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931.
Various formulations of fire-extinguishing materials, including aqueous film-forming foams (AFFFs), were used as part of fire-training exercises conducted at Wurtsmith Air Force Base (WAFB) in northeastern Michigan from the 1950s until the base was decommissioned in 1993. As a result of past fire-training exercises, AFFF-laden wastewater containing fuels, solvents, and other materials directly entered groundwater without prior treatment. Perfluorinated surfactants are key components in some AFFF formulations. In this study, groundwater was analyzed for perfluoroalkanesulfonates and perfluorocarboxylates. Perfluoroalkanesulfonates were directly detected using negative-ion electrospray ionization mass spectrometry. Derivatized perfluorocarboxylates were detected using electron impact gas chromatography-mass spectrometry. Groundwater from wells around fire-training area FTA-02 at WAFB contained four perfluorinated surfactants ranging in concentration from 3 to 120 microg L(-1): perfluorooctanesulfonate (PFOS); perfluorohexanesulfonate; perfluorooctanoate; and perfluorohexanoate. This is the first report demonstrating that PFOS, recently shown to be toxic to organisms ranging from zooplankton to primates, is still present in groundwater in measurable quantities five or more years after its last known use. 相似文献
932.
W. Scott Hall Steven J. Bushong Lenwood W. Hall Jr. Michael J. Lenkevich Alfred E. Pinkney 《Environmental monitoring and assessment》1988,11(1):33-42
Dissolved copper and selected water chemistry parameters were monitored for 11 months in Chesapeake Bay, U.S.A. Dissolved copper concentrations in four recreational marinas, a large harbor, two major river systems, and a heavily used shipping canal ranged from below detectable levels to 80 g L-1 (\-X=11.7 g L-1). Dissolved copper was detected >91% of the time at five locations. Lowest copper concentrations were found in Potomac River, Baltimore Harbor, Pier One Marina, and C & D Canal (\-X=6–10 g L-1; slightly higher levels of dissolved copper were found in Choptank River (\-X=12 g L-1). Highest levels of copper were detected in Port Annapolis, Hartge, and Piney Narrows Marinas (\-X=13–18 g L-1), with the highest values observed in the study (70 and 80 g L-1) found in two of these marinas. Copper in the three marinas with highest dissolved copper levels could have been toxic to some of the more sensitive aquatic species. Intensive study of one marina indicated that a likely source of dissolved copper was the recreational boats housed in the marina. 相似文献
933.
Lenwood W. Hall Jr. Michael A. Unger Michael C. Ziegenfuss John A. Sullivan Steven J. Bushong 《Environmental monitoring and assessment》1992,22(1):15-38
This study was designed to: (1) evaluate dibutyltin (DBT) and tributyltin (TBT) bi-weekly in the water column for four months during the peak boating season (June–September, 1989) at seven stations in the Back Creek and Severn River area of Maryland waters of Chesapeake Bay; (2) compare butyltin values from the 1989 study with values obtained from a similar butyltin monitoring study conducted in 1988 (after Maryland TBT legislation) and 1986 (before Maryland TBT legislation); (3) determine the extent of TBT paint use in the Back Creek area by surveying boat owners; (4) determine dissolved copper concentrations from three of the seven stations bi-weekly during the four-month study; and (5) compare dissolved copper concentrations at these stations with previous copper data collected in 1988.Mean four-month DBT concentrations ranged from 10 to 73 ng/L at the seven stations. Highest DBT concentrations occurred at Station 1 in a marina; lowest concentrations occurred at Station 7 in the Severn River. Mean four-month TBT concentrations ranged from 177 ng/L at Station 1 (marina) to 21 ng/L at Station 7 (Severn River). Maximum TBT concentrations of 361 and 570 ng/L occurred at marina SDtations 1 and 3, respectively. Temporal trends in both DBT and TBT (station mean concentrations by date) showed that peak concentrations occurred during the early part of the boating season followed by reductions in late summer and early fall. Spike concentrations of both DBT (117 and 62 ng/L) and TBT (308 and 366 ng/L) were reported on two sampling dates near a boat maintenance facility in Back Creek.There was a significant reduction in DBT concentrations from 1986 to 1989 when date was treated as a fixed effect. However, TBT concentrations were not significantly reduced between 1986 and 1989 when mean concentrations of TBT were averaged across stations and dates for each year. A significant reduction was reported at Station 1 (marina station) when each station was examined for differences between years. TBT was also reported to significantly decrease (p=0.0442) at Station 7 between 1988 and 1989. A boat owner survey in the study area showed that 6% of the recreational boats that were surveyed were painted with TBT paint in 1989. This was a significant decrease in TBT paint use from the previous year when 31% of recreational boat owners surveyed used TBT paints.An evaluation of dissolved copper concentrations at three stations in the study area in 1989 showed that mean concentrations from bi-weekly sampling for four months was 10 g/L at Station 1, 7.8 g/L at Station 4 and 2.7 g/L at Station 7. Copper concentrations decreased with distance away from the Back Creek marinas. Copper concentrations at all three stations were significantly lower in 1989 than in 1988. 相似文献
934.
