全文获取类型
收费全文 | 460篇 |
免费 | 9篇 |
国内免费 | 6篇 |
专业分类
安全科学 | 24篇 |
废物处理 | 20篇 |
环保管理 | 111篇 |
综合类 | 40篇 |
基础理论 | 126篇 |
污染及防治 | 107篇 |
评价与监测 | 25篇 |
社会与环境 | 17篇 |
灾害及防治 | 5篇 |
出版年
2023年 | 4篇 |
2022年 | 3篇 |
2021年 | 5篇 |
2019年 | 6篇 |
2018年 | 11篇 |
2017年 | 7篇 |
2016年 | 15篇 |
2015年 | 12篇 |
2014年 | 18篇 |
2013年 | 30篇 |
2012年 | 15篇 |
2011年 | 33篇 |
2010年 | 10篇 |
2009年 | 16篇 |
2008年 | 19篇 |
2007年 | 25篇 |
2006年 | 21篇 |
2005年 | 9篇 |
2004年 | 19篇 |
2003年 | 14篇 |
2002年 | 16篇 |
2001年 | 15篇 |
2000年 | 17篇 |
1999年 | 4篇 |
1998年 | 9篇 |
1997年 | 9篇 |
1996年 | 12篇 |
1995年 | 9篇 |
1994年 | 9篇 |
1993年 | 5篇 |
1992年 | 8篇 |
1991年 | 12篇 |
1990年 | 4篇 |
1989年 | 7篇 |
1988年 | 3篇 |
1987年 | 7篇 |
1986年 | 1篇 |
1985年 | 7篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1982年 | 9篇 |
1981年 | 5篇 |
1978年 | 3篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有475条查询结果,搜索用时 46 毫秒
31.
Jeffrey S. Gaffney Nancy A. Marley Mary M. Cunningham V. Rao Kotamarthi 《Journal of the Air & Waste Management Association (1995)》2013,63(8):1228-1235
Abstract Natural radionuclides have been proposed as a means of assessing the transport of ozone (O3) and aerosols in the troposphere. Beryllium-7 (7Be) is produced in the upper troposphere and lower stratosphere by the interaction of cosmogenic particles with atmospheric nitrogen and oxygen. 7Be has a 53.29-day half-life (478 keV γ) and is known to attach to fine particles in the atmosphere once it is formed. It has been suggested that O3 from aloft can be transported into rural and urban regions during stratospheric–tropospheric folding events leading to increased background levels of O3 at the surface. 7Be can be used as a tracer of upper atmospheric air parcels and the O3 associated with them. Aerosol samples with a 2.5-µm cutoff were collected during 12-hr cycles (day/night) for a 30-day period at Deer Park, TX, near Houston, in August– September of 2000, and at Waddell, AZ, near Phoenix, in June–July of 2001. A comparison of 7Be levels with 12-hr O3 averages and maxima shows little correlation. Comparison of nighttime and daytime O3 levels indicate that during the day, when mixing is anticipated to be higher, the correlation of 7Be with O3 in Houston is approximately twice that observed at night. This is consistent with mixing and with the anticipated loss of O3 by reaction with nitric oxide (NO) and dry deposition. At best, 30% of the O3 variance can be explained by the correlation with 7Be for Houston, less than that for Phoenix where no significant correlation was seen. This result is consistent with the intercept values obtained for 7Be correlations with either O3 24-hr averages or O3 12-hr maxima and is also in the range of the low O3 levels (25 ppb) observed at Deer Park during a tropical storm event where the O3 is attributable primarily to background air masses. That is, maximum background O3 level contributions from stratospheric sources aloft are estimated to be in the range of 15–30 ppb in the Houston, TX, and Phoenix, AZ, area, and levels above these are because of local tropospheric photochemical production. 相似文献
32.
Occurrence of glyphosate and acidic herbicides in select urban rivers and streams in Canada, 2007 总被引:2,自引:1,他引:1
33.
Michelle L. Soupir Saied Mostaghimi Nancy G. Love 《Journal of the American Water Resources Association》2008,44(6):1591-1599
Abstract: Remediation of waters impaired by bacterial indicators is usually dictated by total maximum daily load plans, which are heavily dependent on fate and transport modeling of bacterial indicators. Nonpoint source pollution models are most frequently used to assess bacterial transport to surface waters and most models typically simulate bacterial transport as a dissolved pollutant. Previous studies have found that cells preferentially attach to sediments; however, a variety of techniques have been used to assess attachment including filtration, fractional filtration, and centrifugation. In addition, a variety of chemical and physical dispersion techniques are used to release attached and bioflocculated cells from particulates. Here we developed and validated an easy‐to‐replicate laboratory procedure for separation of unattached from attached E. coli which will also identify particle sizes to which E. coli preferentially attach. Physical and chemical dispersion techniques were evaluated and a combined hand shaker treatment for 10 min followed by dilutions in 1,000 mg/l of Tween 85 significantly increased total E. coli concentrations by 31% when compared with a control. In order to separate unattached from attached fractions, two commonly used techniques, fractional filtration, and centrifugation were combined. The filtration and centrifugation treatments did not reduce E. coli concentrations when compared with a control (p > 0.05), indicating that damage was not inflicted upon the E. coli cells during the separation procedure. 相似文献
34.
