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   90526篇
  免费   1272篇
  国内免费   1351篇
安全科学   3813篇
废物处理   3281篇
环保管理   13968篇
综合类   21524篇
基础理论   26290篇
环境理论   74篇
污染及防治   14597篇
评价与监测   5375篇
社会与环境   3661篇
灾害及防治   566篇
  2022年   837篇
  2021年   836篇
  2020年   713篇
  2019年   873篇
  2018年   1132篇
  2017年   1174篇
  2016年   2190篇
  2015年   1859篇
  2014年   2607篇
  2013年   9305篇
  2012年   2258篇
  2011年   2568篇
  2010年   3321篇
  2009年   3459篇
  2008年   2044篇
  2007年   1905篇
  2006年   2271篇
  2005年   2238篇
  2004年   2559篇
  2003年   2379篇
  2002年   1922篇
  2001年   2180篇
  2000年   1968篇
  1999年   1496篇
  1998年   1366篇
  1997年   1359篇
  1996年   1476篇
  1995年   1576篇
  1994年   1461篇
  1993年   1320篇
  1992年   1302篇
  1991年   1276篇
  1990年   1232篇
  1989年   1188篇
  1988年   1037篇
  1987年   971篇
  1986年   985篇
  1985年   1066篇
  1984年   1161篇
  1983年   1160篇
  1982年   1173篇
  1981年   1095篇
  1980年   942篇
  1979年   925篇
  1978年   817篇
  1977年   716篇
  1976年   637篇
  1975年   603篇
  1973年   632篇
  1972年   636篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
521.
Many Superfund/hazardous chemical sites include waterbodies whose sediments contain hazardous chemicals. With the need to assess, rank, and remediate contaminated sediments at such sites, as well as in other waterways, regulators seek a simple, quantitative assessment approach that feeds easily into a decision‐making scheme. Numeric, co‐occurrence‐based “sediment quality guidelines” have emerged with the appearance of administrative simplicity. However, the very foundation of the co‐occurrence approach, based on the total concentrations of a chemical(s) in sediment, is technically invalid; its application relies on additional technically invalid presumptions. Use of technically invalid evaluation approaches renders any assessment of the significance of sediment contamination unreliable. This article reviews the technical roots and assumptions of the co‐occurrence‐based SQGs, the fundamental flaws in the rationale behind their development and application, and their misapplication for sediment quality evaluation. It also reviews concepts and approaches for the more reliable evaluation, ranking, and cleanup assessment of contaminated sediments at Superfund sites and elsewhere. © 2005 Wiley Periodicals, Inc.  相似文献   
522.
In 1995, the U.S. Environmental Protection Agency (US EPA) initiated the Brownfields Program to help local governments clean up and reuse hundreds of thousands of contaminated former factories and transportation and other commercial sites in cities and industrialized suburbs. By the end of 2002, the Brownfields Program had distributed grants of about $200,000 each to 436 local governments. Program grants have diffused through federal, state, regional, and local levels of government and private and not‐for profit organizations, and have reached into economically distressed neighborhoods. As expected, grant recipients disproportionately had a legacy of contaminated industrial sites and relatively large African American and/or Latino populations. But abandoned factories and environmental justice concerns do not completely explain the geographical distribution of recipients. Award winners tended to be larger cities with more capacity to compete for grants and were likely to be connected to sources of information about the grant opportunity and to decision makers. With a few exceptions, recipients consider the program to be highly successful at stimulating entrepreneurs to remediate and redevelop sites and, sometimes, surrounding neighborhoods. © 2005 Wiley Periodicals, Inc.  相似文献   
523.
Public Perception of Flood Hazard in the Niger Delta,Nigeria   总被引:3,自引:0,他引:3  
Summary Our study had the aim of understanding how floodplain dwellers regard the risk of flooding. About 500 questionnaires were administered to landowners in the selected settlements in the study area using systematic random sampling. The results of analysis show, among other things, that the population regards most important the causes of floods as heavy, prolonged rainfall and river overflow. Nevertheless, they have little knowledge of the frequency of severe floods, and flood alleviation schemes. Most flood victims do not get compensation or relief during flood disaster, and the reason why they remain in the study area is influenced by their occupations, especially fishing, subsistence agriculture, and the presence of crude oil in the region which has attracted many migrants who cannot afford the high cost of accommodation and are therefore forced to live in vulnerable areas of the floodplain. Finally, the study concludes that flood control in the region needs the cooperation of government, community efforts and an enlightenment programmes through environmental education and mass media.  相似文献   
524.
