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951.
G. Theodoridis V. Karagiannis D. Valougeorgis 《Water, Air, & Soil Pollution: Focus》2002,2(5-6):525-539
A detailed simulation of the Goettinger Strasse pollutantdispersion problem is performed using the CFD code CFX-TASCflow for different wind directions. Two turbulencemodels, the k- and the RSM are adopted on three gridrefinement levels. Besides the typical reference gridimplemented by the TRAPOS group, two different gridresolutions are introduced. The first refinement is in thewhole street canyon region on the x-y level, while thesecond one is local in all three directions. Validation ofall involved computational schemes is performed based onrelative available experimental data. The computed velocityfields and concentration contours imply that the typicalreference grid is a suitable choice for the velocityfields, while local grid refinement in all three directionsin a small region containing the receptor is required toupgrade the pollutant concentration results with modestadditional computational effort. Finally the RSM modelresulted in smaller concentration levels. The k-model compared to the RSM seems a more appropriate choiceto solve this particular problem. 相似文献
952.
P. D. Kalabokas J. G. Bartzis P. Papagiannakopoulos 《Water, Air, & Soil Pollution: Focus》2002,2(5-6):703-716
Oil refining is among the industrial activities that emit considerable amounts of air pollutants into the atmosphere. Nitrogen oxides are important air pollutants that are emitted by oil refineries as products of combustion processes. The ambient air concentrations of nitrogen oxide (NO) and nitrogen dioxide (NO2) were monitored continuously at a site close to an oil refinery, near the city of Corinth in Greece, during autumn 1997 together with the main meteorological parameters. The contribution of the oil refinery to the measured atmospheric levels of nitrogen oxides was estimated. The ambient air concentration of nitrogen oxides in the area surrounding the oil refinery were generally lower than the ambient air concentrations in the urban area of Athens in Greece, and the NO2 levels were always below the existing air quality standards. The influence of the refinery emitted NOx in the photochemical production of ozone seems to be more important in terms of human and vegetation exposure given the high ozone backgrounds measured in the area. 相似文献
953.
Water, even in its natural environment, contains some level of impurities. Water is nearly a universal solvent. It contains dissolved solids and gases, and hosts a number of micro-organisms. The exploitation of groundwater by means of boreholes for supplying small user groups and rural communities with water has been widely applied in certain parts of the world for several decades. In recent years this practice has spread all over the globe, and hundred of thousands of boreholes have beendrilled to tap low-yield aquifers. It is evident that such boreholes require pumps for lifting thewater. In developing countries these are usually handpumps, butsolar as well as other systems with submersible pumps are also used, depending upon the energy sources available and the financial means of the beneficiaries. This article gives a general overview of groundwater quality with regard to itsphysico-chemical composition. The results presented originatefrom the experience gained from handpump equipped boreholes within the UNICEF through German Centre for Technical EducationTransfer executed inter-regional UNDP-Handpumps Project inWest African Regions. Particular attention is paid to presenting corrosion onthe water quality of wells in terms of iron concentrationand other parameters. Furthermore, the corrosion attack ongalvanised iron, the effect of biofilms on the corrosionrate, and the difference between internal and externalcorrosion of rising mains are shown. 相似文献
954.
Hilhorst D 《Disasters》2002,26(3):193-212
Quality enhancement of humanitarian assistance is far from a technical task. It is interwoven with debates on politics of principles and people are intensely committed to the various outcomes these debates might have. It is a field of strongly competing truths, each with their own rationale and appeal. The last few years have seen a rapid increase in discussions, policy paper and organisational initiatives regarding the quality of humanitarian assistance. This paper takes stock of the present initiatives and of the questions raised with regard to the quality of humanitarian assistance. 相似文献
955.
Only a few empirical studies on forest aesthetics have adopted a water-based perspective for observers and have investigated
the perceived visual quality of forested shorelines. In forested environments with many lakes, such as the boreal forest in
the Canadian Shield, individuals have greater exposure to forests from water-based rather than in-stand vantage points. This
study employed the psychophysical research direction to explore the relationships between scenic beauty and biophysical characteristics
of the forested shorelines in the boreal forests. Two model forms were tested. One model related the variation of shoreline
forest aesthetic evaluations of near-vista views (140 m offshore) to a set of forest mensuration data. Tree size, tree mortality,
conifer shrubs, tree density, amount of hardwood, and slope explained 60.2% of the variance in scenic beauty between the study
sites. A second model was calibrated to test the relationship between an already existing ecosystem vegetation classification
system and the aesthetic evaluations of the same forested shorelines. When the ecosystem classification was simplified to
eight groups, the model explained 48.5% of variance. These models suggest that the psychophysical approach to studying aesthetics
can be applied successfully to near-vista evaluations of scenic beauty. The finding that a forest ecosystem classification
system is highly related to scenic beauty suggests that, at least in the boreal forest, managers can reasonably estimate the
scenic beauty of forested shoreline environments from an ecosystem classification, with little need for intensive data on
these sites. 相似文献
956.
Lowest Effect Levels of Lead and Mercury on Decomposition of Mor Layer Samples in a Long-Term Experiment 总被引:2,自引:0,他引:2
Indications of possible negative effects of lead (Pb) and mercury(Hg) on microbial respiration in Southern Swedish forest humus layers led to experiments on dose-response relationships by additions of metal salts in the laboratory. Respiration rates andweight loss due to decomposition of organic material were measured. For relevance to field situations metal doses were low,the time span was long, 550 days including freeze storage, and microbial activity was kept up by plant litter additions. We looked for effects of Pb and Hg at levels moderately elevated above the Southern Swedish reference, as well as combined effectsof Pb + Hg. A reduction in respiration and decomposition of10% was found at about 225–245 g g-1 of total Pb, i.e. ata Pb level elevated 3.5 times. Although small effects of Hg werefound even at the lowest dose level, 10% inhibition of microbialactivity appeared temporarily at about 2–3 g g-1 of total Hg, i. e. at 6–8 times the reference level. There were nolong-term additive effects of Pb and Hg on decomposition. Type of anion had a strong influence on the test, chlorides of Pbbeing more toxic than nitrates. Long-term monitoring and maintenance of microbial activity during the experiment were prerequisites for the occurrence of effects at low metal levels. 相似文献
957.
958.
主成分分析法在三江交汇处水质分析中的应用 总被引:1,自引:0,他引:1
本文应用主成分分析法,利用三江交汇处的三个断面从1984年到1998年的监测资料对交汇处的水质做分析,分析前先对量化数据标准化处理,处理后提取主成分,并且计算其贡献率和累计贡献率,再由相应的特征向量得到主成分的线性表达式。结果表明:五项影响因素中,三个断面桔水期均受亚硝酸盐氮的影响比较大,丰水期和平水期均受悬浮物和化学需氧量的影响比较大。交汇前,小南门断面的水质综合污染最严重,凉姜沟断面的水质综合污染最轻;交汇后,三江口断面的水质在两者的缓冲下,水质综合污染居中。则说明主成分分析法为河流的综合治理提供了科学依据。 相似文献
959.
960.