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331.
Fate and effect of monoalkyl quaternary ammonium surfactants in the aquatic environment 总被引:1,自引:0,他引:1
García MT Ribosa I Guindulain T Sánchez-Leal J Vives-Rego J 《Environmental pollution (Barking, Essex : 1987)》2001,111(1):169-175
The effect of the alkyl chain of quaternary ammonium-based surfactants on their aquatic toxicity and aerobic biodegradability has been studied. Two families of monoalkylquats surfactants were selected: alkyl trimethyl ammonium and alkyl benzyl dimethyl ammonium halides. Acute toxicity tests on Daphnia magna and Photobacterium phosphoreum were carried out and EC50 values in the range of 0.1-1 mg/l were obtained for the two series of cationic surfactants. Although the substitution of a benzyl group for a methyl group increases the toxicity, an incremental difference in toxicity between homologs of different chain length were not observed. Biodegradability of the different homologs was determined not only in standard conditions but also in coastal water, both tests yielding similar results. An increase in the alkyl chain length or the substitution of a benzyl group for a methyl group reduces the biodegradation rate. The degradation of these compounds in coastal waters was associated with an increase in bacterioplankton density, suggesting that the degradation takes place because the compound is used as a growth substrate. 相似文献
332.
Marín E Hernández E Bourhim S Rúa A 《Journal of the Air & Waste Management Association (1995)》2001,51(9):1346-1350
The annual average concentrations (1986-1997) of the major ions SO4(2-), NO3-, Cl-, NH4+, Na+, Mg2+, Ca2+, and K+ in precipitation are analyzed for selected EMEP stations. The objective is to determine the ion patterns or typologies in precipitation by principal component analysis (PCA) combined with a cluster analysis. SO4(2-) and NO3- ions are predominant in central and eastern Europe. This area corresponds to high emissions of SO2 and NO2. Sea spray ions are predominant in coastal sites. The soil components show an important contribution in southern Europe, possibly due to the soil dust transported from northern Africa. 相似文献
333.
Integral quantities, wind run, S, and recirculation factor, R, useful for describing air flow, are calculated and combined with CO2 mixing ratios. Meteorological observations were obtained from a RASS sodar and CO2 mixing ratios from a continuous analyzer installed at a rural site in the upper Spanish plateau. The measuring campaign spread
over 3 years and two approaches were followed. The first approach considered integral quantities on a daily basis and two
classifications of air flow, to date scarcely used. The first classification distinguished among stagnation, recirculation,
and ventilation, the second considering synoptic, meso-, and local scales. Moreover, 52.94% of daily values handled in this
paper corresponded to ventilation and 49.70% to synoptic scale. The main goal of this approach is the subsequent link between
the two classifications: the synoptic scale was associated with ventilation, mesoscale with recirculation and local scale
partially with recirculation. CO2 observations were distributed in air flow groups following these classifications and mesoscale processes were satisfactorily
described since noticeable evidence of transport from nearby cities was observed. In the second approach, S and R pairs were used and CO2 mixing ratios were distributed following percent intervals of ventilation, calculated by binning these pairs. The main goal
of the second approach is to consider only three groups of mixing ratios. In the first group, with high ventilation, mixing
ratios were low. With intermediate ventilation, mixing ratios were medium, and with low ventilation mixing ratios were high.
A contrast of 21 ppm between the third and first groups was obtained at the 95th percentile. Finally, the second group provided
a contrast of 3 ppm between north and south directions and also between east and west attributed to transport from nearby
cities. 相似文献
334.
Peña-García A de Oña Lopez R Espín Estrella A Aznar Dols F Calvo Poyo FJ Molero Mesa E de Oña López J 《Journal of Safety Research》2010,41(5):385-389