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51.
Gilberto Fuentes García Humberto Bravo Álvarez Rodolfo Sosa Echeverría Sergio Rosas de Alba Víctor Magaña Rueda Ernesto Caetano Dosantos 《Journal of the Air & Waste Management Association (1995)》2017,67(9):973-985
Atmospheric mercury in the environment as a result of the consumption of fossil fuels, such as coal used in electricity generation, has gained increased attention worldwide because of its toxicity, atmospheric persistence, and bioaccumulation. Determining or predicting the concentration of this pollutant in ambient air is essential for determining sensitive areas requiring health protection. This study investigated the spatiotemporal variability of gaseous elemental mercury (GEM) concentrations and its dry deposition surrounding the Presidente Plutarco Elías Calles (CETEPEC) coal-fired power plant, located on Mexico’s Pacific coast. The CALPUFF dispersion model was applied on the basis of the daily consumption of coal during 2013 for each generating unit in the power plant and considering the local scale. The established 300-ng/m3 annual average risk factor considered by the U.S. Department of Health and Human Services (U.S. DHHS) and Integrated Risk Information System (IRIS) must not be exceeded to meet satisfactory air quality levels. An area of 65 × 60 km was evaluated, and the results show that the risk level for mercury vapor was not exceeded because the annual average concentration was 2.8 ng/m3. Although the predicted risk level was not exceeded, continuous monitoring studies of GEM and of particulates in the atmosphere, soil, and water may be necessary to identify the concentration of this pollutant, specifically that resulting from coal-fired power plants operated in environmental areas of interest in Mexico. The dry mercury deposition was low in the study area; according to the CALPUFF model, the annual average was 1.40E?2 ng/m2/sec. These results represent a starting point for Mexico’s government to implement the Minamata Convention on Mercury, which Mexico signed in 2013.Implications: The obtained concentrations of mercury from a bigger coal-fired plant in Mexico, through the application of the CALPUFF dispersion model by the mercury emissions, are below the level recommended according to the US Department of Health and Human Services and Integrated Risk Information System. These results provide evidence of important progress in the planning and installation to the future of monitoring mercury stations in the area of interest. 相似文献
52.
Hector G. Riveros Alfredo Alba Pilar Ovalle Beatriz Silva Ernesto Sandoval 《Journal of the Air & Waste Management Association (1995)》2013,63(5):459-462
ABSTRACT From the analysis of data of the Inspection/Maintenance (I/M) program, and of the long-term trend of ambient CO concentrations in Mexico City, it is inferred that three-way catalysts (TWCs) have a 45% efficiency, well below the expected 90% value. The most probable causes are sulfur poisoning, lead contamination, and ceramic breakage due to bumps and potholes on the streets. Also, we have found a ratio between the average daily peak value of atmospheric CO and gasoline consumption: (11 ± 1) ppbCO/MLm (million liters of gasoline per month) in 1988 decaying to (10 ±1) in 1991 for Mexico City before the introduction of TWCs. In addition, we found a correlation between the monthly averages of CO daily peak and meteorological variables, explaining most of the seasonal changes using only the intensity of the inversion layer and surface wind speed. 相似文献
53.
Ernesto Di Maio Raed Mali Salvatore Iannace 《Journal of Polymers and the Environment》2010,18(4):626-633
Conventional direct melt mixing technology was investigated on zein and kafirin, two vegetable proteins extracted, respectively,
from maize and sorghum. A lab scale internal mixer has been used to thoroughly study the thermo-plasticization process of
the proteins with several plasticizers. Different compositions were investigated under different processing conditions. In
particular, the lengthy procedures of forming the protein/solvent/plasticizer solution followed by drying or the protein/plasticizer
emulsion followed by the precipitation of the extrudable resin, reported in the literature for these systems, were avoided
and the protein and plasticizer were directly fed into the mixer to obtain a plastic-like material. The effect of plasticizer
type and content and mixing process variables on the mechanical properties was analyzed. Compression molded slabs were transparent,
strong and flexible, with properties similar to the cast films reported in the literature, prepared with the same type of
plasticizers. However, lower plasticizer content was sufficient to produce equally flexible films, proving an enhanced plasticization
efficiency of the mixing process, as compared to casting. 相似文献
54.
