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   3312篇
  免费   68篇
  国内免费   33篇
安全科学   120篇
废物处理   102篇
环保管理   609篇
综合类   521篇
基础理论   868篇
环境理论   9篇
污染及防治   797篇
评价与监测   192篇
社会与环境   148篇
灾害及防治   47篇
  2023年   15篇
  2022年   17篇
  2021年   39篇
  2020年   20篇
  2019年   32篇
  2018年   79篇
  2017年   76篇
  2016年   83篇
  2015年   86篇
  2014年   95篇
  2013年   243篇
  2012年   156篇
  2011年   202篇
  2010年   149篇
  2009年   163篇
  2008年   174篇
  2007年   205篇
  2006年   205篇
  2005年   150篇
  2004年   107篇
  2003年   102篇
  2002年   116篇
  2001年   65篇
  2000年   59篇
  1999年   49篇
  1998年   50篇
  1997年   60篇
  1996年   46篇
  1995年   54篇
  1994年   49篇
  1993年   29篇
  1992年   31篇
  1991年   23篇
  1990年   23篇
  1989年   11篇
  1988年   14篇
  1987年   14篇
  1986年   19篇
  1985年   17篇
  1984年   19篇
  1983年   21篇
  1982年   17篇
  1981年   16篇
  1980年   18篇
  1979年   20篇
  1978年   13篇
  1977年   10篇
  1965年   11篇
  1963年   8篇
  1957年   10篇
排序方式: 共有3413条查询结果,搜索用时 20 毫秒
111.
An assessment of the heavy metal content and biological pollution burden of an abattoir dumpsite, an automobile carwash, the Ikpoba River, and a private water borehole located near the abattoir dumpsite was conducted in Benin City in Southern Nigeria, during the rainy and dry seasons. The water samples’ pH was lower than the permissible values, with the river water displaying color and possessing a slight odor. Iron concentrations exceeded the permissible limits for drinking water at all four of the sampling stations in the study area, although not in samples collected from the control station, station 5, a public water borehole that is located some distance away. Lead values were higher than drinking water standards in the samples collected from stations 1 through 4, with some exceptions during the rainy season. Copper, nickel, arsenic, chromium, and aluminum were detected in three out of the four sampling stations located within the study area. However, these metals were detected at levels that were within regulatory limits. The detection of three metals (iron, lead, and zinc) within the study area at levels exceeding drinking water limits suggested that a complete cycle of movement of pollutants into the sampling stations had occurred. Significant biological presences were also detected, as the Ikpoba River water had a standard plate count (SPC) of 130 most probable number (MPN) and a 22 MPN presumptive coliform count (PCC) or 22 MPN. However, Escherichia coli (E. coli) confirmatory tests recorded less than 2 MPN in both seasons. The study has shown that the quality of water in the river may be compromised by effluent discharges from the dumpsite and the carwash channel. Therefore, this situation requires more stringent enforcement of local environmental laws and maintenance of safe distances between domestic and industrial waste sources and domestic or private water wells.  相似文献   
112.
Across the western United States, environmental water transaction programs (EWTPs) restore environmental flows by acquiring water rights and incentivizing changes in water management. These programs have evolved over several decades, expanding from relatively simple two‐party transactions to multiobjective deals that simultaneously benefit the environment and multiple water‐using sectors. Such programs now represent an important water management tool and provide an impetus for collaboration among stakeholders; yet, most evaluations of their effectiveness focus exclusively on environmental outcomes, without adequate attention to impacts on other water users or local economies. To understand how these programs affect stakeholders, a systematic, multiobjective evaluation framework is needed. To meet this need, we developed a suite of environmental and socioeconomic indicators that can guide the design and track the implementation of water transaction portfolios, and we applied them to existing EWTPs in Oregon and Nevada. Application of the indicators quantifies impacts and helps practitioners design water transaction portfolios that avoid unintended consequences and generate mutually beneficial outcomes among environmental, agricultural, and municipal interests.  相似文献   
113.
Phosphorus (P) inputs to sewage treatment works (STW) come from a variety of sources and filtration of treated wastewater prior to discharge into receiving waters is a common practice. This means P in treated wastewaters may be present in forms that are potentially more bioavailable and mobile. We conducted a 2-year study to determine P species up and downstream of two STW outfalls into two tributaries of the River Thames. Downstream of the outfalls, P concentrations in both rivers were frequently greater by an order of magnitude for all species of P. A high proportion of total P (TP) in the downstream waters was determined as dissolved, which was largely comprised of soluble reactive P (SRP) - considered as the most bioavailable P species. Furthermore no significant difference in SRP was found in receiving waters passed through 0.45 and 0.10 μm filters. This means that P from STWs occurs in <0.1 μm fraction size, which will not readily settle to the channel bed and is more easily assimilated by biota. This distinguishes STW inputs from agricultural runoff where a high proportion of P occurs as particulate P which is both less bioavailable and more likely to settle to the channel bed. This implies that STWs derived P is likely to have a greater adverse impact on the receiving river than agricultural runoff.  相似文献   
114.
