全文获取类型
收费全文 | 858篇 |
免费 | 33篇 |
国内免费 | 9篇 |
专业分类
安全科学 | 30篇 |
废物处理 | 19篇 |
环保管理 | 312篇 |
综合类 | 93篇 |
基础理论 | 256篇 |
污染及防治 | 129篇 |
评价与监测 | 34篇 |
社会与环境 | 17篇 |
灾害及防治 | 10篇 |
出版年
2023年 | 5篇 |
2022年 | 18篇 |
2021年 | 14篇 |
2020年 | 24篇 |
2019年 | 18篇 |
2018年 | 21篇 |
2017年 | 40篇 |
2016年 | 30篇 |
2015年 | 23篇 |
2014年 | 33篇 |
2013年 | 53篇 |
2012年 | 44篇 |
2011年 | 50篇 |
2010年 | 40篇 |
2009年 | 33篇 |
2008年 | 41篇 |
2007年 | 39篇 |
2006年 | 37篇 |
2005年 | 23篇 |
2004年 | 36篇 |
2003年 | 34篇 |
2002年 | 29篇 |
2001年 | 19篇 |
2000年 | 13篇 |
1999年 | 15篇 |
1998年 | 13篇 |
1997年 | 16篇 |
1996年 | 12篇 |
1995年 | 11篇 |
1994年 | 11篇 |
1993年 | 13篇 |
1992年 | 10篇 |
1991年 | 11篇 |
1990年 | 7篇 |
1989年 | 12篇 |
1988年 | 4篇 |
1987年 | 9篇 |
1986年 | 6篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 5篇 |
1982年 | 6篇 |
1980年 | 3篇 |
1979年 | 3篇 |
1977年 | 2篇 |
1976年 | 2篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1971年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有900条查询结果,搜索用时 15 毫秒
481.
Thomas C. Brown Jonathan G. Taylor Bo Shelby 《Journal of the American Water Resources Association》1991,27(6):979-989
ABSTRACT: A variety of methods have been used to learn about the relation between streamfiow and recreation quality. Regardless of method, nearly all studies found a similar nonlinear relation of recreation to flow, with quality increasing with flow to a point, and then decreasing for further increases in flow. Points of minimum, optimum, and maximum flow differ across rivers and activities. Knowledge of the effects of streamflow on recreation, for the variety of relevant activities and skill levels, is an important ingredient in the determination of wise streamflow policies. 相似文献
482.
Deborah Ulinski Potter Michael P. Stevens Judy L. Meyer 《Journal of the American Water Resources Association》1982,18(4):627-633
ABSTRACT: Information on biologically important physical and chemical variables is presented for Lake Oconee, a newly impounded pumped storage reservoir in Georgia. During its first summer, when no pumping occurred, temperature, oxygen, pH, inorganic nitrogen, and phosphorus were vertically stratified with severe hypolimnetic oxygen depletion. During the second summer, when pumped storage was in operation, more homogenous vertical profiles, generally higher oxygen, and lower dissolved nutrient concentrations were observed. These pumped storage effects were observed at all stations, rather than being confined to the immediate vicinity of the dam. 相似文献
483.
Marca Weinberg Cathy A. Lawrence Jamie D. Anderson Jonathan R. Randall Luis W. Botsford Curtis J. Loeb Cedric S. Tadokoro Gerald T. Orlob Paul Sabatier 《Journal of the American Water Resources Association》2002,38(2):367-384
ABSTRACT: This paper brings together spatially and temporally explicit mechanistic models of hydrodynamic, water quality, and ecological processes with an economic model to examine water management alternatives for California's Sacramento River and Delta ecosystem, a large‐scale watershed. Overallocated water supplies in most years, combined with increasing demand for water for environmental purposes, have created a politically charged atmosphere and a need for quantitative assessment of the implications of policy alternatives. By developing and analyzing a common set of policy scenarios, this integrated framework allows us to consider tradeoffs between agricultural economic factors, water quality, and population dynamics for two at‐risk fish species. We analyze two rather extreme types of policy options; one involves structural modifications to change the flow of water within the watershed but no change in water diversions, while the other reallocates water from agricultural users to fish and wildlife. Results suggest that substantial environmental improvements could be made at a relatively modest cost to farmers (1 to 4 percent reductions in revenues) but that those costs could be significant locally. In addition to tradeoffs between farmers and environmental interests, results suggest that policy makers may need to balance competing environmental objectives. 相似文献
484.
