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361.
The potential adverse effects on human health of hazardous waste incinerators (HWIs) are a subject of concern. The construction of the first and till now only HWI in Spain finished in 1999. In 2007, after approximately 9 years of regular operations in the facility, the concentrations of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) were determined by HRGC/HRMS in samples of adipose tissue of 15 autopsied subjects living in the area under potential impact of the HWI (Constantí, Tarragona County, Catalonia). These data were compared with the levels found in two previous surveys performed in 1998 (baseline) and 2002. The current mean PCDD/F concentration in adipose tissue was 14.6 pg WHO-TEQ/g of fat (range: 3.3–55.4 pg WHO-TEQ/g of fat). It means significant changes (a reduction of 64% and an increase of 47%) in the mean PCDD/F levels in comparison to those found in 1998 and 2002: 40.1 and 9.9 pg WHO-TEQ/g of fat, respectively. Women showed higher levels of PCDD/F than men (23.8 vs 11.2 pg WHO-TEQ/g of fat). The increase in the last 5 years would not be directly attributable to exposure to PCDD/F emitted by the HWI, as other biological monitors such as human plasma and milk decreased during the same period. 相似文献
362.
This study reports on the effect of microwave radiation for inactivation of Ascaris lumbricoides eggs in 25 g of soil compared to ultraviolet irradiation and ozone expose. Microwave radiation at 700 W with 14% water content (w/w) achieved approximately 2.5 log inactivation of eggs in soil within 60 s. On the other hand, UV irradiation at 3 mW cm−2 with and without shaking soil for 3600 s achieved approximately 0.32 and 0.01 log inactivation of eggs, respectively. In ozone treatment, 0.13 log inactivation of eggs was achieved with 5.8 ± 0.7 mg L−1 of dissolved ozone dose for 30 min in a continuous diffusion reactor. In addition, the inactivation of eggs by three disinfection techniques was conducted in water in order to compare the inactivation efficiency of eggs in soil. The inactivation efficiency of microwave radiation was found to be no significant difference between in soil and water. However, the inactivation efficiency of UV irradiation was significantly increased in water while in ozone expose there was no significant difference between in soil and water. Microwave treatment thus proved to be the most efficient method in controlling A. lumbricoides eggs in soil. 相似文献
363.
Degassing of H/He, CFCs and SF6 by denitrification: Measurements and two-phase transport simulations
Ate Visser Joris D. Schaap Hans Peter Broers Marc F.P. Bierkens 《Journal of contaminant hydrology》2009,103(3-4):206-218
The production of N2 gas by denitrification may lead to the appearance of a gas phase below the water table prohibiting the conservative transport of tracer gases required for groundwater dating. We used a two-phase flow and transport model (STOMP) to study the reliability of 3H/3He, CFCs and SF6 as groundwater age tracers under agricultural land where denitrification causes degassing. We were able to reproduce the amount of degassing (R2 = 69%), as well as the 3H (R2 = 79%) and 3He (R2 = 76%) concentrations observed in a 3H/3He data set using simple 2D models. We found that the TDG correction of the 3H/3He age overestimated the control 3He/3He age by 2.1 years, due to the accumulation of 3He in the gas phase. The total uncertainty of degassed 3H/3He ages of 6 years (± 2 σ) is due to the correction of degassed 3He using the TDG method, but also due to the travel time in the unsaturated zone and the diffusion of bomb peak 3He. CFCs appear to be subject to significant degradation in anoxic groundwater and SF6 is highly susceptible to degassing. We conclude that 3H/3He is the most reliable method to date degassed groundwater and that two-phase flow models such as STOMP are useful tools to assist in the interpretation of degassed groundwater age tracer data. 相似文献
364.
