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The history of incineration in Los Angeles from 1943 to the present is reviewed as representative of all southern California areas.  相似文献   
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Ambient air concentrations of fluorocarbon 11 (fluorotrichloromethane) and fluoro-carbon 12 (dichlorodifluoromethane) have been measured using a gas chro-matograph equipped with a pulsed, electron capture detector. Air samples taken on a moderately smoggy day in July 1970, at several locations near Los Angeles gave average readings of fluorocarbon 12, 0.7 ppb and fluorocarbon 11, 0.56 ppb. These readings were contrasted with those taken in early February 1973 when the air was clear and marked with turbulence due to several seasonal rain storms. The readings of both fluorocarbon 1 1 and 12 averaged about 25% less during clear weather than those taken during moderate smog. The effects of weather conditions on the concentration were also dramatically pointed out by the February samples, in that as much as a tenfold change in concentrations of both fluorocarbons from location to location and from day to day at the same location was observed. A concentration versus altitude study clearly revealed that fluorocarbons are trapped by an inversion layer. Examination of air samples taken in the vicinity of factories known to be users of fairly large quantities of fluorocarbons revealed in part how large users contribute to the atmospheric concentrations of fluorocarbons. A comparison of fluorocarbon levels in homes and public buildings with ambient outside air levels revealed that the concentrations in some homes and buildings may be as much as several thousand times as high as levels in outside air. Inside the homes and public buildings, levels were as high as one-half of a part per million. Long term photolysis studies in simulated sunlight of both fluorocarbons 11 and 12 in ambient air samples and in air samples with 1 ppm of hydrocarbon and 1 ppm of nitrogen oxides revealed that the two fluorocarbons are photochemically stable even when photolyzed for several weeks.  相似文献   
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ABSTRACT

Ambient particles contain substantial quantities of material that can be lost from the particles during sample collection on a filter. These include ammonium nitrate and semi-volatile organic compounds. As a result, the concentrations of these species are often significantly in error for results obtained with a filter pack sampler. The accurate measurement of these semi-volatile fine particulate species is essential for a complete understanding of the possible causes of health effects associated with exposure to fine particles. Past organic compound diffusion denuder samplers developed by the authors (e.g., the Brigham Young University Organic Sampling System [BOSS]) are not amenable to routine field use because of the need to independently determine the gas-phase semi-volatile organic material efficiency of the denuder for each sample. This problem has been eliminated using a combined virtual impactor, particle-concentrator inlet to provide a concentrated stream of 0.1-2.5-μm particles. This is followed by a BOSS diffusion denuder and filter packs to collect particles, including any semi-volatile species lost from the particles during sampling. The samp ler (Particle Concentrator-Brigham Young University Organic Sampling System [PC-BOSS]) contains a post-denuder multifilter pack unit to allow for the routine collection of several sequential samples. The PC-BOSS can be used for the determination of both fine particulate nitrate and semi-volatile organic material without significant “positive” or “negative” sampling artifacts. Validation of the sampler for the determination of PM2.5 sulfate and nitrate based on comparison of results obtained at Riverside, CA with collocated PC-BOSS, annular denuder, and Chem Spec samplers indicates the PC-BOSS gives accurate results for these species with a precision of ±5-8%. An average of 33% of the PM2.5 nitrate was lost from the particles during sampling for both denuder and single filter samplers.  相似文献   
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Aerosol concentrations of carbonaceous material, sulfate, and nitrate for samples obtained using a newly designed PC-BOSS are reported. The results indicated that PM2.5 composition in Atlanta was dominated by sulfate and organic material, with low concentrations of particulate nitrate. Observed average particulate component concentrations for the 26-day study period were: sulfate, 12.2 μg/m3 (17.0 μg/m3 as ammonium sulfate); non-volatile organic material, 11.4 μg OM/m3 (assumes organic material, OM, is 61% C); semi-volatile organic compounds (SVOC) lost from particles during sampling, 5.3 μg OM/m3; filter retained nitrate, 0.1 μg/m3 (0.2 μg/m3 as ammonium nitrate); nitrate lost from particles, 0.3 μg/m3 (0.4 μg/m3 as ammonium nitrate); and soot (elemental carbon), 1.5 μg/m3. The PC-BOSS particle concentrator efficiency was obtained by comparison of the PC-BOSS sulfate data with sulfate data obtained from the Federal Reference Method (FRM) sampler. A modification of the PC-BOSS design to allow independent determination of this parameter is recommended.  相似文献   
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Recent evidence indicates that acid rain is a growing environmental phenomenon of potentially far reaching consequences and increasing geographical extent in North America. Acid rain is but one aspect of the broader problem of atmospheric deposition which includes snow, fog, and dry deposition of material. First noticed and studied in the Scandinavian countries, acid precipitation has now been well documented in the United States, first in the northeast and more recently throughout much of the United States east of the Mississippi River. Numerous streams and lakes in regions with poorly buffered soils have become devoid of fish, have an impoverished aquatic flora and fauna, and are changing toward conditions of low aquatic productivity. Evidence also indicates that acid precipitation may cause damage to forest growth, crop production, wildlife, and man-made materials such as buildings, metals, paints, and statuary.  相似文献   
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Summary Our environmental situation continues to decline faster than ever. This is demonstrated by, the growing spread of pollution of both the water and atmospheric systems, erosion of topsoil, tropical deforestation, desertification, mass extinction of species, depletion of the ozone layer, and climatic dislocations. Compounding the impact of these problems is growth in human numbers in developing countries, together with the associated factor of extensive poverty. The author asks why our environmental situation should continue to decline, despite a remarkable outburst of awareness on the part of the general public and its political leaders since the time of the Stockholm Conference on the Human Environment. The author concludes that the problem does not lie with inadequate effort, rather with misdirected effort: we persist in tackling the symptoms of problems, rather than the problems themselves, let alone the sources of the problems. The paper broaches these issues within a context of fast-growing interdependence among the community of nations — both economic and ecological interdependence — which presents yet more problems, but also raises many opportunities for creative action.Professor Norman Myers is a consultant in environment and development. He has worked since 1970 on the general subject area of environment and natural resources, with emphasis on species, gene reservoirs and tropical forests. He was undertaken this consultancy work for the Rockefeller Brothers Fund, US National Academy of Sciences, the World Bank, OECD, the Smithsonian Institution, UN agencies, World Resources Institute, US National Research Council and IUCN, among other organizations. His main professional interest lies with resource relationships between the developed and developing worlds.Among his recent publications areThe Sinking Ark (Pergamon Press, Oxford and New York, 1979);Conversion of Tropical Moist Forests (National Research Council, Washington D.C., 1980);A Wealth of Wild Species (Westview Press, Boulder, Colorado, 1983);The Primary Source (W. W. Norton, New York, 1984); andThe Gaia Atlas of Planet Management (Doubleday, New York, and Pan Books, London, 1985).Norman Myers is an Advisory Board Member and regular contributor toThe Environmentalist.  相似文献   
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