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301.
Larry D. Harris 《Environmental management》1988,12(5):675-693
There is no longer any doubt that cumulative impacts have important effects on wetland vertebrates. Interactions of species diversity and community structure produce a complex pattern in which environmental impacts can play a highly significant role. Various examples show how wetlands maintain the biotic diversity within and among vertebrate populations, and some of the ways that environmental perturbations can interact to reduce this diversity.The trophic and habitat pyramids are useful organizing concepts. Habitat fragmentation can have severe effects at all levels, reducing the usable range of the larger habitat generalists while threatening the genetic integrity of small, isolated populations. The complexity of trophic interactions, and the propensity, or necessity, of vertebrates to switch from one food source to another—something we know little about—makes using food chain support as a variable for predicting environmental impacts very questionable.Historical instances illustrate the effects of the accumulation of impacts on vertebrates. At present it is nearly impossible to predict the result of three or more different kinds of perturbations, although long-range effects can be observed. One case in point is waterfowl; while their ingestion of lead shot, harvesting by hunters during migration, and loss of habitat have caused waterfowl populations to decline, the proportional responsibility of these factors has not been determined.Further examples show multiplicative effects of similar actions, effects with long time lags, diffuse processes in the landscape that may have concentrated effects on a component subsystem, and a variety of other interactions of increasing complexity. Not only is more information needed at all levels; impacts must be assessed on a landscape or regional scale to produce informed management decisions. I conclude that a system of replicate wetland reserves that are allowed to interact naturally with the surrounding landscape will be more effective in preserving biotic diversity than isolated sanctuaries. 相似文献
302.
Evaluating cumulative effects on wetland functions: A conceptual overview and generic framework 总被引:2,自引:0,他引:2
This article outlines conceptual and methodological issues that must be confronted in developing a sound scientific basis for investigating cumulative effects on freshwater wetlands. We are particularly concerned with: (1) effects expressed at temporal and spatial scales beyond those of the individual disturbance, specific project, or single wetland, that is, effects occurring at the watershed or regional landscape level; and (2) the scientific (technical) component of the overall assessment process. Our aim is to lay the foundation for a research program to develop methods to quantify cumulative effects of wetland loss or degradation on the functioning of interacting systems of wetlands. Toward that goal we: (1) define the concept of cumulative effects in terms that permit scientific investigation of effects; (2) distinguish the scientific component of cumulative impact analysis from other aspects of the assessment process; (3) define critical scientific issues in assessing cumulative effects on wetlands; and (4) set up a hypothetical and generic structure for measuring cumulative effects on the functioning of wetlands as landscape systems.We provide a generic framework for evaluating cumulative effects on three basic wetland landscape functions: flood storage, water quality, and life support. Critical scientific issues include appropriate delineations of scales, identification of threshold responses, and the influence on different functions of wetland size, shape, and position in the landscape.The contribution of a particular wetland to landscape function within watersheds or regions will be determined by its intrinsic characteristics, e.g., size, morphometry, type, percent organic matter in the sediments, and hydrologic regime, and by extrinsic factors, i.e., the wetland's context in the landscape mosaic. Any cumulative effects evaluation must take into account the relationship between these intrinsic and extrinsic attributes and overall landscape function. We use the magnitude of exchanges among component wetlands in a watershed or larger landscape as the basis for defining the geographic boundaries of the assessment. The time scales of recovery for processes controlling particular wetland functions determine temporal boundaries. Landscape-level measures are proposed for each function. 相似文献
303.
This paper examines opportunities to improve the environmental and economic performance of cropping systems through intensified
application of information in agrichemical management. Through intensified application of information, both net farm income
and environmental quality may increase through more closely matching the specific needs of the crop with the type, timing,
and volume of chemical inputs used in crop production.
This study examines the current status and future prospect of agrichemical dealers offering information intensive agrichemical
management services to producers.