Plaza C Xing B Fernández JM Senesi N Polo A 《Environmental pollution (Barking, Essex : 1987)》2009,157(1):257-263
Binding of two model polycyclic aromatic hydrocarbons (PAHs), phenanthrene and pyrene, by humic acids (HAs) isolated from an organic substrate at different stages of composting and a soil was investigated using a batch fluorescence quenching method and the modified Freundlich model. With respect to soil HA, the organic substrate HA fractions were characterized by larger binding affinities for both phenanthrene and pyrene. Further, isotherm deviation from linearity was larger for soil HA than for organic substrate HAs, indicating a larger heterogeneity of binding sites in the former. The composting process decreased the binding affinity and increased the heterogeneity of binding sites of HAs. The changes undergone by the HA fraction during composting may be expected to contribute to facilitate microbial accessibility to PAHs. The results obtained also suggest that bioremediation of PAH-contaminated soils with matured compost, rather than with fresh organic amendments, may result in faster and more effective cleanup. 相似文献
365.
污水处理中紫外消毒方法与传统消毒方法相比之下具有不需要投加化学药剂、不产生有毒有害副产物、消毒效率高、操作简单、便于运行管理等特点。本文着重介绍了目前用于消毒的紫外灯的种类,并阐述了浊度、微生物种类、光复活性能等影响紫外消毒效果的因素,最后对未来紫外消毒方法发展的前景做出了分析。 相似文献
366.
Michael W. Suplee Vicki Watson Mark Teply Heather McKee 《Journal of the American Water Resources Association》2009,45(1):123-140
Abstract: A public opinion survey was carried out in Montana to ascertain if the public identifies a level of benthic (bottom‐attached) river and stream algae that is undesirable for recreation. The survey had two parts; an On‐River survey and a By‐Mail survey. The On‐River survey was conducted via 44 trips randomly scheduled throughout the state during which recreators were interviewed in‐person at the stream. Selection of stream segments and survey dates/times was based on known, statewide recreational use patterns. By‐Mail survey forms were sent to 2,000 individuals randomly selected from Montana’s Centralized Voter File (CVF) available from the Montana Secretary of State. The CVF was current through 2004 and represented over 85% of the state’s eligible voting population. In both surveys, eight randomly ordered photographs depicting varying levels of stream benthic algae were presented, and participants were asked if the algae level shown was desirable or undesirable for recreation. Survey form design, selection of photographs, and pretesting followed acceptable protocols that limited unintentional bias through survey execution. There were 433 returned forms (389 complete) for the By‐Mail survey, while the On‐River survey documented 563 interviews. In both surveys, as benthic algal chlorophyll a (Chl a) levels increased, desirability for recreation decreased. (Other measures of benthic algae biomass are presented as well.) For the public majority, mean benthic Chl a levels ≥200 mg/m2 were determined to be undesirable for recreation, whereas mean levels ≤150 mg Chl a/m2 were found to be desirable. Error rates were within the survey’s statistical design criteria (≤5%). The largest potential error source was nonresponse in the By‐Mail survey; however, the population represented by nonrespondents would have to exhibit profoundly different perceptions of river and stream algae to meaningfully alter the results. Results support earlier work in the literature suggesting 150 mg Chl a/m2 represents a benthic algae nuisance threshold. 相似文献
367.