A study of a watershed planning process in the Cache River Watershed in southern Illinois revealed that class divisions, based on property ownership, underlay key conflicts over land use and decision-making relevant to resource use. A class analysis of the region indicates that the planning process served to endorse and solidify the locally-dominant theory that landownership confers the right to govern. This obscured the class differences between large full-time farmers and small-holders whose livelihood depends on non-farm labor. These two groups generally opposed one another regarding wetland drainage. Their common identity as “property owner” consolidated the power wielded locally by large farmers. It also provided an instrument – the planning document – for state and federal government agencies to enhance their power and to bring resources to the region. The planning process simultaneously ameliorated conflicts between government agencies and the large farmers, while enhancing the agencies’ capacity to reclaim wetlands. In this contradictory manner, the plan promoted the environmental aims of many small-holders, and simultaneously disempowered them as actors in the region’s political economy. An erratum to this article is available at .  相似文献   
525.
526.
Using resource-monitoring data from seven protected areas, the effectiveness of three campfire policies—campfire ban, designated campfires, and unregulated campfires—were assessed based on the number of fire sites and the amount of tree damage. Results indicate that unregulated campfire policies permitted substantial numbers of fire sites and tree damage in campsites, although fire bans did not eliminate or even substantially decrease these problems. A designated campfire policy was effective in decreasing number of fire sites, but little difference was found among policies regarding tree damage. Given the importance of campfires to visitor experiences, campfire prohibitions could be viewed as unnecessarily restrictive based on their limited success in preventing resource damage. Conclusions encourage protected-area managers to consider designated campfire policies and prohibitions on axes, hatchets, and saws to better meet resource protection and visitor experience mandates.  相似文献   
527.
528.
Few moral arguments have been made against vegetarian diets. One exception is the “Logic of the Larder:” We do animals a favor by purchasing their meat, eggs, and milk, for if we did not purchase these products, fewer animals would exist. This argument fails because many farm animals have lives that are probably not worth living, while others prevent a significant number of wild animals from existing. Even if this were not so, the purchase of animal products uses resources that could otherwise be used to bring a much greater number of animals into existence.  相似文献   
529.
In this study the possibility of both chemical and combined chemical + thermal activation of municipal solid waste incinerator bottom ash was investigated. A number of chemical activators including Na2SiO3·9H2O, NaOH, Na2SO4 and CaCl2·2H2O were individually added at varying concentrations to bottom ash/Portland cement mixtures having different bottom ash contents. The effect of the selected compounds was evaluated in terms of macroscopic properties including mechanical strength and composition of cementitious materials/water slurries. The results showed that Na-based activators were not capable of improving the characteristics of the cementitious products if compared to Portland cement under both normal and accelerated curing. Conversely, the use of calcium chloride at 40 °C-curing did promote the pozzolanic properties of bottom ash, leading to UCS values of 45.5 and 60.0 MPa after 10 and 20 days, respectively, as opposed to a value of 43.6 MPa obtained after 28 days for Portland cement under normal curing conditions.  相似文献   
530.
Recycling operations have become one of the primary strategies for waste management, worldwide. Especially, recycling operations are viewed as among the most effective techniques for reducing the amount of municipal solid waste disposed at landfill sites. Botswana's environmental policy on recycling stipulates, among others, that all waste management authorities should provide information on the classification and quantities of controlled waste targeted for recycling. This paper, therefore, examines the extent to which recycling operations in Botswana have either been conducted in compliance with or in violation of some major environmental requirements as enunciated on statutory guidelines. Compatibility between environmental policies on recycling and actual practice is evaluated focusing on two companies (Dumatau trading and Botswana Tissue) involved in recycling operation. Data from the two companies is complemented by one collected from the Gaborone landfill site. Finally, this study discusses on the role played by various stakeholders in policy formulation and implementation with particular emphasis being placed on a select number of non-governmental organisations (NGO).  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