Ernesto Salzano Francesco Cammarota Almerinda Di Benedetto Valeria Di Sarli 《Journal of Loss Prevention in the Process Industries》2012,25(3):443-447
The effects of enriching natural gas with hydrogen on local flame extinction, combustion instabilities and power output have been widely studied for both stationary and mobile systems. On the contrary, the issues of explosion safety for hydrogen–methane mixtures are still under investigation.In this work, experimental tests were performed in a 5 L closed cylindrical vessel for explosions of hydrogen–methane mixtures in stoichiometric air. Different compositions of hydrogen–methane were tested (from pure methane to pure hydrogen) at varying initial pressures (1, 3 and 6 bar).Results have allowed the quantification of the combined effects of both mixture composition (i.e., hydrogen content in the fuel) and initial pressure on maximum pressure, maximum rate of pressure rise and burning velocity. The measured burning velocities were also correlated by means of a Le Chatelier’s Rule-like formula. Good predictions have been obtained (at any initial pressure), except for mixtures with hydrogen molar content in the fuel higher than 50%. 相似文献
55.
José Gianottp Guillermo Stettler Ernesto Haggp Adriana Pajares Sonia G. Bertolotti Norman A. García 《毒物与环境化学》2013,95(3-4):461-470
Nonylphenol (nonyl‐P) belongs to the classification of persistent organic pollutants. In this work we demonstrate that the contaminant suffers photooxygenation when exposed to visible light Eosin‐photosensitized irradiation. The mechanism was identified as a singlet molecular oxygen‐mediated photooxidation. Rate constants for the process, determined by time‐resolved phosphorescence detection of singlet molecular oxygen, are in the range 105‐107 M‐1 s‐1, depending on the characteristics of the reaction medium. The photooxidative process is more efficient when performed in highly polar alkaline medium. The aggregation of nonyl‐P molecules in pure water decreases the rates of sensitized photooxidation of nonyl‐P and also those of polychlorophenolic contaminants, employed as photooxidizable model compounds, when photolyzed in the presence of nonylphenol. These results are discussed in terms of a micellar effect. 相似文献
56.
Eduardo Ríos-Jara Cristian Moisés Galván-Villa Fabián Alejandro Rodríguez-Zaragoza Ernesto López-Uriarte Vicente Teófilo Muñoz-Fernández 《Environmental management》2013,52(2):335-347
The popularity of ecotourism in the marine protected areas of Mexico has increased over the last 10 years; in particular there is a large development of a SCUBA diving industry in the Mexican Pacific including Isabel Island. Given the risks associated with human activity in the marine environments around this island, we propose two ecotourism management strategies: (1) the creation and use of underwater trails, and (2) the estimation of the specific tourism carrying capacity (TCC) for each trail. Six underwater trails were selected in sites that presented elements of biological, geological, and scenic interest, using information obtained during field observations. The methodology used to estimate the TCC was based upon the physical and biological conditions of each site, the infrastructure and equipment available, and the characteristics of the service providers and the administrators of the park. Correction factors of the TCC included elements of the quality of the visit and the threat and vulnerability of the marine environment of each trail (e.g., divers’ expertise, size and distance between groups of divers, accessibility, wind, coral coverage). The TCC values ranged between 1,252 and 1,642 dives/year/trail, with a total of 8,597 dives/year for all six trails. Although these numbers are higher than the actual number of recreational visitors to the island (~1,000 dives per year), there is a need for adequate preventive management if the diving sites are to maintain their esthetic appeal and biological characteristics. Such management might be initially directed toward using only the sites and the TCC proposed here. 相似文献
57.