115.
ABSTRACT

The global industrial food system is increasingly recognised as a source of poor health that deepens social and economic inequity. Health advocates, policy makers, and food activists strive to improve nutrition and food access across racial and ethnic divides; however, given established approaches, they may miss fundamental pathways for improving health and justice comprehensively. While food access and nutrition are often identified as primary concerns for marginalised communities and the reason for food insecurity and food-related illness, critical food justice scholars use a more expansive lens to suggest a democratised food system is needed, and that solutions based solely in access to healthy food can undermine more systemic approaches. Our research extends this analysis, highlighting the importance of endemic food culture (foodways) as a tool for retaining identity, building community, and maintaining health among refugee populations in one community in Salt Lake City, Utah. Further, this work suggests that community engagement and expertise is essential in leveraging foodways such that marginalised communities can effectively resist cheap, unhealthy, and placeless calories.  相似文献   
116.
117.
Lakes Manapouri and Te Anau, in Fiordland National Park, became the center of a major controversy after the New Zealand government offered their water resource to an overseas aluminum smelting consortium for electricity generation. Although the scheme proceeded, the lake levels were not raised as originally proposed. Rather, government sought guidelines to optimize hydroelectric potential while maintaining ecological stability of the vulnerable, largely forested, glaciated lakeshores. Guidelines were derived by relating the vegetation zonation to the natural lake-level fluctuations recorded daily for 37 years. Ahigh operating range in the upper third of the lakes' natural ranges, based on flood tolerances of the woody shoreline species, restricts both duration and frequency. Alow operating range (ca. lower third) safeguards stability of shoreline sediments by limiting drawn-down rates, duration, and frequency. Themain operating range (ca. middle third) has few limitations. These guidelines, which allow utilization of ca. 93% of the water resource, have now been verified by instances of flooding and draw-down rates that exceeded the natural rates recorded earlier. The guidelines were officially accepted by the government in 1977 as a basis for managing the valuable multiple resources of these two lakes and their environs, and they were formalized in legislation in 1981. The details and merits of the guideline approach are discussed.  相似文献   
118.
ABSTRACT: There is considerable potential for use of channel dimension data in planning-level models for resource and impact assessment. The channel dimension data is used to route flows and sediment through the basin. The cost of obtaining actual surveyed data for large watersheds is typically prohibitive. Predictive equations have been developed based on 674 stations from watersheds across the United States which encompass a wide variety of channel types and sizes. These equations were tested against an independent data set and found to be adequate for use in planning-level models. Future research is advocated which would include data from regions and stream types not included in this study.  相似文献   
119.
ABSTRACT: The density and distribution of land uses has important consequences for the planning of sewerage systems and for the costs of these systems. This paper examines these consequences using a simplified service area model. The model determines the area to be served by a central waste treatment plant, where alternative on-lot disposal systems are also available. The model is applied to various urban area configurations, which are summarized by their total populations and by their population density distributions. Both minimum regional cost and minimum local cost service area configurations are determined. In addition, the sensitivity of the model to the parameters of the cost and population density functions is assessed. It is found that the model is most sensitive to the parameters of the collection cost function.  相似文献   
120.
ABSTRACT: The Ontario Ministry of the Environment has based its water quality management approach on a set of guidelines published in 1970. In light of the changing societal and economic background, advancement in technology and scientific knowledge, and philosophical attitudes towards water management, the water management program was recently revised. Factors influencing the revised approach, including federal-provincial interrelationships and international commitments under the Canada-U.S. Agreement, are summarized. The revised program consists of a goal statement, policies to implement this goal, revised water quality objectives, and detailed implementation procedures for field staff use. Rather than promulgating regulations to impose arbitrary effluent or receiving water standards on a province-wide basis, the revised approach involves the imposition of legally enforceable effluent requirements on a case-by-case basis. Although the paper emphasizes the surface water quality program, it also outlines the Ministry's goals, policies, and procedures for the management of surface-water quantity, as well as ground water quality and quantity.  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