485.
Gareth K. Phoenix Jonathan R. Leake David J. Read J. Philip Grime John A. Lee 《Water, Air, & Soil Pollution: Focus》2004,4(6):159-167
Semi-natural calcareous and acidic grasslands are known to be sensitive to increased atmospheric N deposition. However, the fate of pollutant N within these systems is unknown. This paper reports on the first studies to determine the fate of added N within a calcareous and an acidic grassland subject to long-term simulated enhanced N deposition. Intact soil/turf cores were removed from field plots treated for six years with enhanced N deposition (ambient +0, +35 and +140 kg N ha–1 year–1). Cores were inserted into lysimeters and output fluxes of N were monitored in detail. Complete N budgets—calculated from the N flux data—showed considerable accumulation of N within the treated grasslands, up to 76% and 38% of pollutant N in the calcareous and acidic grasslands respectively. In the second study, the short-term (21 day) fate of pollutant N was determined by tracing 15N labelled ammonium nitrate (+35 kg N ha–1 year–1) though the acidic and calcareous lysimeters into plant, soil and leachate pools. Up to 91% and 59% of 15N was recovered in soils and vegetation of the calcareous and acidic grasslands respectively, with negligible amounts recovered in soil extractable ammonium and nitrate (<0.3%) and in leachate (<0.02%). This rapid short-term immobilisation of pollutant N supports the long-term accumulation of the element calculated from the N flux study. 相似文献
486.
Lead levels in different environmental media (soil, grass leaves, water, ceramics, pencil, paint, crayons and cosmetics) were determined to assess the major sources of lead exposure in Thohoyandou, South Africa. Soil and plant leaves were used as indicators of Pb pollution from vehicle exhaust emissions. After digestion with concentrated acids (HNO3, HCl and HClO4) Pb concentrations were determined in triplicate using a flame atomic absorption spectrometer. The mean Pb concentrations at the kerb of selected busy roads were 205.5 ± 90, 273.0 ± 90 and 312.8 ± 81 μg g−1 and 154.7 ± 67, 182.9 ± 76 and 240.6 ± 66 μg g−1 for soil and plant leaves (dry weight) respectively. These concentrations were substantially higher than the values found on soils 50 m away from the roads (97.4 ± 11 μg g−1). Pb concentrations in plants collected further away from the road (50 m) were substantially lower (71.8 ± 9.0 μg g−1). The observed levels on soil are lower than the UK critical value of 500 μg g−1 for gardens and allotments; and 2000 μg g−1 for parks and open space as well as the Canadian values for agricultural (375 μg g−1), residential (500 μg g−1 and industrial (1000 μg g−1). From these data it was clear that Pb concentrations in soil samples were substantially higher than the levels obtained for plant leaves. The Pb levels in green crayons, blue crayons, pencils (from China & Germany), were 10650 ± 75.2, 8200 ± 52.4, 1160 ± 50.2, 79 ± 10.1 μg g−1 for the inner contents; and 4870 ± 58.1, 5650 ± 55.5, 1950 ± 46.6, 60 ± 12.9 μg g−1 for the outer surface paint respectively. The ceramics showed Pb levels of 630 ± 50.3 μg g−1 (saucer) and 560 ± 32.2 μg g−1 (cup), while the inner contents and outer surface paint showed 480 ± 32.4 and 318 ± 21.2 μg g−1 of Pb respectively. Early morning tap water flush gave a Pb level of 20.6 ± 5.6 μg Pb l−1. This value is higher than the WHO and FDA maximum permissible concentrations of 10 μg l−1 and 15 μg l−1 respectively. 相似文献
487.
