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191.
Effects of Forest Fragmentation and Habitat Degradation on West African Leaf-Litter Frogs 总被引:1,自引:0,他引:1
Abstract: Habitat degradation alters the dynamics and composition of anuran assemblages in tropical forests. The effects of forest fragmentation on the composition of anuran assemblages are so far poorly known. We studied the joint influence of forest fragmentation and degradation on leaf-litter frogs. We specifically asked whether the processes structuring leaf-litter anuran assemblages in fragmented forests are the same as those in continuous forests. We analyzed anuran assemblages with respect to habitat characteristics, including fragmentation and degradation parameters. In comparison with continuous forests, species richness and diversity were lower and assemblage composition was altered in forest fragments. These changes seemed to be mainly caused by habitat degradation rather than forest fragmentation. Availability of aquatic sites for breeding, vegetation structure (including those variables indicating degradation), and leaf-litter cover had the most influence on the presence of single species. The comparatively small impact of fragmentation on anurans might be due to the location of the study area; it still possessed large tracts of continuous forest. These forest blocks may stabilize the regional rainforest climate and thus weaken the effects of fragmentation . 相似文献
192.
Impacts of Man-Made Landscape Features on Numbers of Estuarine Waterbirds at Low Tide 总被引:2,自引:0,他引:2
The potential impact of human disturbance on wintering waterbirds using intertidal mudflats was considered by relating their
numbers to the presence of nearby footpaths, roads, railroads, and towns. Data were obtained for six English estuaries from
the Wetland Bird Survey Low Tide Count scheme. Counts were undertaken monthly from November to February, and data were available
for an average of 2.8 years per estuary for the period 1992–1993 to 1999–2000. Count sections and the positions of man-made
landscape features were mapped using a GIS. Generalized linear models tested whether bird numbers varied according to the
estuary, month, area, whether or not the section bordered water, and the proportion of each section within a specified distance
of each landscape feature. In addition, the proximity of sections to the nearest footpath access point was considered. Numbers
of six of nine species, northern shelduck (Tadorna tadorna), red knot (Calidris canutus), dunlin (Calidris alpina), black-tailed godwit (Limosa limosa), Eurasian curlew (Numenius arquata) and common redshank (Tringa totanus), were significantly lower where a footpath was close to a count section, while those of brant (Branta bernicla) were greater. Northern shelduck, black-bellied plover (Pluvialis squatarola), dunlin, and black-tailed godwit numbers were reduced close to railroads and those of common ringed plover (Charadrius hiaticula), black-bellied plover, and Eurasian curlew close to roads. Common ringed plover numbers were greater close to towns. The
relative distances to which species were affected by footpaths corresponded to published information concerning their flight
distances in response to human disturbance. The study provided evidence that sustained disturbance associated with footpaths,
roads, and railroads reduced local habitat quality for waterbirds and the carrying capacity of estuaries. 相似文献
193.
Setting Priorities for Research on Pollution Reduction Functions of Agricultural Buffers 总被引:4,自引:0,他引:4
Dosskey MG 《Environmental management》2002,30(5):0641-0650
The success of buffer installation initiatives and programs to reduce nonpoint source pollution of streams on agricultural
lands will depend the ability of local planners to locate and design buffers for specific circumstances with substantial and
predictable results. Current predictive capabilities are inadequate, and major sources of uncertainty remain. An assessment
of these uncertainties cautions that there is greater risk of overestimating buffer impact than underestimating it.
Priorities for future research are proposed that will lead more quickly to major advances in predictive capabilities. Highest
priority is given for work on the surface runoff filtration function, which is almost universally important to the amount
of pollution reduction expected from buffer installation and for which there remain major sources of uncertainty for predicting
level of impact. Foremost uncertainties surround the extent and consequences of runoff flow concentration and pollutant accumulation.
Other buffer functions, including filtration of groundwater nitrate and stabilization of channel erosion sources of sediments,
may be important in some regions. However, uncertainty surrounds our ability to identify and quantify the extent of site conditions
where buffer installation can substantially reduce stream pollution in these ways.
Deficiencies in predictive models reflect gaps in experimental information as well as technology to account for spatial heterogeneity
of pollutant sources, pathways, and buffer capabilities across watersheds. Since completion of a comprehensive watershed-scale
buffer model is probably far off, immediate needs call for simpler techniques to gage the probable impacts of buffer installation
at local scales. 相似文献
194.
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196.
MICHAEL R. ELLIOTT PATRICIA F. WALLER TRIVELLORE E. RAGHUNATHAN JEAN T. SHOPE 《Traffic injury prevention》2013,14(3):167-178
Previous research has indicated that offenses are better predictors of subsequent crashes than crashes themselves. We examined this hypothesis for 13,800 young beginning drivers in Michigan for up to nine years during the initial years of driving. Our analyses indicated that previous-year offenses are better predictors of both subsequent-year offenses and crashes than either previous-year crashes or at-fault crashes. This finding also held for the apparently higher-risk subset of subsequent-year serious offenses and at-fault crashes. Although there were no gender differences in the predictive power of crashes, it was found that the predictive power of previous offenses to subsequent serious offenses was significantly stronger for women than for men. The predictive power of incidents appeared to increase somewhat with increasing driving experience, suggesting that early incidents may be more attributable to inexperience, a characteristic of all beginning drivers, while later incidents may be more attributable to individual differences. 相似文献