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101.
Using diatoms to assess the impacts of prehistoric, pre-industrial and modern land-use on Danish lakes 总被引:2,自引:1,他引:1
Emily G. Bradshaw Anne Birgitte Nielsen N. John Anderson 《Regional Environmental Change》2006,6(1-2):17-24
The impact of contemporary agriculture on Danish lakes is acknowledged to be extreme. In particular, high loading of nutrients
from agricultural soils contributes to the eutrophic conditions found in many of Denmark’s lakes. Palaeolimnological studies
have shown that human disturbance of the Danish landscape since the introduction of agriculture around 6,000 years ago has
had a major impact on lake ecosystems. The European Union’s Water Framework Directive requires an evaluation of reference
conditions for lakes, the conditions expected with only minimal human impact. Monitoring data and palaeolimnological studies
of Danish lakes demonstrate that many of the most detrimental effects of eutrophication have been experienced in recent decades.
A new study has suggested that the reference status for Danish lakes may be set to the status in ad 1850–1900, probably providing attainable, realistic restoration targets for many sites. The aims of this study were to explore
the impacts of past and contemporary land-use on Danish lakes, and to consider how appropriate the use of 1850 as a date to
define reference status is for these sites. Catchment land-cover data for ad 1800, taken from historical maps, and sedimentary diatom assemblages of the same age, from dated sediment cores, were used
to assess the impact of pre-industrial land-use on 20 Danish lakes. Analysis of contemporary land-cover data and surface-sediment
diatom assemblages for the 20 sites was also made. In-lake total phosphorus (TP) concentrations were estimated using the sedimentary
diatom assemblages and an existing calibration dataset for Danish lakes. The percentage of the lake catchment that was agricultural
land in ad 1800 explained 8.8% of the total variation in the diatom data. The land-cover variables ‘built-up areas’ and ‘plantations’,
together explained 16.9% of the variation in the diatom data for the modern samples. Diatom-inferred TP concentrations were
high for both ad 1800 (mean 112 μg TP L−1) and the present (mean 122 μg TP L−1), the latter estimates reflecting efforts in recent decades to reduce nutrient loading to Danish lakes following very high
levels of nutrient enrichment post-1950. The data presented highlight the impact that human activities 200 years ago, particularly
agriculture, had on Danish lake systems. The long cultural history and major anthropogenic disturbance of the Danish landscape
mean that true reference conditions for lakes (or ‘baseline’ conditions, those found prior to human impacts) can be found
only by considering century to millennial timescales. 相似文献
102.
Trevor H. Booth 《Environmental management》1986,10(3):351-358
The Food and Agriculture Organization's (FAO) land evaluation methodology provides a procedure for assessing the suitability of land units within a study area for different land uses. This article describes the use of theLuplan computerized land-use planning package to provide an explicit means to select the land use for each land unit which best satisfies defined policies. The use of the package is demonstrated in a study that allocated multiple use activities within a native forest. 相似文献
103.
Ecological planning: A review 总被引:4,自引:0,他引:4
Beginning with the passage of the National Environmental Policy Act in 1969, the federal government of the United States has enacted numerous pieces of legislation intended to protect or conserve the environment. Other national governments have also enacted environmental legislation during the past two decades. State and local governments have also adopted policies concerned with environmental planning and management. Multiple laws and overlapping governmental agency responsibilities have confused development and resource management efforts. A comprehensive methodology that integrates the legal mandates and the agency missions into a common and unified framework is needed. Ecological planning offers such a method. Application of the method allows planners and resource managers to better understand the nature and character of the land and/or resource and therefore make better decisions about its appropriate use or management. The steps taken in an ecological planning process—1) goal setting, 2) inventory and analysis of data, 3) suitability analysis, 4) developing alternatives, 5) implementation, 6) administration, and 7) evaluation—are outlined and explained. Hand-drawn overlays and computer programs as techniques for handling ecological planning information are compared. Observations and suggestions for further research are offered. 相似文献
104.
