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501.
Darbah JN Jones WS Burton AJ Nagy J Kubiske ME 《Journal of environmental monitoring : JEM》2011,13(9):2436-2442
We studied the effect of high ozone (O(3)) concentration (110-490 nmol mol(-1)) on regenerating aspen (Populus tremuloides) and maple (Acer saccharum) trees at an open-air O(3) pollution experiment near Rhinelander WI USA. This study is the first of its kind to examine the effects of acute O(3) exposure on aspen and maple sprouts after the parent trees, which were grown under elevated O(3) and/or CO(2) for 12 years, were harvested. Acute O(3) damage was not uniform within the crowns of aspen suckers; it was most severe in the mature, fully expanded photosynthesizing leaves. Young expanding leaves showed no visible signs of acute O(3) damage contrary to expectations. Stomatal conductance played a primary role in the severity of acute O(3) damage as it directly controlled O(3) uptake. Maple sprouts, which had lower stomatal conductance, smaller stomatal aperture, higher stomatal density and larger leaf surface area, were tolerant of acute O(3) exposure. Moreover, elevated CO(2) did not ameliorate the adverse effects of acute O(3) dose on aspen and maple sprouts, in contrast to its ability to counteract the effects of long-term chronic exposure to lower O(3) levels. 相似文献
502.
Joseph Greene 《Journal of Polymers and the Environment》2007,15(4):269-273
Compostable plastic materials, produced from polylactic acid (PLA), corn starch, or sugarcane, degraded in a green yard-waste
compost environment. The compostable plastics claim to meet ASTM D6400 standards for biodegradation, sustainable plant growth,
and eco-toxicity. Biodegradation was measured by disintegration studies over 20 weeks. The commercially available compostable
products, made from PLA, sugarcane, or corn starch, biodegraded while in a commercial compost facility with other common yard
waste compostable items. The PLA container, cup, and knife completely degraded in 7 weeks at a rate similar to the Avicell
micro-cellulose control. The corn starch-based trash bag and sugarcane plate degraded at a similar rate as the Kraft paper
control. The three materials degraded between 80% and 90% after 20 weeks. 相似文献
503.
Joseph S. Wroblewski Trevor J. Bell Alison I. Copeland Evan N. Edinger Charles Yu Feng James D. Saxby David C. Schneider Jason M. Simms 《Journal of Cleaner Production》2009,17(3):424-430
Iceland scallop (Chlamys islandica) stocks in the North Atlantic are usually pulse harvested, resulting in boom and bust local landings. We describe an adaptive management strategy for a sustainable harvest of Iceland scallops in Gilbert Bay, a Marine Protected Area (MPA) of coastal Labrador. The current management plan for the MPA closes pristine scallop habitat, a practice that under favourable ocean conditions may lead to local reseeding. The community-based co-management structure for the MPA utilizes the local ecological knowledge of fishermen. Scallop harvesters are participating in research on the present state of the resource. Currently scallops are smaller near the mouth of the bay where fishing effort has been concentrated historically. The cooperation of fishers in enforcing area closures and in monitoring the scallop harvest may lead to a sustainable scallop fishery. 相似文献
504.
505.
506.
Joseph L. Tomkins Leigh W. Simmons John Alcock 《Behavioral ecology and sociobiology》2001,50(1):81-89
Males of Dawson's burrowing bee are dimorphic in size. Although large (major) males defeat smaller ones in competition for emerging females and therefore are more likely to mate, majors are greatly outnumbered by half-sized (minor) males. Nesting females might produce many minor males, despite their low reproductive value, because female behaviour is governed by a mixed evolutionarily stable strategy (ESS), in which case the ratio of majors to minors should not be affected by changes in female condition. In contrast, a conditional-strategy hypothesis predicts that older, wing-worn or stressed females unable to forage efficiently should be especially likely to produce minor offspring, which require less brood provisions. To test these alternative hypotheses, we manipulated the condition of nesting female bees by the addition of weights and the removal of their wing margins. These manipulations, done early in the flight season, failed to increase the production of minor males, a result consistent with the mixed-ESS hypothesis. However, unmanipulated females were far more likely to produce minor males if they were small or if they were nesting late in the season, when foraging conditions had deteriorated, findings that are consistent with a conditional provisioning strategy. Thus it appears that the abundance of minor males is the result of a conditional provisioning strategy of nesting females, which may be superimposed on a fixed tendency to produce large offspring early in the season and small ones later. 相似文献
507.
Thomas J. Fredette Joseph D. Germano Drew A. Carey Peggy M. Murray Paula G. Kullberg 《Chemistry and Ecology》1992,7(1):173-194
Geochemical analysis and visual inspection of cores collected from capped dredged material mounds revealed that in many cores, cap material was clearly distinguishable, both visually and chemically, from mound material. Contaminated dredged sediments were disposed in Long Island Sound eleven and seven years prior to sampling, and capped with uncontaminated dredged sediments. Core data provided no conclusive evidence of physical disturbance of, or chemical migration from, the contaminated mound sediments. Obvious chemical gradients of contaminant concentrations, which we propose are indicators of chemical migration, were not detected in the cores. Heterogeneity of the cap and mound sediments in some cores made the interface less distinct. We postulate that the preservation of spatial variability of sediment texture and associated contaminants observed within dredged material mounds is a result of the dredging process. Preservation of the textural and contaminant history of dredged sediments within finegrained cohesive cap materials provides evidence of the absence of physical or chemical disturbance. 相似文献
508.
509.
Budget-Balancing Incentive Mechanisms 总被引:5,自引:0,他引:5
Herriges Joseph A. Govindasamy Ramu Shogren Jason F. 《Journal of Environmental Economics and Management》1994,27(3)
A. P. Xepapadeas [J. Environ. Econom. Management20, 113-26, 1991] developed a pollution abatement incentive mechanism that both reduces the information requirements of a regulator and is "budget-balancing," drawing only on the social gains from pollution abatement to encourage firm compliance. This paper demonstrates that, contrary to Xepapadeas, the budget-balancing system of random penalties cannot be used to induce compliance with the regulator′s objectives if firms are risk neutral. However, the mechanism can be successfully applied if firms are sufficiently risk averse [E. Rasmusen, RAND J. Econom.18, 428-435, 1987]. 相似文献
510.
Joseph M. Quattro Paul L. Leberg Michael E. Douglas Robert C. Vrijenhoek 《Conservation biology》1996,10(1):128-135
Efforts to restore an endangered species in its former range should be based on a sound understanding of evolutionary relationships among remaining natural populations. In this study mitochondrial (mt) DNA diversity within and among Gila River drainage populations of the endangered Sonoran topminnow ( Poeciliopsis occidentalis ) in Arizona was compared to that from neighboring populations in Sonora, Mexico, where the species remains locally abundant. No mtDNA diversity was detected within or among samples from the Gila River basin in Arizona. But considerable variation was found within and among populations from several river systems in Sonora. Examination of mtDNA from a population that inhabits the upper reaches of the Río Yaqui in southeastern Arizona revealed substantial divergence between it and all other populations examined. We comment on the implications of this divergent population for topminnow management in Arizona and argue for more-detailed genetic and morphological studies to determine the distributional limits and specific status of this highly divergent form. 相似文献