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   3022篇
  免费   42篇
  国内免费   25篇
安全科学   163篇
废物处理   154篇
环保管理   612篇
综合类   340篇
基础理论   725篇
环境理论   5篇
污染及防治   754篇
评价与监测   212篇
社会与环境   106篇
灾害及防治   18篇
  2023年   21篇
  2022年   37篇
  2021年   26篇
  2020年   21篇
  2019年   31篇
  2018年   66篇
  2017年   67篇
  2016年   89篇
  2015年   58篇
  2014年   84篇
  2013年   280篇
  2012年   143篇
  2011年   177篇
  2010年   120篇
  2009年   122篇
  2008年   154篇
  2007年   187篇
  2006年   152篇
  2005年   105篇
  2004年   104篇
  2003年   116篇
  2002年   89篇
  2001年   67篇
  2000年   46篇
  1999年   51篇
  1998年   38篇
  1997年   43篇
  1996年   43篇
  1995年   40篇
  1994年   41篇
  1993年   34篇
  1992年   37篇
  1991年   26篇
  1990年   31篇
  1989年   19篇
  1988年   13篇
  1987年   20篇
  1986年   25篇
  1985年   17篇
  1984年   18篇
  1983年   28篇
  1982年   28篇
  1981年   25篇
  1980年   19篇
  1979年   16篇
  1977年   11篇
  1976年   9篇
  1975年   9篇
  1974年   10篇
  1971年   11篇
排序方式: 共有3089条查询结果,搜索用时 31 毫秒
991.
Potential benefits of a continuous monitoring program are presented in the form of questions that can be asked in connection with the information gained from the program. These questions are:

1. Are there process problems of which we are unaware?

2. Will this information be useful in the design of the next plant?

3. Can the information be used for improved process control?

4. Are we losing valuable material?

5. Can we use this information to modify our process for reduced pollution?  相似文献   
992.
There are two principal approaches to the 8-hour carbon monoxide standard: (1) 8-hour moving averages that culminate with every clock hour, and (2) nonoverlapping averages for consecutive 8-hour intervals. Examination of 1972 data for three example sites (Newark, NJ, Camden, NJ, and Spokane, WA) shows that the maximum and the “second high” control values derived from moving averages can be at least 20% higher than corresponding values detected by the consecutive 8-hour intervals. The natural fluctuation in the time of day when the maximum occurs and the variability in episode length make it doubtful that any framework of consecutive 8-hour intervals can adequately portray the essential characteristics of CO exposure. Prudence recommends choice of the moving 8-hour average as more sensitive to actual maximum levels and to short episodes, more faithful to the body’s integrating response to CO exposure, and more equitable in presenting comparisons among stations with differing patterns of daily variation.  相似文献   
993.
The use of leaded gasoline in automobiles equipped with catalytic converters causes deactivation of the converters and leads to significant increases in emissions of reactive hydrocarbons, a precursor of ozone. Such fuel switching may be a contributing factor to the increase in photochemical smog levels recently observed in the South Coast Air Basin (SOCAB).  相似文献   
994.
A comparison was made of over 300 pairs of arsenic results from instrumental neutron activation and flameless atomic absorption analyses of atmospheric particulates collected on glass fiber filters. Atomic absorption analyses involved low temperature ashing of filters at high power levels. No matrix modification chemicals were added to the acid extract which was analyzed. Neutron activation results are on the average 9% higher than those obtained by atomic absorption and the difference is statistically significant. This small difference is probably due to the analytical techniques or acid extraction and not in any important way to losses during low temperature ashing. This conclusion is in sharp contrast to other recently reported situations where low temperature ashing losses in analyzing atmospheric particulate were sizable. Although the atmospheres sampled differed somewhat between these situations the most obvious difference was in the combustibility of the filters used in sampling.  相似文献   
995.
996.
When annual average PM2.5 (fine particulate matter sized 2.5 microns and less) data for 2005 became available in April 2006 and the 3-yr average PM2.5 concentration in an area just north of the Houston Ship Channel reached 15.0 µg/m3, the Texas Commission on Environmental Quality (TCEQ) initiated daily collection of quartz fiber as well as Teflon PM2.5 filter samples for chemical speciation analysis. The purpose of the chemical speciation analysis was to use the speciation data, together with meteorological data and hourly TEOM (tapered element oscillating microbalance) PM2.5 mass data, to identify the causes of the high PM2.5 concentrations affecting the monitoring site and the neighborhood. The ultimate purpose was to target emission reduction efforts to sources contributing to the high measured PM2.5 concentrations. After a year of data collection, it was recognized that a specific source, unpaved driveways and loading areas along the Ship Channel and dirt tracked onto Clinton Drive, the main artery running east-west north of the Ship Channel, were the primary cause for the Clinton Drive site's measuring PM2.5 concentrations significantly higher than other sites in Houston. The source characterization and remediation steps that have led to sustained reduced concentrations are described in this paper.