Insight into future land use and effective ways to control land-use change is crucial to addressing environmental change. A variety of growth-control policies have been adopted by municipal and regional governments within the United States to try to minimize the ecological impact of continued urbanization, but it is often unclear if those policies can meet the stated ecological goals. Land-use-change models provide a way to generate predictions of future change, while exploring the impact of different land-use policies before irreversible transformations occur. In this article, an approach to modeling land-use policies that focuses on their ecological consequences is described. The policy simulation approach was used to predict future land use in the Barnegat Bay and Mullica River watersheds, in southeastern New Jersey, USA. Four commonly used policies were considered: down-zoning, cluster development, wetlands/water buffers, and open space protection. The results of the analysis suggest that none of the policies modeled were able to alter future land-use patterns, raising questions about the effectiveness of commonly adopted land-use policies. However, the policy modeling approach used in this study proved to be a useful way to determine if adoption of a given policy could improve the likelihood of meeting ecological goals. 相似文献
105.
Land-Use and Land-Cover Change and Farmer Vulnerability in Xishuangbanna Prefecture in Southwestern China 总被引:1,自引:0,他引:1
Jianchu X Fox J Vogler JB Yongshou ZP Lixin Y Jie Q Leisz S 《Environmental management》2005,36(3):404-413
This study investigated land-use and land-cover change in three hamlets and two state rubber farms in the Nan-e watershed
of the Xishuangbanna prefecture of Yunnan province in Southwestern China. The overall objective of the study was to understand
how state policies affected land use and land cover and how changes in these variables affected farmer vulnerability to economic,
social, and political events. Emphasis was placed on the cultivation of rubber (Hevea brasiliensis), promoted in southern Yunnan province since the 1950s as a means to meet the demands of rapid economic development. The
study combined remote sensing analysis with secondary data and in-field interviews in order to understand the coupling between
land-use and land-cover change and farmer vulnerability in light of the geographic, historical, and sociopolitical situation. 相似文献
106.
US Federal law mandates that mined land be returned by mine operators to a condition capable of supporting its pre-mining use or a higher use. Previously forested lands have commonly been reclaimed to hayland/pasture or wildlife habitat, and most of these lands have been abandoned from management and rendered non-productive. This situation has left landowners in the position of converting these reclaimed mined lands to forests at a later date, if they choose to make them economically productive. Such land-use conversion, however, comes with a substantial up-front cost to the landowner, which makes the financial viability of such a conversion questionable. We examine the financial viability of reforestation of these previously reclaimed mine lands by calculating land expectation value (LEV) under a range of conditions that include forest type, site quality, and reforestation intensity. We find that conversion to white pine is viable on higher quality sites under low to moderate interest rates with low or high timber prices, but conversion to mixed hardwoods is only profitable under the high price scenario with low interest rates, and only on higher quality sites. We also consider the implications of a shift in reforestation burden from the landowner to the mine operator, and results suggest that including costs of reforestation as part of the mining operation creates a financially viable forest enterprise for landowners under all scenarios for both white pine and mixed hardwoods. Two forms of carbon payments that could encourage reforestation of previously reclaimed mined lands also are examined: an annual payment based upon the total accumulated carbon found on-site in a given year, and an annual payment based on only the increment of carbon storage each year. Our carbon payment results indicate that annual values of up to $5.17 per ton of carbon stored in hardwoods and $9.39 per ton of carbon stored in pines would be required to make reforestation profitable under the poorest conditions (high interest rates, low prices, and poor quality site) when the payment is based on accumulated on-site carbon, although lower values are required under more favorable scenarios. Payments that are based upon the annual increment of carbon must fall in the range of $8.66–$71.88 per ton of carbon stored in hardwoods and $0–$83.29 per ton of carbon stored in pines to make reforestation financially viable. 相似文献
107.