Agrichemical dealers are the focus of this study because: (1) farmers are perceived as ill-prepared to substantially upgrade
the sophistication of their agrichemical management without off-farm support, and (2) dealers enjoy a close relationship with
farmers, which potentially could be expanded to include a variety of information-based services. A mail survey was conducted
of all agrichemical suppliers/applications in Wisconsin. The response rate was 76% (172 of 225).
Substantial numbers of services were found to be offered by many dealers. The majority of these services were related to traditional
yield-enhancement function. Services that have a greater potential to mitigate the negative environmental impacts of inefficient
agrichemical use and have higher on-farm data requirements were found to be less widely offered by dealers. Analysis of constraints
to further development of information-intensive services indicates that dealers offering significant numbers of services are
concerned with constraints external to the dealership, while dealers offering relatively few services perceive internal constraints
as most limiting. This relationship indicates that efforts to accelerate dealerships' development of information-intensive
agrichemical management services should focus on specific constraints operating on targeted dealerships. 相似文献
304.
Jeffery J. Himmelberger Mike Baughman Yelena A. Ogneva-Himmelberger 《Environmental management》1995,19(6):915-922
Whether the proposed Yucca Mountain nuclear waste repository system will adversely impact tourism in southern Nevada is an
open question of particular importance to visitor-oriented rural counties bisected by planned waste transportatin corridors
(highway or rail). As part of one such county's repository impact assessment program, tourism implications of Three Mile Island
(TMI) and other major hazard events have beem revisited to inform ongoing county-wide socioeconomic assessments and contingency
planning efforts. This paper summarizes key research implications of such research as applied to Lincoln County, Nevada. Implications
for other rural counties are discussed in light of the research findings. 相似文献
305.
Jeffrey L. Marion 《Environmental management》1995,19(5):763-771
A recreation impact monitoring system was developed and applied in 1984–1986 and in 1991 to all backcountry river-accessed
campsites within Delaware Water Gap National Recreation Area, Pennsylvania and New Jersey. Results suggest that actions implemented
by park managers in response to problems identified by the initial survey were highly effective in reducing resource degradation
caused by camping. In particular, the elimination of some designated campsites and installation of anchored firegrates reduced
the total area of disturbance by 50%. Firegrate installation provided a focal point that increased the concentration of camping
activities, allowing peripheral areas to recover. As suggested by predictive models, additional resource degradation caused
by increased camping intensities is more than offset by improvements in the condition of areas where use is eliminated. The
capabilities and management utility of recreation impact monitoring programs, illustrated by the Delaware Water Gap monitoring
program, are also presented and discussed. 相似文献
306.
A watershed disturbance index developed by the USDA Forest Service called equivalent roaded area (ERA) was used to assess
the cumulative effect from forest management in California's Sierra Nevada and Klamath mountain ranges. The basins' ERA index
increased as logging and road-building occurred and then decreased over time as management ceased and vegetation recovered.
A refinement of the standard index emphasized disturbances in sensitive, near-channel areas, and evaluated recovery periods
of 20, 30, and 50 years. Shorter recovery periods yielded better correlations between recovering forest systems and aquatic
response than the longer recovery period, as represented by ERA and diversity or dominance, respectively. The refined ERA
index correlated more closely with macroinvertebrate dominance and diversity information that was available for part of the
study period. A minimum ERA threshold of 5% was detected, below which no effect to the macroinvertebrate community was observed.
Above this threshold, elevated ERA values were associated with a decline in macroinvertebrate diversity and an increase in
dominance of the top five taxa. Use of an ERA technique that emphasizes near-channel areas and biological thresholds would
contribute to the Forest Service's implementation of ecosystem management. 相似文献
307.
