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31.
Kenneth R. Sheehan Michael P. Strager Stuart A. Welsh 《Environmental Modeling and Assessment》2013,18(2):209-219
Stream habitat assessments are commonplace in fish management, and often involve nonspatial analysis methods for quantifying or predicting habitat, such as ordinary least squares regression (OLS). Spatial relationships, however, often exist among stream habitat variables. For example, water depth, water velocity, and benthic substrate sizes within streams are often spatially correlated and may exhibit spatial nonstationarity or inconsistency in geographic space. Thus, analysis methods should address spatial relationships within habitat datasets. In this study, OLS and a recently developed method, geographically weighted regression (GWR), were used to model benthic substrate from water depth and water velocity data at two stream sites within the Greater Yellowstone Ecosystem. For data collection, each site was represented by a grid of 0.1 m2 cells, where actual values of water depth, water velocity, and benthic substrate class were measured for each cell. Accuracies of regressed substrate class data by OLS and GWR methods were calculated by comparing maps, parameter estimates, and determination coefficient r 2. For analysis of data from both sites, Akaike’s Information Criterion corrected for sample size indicated the best approximating model for the data resulted from GWR and not from OLS. Adjusted r 2 values also supported GWR as a better approach than OLS for prediction of substrate. This study supports GWR (a spatial analysis approach) over nonspatial OLS methods for prediction of habitat for stream habitat assessments. 相似文献
32.
Lai VW Kanaki K Pergantis SA Cullen WR Reimer KJ 《Journal of environmental monitoring : JEM》2012,14(3):743-751
Terrestrial snails are consumed by humans occasionally and they are an important food source for many creatures including fish and birds. Little is known about arsenic speciation in these gastropods, let alone life cycle variations. Here we report on the arsenic speciation in freshwater snails from Pender Island and Vancouver Island, B.C., Canada, which was determined on methanol/water extracts (43-59% extraction efficiency) by using high performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS) and HPLC-electrospray tandem mass spectrometry. The tetramethylarsonium ion, oxo-arsenosugars and thio-arsenosugars are the main arsenic species encountered. Arsenobetaine, which is commonly found in the marine environment, is minor. Live bearing snails Viviparidae sp. from Pender Island were maintained in aquaria and the arsenic speciation in the unborn, newly born, and adult animals was monitored. Oxo-arsenosugars predominate in the adults, whereas thio-arsenosugars seem to predominate in juveniles, suggesting that these arsenicals are snail metabolites. 相似文献
33.
Demonstrating Contaminant Degradation at an MGP Site With Metabolic Gas Flux and Radio Carbon Dating
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Sean M. Carroll Aaron D. Peacock Julio Zimbron Kenneth N. Alepidis Jeffrey A. Clock 《补救:环境净化治理成本、技术与工艺杂志》2017,27(2):51-64
Obtaining lines of evidence indicating that contamination in sediment environments is degrading and being transformed to less toxic forms is an important component of building support for a monitored natural recovery remedy for contaminated sediments. This project was a field demonstration of manufactured gas plant contaminant degradation in river sediments using metabolic gas flux and was performed in an urban area section of a river in northeastern Indiana. CO2 sorbent traps were deployed to measure CO2 flux from the river sediments. Sediment samples were collected and analyzed for polycyclic aromatic hydrocarbon (PAH) concentrations and for microbial community composition using molecular techniques. The results showed that the deployment was successful, measuring CO2 flux at all sediment locations and demonstrating that microbial contaminant degrading activity was occurring in the sediments. Radio carbon dating showed a significant portion of the CO2 being generated (approximately 19–27 percent) was the result of fossil fuel degradation. Molecular results showed that the microbial community consisted of phylotypes known to be associated with monocyclic aromatic and PAH degradation. ©2017 Wiley Periodicals, Inc. 相似文献
34.
Kharuk Viacheslav I. Im Sergei T. Petrov Ilya A. Dvinskaya Mariya L. Fedotova Elena V. Ranson Kenneth J. 《Regional Environmental Change》2017,17(3):803-812
Regional Environmental Change - Increased dieback and mortality of “dark needle conifer” (DNC) stands (composed of fir (Abies sibirica), Siberian pine (Pinus sibirica) and spruce (Picea... 相似文献
35.
