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多关键词组合加权文献检索方法研究 被引量:7
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作者 乔林 糜仲春 +1 位作者 刘亮 张群 《情报学报》 CSSCI 北大核心 2006年第4期420-427,共8页
在进行文献检索特别是多关键词文献检索时,现有科学搜索引擎的检索结果排序存在一些问题。本文推导了两关键词加权文献检索的相关度计算公式,在此基础上提出了多关键词组合加权文献检索方法,并与文献年平均被引频次指标相结合,确定... 在进行文献检索特别是多关键词文献检索时,现有科学搜索引擎的检索结果排序存在一些问题。本文推导了两关键词加权文献检索的相关度计算公式,在此基础上提出了多关键词组合加权文献检索方法,并与文献年平均被引频次指标相结合,确定综合考虑文献相关度和文献质量的排序分数。最后,通过实例分析验证了该方法的有效性。 展开更多
关键词 加权文献检索 多关键词组合 年平均被引频次 科学搜索引擎
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Hepatitis C virus in Pakistan:A systematic review of prevalence,genotypes and risk factors 被引量:12
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作者 Yasir Waheed Talha Shafi +1 位作者 Sher Zaman Safi Ishtiaq Qadri 《World Journal of Gastroenterology》 SCIE CAS CSCD 2009年第45期5647-5653,共7页
In Pakistan more than 10 million people are living with Hepatitis C virus (HCV), with high morbidity and mortality. This article reviews the prevalence, genotypes and factors associated with HCV infection in the Pakis... In Pakistan more than 10 million people are living with Hepatitis C virus (HCV), with high morbidity and mortality. This article reviews the prevalence, genotypes and factors associated with HCV infection in the Pakistani population. A literature search was performed by using the keywords; HCV prevalence, genotypes and risk factors in a Pakistani population, in Pubmed, PakMediNet and Google scholar. Ninetyone different studies dating from 1994 to May 2009 were included in this study, and weighted mean and standard error of each population group was calculated. Percentage prevalence of HCV was 4.95% ± 0.53% in the general adult population, 1.72% ± 0.24% in the pediatric population and 3.64% ± 0.31% in a young population applying for recruitment, whereas a very high 57% ± 17.7% prevalence was observed in injecting drug users and 48.67% ± 1.75% in a multi-transfused population. Most prevalent genotype of HCV was 3a. HCV prevalence was moderate in the general population but very high in injecting drug users and multi-transfused populations. This data suggests that the major contributing factors towards increased HCV prevalence include unchecked blood transfusions and reuse of injection syringes. Awareness programs are required to decrease the future burden of HCV in the Pakistani population. 展开更多
关键词 Hepatitis C virus PREVALENCE GENOTYPES Blood transfusions INJECTIONS
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