35.
36.
This article addresses the development of an agricultural productivity equation for predicting new soil (neo-sol) plant growth potential in Clay County, Minnesota, USA. Soil factors examined in the study include percent organic matter, percent slope, percent rock fragments, hydraulic conductivity, electrical conductivity, pH, topographic position, available water-holding capacity, bulk density, and percent clay. Squared terms and two-factor interaction terms were also examined as possible regressors. A best equation was selected that had a multiple coefficient of determination of 0.7399 and has five significant regressors and intercept withP.0001. The regressors are hydraulic conductivity, percent slope squared, bulk density times percent rock fragments, electrical conductivity times percent rock fragments, and electrical conductivity times percent organic matter. The regressors predict soil suitability for a general crop model. The crops included in the model are wheat, oats, barley, soybeans, sugar beets, sunflowers, and grasses/legumes. 相似文献
37.
William F. Porter Nancy E. Mathews H. Brian Underwood Richard W. Sage Jr. Donald F. Behrend 《Environmental management》1991,15(6):809-814
Populations of white-tailed deer (Odocoileus virginianus) inhabiting many state and national parks and suburban areas have grown to the point that they conflict with human activities.
Conflicts range from destruction of vegetation through browsing to public perception that diseases carried by deer pose threats
to human health. Traditional modes of hunting to control populations are inappropriate in many of these areas because of intense
human development and activity. This article explores an alternative approach for population reduction based on deer social
organization. Female white-tailed deer are highly philopatric and female offspring remain near their dams for life. This suggests
that a population expands slowly as a series of overlapping home ranges in a form analogous to the petals on a rose. Incorporating
the rose petal concept into a model of population growth shows that removal of deer by family unit can potentially alleviate
conflicts in localized areas for as many as 10–15 yr. 相似文献
38.
Nancy Pollock-Ellwand 《Journal of Agricultural and Environmental Ethics》1994,7(2):189-203
Conclusion I have argued, then, that is simplistic and potentially dangerous to suppose that a contractarian model can adequately account
for all of the moral relations in agriculture or serve singularly as a basis for policy. Conversely, I do not naively argue
that we ought simply to replace a contractarian based agricultural ethic with an ethic of care such as the one I have outlined.
A single farmer may be a spouse, parent, son or daughter, caretaker of land, keep of animals, business operator and partner,
employer, processor, and consumer. Agriculture itself encompasses all of these relations. Both our ethical systems and social
and economic policies must reflect and build on this diversity of contexts and associated practices. 相似文献
39.
Nitrogen in aquatic ecosystems 总被引:6,自引:0,他引:6
Rabalais NN 《Ambio》2002,31(2):102-112
Aquatic ecosystems respond variably to nutrient enrichment and altered nutrient ratios, along a continuum from fresh water through estuarine, coastal, and marine systems. Although phosphorus is considered the limiting nutrient for phytoplankton production in freshwater systems, the effects of atmospheric nitrogen and its contribution to acidification of fresh waters can be detrimental. Within the estuarine to coastal continuum, multiple nutrient limitations occur among nitrogen, phosphorus, and silicon along the salinity gradient and by season, but nitrogen is generally considered the primary limiting nutrient for phytoplankton biomass accumulation. There are well-established, but nonlinear, positive relationships among nitrogen and phosphorus flux, phytoplankton primary production, and fisheries yield. There are thresholds, however, where the load of nutrients to estuarine, coastal and marine systems exceeds the capacity for assimilation of nutrient-enhanced production, and water-quality degradation occurs. Impacts can include noxious and toxic algal blooms, increased turbidity with a subsequent loss of submerged aquatic vegetation, oxygen deficiency, disruption of ecosystem functioning, loss of habitat, loss of biodiversity, shifts in food webs, and loss of harvestable fisheries. 相似文献
40.
Stanley A. Changnon Nancy E. Westcott 《Journal of the American Water Resources Association》2002,38(5):1467-1475
ABSTRACT: Operations of a dense raingage network in the Chicago area since 1989 provided data to assess the temporal and spatial distributions of heavy rainstorms. The 12‐year average was 4.4 storms per year, 40 percent more than in the 1948 to 1980 period, reflecting an ongoing Midwestern increase in heavy rains. The total rainfall from the 53 heavy rainstorms maximized over the city, reflecting previous observations that the influence of the city and Lake Michigan on the atmosphere causes an increase in heavy rains. Impacts from the record high number of eight storms in 2001 revealed that efforts to control flooding including the Deep Tunnel system, had reduced street and basement flooding in the moderate intensity storms, but the two most intense storms, each with 100‐year rainfall values, led to excessive flooding and a need to release flood waters into Lake Michigan. Results suggest continuing increases in the number of heavy rainstorms in future years, which has major implications for water managers in Chicago and elsewhere. 相似文献