Kenneth J. Tobin Marvin E. Bennett 《Journal of the American Water Resources Association》2017,53(3):593-604
Historically, many watershed studies have been based on using the streamflow flux, typically from a single gauge at the basin's outlet, to support calibration. In this setting, there is great potential for equifinality of parameters during the optimization process, especially for parameters that are not directly related to streamflow. Therefore, some of the optimal parameter values achieved during the autocalibration process may be physically unrealistic. In recent decades a vast array of data from land surface models and remote sensing platforms can help to constrain hydrologic fluxes such as evapotranspiration (ET). While the spatial resolution of these ancillary datasets varies, the continuous spatial coverage of these gridded datasets provides flux measurements across the entire basin, in stark contrast to point‐based streamflow data. This study uses Global Land Evaporation: the Amsterdam Model data to constrain Soil and Water Assessment Tool parameter values associated with ET to a more physically realistic range. The study area is the Little Washita River Experimental Watershed, in southern Oklahoma. Traditional objective metrics such as the Nash‐Sutcliffe coefficients record no performance improvement after application of this method. However, there is a dramatic increase in the number of days with receding flow where simulations match observed streamflow. 相似文献
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37.
Kenneth T. Fellows Michael J. Pilat 《Journal of the Air & Waste Management Association (1995)》2013,63(6):887-893
The sorption of hydrochloric acid (HCI) by thermally decomposed sodium bicarbonate (NaHCO3) was investigated using a fixed-bed reactor containing sorbent particles dispersed in a bed of spherical glass beads. The gas flow rate (68° F and 760 mm Hg) was 0.039 cfm (1.1 liter/min) and the bed had a cross-sectional area of 0.0055 sq. ft. (5.1 sq. cm). The influence of particle diameter (10, 45 and 163 μm), temperature (225, 275, 375, 455, and 550° F), superficial gas velocity (11 and 21 fpm at reactor conditions, 375° F), and Inlet HCI gas concentration (415 ppm and 760 ppm in N2, 275 and 455° F) were studied. Results showed that HCI sorption increased strongly with increasing temperature but was only weakly dependent on particle diameter, superficial gas velocity, and HCI gas concentration. 相似文献
38.
39.
C. Jean Bustard Kenneth M. Cushing Ramsay L. Chang 《Journal of the Air & Waste Management Association (1995)》2013,63(9):1240-1249
Pulse-jet fabric filters (PJFFs) are widely used in U.S. industrial boiler applications and in utility and industrial boilers abroad. Their small size and reduced cost relative to more conventional reverse-gas baghouses makes the use of PJFFs appear to be an attractive particulate control option for utility boilers. This paper (Part 2 of a three-part series) summarizes the results of pilot PJFF studies sponsored by the Electric Power Research Institute at different utility sites in the United States. The purpose of these tests is to evaluate PJFF performance for U.S. fossil-fuel-fired applications. These data are also used to corroborate the results of a recent worldwide survey of PJFF user experience, as described in Part 1 of this series. Part 3 will provide a cost comparison of PJFFs to other particulate control options such as electrostatic precipitators and reverse-gas baghouses. 相似文献
40.
Mae Sexauer Gustin Kenneth Ladwig 《Journal of the Air & Waste Management Association (1995)》2013,63(3):320-330
Abstract Some mercury (Hg) naturally present in coal is retained in the fly ash remaining after combustion. Concern has been raised regarding the potential for release of this Hg to the environment. The exchange of Hg between fly ash and the atmosphere was measured in the laboratory and in situ at a fly ash landfill. All samples of fly ash used in the laboratory study, with the exception of that derived from lignite-type coal, acted as a sink for atmospheric Hg. Deposition rates were found to increase as air Hg concentrations increased and to decrease with incident light and increased temperature. Addition of water to fly ash samples resulted in re-emission of deposited atmospheric Hg. Deposition was the dominant flux measured in situ at a fly ash landfill. Atmospheric Hg was deposited to all samples collected as part of two demonstration projects using carbon injection for enhanced Hg capture. Hg concentrations of extracts derived using U.S. Environmental Protection Agency Method 1312 (Synthetic Precipitation Leaching Procedure) were ≤14.4 ng/L. Data developed demonstrate that fly ash, including that collected from Hg removal projects, will release little Hg to the air or water, and under certain conditions, absorbs Hg from the air. 相似文献