The targeting of rural environmental policies: an assessment of agri‐environmental schemes in the UK
Clive Potter Hadrian Cook Charlotte Norman 《Journal of Environmental Planning and Management》1993,36(2):199-216
The targeting of environmental policies holds the key to their effectiveness and value for money. In this paper we look specifically at the targeting of the various agri‐environmental schemes likely to be on offer to UK farmers under a reformed Common Agricultural Policy. The manner in which these schemes are targeted—at groups of farmers or areas of land—and the precision with which target groups or target land is identified will be critical in their success or failure. One approach is to target the farming systems thought most environmentally sensitive. This avoids drawing lines on a map and may allow policy makers to channel money into the hands of economically disadvantaged farmers or those vulnerable to policy change. But there is also a need for a more radical and geographically‐targeted approach if problems like soil erosion and aquifer protection—requiring drastic land use shifts within specified areas—are to be tackled effectively. We assess the scope for using existing datasets to identify land that should be targeted under an American‐style Conservation Reserve Programme in the UK. 相似文献
488.
489.
Urban-wildland issues have become among the most contentious and problematic issues for forest managers. Using data drawn
from surveys conducted by the authors and others, this article discusses how public knowledge and perceptions of fire policies
and fire hazards change over time, the kinds of policy responses homeowners prefer as a way of preventing fire hazards at
the urban-wildland interface, and how citizens view their own obligations as participants in interface issues. These data
show that public attitudes toward fire have changed significantly over the past two decades and that educating the public
about fire and the managers' use of fire can have positive effects on behavior. Yet, modifying the individual's behavior in
regard to interface fire risks must also deal with important issues of individual incentives, the distribution of costs, and
unanticipated policy impacts. 相似文献
490.
The rise in aluminium demand in the world has significantly increased the generation of bauxite residue which occupies huge areas of land worldwide. Direct revegetation of residue storage areas has been unsuccessful because of the high alkalinity and salinity, and poor nutrient contents of the fine residue (red mud). This paper describes glasshouse and field experiments evaluating the potential use of sewage sludge as an organic ameliorant for gypsum amended red mud. The growth of Agropyron elongatum in red mud receiving gypsum (0 and 38.5 t ha−1) and sewage sludge (0, 38.5 and 77 t ha−1) amendment was assessed in a glasshouse study. Leachate and soil analyses revealed that gypsum was effective in reducing the pH, EC and ESP of red mud, while sewage sludge gave additional reductions in EC, Na and ESP. No evidence of any significant increases in heavy metal contents were observed in the leachates following sewage sludge amendment. However, soil Al contents were more available in red mud receiving only sewage sludge treatment. Sewage sludge amendment significantly increased dry weight yield and provided sufficient nutrients for plant growth except K which was marginal. No heavy metal accumulation was observed in Agropyron. Following that, a field experiment was performed having red mud amended with sewage sludge (38.5, 77 and 154 t ha−1) and gypsum (38.5 and 77 t ha−1) to evaluate their effects on soil physical properties of red mud. Sewage sludge significantly reduced soil bulk density (25%) and particle density (9%) and increased the total porosity of red mud (8%). Hydraulic conductivity also increased from 1.5 to 23 × 10−5 m s−1. Plant cover percentage and dry weight yield of Agropyron increased with an increase in gypsum and sewage sludge amendment. The results confirm that sewage sludge is effective in improving both soil structure and nutrient status of gypsum amended red mud. The use of sewage sludge for red mud revegetation provides not just an option for sludge disposal, but also a cost effective revegetation strategy for bauxite refining industry. 相似文献