An investigation of distributed lag models in the context of air pollution and mortality time series analysis 总被引:3,自引:0,他引:3
Roberts S 《Journal of the Air & Waste Management Association (1995)》2005,55(3):273-282
In particulate air pollution mortality time series studies, the particulate air pollution exposure measure used is typically the current day's or the previous day's air pollution concentration or a multi-day moving average air pollution concentration. Distributed lag models (DLMs) that allow for differential air pollution effects that are spread over multiple days are seen as an improvement over using a single- or multi-day moving average air pollution exposure measure. However, at the current time, the statistical properties of DLMs as a measure of air pollution exposure have not been investigated. In this paper, a simulation study is used to investigate the performance of DLMs as a measure of air pollution exposure in comparison with single- and multi-day moving average air pollution exposure measures under various forms for the true effect of air pollution on mortality. The simulation study shows that DLMs offer a more robust measure of the effect of air pollution on mortality and avoid the potential for a large negative bias compared with single- or multi-day moving average air pollution exposure measures. This is important information. In many U.S. cities, particulate air pollution concentrations are observed only once every six days, meaning it is often only possible to use single-day particulate air pollution exposure measures. The results from this paper will help quantify the magnitude of the negative bias that can result from using single-day exposure measures. The implications of this work for future air pollution mortality time series studies are discussed. The data used in this paper are concurrent daily time series of mortality, weather, and particulate air pollution from Cook County, IL, for the period 1987-1994. 相似文献
935.
Mapping and Modeling the Biogeochemical Cycling of Turf Grasses in the United States 总被引:6,自引:0,他引:6
Milesi C Running SW Elvidge CD Dietz JB Tuttle BT Nemani RR 《Environmental management》2005,36(3):426-438
Turf grasses are ubiquitous in the urban landscape of the United States and are often associated with various types of environmental
impacts, especially on water resources, yet there have been limited efforts to quantify their total surface and ecosystem
functioning, such as their total impact on the continental water budget and potential net ecosystem exchange (NEE). In this
study, relating turf grass area to an estimate of fractional impervious surface area, it was calculated that potentially 163,800
km2 (± 35,850 km2) of land are cultivated with turf grasses in the continental United States, an area three times larger than that of any irrigated
crop. Using the Biome-BGC ecosystem process model, the growth of warm-season and cool-season turf grasses was modeled at a
number of sites across the 48 conterminous states under different management scenarios, simulating potential carbon and water
fluxes as if the entire turf surface was to be managed like a well-maintained lawn. The results indicate that well-watered
and fertilized turf grasses act as a carbon sink. The potential NEE that could derive from the total surface potentially under
turf (up to 17 Tg C/yr with the simulated scenarios) would require up to 695 to 900 liters of water per person per day, depending
on the modeled water irrigation practices, suggesting that outdoor water conservation practices such as xeriscaping and irrigation
with recycled waste-water may need to be extended as many municipalities continue to face increasing pressures on freshwater. 相似文献
936.
