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   3438篇
  免费   340篇
  国内免费   876篇
安全科学   426篇
废物处理   152篇
环保管理   340篇
综合类   2026篇
基础理论   473篇
污染及防治   597篇
评价与监测   233篇
社会与环境   232篇
灾害及防治   175篇
  2024年   27篇
  2023年   60篇
  2022年   152篇
  2021年   134篇
  2020年   174篇
  2019年   125篇
  2018年   122篇
  2017年   179篇
  2016年   144篇
  2015年   184篇
  2014年   226篇
  2013年   249篇
  2012年   306篇
  2011年   304篇
  2010年   278篇
  2009年   270篇
  2008年   265篇
  2007年   230篇
  2006年   261篇
  2005年   194篇
  2004年   154篇
  2003年   110篇
  2002年   121篇
  2001年   97篇
  2000年   77篇
  1999年   41篇
  1998年   26篇
  1997年   34篇
  1996年   21篇
  1995年   18篇
  1994年   18篇
  1993年   14篇
  1992年   7篇
  1991年   10篇
  1990年   6篇
  1989年   2篇
  1987年   2篇
  1985年   1篇
  1984年   1篇
  1981年   4篇
  1980年   4篇
  1979年   2篇
排序方式: 共有4654条查询结果,搜索用时 78 毫秒
991.
992.
993.
994.
Environmental Geochemistry and Health - Unfortunately, in the original publication of the article, Prof. Yong Sik Ok’s affiliation was incorrectly published.  相似文献   
995.
The trade in wild animals involves one‐third of the world's bird species and thousands of other vertebrate species. Although a few species are imperiled as a result of the wildlife trade, the lack of field studies makes it difficult to gauge how serious a threat it is to biodiversity. We used data on changes in bird abundances across space and time and information from trapper interviews to evaluate the effects of trapping wild birds for the pet trade in Sumatra, Indonesia. To analyze changes in bird abundance over time, we used data gathered over 14 years of repeated bird surveys in a 900‐ha forest in southern Sumatra. In northern Sumatra, we surveyed birds along a gradient of trapping accessibility, from the edge of roads to 5 km into the forest interior. We interviewed 49 bird trappers in northern Sumatra to learn which species they targeted and how far they went into the forest to trap. We used prices from Sumatran bird markets as a proxy for demand and, therefore, trapping pressure. Market price was a significant predictor of species declines over time in southern Sumatra (e.g., given a market price increase of approximately $50, the log change in abundance per year decreased by 0.06 on average). This result indicates a link between the market‐based pet trade and community‐wide species declines. In northern Sumatra, price and change in abundance were not related to remoteness (distance from the nearest road). However, based on our field surveys, high‐value species were rare or absent across this region. The median maximum distance trappers went into the forest each day was 5.0 km. This suggests that trapping has depleted bird populations across our remoteness gradient. We found that less than half of Sumatra's remaining forests are >5 km from a major road. Our results suggest that trapping for the pet trade threatens birds in Sumatra. Given the popularity of pet birds across Southeast Asia, additional studies are urgently needed to determine the extent and magnitude of the threat posed by the pet trade.  相似文献   
996.
Municipal solid waste management (MSWM) in China warrants particular attention as China has become the largest MSW generator in the world and the total amount of MSW it produces continues to increase. In recent years, central and local governments have made great efforts to improve MSWM in China. New regulations and policies have been issued, urban infrastructure has been improved, and commercialization and international cooperation have been encouraged. Considering these developments, an overview is necessary to analyze the current state as well as new opportunities and challenges regarding MSWM in China. This paper shows that since the late 1990s, the amount of MSW collected has been largely decoupled from economic growth and incineration has become an increasingly widespread treatment method for MSW. We identify and discuss four major challenges and barriers related to China’s MSWM, and propose an integrated management framework to improve the overall eco-efficiency of MSWM.  相似文献   
997.
The resin capsule system (RCS) was tested as a means of providing data on the presence and forms of volatile hydrocarbons. Results indicated that resin capsules provided data showing sensitivity to soil variables (texture and moisture content) and time. The objectives of this paper are to evaluate the RCS methodology and to determine whether carbonaceous resin capsules provide results that can be described by fundamental chemical partitioning and kinetic principles. Findings revealed a significant relationship between quantities of benzene, toluene, ethylbenzene, and xylene adsorbed on the capsule and quantities partitioned into the vapor phase. Kinetic evaluation indicated that the vapor adsorption by the resin capsule is regulated by diffusion processes. No verification of rate-limiting processes was possible due to limitations imposed by the experimental design, but it appears that during early stages, adsorption rate was limited by vapor diffusion through the soil. The resin capsule data also reflected differences that would be expected due to properties of the organic liquids present. These results provide further evidence that the RCS could be developed to suggest direct in situ monitoring to reveal quantities and nature of organic substances in soils.  相似文献   
998.
An evaluation is needed to monitor the progress of sustainable development (SD) in rice production systems. The purpose of this study is to provide policy inputs, examine the sustainability of rice production, and determine major policy areas. A requisite set of 12 indicators of three dimensions of SD, namely economic, was generated by employing an assemblage of top–down and bottom–up approaches. The data were gathered from farm households’ survey as well as in-depth discussion with stakeholders from the regions that represent irrigated, rain-fed lowland, rain-fed upland, flood-prone, and saline-prone rice-growing ecosystems in Bangladesh. By constructing composite indicators, the results revealed that 44 % of rice growers were economically viable, environmentally sound, and socially developed. The irrigated rice production system was found to be the most sustainable. The path analysis measured the contribution of the indicators to the index, and results highlighted that rice growers’ knowledge, skills, and social networks development, improving land productivity, and integrated nutrient management were essential for promoting sustainable rice production. However, the study findings suggest that pluralistic (i.e., government and non-government) agricultural advisory services can serve as an engine of transition to rice production sustainability in which a multi-year planning and strategy formulation are crucial besides investing in the modernization of extension services. Overall and ecosystem-specific policy implications that emerged from the findings of this study are outlined.  相似文献   
999.
对旧建筑物拆除,诸如墙体、基础、砖石建筑物、地板、油罐等容器、铜结构和特殊结构建筑物的拆除中的一般安全技术措施、拆除设施的设置、警告装置、安全装置,均作了较具体而明确的要求;对机械法拆除和爆破法拆除两种拆除方法中的安全技术要求,也有简要论述。  相似文献   
1000.
高温碟形双金属片是火警温度继电器的核心元件,结构复杂,为了研究其受热动作响应特性,采用有限元分析方法,通过Solidworks结合ANSYS对双金属片进行热-结构耦合场分析,获得了碟形双金属片的受热动作响应特性,并且通过不断改变高温碟形双金属片的外形结构进行求解分析,根据分析结果总结高温碟形双金属片的结构与其受热动作响应特性之间的关系,为高温碟形双金属片的结构参数设计和数据调节提供理论依据。  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