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281.
Watson JG Chow JC Lowenthal DH Stolzenburg MR Kreisberg NM Hering SV 《Journal of the Air & Waste Management Association (1995)》2002,52(7):822-827
Aerosol size distributions are presented for a winter intensive study at the Fresno Supersite. The size distributions were consistent with and predictive for continuous PM2.5 measured by beta attenuation. They varied temporally with respect to source type and intensity, with the smallest mean diameters associated with high NOx concentrations during weekday morning rush hours. Conversely, small and large particle and black carbon (BC) concentrations were higher during Sunday and weekday evenings in response to traffic and residential wood combustion emissions. Ambient PM2.5 light scattering (Bsp) was precisely but systematically underestimated during winter, probably because of heating in the sample shelter. 相似文献
282.
Chow JC Engelbrecht JP Freeman NC Hashim JH Jantunen M Michaud JP Saenz de Tejada S Watson JG Wei F Wilson WE Yasuno M Zhu T 《Chemosphere》2002,49(9):873-901
Determining human exposure to suspended particulate concentrations requires measurements that quantify different particle properties in microenvironments where people live, work, and play. Particle mass, size, and chemical composition are important exposure variables, and these are typically measured with time-integrated samples on filters that are later submitted to laboratory analyses. This requires substantial sample handling, quality assurance, and data reduction. Newer technologies are being developed that allow in-situ, time-resolved measurements for mass, carbon, sulfate, nitrate, particle size, and other variables. These are large measurement systems that are more suitable for fixed monitoring sites than for personal applications. Human exposure studies need to be designed to accomplish specific objectives rather than to serve too many purposes. Resources need to be divided among study design, field sampling, laboratory analysis, quality assurance, data management, and data analysis phases. Many exposure projects allocated too little to the non-measurement activities. 相似文献
283.
Paul B Downing William D Watson 《Journal of Environmental Economics and Management》1974,1(3):219-236
The goal of this paper is to determine the likely effect on a firm's control actions of alternative implementation and enforcement policies available to the control agency. Three alternatives are studied, legal enforcement through the new source performance standards set forth by EPA, and two effluent fee enforcement alternatives. First, a generalized model of the effects of implementation and enforcement policies on the firm's control action is developed. This model assumes that the firm is an expected cost minimizer. The model is then applied to the case of particulate matter discharges from coal-fired power plants in order to estimate empirically the effect of policy alternatives on the firm's control efforts. Finally, the results of the model and its empirical application are used to develop policy functions which relate control to the values of various policy parameters. These results lead us to several policy recommendations. 相似文献
284.
285.
Hansen AD Lowenthal DH Chow JC Watson JG 《Journal of the Air & Waste Management Association (1995)》2001,51(4):593-600
Aerosol light absorption as black carbon (BC) was measured from November 19, 1995, to February 6, 1996, at a location 0.65 km downwind of the center of McMurdo Station on the Antarctic coast. The results show a bimodal frequency distribution of BC concentrations. Approximately 65% of the measurements were found in a mode at a low range of concentrations centered at approximately 20 ng/m3. These concentrations are higher than those found at other remote Antarctic locations and probably represent contamination from the station. The remaining measurements were in a high-concentration mode (BC approximately 300 ng/m3), indicating direct impact of local emissions from combustion activities at the station. High values of BC were associated with winds from the direction of the station, and the BC flux showed a clear directionality. Maximum BC concentrations occurred between 7:00 and 11:00 a.m. The "polluted" mode accounted for more than 80% of the BC frequency-weighted impact at this location. 相似文献
286.
Watson TB 《Journal of the Air & Waste Management Association (1995)》1995,45(1):29-35
This paper describes a portable, low-cost whole air sampler capable of collecting 12 1-L samples in tedlar bags and using a single "D" cell for power. The results are presented from two tests of an intensive sampling and analysis method for measuring ambient carbon monoxide (CO) concentrations in urban areas using this sampler. The method is evaluated in comparison with an approved continuous CO analyzer, in intercomparisons of the results of re-analysis of the samples, and by examination of the results from co-located samplers. The precision of the analytical method was found to be +/-0.30 ppmv. The precision of the sampling method was found to be +/-0.73 ppmv and therefore is the limiting factor in the method's overall precision. These values are sufficient to verify attainment of National Ambient Air Quality Standards (NAAQS) levels in urban areas. Improvements in the sampler and analytical procedure are discussed. 相似文献
287.