Implications: With PM2.5 exceedances it can be essential to have or develop chemical speciation data as part of the process of identifying the source types causing exceedances of an annual standard. Positive matrix factorization (PMF) analysis proved to be a powerful tool that identified the two locally emitted species contributing to exceedances, which did not occur at other sites in the region. They were calcium sulfate (gypsum), an industrial by-product, and soil minerals. Other data analysis approaches were necessary to distinguish North African dust events, which PMF failed to identify.  相似文献   
997.
998.
Strategies for control of ozone aim at regulation of its chemical precursors, non-methane organic compounds (NMOC) and nitrogen oxides (NOx). It is therefore important to analyze how these precursors vary temporally and geographically. This study finds significant and important differences among four Texas ozone nonattainment sites, Dallas, Ft. Worth, El Paso, and Houston, for 1984, 1985, and 1986 for NMOC, NOx, and their ratio NNR. These differences were detected through nonparametric analysis of variance and Student-New-man-Keuls’s test for multiple comparisons on rank-transformed data. A noteworthy feature of the data analysis is its attention to the assumptions underlying the statistical methods. Classical models based on normal or lognormal theory had to be abandoned for lack of realism. It is demonstrated how alternative models may be applied to yield appropriate, rather than inappropriate, conclusions.  相似文献   
999.
The State of Florida passed The Florida Solid Waste Management Act of 1988 mandating that county recycling programs be initiated by July 1, 1989. The legislation further expressed the goal that, at a minimum, recycling efforts reduce the amount of solid waste requiring final disposal or resource recovery by 30 percent by the end of 1994. This study was performed to determine the impact on recycle markets when the amounts of materials recycled from the municipal solid waste stream are increased by 30 percent in Florida.

The composition of the municipal waste stream was quantified in terms of the amounts of paper, plastic, metals, glass, and rubber. The effect of a 30 percent increase in the recycle rate of each class of material was calculated and compared to existing recycle rates in the State of Florida. It was determined that there are few capacity constraints on the increase in recycle rates for aluminum, steel (i.e., tin cans), and color separated glass. There are, however, serious constraints on increasing recycle rates for paper, plastics and rubber tires.  相似文献   
1000.
ABSTRACT

Based on the available evidence of health effects, the U.S. Environmental Protection Agency (EPA) has been evaluating the need to regulate mercury releases to the environment. In response to the congressional mandates in The 1990 Clean Air Act Amendments (CAAA), the EPA has issued the Mercury Study Report and the Study of Hazardous Air Pollutant Emissions from Electric Utility Steam Generating Units Report. In spite of the enormous effort represented by these reports, as well as the efforts of both the U.S. Department of Energy (DOE) and the Electric Power Research Institute (EPRI), in conducting the field measurement programs that form the basis for these reports, a definitive answer on the need for mercury regulation has not been found. However, the EPA, as well as other regulatory agencies and health researchers, have suggested a “plausible link” between anthropogenic sources emitting mercury and the methylation, bioaccumulation in the food chain, and adverse health effects in humans and wildlife.

Policy-makers have recognized that regulations must be based on good science and that a number of issues still remain. These issues can generally be grouped into four main categories: emissions inventory, control technology, fate of releases, and health effects. This paper will discuss recent, ongoing, and planned studies to address the remaining issues regarding the presence of mercury in the environment, with an emphasis on those studies that are directly related to the DOE/Federal Energy Technology Center’s (FETC) programmatic effort.  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