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111.
Candis S. Claiborn Dennis Finn Timothy V. Larson Jane Q. Koenig 《Journal of the Air & Waste Management Association (1995)》2013,63(8):1440-1445
ABSTRACT The revised National Ambient Air Quality Standards for PM include fine particulate standards based upon mass measurements of PM25. It is possible in arid and semi-arid regions to observe significant coarse mode intrusion in the PM2.5 measurement. In this work, continuous PM10, PM2.5, and PM1.0 were measured during several windblown dust events in Spokane, WA. PM2 5 constituted ~30% of the PM10 during the dust event days, compared with ~48% on the non-dusty days preceding the dust events. Both PM10 and PM2.5 were enhanced during the dust events. However, PM1.0 was not enhanced during dust storms that originated within the state of Washington. During a dust storm that originated in Asia and impacted Spokane, PM1.0 was also enhanced, although the Asian dust reached Washington during a period of stagnation and poor dispersion, so that local sources were also contributing to high particulate levels. The “intermodal” region of PM, defined as particles ranging in aerodynamic size from 1.0 to 2.5 um, was found to represent a significant fraction of PM25 (~51%) during windblown dust events, compared with 28% during the non-dusty days before the dust events. 相似文献
112.
Geochemical parameters influencing tungsten mobility in soils 总被引:2,自引:0,他引:2
Bednar AJ Jones WT Boyd RE Ringelberg DB Larson SL 《Journal of environmental quality》2008,37(1):229-233
The biogeochemistry of tungsten and its effects on mobility have recently gained attention due to the existence of human cancer clusters, such as in Fallon, NV. Tungsten exists in many environmental matrices as the soluble and mobile tungstate anion. However, tungsten can polymerize with itself and other anions, creating poly- and heteropoly-tungstates with variable geochemical and toxicological properties. In the present work, geochemical parameters are determined for tungstate species in a model soil that describe the potential for tungsten mobility. Soluble tungsten leached from a metallic tungsten-spiked soil after six to twelve months aging reached an equilibrium concentration >150 mg/L within 4 h of extraction with deionized water. Partition coefficients determined for various tungstate and polytungstate compounds in the model soil suggest a dynamic system in which speciation changes over time affect tungsten geochemical behavior. Partition coefficients for tungstate and some poly-species have been observed to increase by a factor of 3 to 6 over a four month period, indicating decreased mobility with soil aging. 相似文献
113.
Policy-makers and public participation analysts face the question of who should be involved in environmental decision-making. Participants are often representatives of organized groups who share similar demographic and other characteristics. This raises concerns about the degree to which the interests and opinions of others are represented. The research presented here investigates the nature and degree of differences in environmental attitudes, specifically those toward water resource management efforts, among people who do and do not participate in place-based groups in metropolitan Portland, Oregon. Neighborhood associations and a watershed council were the focus of this research due to their involvement in land-use planning and resource activities. Thirty-four individual attitudinal judgments were evaluated, along with four indices representing attitudes toward resource protection goals, government, regulations, and economic measures. Survey findings revealed watershed council participants were more supportive of resource protection compared to others on all attitudinal dimensions except anthropocentric goals. In contrast, neighborhood association participants are relatively representative of non-participants except for heightened support for economic strategies. Participants in both groups exhibited higher socioeconomic status than non-participants. Written survey comments highlighted the perceived value of on-the-ground projects incorporating local input and feedback while interviews provided insights on how to expand participation in place-based groups and resource protection efforts. 相似文献
114.
Methods for describing the exposure patterns of forests to atmospheric ozone concentrations are compared with special emphasis on the situation at high altitudes, such as the Appalachian Mountains of the eastern USA. Limitations to the use of ozone concentration as mass per unit volume are discussed and a correction for temperature and pressure changes is derived. If identical ozone mass concentrations were measured at two sites separated by 2000 m elevation, the ozone flux at the lower site would exceed the flux at the higher site by 4-8% due to temperature and pressure effects on both air volume and ozone deposition velocity. It is recommended that ozone exposures be described in terms of 'flux-corrected' mass concentrations or volumetric mixing ratios when ambient ozone data from sites at different altitudes are to be compared. 相似文献
115.
Merrill A. Peterson Susanne Dobler Erica L. Larson Danielle Juárez Tim Schlarbaum Kirsten J. Monsen Wittko Francke 《Chemoecology》2007,17(2):87-96
Summary. Chemical signals frequently underlie sexual isolation between insect species. Our understanding of the evolutionary forces
influencing these signaling systems is known for very few systems, challenging both our efforts to understand insect speciation,
and our ability to predict long-term changes in the chemical communication systems of insects. Thus, we are in need of more
systems in which both the chemical signals causing sexual isolation and the evolutionary forces driving sexual isolation are
understood. Sexual isolation in the hybrid zone between Chrysochus cobaltinus and C. auratus has apparently increased in response to natural selection against hybridisation (i.e. reinforcement). Previous experiments
suggested that this isolation was due, at least in part, to male preferences for conspecific females. Here, we confirm this
role of male choice, and document that male mate choice in this system is influenced by cuticular hydrocarbon (CHC) profiles.