V. Etyemezian M. Tesfaye A. Yimer J.C. Chow D. Mesfin T. Nega G. Nikolich J.G. Watson M. Wondmagegn 《Atmospheric environment (Oxford, England : 1994)》2005,39(40):7849-7860
Twenty-one samples were collected during the dry season (26 January–28 February 2004) at 12 sites in and around Addis Ababa, Ethiopia and analyzed for particulate matter with aerodynamic diameter <10 μm (PM10) mass and composition. Teflon-membrane filters were analyzed for PM10 mass and concentrations of 40 elements. Quartz-fiber filters were analyzed for chloride, sulfate, nitrate, and ammonium ions as well as elemental carbon (EC) and organic carbon (OC) content. Measured 24-h PM10 mass concentrations were <100 and 40 μg m−3 at urban and suburban sites, respectively. PM10 lead concentrations were <0.1 μg m−3 for all samples collected, an important finding because the government of Ethiopia had stopped the distribution of leaded gasoline a few months prior to this study. Mass concentrations reconstructed from chemical composition indicated that 34–66% of the PM10 mass was due to geologically derived material, probably owing to the widespread presence of unpaved roads and road shoulders. At urban sites, EC and OC compounds contributed between 31% and 60% of the measured PM10 while at suburban sites carbon compounds contributed between 24% and 26%. Secondary sulfate aerosols were responsible for <10% of the reconstructed mass in urban areas but as much as 15% in suburban sites, where PM10 mass concentrations were lower. Non-volatile particulate nitrate, a lower limit for atmospheric nitrate, constituted <5% and 7% of PM10 at the urban and suburban sites, respectively. At seven of the 12 sites, real-time PM10 mass, real-time carbon monoxide (CO), and instantaneous ozone (O3) concentrations were measured with portable nephelometers, electrochemical analyzers, and indicator test sticks, respectively. Both PM10 and CO concentrations exhibited daily maxima around 7:00 and secondary peaks in the late afternoon and evening, suggesting that those pollutants were emitted during periods associated with motor-vehicle traffic, food preparation, and heating of homes. The morning concentration maxima were likely accentuated by stable atmospheric conditions associated with overnight surface temperature inversions. Ozone concentrations were measured near mid-day on filter sample collection days and were in all cases <45 parts per billion. 相似文献
288.
D. Rayfield J.W.S. Longhurst A.F.R. Watson T. Hewison D.W. Raper D.E. Conlan B. Owen 《The Environmentalist》1998,18(3):175-182
Road transport is a major contributor to urban air pollution. The introduction of local air qua lity management in the UK will require objective test procedures to evaluate and prioritise the air pollution benefits of existing transport systems and proposed developments. This methodology has been developed to assist the land use and transport planning professionals in evaluating current and potential future impacts on air quality. The method couples an emissions estimation procedure to a traffic flow database. It requires data on emission factors, the composition of the vehicle fleet, vehicle control technologies and the daily traffic flow profile. With these data, it is possible to generate emission estimates per kilometre, link or road as selected by the user. Forecasts can be made by varying input variables. The current methodology allows prediction of five or more pollutant species/classes, limited only by availability of emission factors. The method utilises a commercially available personal computer based spreadsheet. Further coupling of the method to a geographical information system will improve the decision support capability of the method. 相似文献
289.
290.
R. Williamson M. E. D. Allison T. J. Bentley S. M. C. Lim E. Watson J. Chapple S. Adam M. Boulton 《黑龙江环境通报》1989,9(10):727-734
Inexpensive and accurate carrier testing for cystic fibrosis (CF) will be possible in the near future. There are no existing studies on the attitudes of English persons in the community to carrier testing for CF or any other recessive disorder. We have conducted a trial study of 166 persons at two schools, two doctors' surgeries, and a family planning clinic. Only a minority had clear pre-existing knowledge of cystic fibrosis and its genetic nature. However, over 80 per cent of those questioned expressed interest in knowing their carrier status. Although it is well known that uptake can only be assessed when a service is in place, and while further studies are required to confirm that testing will be of interest to couples of reproductive age with no previous knowledge of CF, the data strongly suggest that there will be interest in communitywide testing for CF carrier status when such a test becomes available in the United Kingdom. 相似文献