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   475篇
  免费   30篇
  国内免费   8篇
安全科学   19篇
废物处理   14篇
环保管理   207篇
综合类   94篇
基础理论   45篇
环境理论   1篇
污染及防治   8篇
评价与监测   10篇
社会与环境   105篇
灾害及防治   10篇
  2024年   2篇
  2023年   5篇
  2022年   6篇
  2021年   6篇
  2020年   6篇
  2019年   18篇
  2018年   9篇
  2017年   16篇
  2016年   23篇
  2015年   15篇
  2014年   18篇
  2013年   31篇
  2012年   28篇
  2011年   37篇
  2010年   29篇
  2009年   15篇
  2008年   14篇
  2007年   31篇
  2006年   20篇
  2005年   24篇
  2004年   26篇
  2003年   23篇
  2002年   21篇
  2001年   14篇
  2000年   19篇
  1999年   12篇
  1998年   4篇
  1997年   3篇
  1996年   5篇
  1995年   13篇
  1994年   4篇
  1993年   7篇
  1992年   1篇
  1991年   2篇
  1984年   2篇
  1983年   1篇
  1978年   1篇
  1975年   1篇
  1972年   1篇
排序方式: 共有513条查询结果,搜索用时 312 毫秒
201.
科技期刊作为一种专业性较强的学术性刊物,不同于其他通俗性时尚刊物,它的受众面较为狭窄,读者群也受到相应的限制,而要在社会主义市场经济体制下求得生存与发展,必须走向市场、适应新形势,在市场竞争中取得社会效益与经济效益的统一,开拓出新的局面。  相似文献   
202.
本文指出,把旅游资源优势转化为经济优势是河南旅游业发展的关键,转化的方式是将旅游资源变为旅游产品,转化的原则是市场的需求,转化的步骤是根据市场需求,对旅游资源进行筛选,加工成适销对路的产品再推向旅游市场.  相似文献   
203.
The red bishop (Euplectes orix) is a highly polygynous and colonial weaverbird. Males construct several nests within their territories to which they try to attract females, and females are solely responsible for incubation and raising offspring. In this paper, we describe the characteristics of the red bishop’s mating system as a biological market and investigate the role of nests built by males as a traded commodity in a mating market. As timing of breeding in red bishops in arid and semi-arid zones depends on rainfall patterns which are often unpredictable, there are temporal changes in demand for and supply of nests within a breeding season, with breeding activities of males and females being highly synchronised. We found that males increased their nest-building speed with increased female breeding activity independently of rainfall, indicating that supply follows demand in this mating market. The supply of nests was always larger than the demand for nests. Construction costs for nests increased with demand for nests as indicated by shorter nest-building duration and shorter building delays between two consecutively built nests at times of high breeding activity. Males as a trading class are chosen according to the age of their nests offered, with young nests having a higher probability of being accepted by females. Furthermore, female choosiness with regard to nest age decreased when their own market value decreased, as predicted by biological market theory. The temporal changes of breeding activity together with the female preference for young and fresh nests require that males quickly adjust nest-building activity to varying female demand for new nests. However, males with a better adjustment of building speed to female breeding activity did not gain higher mating success.  相似文献   
204.
土肥的基础地位是不随社会性质或社会经济类型的变化而变化的,它既具重要性,又具长久性.市场经济是仍然需要土肥科技的.土肥科技的教学、科研和推广的力度必须加大,局面必须改观,且宜快不宜迟.土肥科技工作者一定要将培肥地力作为中心工作.根据广东的实际,增施有机肥是培肥地力的主要措施,因而抓秸秆还田和发展冬绿肥是我们工作的重点.  相似文献   
205.
