首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   21篇
  免费   0篇
  国内免费   3篇
废物处理   1篇
环保管理   6篇
综合类   3篇
基础理论   3篇
污染及防治   6篇
评价与监测   4篇
社会与环境   1篇
  2023年   2篇
  2022年   3篇
  2021年   1篇
  2020年   2篇
  2019年   2篇
  2017年   1篇
  2015年   1篇
  2014年   2篇
  2013年   1篇
  2012年   1篇
  2010年   1篇
  2008年   1篇
  2006年   1篇
  2005年   3篇
  2003年   1篇
  1994年   1篇
排序方式: 共有24条查询结果,搜索用时 140 毫秒
21.
Environmental Science and Pollution Research - Although plastic induces environmental damages, almost the consumption of poly(vinyl chloride) never stops increasing. Therefore, this work abstracted...  相似文献   
22.
Microporous chitosan (CS) membranes were directly prepared by extraction of poly(ethylene glycol) (PEG) from CS/PEG blend membrane and were examined for iron and manganese ions removal from aqueous solutions. The different variables affecting the adsorption capacity of the membranes such as contact time, pH of the sorption medium, and initial metal ion concentration in the feed solution were investigated on a batch adsorption basis. The affinity of CS/PEG blend membrane to adsorb Fe(II) ions is higher than that of Mn(II) ions, with adsorption equilibrium achieved after 60 min for Fe(II) and Mn(II) ions. By increasing CS/PEG ratio in the blend membrane the adsorption capacity of metal ions increased. Among all parameters, pH has the most significant effect on the adsorption capacity, particularly in the range of 2.9-5.9. The increase in CS/PEG ratio was found to enhance the adsorption capacity of the membranes. The effects of initial concentration of metal ions on the extent of metal ions removal were investigated in detail. The experimental data were better fitted to Freundlich equation than Langmuir. In addition, it was found that the iron and manganese ions adsorbed on the membranes can be effectively desorbed in 0.1 mol/L HCl solution (up to 98% desorption efficiency) and the blend membranes can be reused almost without loss of the adsorption capacity for iron and manganese ions.  相似文献   
23.
An atmospheric pollution survey was carried out at 13 sites in Karachi, Pakistan, simultaneously from 0600 h to 2100 h for 15 consecutive days in May 1990 which also included meteorological measurements. The monitoring sites were included along the prevailing wind patterns in Karachi. Carbon monoxide levels in the ambient air were found to reach 9–10 ppm along the busy urban streets whereas CO2 level exceeded 370 ppm in these areas. Our survey indicates that NO2 levels were exceeding U.S. ambient air quality standards. Maxmum NO2 concentrations were observed (0.3–0.5 ppm) during the daytime from 0600 h to 2100 h. The surface ozone maximum around noon at the inland sites reached the levels of 40 ppb and 50 ppb respectively compared to upwind coastal Sites 1 level of 25 ppb. The Pb concentrations were approximately 3- to 7-fold higher than average, which corresponded well to urban air. Fossil fuel SO4 (excess) and NO3 were apportionally based on the assumption that these two anions were present as (NH4)2SO4, and NH4NO3 in the aerosols. In the eastern part of the city atmospheric sulphate (SO4) shows the combustion of coal as its source from the vicinity and downwind of a steel manufacturing plant.  相似文献   
24.
The estimation of population density animal population parameters, such as capture probability, population size, or population density, is an important issue in many ecological applications. Capture–recapture data may be considered as repeated observations that are often correlated over time. If these correlations are not taken into account then parameter estimates may be biased, possibly producing misleading results. We propose a generalized estimating equations (GEE) approach to account for correlation over time instead of assuming independence as in the traditional closed population capture–recapture studies. We also account for heterogeneity among observed individuals and over-dispersion, modelling capture probabilities as a function of covariates. The GEE versions of all closed population capture–recapture models and their corresponding estimating equations are proposed. We evaluate the effect of accounting for correlation structures on capture–recapture model selection based on the quasi-likelihood information criterion (QIC). An example is used for an illustrative application and for comparison to currently used methodology. A Horvitz–Thompson-like estimator is used to obtain estimates of population size based on conditional arguments. A simulation study is conducted to evaluate the performance of the GEE approach in capture-recapture studies. The GEE approach performs well for estimating population parameters, particularly when capture probabilities are high. The simulation results also reveal that estimated population size varies on the nature of the existing correlation among capture occasions.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号