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   505篇
  免费   11篇
  国内免费   9篇
安全科学   21篇
废物处理   13篇
环保管理   137篇
综合类   50篇
基础理论   94篇
污染及防治   132篇
评价与监测   46篇
社会与环境   21篇
灾害及防治   11篇
  2021年   6篇
  2020年   2篇
  2019年   5篇
  2018年   5篇
  2017年   6篇
  2016年   8篇
  2015年   14篇
  2014年   15篇
  2013年   65篇
  2012年   20篇
  2011年   22篇
  2010年   20篇
  2009年   17篇
  2008年   21篇
  2007年   27篇
  2006年   24篇
  2005年   20篇
  2004年   13篇
  2003年   19篇
  2002年   13篇
  2001年   9篇
  2000年   12篇
  1999年   8篇
  1998年   6篇
  1997年   5篇
  1996年   4篇
  1995年   9篇
  1994年   13篇
  1993年   9篇
  1992年   7篇
  1991年   8篇
  1990年   7篇
  1989年   4篇
  1988年   7篇
  1987年   4篇
  1986年   3篇
  1985年   2篇
  1984年   3篇
  1983年   9篇
  1982年   8篇
  1981年   8篇
  1980年   11篇
  1979年   8篇
  1978年   5篇
  1977年   3篇
  1976年   3篇
  1975年   2篇
  1973年   2篇
  1971年   1篇
  1968年   1篇
排序方式: 共有525条查询结果,搜索用时 15 毫秒
441.
Baxter Healthcare's Cardio Vascular Group (CVG) has formed a partnership with Advanced Environmental Technical Services (AETS, formerly called AETC), an 18-year-old environmental services company based in Flanders, New Jersey. With annual revenues of nearly $100 million, AETS is the largest privately owned environmental service company of its kind. Creating a partnership with providers of hazardous waste services has become necessary for many companies that find themselves downsizing and focusing their limited resources on their core businesses. More than merely waste haulers, hazardous waste management companies are being called on to train employees, develop environmental budgets, and even serve as on-site waste managers. AETS and Baxter Healthcare's CVG have created such a partnership and have successfully reduced Baxter's hazardous waste production by 56 percent since 1992. The lessons learned from this partnership are reported in this article.  相似文献   
442.
ABSTRACT: The elimination of groundwater overdraft was a key feature of the 1980 Arizona Groundwater Management Act. To achieve this goal, the Arizona Department of Water Resources identified several Active Management Areas and developed urban, industrial, and agricultural water conservation plans. This study examines the reductions in groundwater use through agricultural water conservation in the Phoenix Active Management Area (AMA). Linear programming models are developed to analyze changes in groundwater use and net returns to agriculture over a 38-year period, 1990 to 2025, for farming areas in the Phoenix AMA. Results indicate that the agricultural conservation program provides only modest groundwater savings under a wide range of scenarios. The low level of savings is partly due to the current economically efficient use of water. Other policy measures such as retiring agricultural land may be necessary if the Phoenix AMA is to meet its overdraft reduction goals; even if urban water conservation goals are met.  相似文献   
443.
444.
445.
The effects of addition of calcium hydroxide on aluminum sulphate(or alum) coagulation for removal of natural organic matter(NOM) and its subsequent effect on the formation potentials of two major types of regulated disinfection byproducts(DBPs),haloacetic acids(HAAs) and trihalomethanes(THMs),have been examined.The results revealed several noteworthy phenomena.At the optimal coagulation pH(i.e.6),the coagulation behavior of NOM water solutions versus alum dose,showed large variation and a consequent great change in the formation potentials of the DBPs at certain coagulant doses.However,with addition of a relatively small amount of Ca(OH) 2,although the zeta potential of coagulated flocs remained almost the same,NOM removal became more consistent with alum dose.Importantly,also the detrimental effect of charge reversal on NOM removal at the low coagulant dose disappeared.This resulted in a steady decrease in the formation potentials of DBPs as a function of the coagulant dose.Moreover,the addition of Ca(OH) 2 broadened the pH range of alum coagulation and promoted further reduction of the formation potentials of the DBPs.The enhancement effects of Ca(OH) 2 assisted alum coagulation are especially pronounced at pH 7 and 8.Finally,synchronous fluorescence spectra showed that the reduction in DBPs formation potential by Ca(OH) 2-assisted alum coagulation was connected to an enhanced removal of small hydrophobic and hydrophilic HA molecules.Ca(OH) 2-assistance of alum coagulation appeared to increase substantially the removal of the hydrophilic HA fraction responsible for HAAs formation,prompting further reduction of HAA formation potentials.  相似文献   
446.
