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331.
Michael B. Sonnen Larry C. Davis 《Journal of the American Water Resources Association》1979,15(2):404-419
ABSTRACT: Two analytical methods are presented and demonstrated for evaluating the monetary and nonmonetary benefits of wild rivers. In the traditional benefit-cost context special techniques are required to show that any wild river is worthy of preservation. The methods presented allow for the possibility of low development levels in river basins to be optimal, although advanced development can also be shown to be most efficient in some circumstances. That is, the methods are not directed to the wild condition only but to the entire spectrum of development possibilities. The applications of the methods to two adjacent subbasins in the State of Washington each showed that the currently undeveloped basin should be left in its wild condition, while the partially developed basin next door should be developed even more fully. 相似文献
332.
Edward R. Kaynor Irving Howards 《Journal of the American Water Resources Association》1971,7(6):1117-1127
Study of water resource decision-making in Massachusetts demonstrates the existence of many institutional constraints such as the established fee system for consulting engineers, the funding of certain agencies, the institutionalization of equity concerns, overrepresentation of interests, and incompatibility of agency goals. These institutional constraints are attributable in part to certain broadly-based value-orientations such as the American pragmatic tradition. However, various lines of evidence indicate that these constraints are less important than other factors in the etiology of decisional outcomes. The outcomes of the decision processes were found to be at variance with the decisions studied, a fact leading to the conclusion that choice of decisions for study should be given more attention. The authors conclude that institutional constraints are important if one is interested in studying how decisions are made, but that what actually happens in the long run cannot be easily ascertained by studying either institutions or the decision-making process. They suggest the need for more research utilizing the incremental theories of Carl Lindblom and the side-effect theories of Albert O. Hirschman. 相似文献
333.
Stephen M. Barrager 《Journal of the American Water Resources Association》1974,10(4):759-765
ABSTRACT: A case study is used to demonstrate a methodology for measuring the residential property value benefit of water pollution abatement. Increases in the value of single-family homes attributable to improvement in the water quality of the nearby Willamette River (Clackamas County, Oregon) were measured using a regression analysis technique. Sales prices and tax assessment data were used to estimate the change in property values coincident with the changes in water quality. The percentage increase in property value due to pollution abatement is expressed as a function of the distance between properties and the river bank. 相似文献
334.
Landscape pattern and composition metrics are potential indicators for broad-scale monitoring of change and for relating change to human and ecological processes. We used a probability sample of 20-km × 20-km sampling blocks to characterize landscape composition and pattern in five US ecoregions: the Middle Atlantic Coastal Plain, Southeastern Plains, Northern Piedmont, Piedmont, and Blue Ridge Mountains. Land use/land cover (LULC) data for five dates between 1972 and 2000 were obtained for each sample block. Analyses focused on quantifying trends in selected landscape pattern metrics by ecoregion and comparing trends in land cover proportions and pattern metrics among ecoregions. Repeated measures analysis of the landscape pattern documented a statistically significant trend in all five ecoregions towards a more fine-grained landscape from the early 1970s through 2000. The ecologically important forest cover class also became more fine-grained with time (i.e., more numerous and smaller forest patches). Trends in LULC, forest edge, and forest percent like adjacencies differed among ecoregions. These results suggest that ecoregions provide a geographically coherent way to regionalize the story of national land use and land cover change in the United States. This study provides new information on LULC change in the southeast United States. Previous studies of the region from the 1930s to the 1980s showed a decrease in landscape fragmentation and an increase in percent forest, while this study showed an increase in forest fragmentation and a loss of forest cover. 相似文献
335.
Landscape Changes in the Mullica River Basin of the Pinelands National Reserve,New Jersey,USA 总被引:1,自引:0,他引:1
In 1979, the Pinelands Commission was established as a regional land-use planning and regulatory agency charged with the implementation of a Comprehensive Management Plan (CMP) for the Pinelands National Reserve (New Jersey, USA). The CMP was created to balance land preservation and development interests in the Reserve. Because water-quality degradation from developed and agricultural landscapes is associated with changes in the composition of biological communities, monitoring landscape changes provides one of the most direct measures of the impact of land-use policies on the Pinelands ecosystem. In this study, we prepared detailed, land-cover maps within randomly selected aerial-photograph plots for a major watershed in the Reserve. We used these land-cover maps to quantify changes in landscape composition and structure (i.e., patch size, patch area, and number of patches) and characterize land-cover transitions in the basin between 1979 and 1991. Because the study period represented the first 12 years of the regional-planning effort in the Reserve, we evaluated the relationship between land-cover transitions and Commission management-area designations which permit different land-use intensities. Although the landscape composition was similar in 1979 and 1991, we found an increase in the total area and number of developed-land, managed-grassland, and barren-land patches. An increase in the number of patches and a decrease in the total area and median and third-quartile patch sizes for forest land and for all patches regardless of cover type indicated that fragmentation of forest land and the landscape as a whole occurred during the study period. The major land-cover transitions that occurred during the period were the loss of forest land to development and associated cover types and the conversion of one agricultural type to another. Overall, land-cover transitions during the period were found to be consistent with the Commission management-area designations, which indicated that the regional-planning effort has been successful in directing human activities to appropriate areas of the basin. 相似文献
336.
Ecosystem management and sustainable forestry on mixed ownership landscapes will require some level of cross-boundary coordination
or management. Oregon's experiment with local, voluntary, collaborative forums, called watershed councils, is one mechanism
to foster cross-boundary management. Fifty qualitative, in-depth interviews in three study areas were conducted with nonindustrial
private forest (NIPF) landowners, watershed council members, and agency employees to learn how and why landowners participate
(or not) on watershed councils. Study areas were located in three different areas of the state to reflect different ecological
and organizational settings. Our case study identified three themes—stewardship ethic, property rights amid uncertainty, and
action orientation—that were most salient among landowners when deciding to participate in their local watershed council.