Specifically, male C. cobaltinus responses to control cadavers and conspecific female cadavers painted with different cuticular hexane extracts, together
with analyses of the composition of those extracts, revealed that male mate choice is governed by CHC profiles. Multivariate
analyses of GC profiles demonstrated that those profiles are indeed both sex- and species-specific. Although GC-MS enabled
identification and quantification of the specific cuticular hydrocarbons, we have not yet determined which individual compounds
govern mate choice. Having established that CHCs influence sexual isolation in this system, we can now assess the evolutionary
lability of these cues, which will inform both our understanding of speciation, and of the conditions under which the chemical
signaling systems that influence mate choice in insects can evolve. 相似文献
116.
R. J. Larson 《Marine Biology》1980,58(2):123-132
Nonterritorial Sebastes carnatus and S. chrysomelas existed, along with territorial individuals, at 3 tagging sites off southern California, USA, which were monitored for nearly 1 yr. To test the hypothesis that territoriality affected adult density in these species, territorial fish were removed and the subsequent utilization of vacated territories by other fish was monitored. Intrusion of other fish into vacated territories increased significantly in 90% of the removals. Other fish colonized both the feeding and sheltering parts of the vacated territories, indicating that the previous owners had successfully defended both parts of their territories. Many of the colonizers had already possessed territories; they expanded their territories or moved into presumably better havitat. Several previously-nonterritorial fish also moved into vacated areas, and at least some of them appeared to establish territories. These fish, then, had previously been capable of establishing territories, but were prevented from doing so by resident territory holders. Thus territoriality, rather than such other factors as predation or low recruitment, limited the number of territorial fish at each site. However, territorial fish did not inhibit the settlement of larval recruits, and the relative mortality rates of older territorial vs nonterritorial fish were not determined. Thus the question of whether territoriality was a major factor controlling total density remains unresolved. 相似文献
117.
R. J. Larson E. A. Bookland R. T. Williams K. M. Yocom D. A. Saucy M. B. Freeman G. Swift 《Journal of Polymers and the Environment》1997,5(1):41-48
The biodegradability (mineralization to carbon dioxide) of acrylic acid oligomers and polymers was studied in activated sludge
obtained from continuous-flow activated sludge (CAS) systems exposed to mixtures of low molecular weight (Mw < 8000) poly(acrylic
acid)s and other watesoluble polymers [poly(ethylene glycol)s] in influent wastewater. Dilute preparations of activated sludge
from the CAS units were tested for their ability to mineralize acrylic acid monomer and dimer, as well as a series of model
acrylic acid oligomers and polymers (Mw 500, 700, 1000, 2000, and 4500), as sole carbon and energy sources. Complete mineralization
of acrylic acid monomer and dimer was observed in low-biomass sludge preparations previously exposed to the polymer mixture,
based on carbon dioxide production and residual dissolved organic carbon analyses. Extensive (though incomplete) degradation
was also observed for the low molecular weight acrylic acid oligomers (Mw 500 and 700), but degradation dropped off sharply
for the 1000, 2000, and 4500 Mw polymers. Radiochemical (14C) data also confirmed the low degradation potential of the 1000, 2000, and 4500 Mw materials. Degradation of two commercial
poly(ethylene glycol)s at 1000 and 3400 Mw was complete and comparable to that of the acrylic acid monomer and dimer. Our
results indicate that mixed populations of activated sludge microorganisms can extensively metabolize acrylic acid oligomers
of seven units or less. Complete mineralization, however, could be confirmed only for the monomer and dimer material, and
carbon mass balance data suggested that the true molecular weight cutoff for complete biodegradation was significantly less
than the 500–700 Mw range tested. 相似文献
118.
119.
L. Douglas James Dean T. Larson Daniel H. Hoggan Terrence F. Glover 《Journal of the American Water Resources Association》1980,16(6):1020-1029
ABSTRACT: Many practices followed uniformly nationwide in the federal flood control and floodplain management programs are inappropriate or even counter productive in the arid Utah climate. An analysis of the 130-year Utah flood history, the structural and nonstructural flood programs in the state, and local perceptions obtained by field visits and interviews in 35 Utah communities revealed a number of such inefficiencies. Since flood flows dissipate quickly when they emerge from mountain watersheds onto desert lowlands, risks are concentrated near the apex of alluvial fans, include hazard from mud as well as water flow, and are compounded by canal interception of flood waters. Because of variation in the area flooded from one event to the next, floodplain mapping has tended to show risks too high in mapped areas and too low outside. Traditional channelization carries floods downstream past where they would dissipate naturally. The federal government needs to become more active in developing better flood hazard delineation and structural and nonstructural designs for arid areas. State government can help by providing a forum where communities can exchange experiences, reviewing structural designs prepared by local government, and providing local communities with technical expertise for dealing with federal agencies. 相似文献
120.
Felix R. De Bie Marcus G. Davey Abby C. Larson Jan Deprest Alan W. Flake 《黑龙江环境通报》2021,41(1):145-158
Extreme prematurity remains a major cause of neonatal mortality and severe long-term morbidity. Current neonatal care is associated with significant morbidity due to iatrogenic injury and developmental immaturity of extreme premature infants. A more physiologic approach, replacing placental function and providing a womb-like environment, is the foundational principle of artificial placenta (AP) and womb (AW) technology. The concept has been studied during the past 60 years with limited success. However, recent technological advancements and a greater emphasis on mimicking utero-placental physiology have improved the success of experimental models, bringing the technology closer to clinical translation. Here, we review the rationale for and history of AP and AW technology, discuss the challenges that needed to be overcome, and compare recent successful models. We conclude by outlining some remaining challenges to be addressed on the path towards clinical translation and opportunities for future research. 相似文献