期刊文献+
共找到3篇文章
< 1 >
每页显示 20 50 100
几种抽样信号的频谱分析 被引量:1
1
作者 范绿蓉 徐洪波 +1 位作者 田科英 徐小平 《高等函授学报(自然科学版)》 1997年第5期15-16,25,共3页
关键词 抽样信号 频谱分析 模拟信号 理想抽样 自然抽样 平顶抽样
下载PDF
Natural history of heartburn:A 10-year population-based study 被引量:2
2
作者 Linda Bjork Olafsdottir Hallgrimur Gudjonsson +1 位作者 Heidur Hrund Jonsdottir Bjarni Thjodleifsson 《World Journal of Gastroenterology》 SCIE CAS CSCD 2011年第5期639-645,共7页
AIM: To study the natural history and prevalence of heartburn at a 10-year interval, and to study the effect of heartburn on various symptoms and activities. METHODS: A population-based postal study was carried out.... AIM: To study the natural history and prevalence of heartburn at a 10-year interval, and to study the effect of heartburn on various symptoms and activities. METHODS: A population-based postal study was carried out. Questionnaires were mailed to the same age- and gender-stratified random sample of the Icelandic population (aged 18-75 years) in 1996 and again in 2006. Subjects were classified with heartburn if they reported heartburn in the preceding year and/or week, based on the definition of heartburn. RESULTS: Heartburn in the preceding year was reported in 42.8% (1996) and 44.2% (2006) of subjects, with a strong relationship between those who experienced heartburn in both years. Heartburn in the precedingweek was diagnosed in 20.8%. There was a significant relationship between heartburn, dyspepsia and irritable bowel syndrome. IndMduals with a body mass index (BMI) below or higher than normal weight were more likely to have heartburn. Heartburn caused by food or beverages was reported very often by 20.0% of subjects. CONCLUSION: Heartburn is a common and chronic condition. Subjects with a BMI below or higher than normal weight are more likely to experience heartburn. Heartburn has a great impact on daily activities, sleep and quality of life. 展开更多
关键词 HEARTBURN FOLLOW-UP Questionnaire study EPIDEMIOLOGY
下载PDF
Extraction of copper and zinc from naturally contaminated copper mine soils: Chemical fractionation analysis and risk assessment
3
作者 XIAO Jiu-hua ZHOU Jun +6 位作者 WANG Zhao-hui LI Si-yue ZHANG Wei-chao FANG Chang-ling GUO Yao-guang XIAO Dong-xue LOU Xiao-yi IU Jian-she 《Journal of Central South University》 SCIE EI CAS CSCD 2018年第6期1274-1284,共11页
The leaching behaviour of Cu and Zn from contaminated soils at a copper mine was investigated using four extractants: citric acid (CA), oxalic acid (OA), ethylenediaminetetraacetic acid (EDTA) and nitrilotriace... The leaching behaviour of Cu and Zn from contaminated soils at a copper mine was investigated using four extractants: citric acid (CA), oxalic acid (OA), ethylenediaminetetraacetic acid (EDTA) and nitrilotriacetic acid (NTA). Six soil samples were characterized for the distribution of four chemical fractions of Cu or Zn (acid-soluble, reducible, oxidizable and residual). For the extraction of Cu, EDTA is more effective than other extmctants when the concentration is less than 0.02 mol/L. The leaching efficiency for Cu was at least 15% higher for EDTA than for the other extractants at the same concentrations. Similar leaching behaviour was observed in the extraction of Zn. After extraction by CA, OA, EDTA or NTA, the acid-soluble fractions and the reducible fractions of Cu were the main fractions extracted. The potential environmental risks related to speciation were evaluated, and after extraction these risks were reduced. 展开更多
关键词 waste dump soil heavy metal LEACHING chemical fractions
下载PDF
上一页 1 下一页 到第
使用帮助 返回顶部