250篇
  1975年   259篇
  1974年   250篇
  1972年   248篇
  1971年   248篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
11.
Article impact statement: The optimism permeating biological conservation should be recalibrated considering the future that present times portend.  相似文献   
12.
13.
14.
Unsustainable wildlife trade affects biodiversity and the livelihoods of communities dependent upon those resources. Wildlife farming has been proposed to promote sustainable trade, but characterizing markets and understanding consumer behavior remain neglected but essential steps in the design and evaluation of such operations. We used sea turtle trade in the Cayman Islands, where turtles have been farm raised for human consumption for almost 50 years, as a case study to explore consumer preferences toward wild‐sourced (illegal) and farmed (legal) products and potential conservation implications. Combining methods innovatively (including indirect questioning and choice experiments), we conducted a nationwide trade assessment through in‐person interviews from September to December 2014. Households were randomly selected using disproportionate stratified sampling, and responses were weighted based on district population size. We approached 597 individuals, of which 37 (6.2%) refused to participate. Although 30% of households had consumed turtle in the previous 12 months, the purchase and consumption of wild products was rare (e.g., 64–742 resident households consumed wild turtle meat [i.e., 0.3–3.5% of households] but represented a large threat to wild turtles in the area due to their reduced populations). Differences among groups of consumers were marked, as identified through choice experiments, and price and source of product played important roles in their decisions. Despite the long‐term practice of farming turtles, 13.5% of consumers showed a strong preference for wild products, which demonstrates the limitations of wildlife farming as a single tool for sustainable wildlife trade. By using a combination of indirect questioning, choice experiments, and sales data to investigate demand for wildlife products, we obtained insights about consumer behavior that can be used to develop conservation‐demand‐focused initiatives. Lack of data from long‐term social–ecological assessments hinders the evaluation of and learning from wildlife farming. This information is key to understanding under which conditions different interventions (e.g., bans, wildlife farming, social marketing) are likely to succeed.  相似文献   
15.
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   
16.
Environmental Science and Pollution Research - Zinc is an essential nutritional trace mineral required for growth and health. The aim of the current work is to compare the effects of bulk zinc...  相似文献   
17.
18.
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   
19.
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