Concentrations of contaminants in sediment deposits can have large spatial variability resulting from geomorphic processes acting over long time periods. Thus, systematic (e.g., regularly spaced sample locations) or random sampling approaches might be inefficient and/or lead to highly biased results. We demonstrate the bias associated with systematic sampling and compare these results to those achieved by methods that merge a geomorphic approach to evaluating the physical system and stratified random sampling concepts. By combining these approaches, we achieve a more efficient and less biased characterization of sediment contamination in fluvial systems. These methods are applied using a phased sampling approach to characterize radiological contamination in sediment deposits in two semiarid canyons that have received historical releases from the Los Alamos National Laboratory. Uncertainty in contaminant inventory was used as a metric to evaluate the adequacy of sampling during these phased investigations. Simple, one-dimensional Monte Carlo simulations were used to estimate uncertainty in contaminant inventory. We also show how one can use stratified random sampling theory to help estimate uncertainty in mean contaminant concentrations. 相似文献
937.
938.
Caustic radioactive wastes that have leaked at Hanford Site (Richland, WA) induce mineral dissolution and subsequent secondary precipitation that influence the fate and transport of contaminants present in the waste solutions. The effects of secondary mineral precipitates, formed after contacting solids with simulated caustic wastes, on the flow path changes and radionuclide immobilization were investigated by reacting quartz, a mixture of quartz and biotite, and a Hanford sediment (Warden soil: coarse-silty, mixed, superactive, mesic Xeric Haplocambids) with simulated caustic tank waste solution. Continuous Si dissolution and concomitant secondary mineral precipitation were the principal reactions observed in both batch and flow-through tests. Nitrate-cancrinite was the dominant secondary precipitate on mineral surfaces after 3- to 10-d reaction times in batch experiments. X-ray microtomography images of a reacted quartz column revealed that secondary precipitates cemented quartz grains together and modified pore geometry in the center of the column. Along the circumference of the packed column, however, quartz dissolution continuously occurred, suggesting that wastes that leaked from buried tanks in the past likely did not migrate vertically as modeled in risk assessments but rather the pathways likely changed to be dominantly horizontal on precipitation of secondary precipitate phases in the Hanford vadose zone. Based on batch equilibrium sorption results on the reacted sediments, the dominant secondary precipitates (cancrinites) on the mineral surfaces enhanced the sorption capacity of typical Hanford sediment for radionuclides 129I(-I), 79Se(VI), 99Tc(VII), and 90Sr(II), all of which are of major concern at the Hanford Site. 相似文献
939.
Jianbiao Lu Ge Sun Steven G. McNulty Devendra M. Amatya 《Journal of the American Water Resources Association》2005,41(3):621-633
ABSTRACT: Potential evapotranspiration (PET) is an important index of hydrologic budgets at different spatial scales and is a critical variable for understanding regional biological processes. It is often an important variable in estimating actual evapotranspiration (AET) in rainfall‐runoff and ecosystem modeling. However, PET is defined in different ways in the literature and quantitative estimation of PET with existing mathematical formulas produces inconsistent results. The objectives of this study are to contrast six commonly used PET methods and quantify the long term annual PET across a physiographic gradient of 36 forested watersheds in the southeastern United States. Three temperature based (Thornthwaite, Hamon, and Hargreaves‐Samani) and three radiation based (Turc, Makkink, and Priestley‐Taylor) PET methods are compared. Long term water balances (precipitation, streamflow, and AET) for 36 forest dominated watersheds from 0.25 to 8213 km2 in size were estimated using associated hydrometeorological and land use databases. The study found that PET values calculated from the six methods were highly correlated (Pearson Correlation Coefficient 0.85 to 1.00). Multivariate statistical tests, however, showed that PET values from different methods were significantly different from each other. Greater differences were found among the temperature based PET methods than radiation based PET methods. In general, the Priestley‐Taylor, Turc, and Hamon methods performed better than the other PET methods. Based on the criteria of availability of input data and correlations with AET values, the Priestley‐Taylor, Turc, and Hamon methods are recommended for regional applications in the southeastern United States. 相似文献
940.