This paper aims to assess the consequences of the amendments made to the Kyoto Protocol during COP 7 in Marrakech. The major issue of hot air and CDM transaction costs is examined using the CERT model to show that primary supply regions, typically those with hot air availability, might control the emissions reduction permit supply market and maximise net export revenues of permit supply by withholding 40 to 60% of available hot air credits. The assumption that primary permit suppliers control permit price via a restriction of hot air supply to the market will inadvertently leave a portion of the market share open to non-Annex B CDM supply, despite potentially extreme variance in CDM transaction costs. A summary table of policy implications on the emissions reduction permit market is also included.  相似文献   
206.
随着全球经济的飞速发展,经济受资源和环境约束的矛盾接近临界。而人们对环境质量的需求不断上升,在此大背景下,节能环保产业应运而生。在介绍国际节能环保产业和分析中国节能环保产业现状的基础上,分析融资渠道不够畅通,市场活力有待激发,资本市场亟待完善,产业创业还需推进等一系列制约中国节能环保产业发展的问题,并从理清管理体制,畅通融资渠道,健全资本市场,推进产业创业等方面给出了建议。  相似文献   
207.
The purpose of this study is to quantify the marginal willingness to pay (MWTP) for clean air in China. We provide the first estimate of MWTP for clean air by implementing a hedonic method using housing price and air quality data from Shanghai. Our estimates imply that air pollution has a significant and negative impact on housing price. We also find that the willingness to pay for better air quality varies significantly across different income groups. This paper helps to deepen our understanding of the economic impacts of air pollution in emerging Asian metropolises where residents are suffering from the most severe respiratory health problems.  相似文献   
208.
We analyze the bipartisan call to ban US exports of commodity mercury. An export ban can generate positive environmental benefits by increasing the scarcity of mercury in developing economies where significant toxic releases occur. We show, however, that a direct mercury purchase and retirement policy can achieve the same foreign environmental goals without adverse impacts on domestic environmental quality. We present qualitative and quantitative evidence that highlight the potential inefficiencies of a mercury export ban as a method of achieving environmental objectives.  相似文献   
209.
Abstract: Illegal international trade in wildlife (excluding fisheries and timber) has been valued at more than US$20 billion. A more precise figure has not been determined in part because of the clandestine nature of the trade, and for this same reason even regional and local levels of wildlife trade are difficult to assess. The application of recent developments in wildlife field‐survey methods (e.g., occupancy) now allows for a more‐accurate estimation of wildlife trade occurrence, including its hidden components at a variety of scales (e.g., regional, local) and periods (e.g., single season, 1 year, multiple years). Occupancy models have been applied in wildlife field studies to address the problem of false absences when conducting presence–absence surveys. Occupancy surveys differ from traditional presence–absence surveys because they incorporate repeat surveys, allowing for the likelihood of detecting a species (the probability of detection) to be estimated explicitly (in contrast to traditional surveys that often incorrectly treat this probability as close to one to allow for estimation of presence). Occupancy methods can be applied to a variety of wildlife‐trade surveys, including, for example, single‐species availability, links between two illegally traded species (i.e., co‐occurrence), and disease occurrence in live trade. In addition, free user‐friendly software (i.e., PRESENCE) allows even nonstatisticians to adequately address this issue. I simulated a hypothetical wildlife‐trade market survey that resulted in an apparent 20% decline in naïve occupancy (proportion of surveyed towns engaged in the trade) over 2 years, but when I accounted for change in probability of detection over the years the difference in occupancy was not statistically significant. As more sophisticated methods, such as occupancy, are applied to wildlife‐trade market surveys, results will be more robust and defensible and therefore, theoretically, more powerful when presented to conservation policy and decision makers.  相似文献   
210.
2012和2013年的废纸市场让很多企业一筹莫展,全球经济不振,国内需求不足,产能过剩,直接影响了造纸行业的生产和销售,作为原料供应商的废纸回收利用行业,必然受到连带影响,整个产业进入低迷阶段.除了外部经济环境的影响,行业内部应该如何调整,产业政策又该怎样引导行业健康发展,将是未来需要持续探讨的课题.  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