Self-organization theories and environmental management: The case of South Moresby,Canada 总被引:1,自引:0,他引:1
This article presents a new approach to the analysis and management of large-scale societal problems with complex ecological, economic, and social dimensions. The approach is based on the theory of self-organizing systems—complex, open, far-from-equilibrium systems with nonlinear dynamics. A brief overview and comparison of different self-organization theories (synergetics, self-organization theory, hypercycles, and autopoiesis) is presented in order to isolate the key characteristics of such systems.The approach is used to develop an analysis of the landuse controversy in the South Moresby area of the Queen Charlotte Islands, British Columbia, Canada. Critical variables are identified for each subsystem and classified by spatial and temporal scale, and discussed in terms of information content and internal/external origin. Eradication of sea otters, introduction of black-tailed deer, impacts of large-scale clearcut logging, sustainability of the coastal forest industry, and changing relations between native peoples and governments are discussed in detail to illustrate the system dynamics of the South Moresby sociobiophysical system. Finally, implications of the self-organizing sociobiophysical system view for regional analysis and management are identified. 相似文献
108.
Runoff from human land-uses is one of the most significant threats to some coastal marine environments. Initiatives to reduce that runoff usually set runoff reduction targets but do not give guidance on how to prioritize the different options that exist to achieve them. This paper demonstrates an easy to interpret economic framework to prioritise investment for conservation projects that aim to reduce pollution of marine ecosystems caused by runoff from agricultural land-uses. We demonstrate how to apply this framework using data on project cost, benefit and feasibility with a subset of projects that have been funded to reduce runoff from subcatchments adjacent to the Great Barrier Reef. Our analysis provides a graphical overview of the cost-effectiveness of the investment options, enables transparent planning for different budgets, assesses the existence of trends in the cost-effectiveness of different categories, and can test if the results are robust under uncertainty in one or more of the parameters. The framework provided solutions that were up to 4 times more efficient than when omitting information on cost or benefit. The presented framework can be used as a benchmark for evaluating results from a range of prioritisation processes against the best possible conservation outcomes. 相似文献
109.
Gregor Levin 《Ecological modelling》2010,221(22):2728-2737
In intensively farmed regions, habitat fragmentation represents a major pressure on biodiversity. Depending on its spatial setting, set-aside land can increase size and connectivity of habitats and thus counteract fragmentation. In 2008, the EU-wide set-aside obligation was suspended and a large proportion of set-aside land was re-cultivated. With Denmark as case we apply an indicator to measure the effect of set-aside land on spatial structure of semi-natural habitats in term of habitat size and connectivity. Furthermore, we model effects of a hypothetical spatial regulation, where set-aside land with the greatest benefit for habitat structure is retained as uncultivated, while set-aside land with the least effect is re-cultivated. The model is applied to individual farms and to farm agglomerations of increasing sizes, enabling us to explore potential effects of cross-farm regulation. The novelty of our approach is the application of observed land-uses changes for modelling a hypothetical regulation working on a range of spatial scales. Results show that after abolition of set-aside schemes the effect of set-aside land on habitat structure was more than halved. Modelled spatial regulation considerably reduces impacts. Effects increase with increasing size of farm agglomerations. However, marginal benefits become negligible at agglomeration sizes over 36 km2. 相似文献
110.
The Pinelands National Reserve was created in 1978 when private interests and federal, state, and local governments allied
to protect 378,000 ha (935,000 acres) of New Jersey's Pine Barrens from encroaching development. An intergovernmental authority,
the Pinelands Commission, manages the reserve by implementing a regional plan to guide development away from environmentally
sensitive areas and into designated growth centers. Through transferable development rights, financial gains from development
in growth centers are used to compensate owners and localities in the reserve who might otherwise have developed their lands.
The national reserve strategy contrasts with other federal strategies for preserving unique environments in which the federal
government exercises exclusive control (e.g., national parks, monuments, and recreation areas). This article describes the
strategy applied in the Pinelands and discusses the conditions in which it may be more or less effective than other strategies
used to protect unique or valued landscapes. It then compares the Pinelands model with the strategies and conditions of california's
Redwood National Park and Point Reyes National Seashore to develop propositions about the circumstances in which one or another
strategy is more likely to be viable. Finally, it applies these propositions to the possibilities for future forest preservation
in New England. 相似文献