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91.
Henry C. Wohlers Herman Newstein Diane Daunis 《Journal of the Air & Waste Management Association (1995)》2013,63(11):753-756
It was planned to install 305 m (1000 ft) of tubing on a television tower to transport ambient air samples from different height levels to pollutant monitoring instruments at ground level. A feasibility study was undertaken to determine the sorption characteristics of sulfur dioxide and carbon monoxide on various conduit materials. Sorption studies were completed on 30.5 m (100 ft) lengths of 1.3 cm (Y2 in) diam tubings of glass, Teflon, tygon, polypropylene, PVC piping, aluminum, and stainless steel. Final tests were completed on 305 m of 1.9 cm (3/4 in) diam stainless steel tubing. The following variables were investigated: tubing diameter, gas concentration, flowrate through the tubing, temperature, humidity, and the effect of sorption with sulfur dioxide and carbon monoxide alone or together. The parameter ranges studied approximated either atmospheric or air sampling conditions. For carbon monoxide, there was no significant difference between the mean inlet and outlet tubing concentrations under the conditions of the study. With sulfur dioxide, there was neither tubing adsorption nor desorption under the experimental parameters studied, except for tygon, PVC, and aluminum. After a conditioning period with sulfur dioxide, tygon, PVC, and aluminum could also be used as air inlet conduits; tygon is not recommended. 相似文献
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Pablo Cicero-Fernandez Victor Torres Alberto Rosales Herman Cesar Kees Dorland Roberto Muñoz 《Journal of the Air & Waste Management Association (1995)》2013,63(11):1586-1593
ABSTRACT The main goal of this study was to evaluate the magnitude of outdoor exposure to fine particulate matter (PM10) potentially experienced by the population of metropolitan Mexico City. With the use of a geographic information system (GIS), spatially resolved PM10 distributions were generated and linked to the local population. The PM10 concentration exceeded the 24-hr air quality standard of 150 μg/m3 on 16% of the days, and the annual air quality standard of 50 μg/m3 was exceeded by almost twice its value in some places. The basic methodology described in this paper integrates spatial demographic and air quality databases, allowing the evaluation of various air pollution reduction scenarios. Achieving the annual air quality standard would represent a reduction in the annual arithmetic average concentration of 14 μg/m3 for the typical inhabitant. Human exposure to particulate matter (PM) has been associated with mortality and morbidity in Mexico City; reducing the concentration levels of this pollutant would represent a reduction in mortality and morbidity and the associated cost of such impacts. This methodology is critical to assessing the potential benefits of the current initiative to improve air quality implemented by the Environmental Metropolitan Commission of Mexico City. 相似文献
95.
Wijnhoven S van der Velde G Leuven RS Eijsackers HJ Smits AJ 《Environmental pollution (Barking, Essex : 1987)》2006,140(3):444-452
Turbation is hypothesized to affect the redistribution of heavy metals in polluted floodplain soils by effects on mobility. This hypothesis was tested in microcosms by turbation of zinc-spiked sediment top layers. Manual turbation caused a fast decrease of the zinc content in the upper 15 cm of the soil, even though turbation was only applied to the upper two centimetres. It was especially zinc attached to colloid and organic matter particles that was redistributed from the top layer. Percolation processes resulted in the attached zinc being drained to depths of more than 15 cm. The decrease in zinc content of the topsoil was even stronger in combination with inundation. No indications were found for the redistribution of zinc as a result of an increase of the extractability with 0.01 M CaCl2 or changes in pH. The findings suggest that mechanical turbation and bioturbation may redistribute heavy metals from topsoils in polluted floodplains just after inundation as observed in these turbation experiments. 相似文献
96.
Regular, self-organized spatial patterns in primary producers have been described in a wide range of ecosystems and are predicted to affect community production and resilience. Although consumers are abundant in most systems, the effect of trophic interactions on pattern formation in primary producers remains unstudied. We studied the effects of top-down control by herbivores on a self-organized landscape of regularly spaced, diatom-covered hummocks alternating with water-filled hollows on an intertidal mudflat in The Netherlands. Spatial patterns developed during spring but were followed by a rapid collapse in summer, leading to a flat landscape with low diatom densities and little variation in sediment bed level. This dramatic decline co-occurred with a gradual increase of benthic herbivores. A manipulative field experiment, where benthic herbivores were removed from the sediment, revealed that both diatom growth and hummock formation were inhibited by the activity of benthic herbivores. Our study provides clear evidence of top-down control of spatial self-organized patterns by benthic herbivores within a biological-geomorphic landscape. 相似文献
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Nayara T. do Prado Ana P. Heitmann Herman S. Mansur Alexandra A. Mansur Luiz C.A. Oliveir Cinthia S. de Castro 《环境科学学报(英文版)》2017,29(7):312-320
This work describes the synthesis of catalysts based on red mud/polyethylene terephthalate(PET) composites and their subsequent heat treatment under N2 atmosphere.The materials were characterized by scanning electron microscopy(SEM),temperature programmed reduction(TPR),Fourier transform infrared spectroscopy(FT–IR),X-ray diffraction(XRD),thermogravimetric(TG) analysis and N2adsorption/desorption.The catalysts were evaluated in the oxidative desulfurization reaction of dibenzothiophene(DBT) in a biphasic system.The results indicated that the PET impregnation on red mud increased the affinity of the catalyst with the nonpolar phase(fuel),in which the contaminant was dissolved,allowing a higher conversion(up to 80%) and selectivity to the corresponding dibenzothiophene sulfone.The sulfone compound is more polar than DBT and diffused into the polar solvent as indicated by the data obtained via gas chromatography–mass spectrometry(GC–MS). 相似文献
98.
The face of the city is its information 总被引:1,自引:0,他引:1
What is it in the externally represented face of the city that makes it recognizable and imaginable? What makes some urban elements and artifacts more legible and better remembered than others? Or put more generally: What makes an object an external representation and what makes it better perceived and/or remembered? Our answer to all these questions is “the information they embody and convey”. Some elements, including those that compose the face of the city, are quantitatively and qualitatively more informative than others and are therefore more legible and better perceived and remembered, quantitatively, in terms of Shannon's theory of information (The Mathematical Theory of Communication, University of Illinois Press, Urbana, IL, 1949), and qualitatively in terms of Haken's (Information and Self-organization: a Macroscopic Approach to Complex Systems, Springer, Heidelberg, 1988/2000) notion of semantic information. In this paper, we elaborate on this point of view in three steps: In the first, we introduce Shannonian information and show how it can be used to define the amount of information externally represented in different urban elements. In the second, we show how this is related to processes of grouping and categorization that give meaning to the face of the city and thus form its semantic information. In the third, we discuss implications for cognition in general and for cognitive mapping in particular. 相似文献
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