Other factors related to competing opportunities were also identified. Our results relate to the social psychological antecedents
to cooperation of perceived consensus, group identity, and legitimacy of authority as well as to applied situations where
cross-boundary coordination and management are goals. 相似文献
337.
An extensive road system with rapidly increasing traffic produces diverse ecological effects that cover a large land area.
Our objective was to evaluate the effect of roads with different traffic volumes on surrounding avian distributions, and its
importance relative to other variables. Grassland bird data (5 years) for 84 open patches in an outer suburban/rural landscape
near Boston were analyzed relative to: distance from roads with 3000–8000 to >30,000 vehicles/day; open-habitat patch size;
area of quality microhabitat within a patch; adjacent land use; and distance to other open patches. Grassland bird presence
and regular breeding correlated significantly with both distance from road and habitat patch size. Distance to nearest other
open patch, irrespective of size, was not significant. Similarly, except for one species, adjacent land use, in this case
built area, was not significant. A light traffic volume of 3000–8000 vehicles/day (local collector street here) had no significant
effect on grassland bird distribution. For moderate traffic of 8000–15,000 (through street), there was no effect on bird presence
although regular breeding was reduced for 400 m from a road. For heavier traffic of 15,000–30,000 (two-lane highway), both
bird presence and breeding were decreased for 700 m. For a heavy traffic volume of ≥30,000 vehicles/day (multilane highway),
bird presence and breeding were reduced for 1200 m from a road. The results suggest that avian studies and long-term surveys
near busy roads may be strongly affected by traffic volume or changes in volume. We conclude that road ecology, especially
the effects extending outward >100 m from roads with traffic, is a sine qua non for effective land-use and transportation policy. 相似文献
338.
Richard A. Cole Frank A. Ward Timothy J. Ward Robert M. Wilson 《Journal of the American Water Resources Association》1990,26(4):597-609
ABSTRACT: This paper describes the development of an interdisciplinary model that analyzes the effects of resource management decisions on New Mexico fishery production, yield, sportfishing effort, and economic benefit to anglers. The model recreates river flows and materials transported through reservoirs and their tailwaters from 1974 through 1987. Solar radiation, water temperature, phosphorus, nitrogen, suspended solids, and water exchange rates determine primary production. Organic loads from watershed sources, added to primary production, form a trophic base for sportfish forage. Fish production is partitioned into biomass and growth of each age class in sportfish and forage fish groups by differential responses to food type, light, water-level fluctuation and predation. Fish biomass, with angler population distribution and site condition, contributes to determining angler effort and economic benefits. Model users can vary and analyze water level and quality, stocking, fishing regulations, site access, site facilities, and site entry fees. The model (on floppy disks with a user manual) is available for operation on MS DOS compatible computers with a hard disk. Contact R. M. Wilson, NMGF, State Capitol, Santa Fe, New Mexico, 87503. 相似文献
339.
A regional framework for establishing recovery criteria 总被引:6,自引:0,他引:6
Robert M. Hughes Thomas R. Whittier Christina M. Rohm David P. Larsen 《Environmental management》1990,14(5):673-683
Effective assessments of aquatic ecosystem recovery require ecologically sound endpoints against which progress can be measured.
Site-by-site assessments of end points and potential recovery trajectories are impractical for water resource agencies. Because
of the natural variation among ecosystems, applying a single set of criteria nationwide is not appropriate either. This article
demonstrates the use of a regional framework for stratifying natural variation and for determining realistic biological criteria.
A map of ecoregions, drawn from landscape characteristics, formed the framework for three statewide case studies and three
separate studies at the river basin scale. Statewide studies of Arkansas, Ohio, and Oregon, USA, streams demonstrated patterns
in fish assemblages corresponding to ecoregions. The river basin study in Oregon revealed a distinct change at the ecoregion
boundary; those in Ohio and Montana demonstrated the value of regional reference sites for assessing recovery. Ecoregions
can be used to facilitate the application of ecological theory and to set recovery criteria for various regions of states
or of the country. Such a framework provides an important alternative between site-specific and national approaches for assessing
recovery rates and conditions. 相似文献
340.
D. Martin Fleming Wilfried F. Wolff Donald L. DeAngelis 《Environmental management》1994,18(5):743-757
Declines in populations of and reproductive success of wood storks and other wading birds have occurred in the Florida Everglades
over the past several decades. These declines have been concurrent with major changes in the Everglades’ landscape characteristics.
Among the plausible hypotheses that relate to landscape change are the following: (1) general loss of habitat; (2) heavy loss
of specific habitat, namely, short-hydroperiod wetlands that provide high prey availability early in the breeding season;
and (3) an increase in frequency of major drying out of the central slough areas, which can affect prey availability late
in the breeding season.
These three hypotheses were compared using an individual-based model of wood stork (Mycteria americana) reproduction. This model simulated the behavior and energetics of each individual wood stork in a breeding colony on 15-min
time intervals. Changes in water depth and prey availability occurred on daily time steps. Simulation results showed a threshold
response in reproductive success to reduction of wetland heterogeneity. Model comparisons in which (1) only short-hydroperiod
wetlands were removed and (2) wetlands of both long and short hydroperiods were removed showed that, for the same loss of
total area, the specific habitat removal caused a much greater reduction in wood stork reproduction, indicating hypothesis
2 may be a more likely explanation than hypothesis 1. Reduction of initial prey availability in the central slough areas (simulating
frequent drying; hypothesis 3) reduced fledging success by an average of more than 90% in the model. 相似文献