Koutrakis P Sax SN Sarnat JA Coull B Demokritou P Oyola P Garcia J Gramsch E 《Journal of the Air & Waste Management Association (1995)》2005,55(3):342-351
Daily particle samples were collected in Santiago, Chile, at four urban locations from January 1, 1989, through December 31, 2001. Both fine PM with da < 2.5 microm (PM2.5) and coarse PM with 2.5 < da < 10 microm (PM2.5-10) were collected using dichotomous samplers. The inhalable particle fraction, PM10, was determined as the sum of fine and coarse concentrations. Wind speed, temperature and relative humidity (RH) were also measured continuously. Average concentrations of PM2.5 for the 1989-2001 period ranged from 38.5 microg/m3 to 53 microg/m3. For PM2.5-10 levels ranged from 35.8-48.2 microg/m3 and for PM10 results were 74.4-101.2 microg/m3 across the four sites. Both annual and daily PM2.5 and PM10 concentration levels exceeded the U.S. National Ambient Air Quality Standards and the European Union concentration limits. Mean PM2.5 levels during the cold season (April through September) were more than twice as high as those observed in the warm season (October through March); whereas coarse particle levels were similar in both seasons. PM concentration trends were investigated using regression models, controlling for site, weekday, month, wind speed, temperature, and RH. Results showed that PM2.5 concentrations decreased substantially, 52% over the 12-year period (1989-2000), whereas PM2.5-10 concentrations increased by approximately 50% in the first 5 years and then decreased by a similar percentage over the following 7 years. These decreases were evident even after controlling for significant climatic effects. These results suggest that the pollution reduction programs developed and implemented by the Comisión Nacional del Medio Ambiente (CONAMA) have been effective in reducing particle levels in the Santiago Metropolitan region. However, particle levels remain high and it is thus imperative that efforts to improve air quality continue. 相似文献
58.
59.
T. Giray Z.-Y. Huang Ernesto Guzmán-Novoa G. E. Robinsons 《Behavioral ecology and sociobiology》1999,47(1-2):17-28
Two factors that influence age at onset of foraging in honeybees are juvenile hormone (JH) and colony age demography (older
bees inhibit behavioral development of younger bees). We tested the hypothesis that genetic variation among bees for these
factors influences genetic variation in behavioral development. Pairs of colonies showing genetic differences in rates of
behavioral development were identified in a screening experiment and bees from these colonies were used for physiological
and behavioral assays. Six pairs were assayed, three with European bees only and three with both European and Africanized
bees. There was genetic variation for the following four components: (1) production of JH in four pairs (experiment 1); (2)
sensitivity to JH in three pairs (experiment 2); (3) sensitivity to social inhibition in three pairs (experiment 3), and (4)
potency of social inhibition in four pairs (experiment 4). Cross-fostering assays (experiment 5), which allowed all four components
to be evaluated simultaneously, revealed genetic variation for production of JH, sensitivity to JH, or sensitivity to social
inhibition in five of six pairs, and potency of social inhibition in five of six pairs. There was often evidence for genotypic
differences in more than one component, and no consistent pattern of association among any of the components. Africanized
bees had faster rates of behavioral development than European bees, but there were no racial differences in patterns of variation
among the four components. These results indicate that there are at least several, apparently distinct, physiological processes
associated with JH and colony age demography upon which natural selection can act to alter the rate of behavioral development
in honeybees.
Received: 8 December 1998 / Received in revised form: 29 July 1999 / Accepted: 8 August 1999 相似文献
60.
Ernesto Bonilla Rocío Contreras Shirley Medina-Leendertz Marylu Mora Virginia Villalobos Milagros Paz 《毒物与环境化学》2013,95(4):742-747
The effect of resveratrol was studied on the life span and motor activity of Drosophila melanogaster treated with manganese (Mn). Two days after emerging from the pupa, male wild type D. melanogaster were fed for 13 days with corn media containing 15?mM Mn. Thereafter, Drosophila were divided into six groups of 300 flies each: (1) the flies remained treated with Mn; (2) began treatment with 0.43?mM resveratrol (Mn-resveratrol group); (3) received no additional treatment (Mn-no treatment group); (4) simultaneously fed with Mn and resveratrol (Mn?+?resveratrol group). In addition, a control (5) with no treatment and another group (6) fed only with resveratrol after emerging from the pupa were included. All Mn-treated flies (group 1) were dead on the 25th day. The life span in the resveratrol group was 91?±?0.33 days (mean?±?S.E.M.) and in Mn-resveratrol flies was 83?±?2 days. These two values were significantly higher than those detected in the control (5) and Mn-no treatment (group 3) flies whose life span were 68?±?0.33 and 67?±?2.31 days, respectively. The Mn?+?resveratrol-fed flies had a markedly higher life span (31?±?1.53 days) than Mn-fed flies (23?±?0.88 days). In the flies that received Mn (Mn and Mn?+?resveratrol groups), the motor activity decreased significantly with respect to control (groups 5) and the Mn–resveratrol and resveratrol groups. In conclusion, resveratrol increased significantly the life span of Mn-treated D. melanogaster. 相似文献