The history of New York City (NYC) is much shorter than those of most European cities, but New York shares in common the problem of providing sufficient water and food to its inhabitants from its watershed and foodshed. These resource provision areas have grown over time and changed in character as they expanded in tandem with the growth of the city. In contrast to some cities, such as Paris, which historically has been supported by local food production, NYC??s status as a trade center has enabled the supply of food from distant sources from early in its history. NYC??s transportation system has rapidly evolved from early roads to canals, railroads, and modern surface and air transport networks. The development of the hydraulic engineering of the City??s reservoir, aqueduct, and tunnel system determined the extent of its water supply watersheds. Deviations from general growth trends in food and water consumption have occurred due to environmental and economic disruptions. As the growth of the city slowed in the last few decades, environmental technology has reduced the impact of the City on its environment, due to water metering, reduction of leakage, and improvements in waste treatment. However, per capita food consumption in the US continues to increase, with implications for the environmental health of New York and its region, as well as other centers of net anthropogenic nutrient inputs.  相似文献   
447.
In this article we develop a concept for the assessment of state’s susceptibility to drought based on a political science perspective. Different sources of capacities and sensitivities need to be taken into account to assess the overall susceptibility of states as political systems. We argue that the overall susceptibility of a society depends on an interplay of state capacity and readiness as main elements of political susceptibility, wealth and economic sensitivity as elements of economic susceptibility and the degree of social integration. To transform the conceptual model into a susceptibility assessment we developed an inference model in order to generate quantitative indices. For this purpose we apply fuzzy set theory using data from our case study regions, namely Andhra Pradesh (India), the Volga region (Russia) and (Southern) Portugal. The resulting computed trends for Portugal suggest that the society will be able to deal even with severe natural conditions due to existing political, economic, and social conditions. The assessment results for the Indian and Russian case study regions, in contrast, give reason for precaution since the occurrence of drought-induced crisis events seems much more likely in the light of more crucial, overall conditions, namely lower degrees of state capacity and readiness as well as, in the case of India, a high economic susceptibility. However, further improvements are possible given the improved availability of data and the integration of more qualitative information. Additionally, the expansion to further case study regions could help validate the overall concept.  相似文献   
448.
A roadway toxics dispersion study was conducted at the Idaho National Laboratory (INL) to document the effects on concentrations of roadway emissions behind a roadside sound barrier in various conditions of atmospheric stability. The homogeneous fetch of the INL, controlled emission source, lack of other manmade or natural flow obstructions, and absence of vehicle-generated turbulence reduced the ambiguities in interpretation of the data. Roadway emissions were simulated by the release of an atmospheric tracer (SF6) from two 54 m long line sources, one for an experiment with a 90 m long noise barrier and one for a control experiment without a barrier. Simultaneous near-surface tracer concentration measurements were made with bag samplers on identical sampling grids downwind from the line sources. An array of six 3-d sonic anemometers was employed to measure the barrier-induced turbulence. Key findings of the study are: (1) the areal extent of higher concentrations and the absolute magnitudes of the concentrations both increased as atmospheric stability increased; (2) a concentration deficit developed in the wake zone of the barrier with respect to concentrations at the same relative locations on the control experiment at all atmospheric stabilities; (3) lateral dispersion was significantly greater on the barrier grid than the non-barrier grid; and (4) the barrier tended to trap high concentrations near the “roadway” (i.e. upwind of the barrier) in low wind speed conditions, especially in stable conditions.  相似文献   
449.
450.
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