Michael Kress Gerald F. Gifford 《Journal of the American Water Resources Association》1984,20(1):61-66
ABSTRACT: Cowpies molded to a standard configuration and size were subjected to simulated rainfall, and the fecal coliform counts were determined using the most probable number (MPN) method of enumeration. The standard cowpie deposits were exposed to simulated rainfall once at ages 2 through 100 days. The effects of rainfall intensity and recurrent rainfall were also tested. Naturally-occurring fecal deposits were also tested to compare their results with those from the standard cowpies. A log-log regression was found to describe the decline in peak fecal coliform release with fecal deposit age. The 100-day-old fecal deposits produced peak counts of 4,200 fecal coliform per 100 milliliters of water. This quantity of release is minimal compared to the release from fresher fecal material. Rainfall intensity had little effect on peak fecal coliform release from fecal deposits that were 2 or 10 days old. At age 20 days the effect of rainfall intensity was significant; the highest intensity gave the lowest peak counts, and the lowest intensity gave the highest peak counts. The effect of rainfall intensity appears to be related to the dryness of the fecal deposits. Peak fecal coliform counts were significantly lowered when the fecal deposits were rained on more than once. This decline was thought to be produced by the loss of bacteria from the fecal deposits during the previous wettings. Standard cowpies produced a peak release regression that was not significantly different from the regression for the natural fecal deposits. Apparently, grossly manipulating the fecal deposits did not significantly change the release patterns. 相似文献
308.
Bryan L. Swift 《Journal of the American Water Resources Association》1984,20(2):223-228
ABSTRACT: An attempt was made to review all available data on the extent and status of riparian ecosystems in the U.S.A. This report presents a synthesis of the findings, including some estimates of how much land was originally covered by woody riparian vegetation, and how much remains in that condition today. A synopsis of information is presented on the status of riparian ecosystems in each of 10 regions: California, Pacific Northwest, Rocky Mountain, Arid Southwest, Plains-Grasslands, Lake States, Corn Belt, Mississippi Delta, Northeast-Appalachian, and Southeast. Woody riparian plant communities once covered an estimated 75 to 100 million acres of land in the contiguous 48 states. Mankind has converted at least two-thirds of that nationwide acreage to other non-forest land uses and it is estimated that only 25 to 35 million acres of riparian plant communities remain in a near natural condition. Across the country, loss of riparian acreages is directly attributable to water resource development (especially channel modification and water impoundment), floodplain clearing for agriculture, and urbanization. In many states of the arid west, the midwest, and the lower Mississippi alluvial valley, riparian vegetation has been reduced in area by more than 80 percent. Riparian woodlands are one of this country's most heavily modified natural vegetation types. 相似文献
309.
Müezzinoglu A 《Environmental management》2000,26(1):47-57
A mediation exercise to resolve the ongoing dispute against these power plant projects at Aliağa was recommended and participated
in by the author in 1997. In this article the basis of the continuing environmental concern about the feared impacts of the
new power plants, procedure, and results of this mediation are mentioned. The basis of the “energy versus environment” dispute
in Aliağa are introduced. Mediation exercise and its end results have been criticized. 相似文献
310.
Patricia N. Manley William J. Zielinski Claudia M. Stuart John J. Keane Amy J. Lind Cathy Brown Beth L. Plymale Carolyn O. Napper 《Environmental monitoring and assessment》2000,64(1):139-152
Monitoring at large geographic scales requires a framework for understanding relationships between components and processes of an ecosystem and the human activities that affect them. We created a conceptual model that is centered on ecosystem processes, considers humans as part of ecosystems, and serves as a framework for selecting attributes for monitoring ecosystems in the Sierra Nevada. The model has three levels: 1) an ecosystem model that identifies five spheres (Atmosphere, Biosphere, Hydrosphere, Lithosphere, Sociocultural), 2) sphere models that identify key ecosystem processes (e.g., photosynthesis), and 3) key process models that identify the "essential elements"that are required for the process to operate (e.g., solar radiation), the human activities ("affectors") that have negative and positive effects on the elements (e.g., air pollution), and the "consequences"of affectors acting on essential elements (e.g., change in primary productivity). We discuss use of the model to select attributes that best reflect the operation and integrity of the ecosystem processes. Model details can be viewed on the web at http://www.r5.fs.fed.us/sncf/spam_report/index.htm(Appendix section). 相似文献