Patrick L. Witmer Paul M. Stewart Christopher K. Metcalf 《Journal of the American Water Resources Association》2009,45(3):734-747
Abstract: Unpaved road‐stream crossings increase sediment yields in streams and alter channel morphology and stability. Before restoration and sedimentation reduction strategies can be implemented, a priority listing of unpaved road‐stream crossings must be created. The objectives of this study were to develop a sedimentation risk index (SRI) for unpaved road‐stream crossings and to prioritize 125 sites in the Choctawhatchee watershed (southeastern Alabama) using this model. Field surveys involved qualitative and quantitative observations of 73 metrics related to waterway conditions, crossing structures, road approaches, and roadside soil erosion. The road‐stream crossing risk analyses involved elimination of candidate metrics based on redundancy, skewness, lack of data, professional judgment, lack of nonzero values, unbalanced box plots, and limited ranges of values. A final selection of 12 metrics formed the SRI and weighed factors involving soil erodibility, road sedimentation abatement features, and stream morphology alteration. The SRI was organized into narrative categories (excellent, good, fair, poor, and very poor) based on the distribution of scores. No excellent sites (scores ≥55) were found in this study, 17 (20.7%) were good (low sedimentation risk), 37 (45.1%) were fair (moderate sedimentation risk), 26 (31.7%) were poor (high sedimentation risk), and two (2.5%) were very poor (high sedimentation risk). There was no significant difference in SRI scores among crossing structure type (round culverts, box culverts, and bridges) (H = 4.31, df = 2, p = 0.058). A future study of the Choctawhatchee watershed involving the same study sites could assess the success of restoration plans and activities based on site score improvement or decline. 相似文献
368.
E. Howard Coker Rollin H. Hotchkiss Dennis A. Johnson 《Journal of the American Water Resources Association》2009,45(4):815-827
Abstract: A present and future challenge for water resources engineers is to extend the useful life of our dams and reservoirs. Ongoing reservoir sedimentation in impoundments must be addressed; sedimentation in many reservoirs already limits project benefits and effective project life. Sustainability requires that incoming sediment be moved downstream past the impounding dam. We use Lewis and Clark Lake, the most downstream of the six Missouri River main stem reservoirs, to demonstrate how a reservoir in advanced stages of its project life could be converted to a sustainable system with local benefits exceeding costs by a factor of 1.5. Full consideration of benefits would further enhance project justification. The proposed strategy involves four phases that will take about 50 years to complete. Cost estimates for this potential project range from the quantitative to the plausible, but it is clear that the results justify a full engineering, environmental, and economic study of this model project. If implemented, the project will create scientific knowledge and develop technologies useful for achieving sustainability at many other reservoirs in the Mississippi River basin and beyond. 相似文献
369.
Charles A. Young Marisa I. Escobar‐Arias Martha Fernandes Brian Joyce Michael Kiparsky Jeffrey F. Mount Vishal K. Mehta David Purkey Joshua H. Viers David Yates 《Journal of the American Water Resources Association》2009,45(6):1409-1423
Young, Charles A., Marisa I. Escobar‐Arias, Martha Fernandes, Brian Joyce, Michael Kiparsky, Jeffrey F. Mount, Vishal K. Mehta, David Purkey, Joshua H. Viers, and David Yates, 2009. Modeling the Hydrology of Climate Change in California’s Sierra Nevada for Subwatershed Scale Adaptation. Journal of the American Water Resources Association (JAWRA) 45(6):1409‐1423. Abstract: The rainfall‐runoff model presented in this study represents the hydrology of 15 major watersheds of the Sierra Nevada in California as the backbone of a planning tool for water resources analysis including climate change studies. Our model implementation documents potential changes in hydrologic metrics such as snowpack and the initiation of snowmelt at a finer resolution than previous studies, in accordance with the needs of watershed‐level planning decisions. Calibration was performed with a sequence of steps focusing sequentially on parameters of land cover, snow accumulation and melt, and water capacity and hydraulic conductivity of soil horizons. An assessment of the calibrated streamflows using goodness of fit statistics indicate that the model robustly represents major features of weekly average flows of the historical 1980‐2001 time series. Runs of the model for climate warming scenarios with fixed increases of 2°C, 4°C, and 6°C for the spatial domain were used to analyze changes in snow accumulation and runoff timing. The results indicated a reduction in snowmelt volume that was largest in the 1,750‐2,750 m elevation range. In addition, the runoff center of mass shifted to earlier dates and this shift was non‐uniformly distributed throughout the Sierra Nevada. Because the hydrologic model presented here is nested within a water resources planning system, future research can focus on the management and adaptation of the water resources system in the context of climate change. 相似文献
370.