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Search Results: 1 - 10 of 290581 matches for " 张瑞娟 "
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76例乳腺肿瘤超声图像预处理研究
The Research on Preprocessing for the Gray-Scale Ultrasound Breast Tumor Images of 76 Cases
 [PDF]

, 刘晴, 刘奇
Hans Journal of Biomedicine (HJBM) , 2015, DOI: 10.12677/HJBM.2015.52002
Abstract:
以76例乳腺肿瘤灰阶超声图像为研究对象,根据医学超声图像的特点及P-M模型的缺点,提出以图像的局部信息确定扩散门限的改进的P-M模型滤波方法,通过采用多种图像预处理算法及上述改进的P-M模型滤波法对76例乳腺肿瘤超声图像进行试验,实验结果显示,改进的P-M模型滤波方法可以更有效的滤除斑点噪声。
This paper mainly focuses on the gray-scale ultrasound breast tumor images. According to the characteristics of ultrasonic image and shortcomings of the P-M model, a modified P-M model filter with local information and spread threshold is proposed. All common pretreatment algorithms are put into experiments and a comparison is made among them. The results show that the modified P-M model filter can more effectively remove the speckle noise.
花色表型变异的分子机制及自然选择
Molecular Mechanisms and Natural Selection of Flower Color Variation
 [PDF]

, 鲁迎青
Botanical Research (BR) , 2016, DOI: 10.12677/BR.2016.56024
Abstract: 花色对吸引传粉者具有非常重要的作用。自然界的花色具有多样性,主要包括色调和着色模式的变异。虽然前人对花色变异的物质和遗传基础做了大量的研究,但许多花色变异模式特别是着色模式的分子机制还不清楚。传粉者与非传粉者因素介导的自然选择对花色表型变异的选择机制也有许多未解之谜。本文主要对已知花色表型变异的分子机制及自然选择对花色表型的选择作用进行综述,以便进一步地探索花色多样性存在的机制和自然选择对花色进化方向的影响。
Flower color plays a key role in attracting pollinators, and a staggering variety of flower color variations including color parameters and pigmentation pattern exist in nature. Though many studies have been done on the molecular mechanisms of flower color variation, there is still much unknown, especially for pigmentation pattern. The contributions of pollinator and non-pollinator agents to natural selection on floral color variation are also unclear. The review discusses recent data on genetic mechanisms and natural selection of flower color variation. The summary may as-sist us to further analyze molecular mechanisms of flower color diversity and role of natural se-lection in flower color variation.
基于分布式非点源有毒污染物模型的农药输移研究
,艳红
农业环境科学学报 , 2013, DOI: 10.11654/jaes.2013.12.022
Abstract: 以山东省临沂流域为研究区,基于分布式非点源有毒污染物模型ESSI-2对当地的农药输移过程进行研究。选取甲基异柳磷为模拟农药种类,基于合理的农药假设数据,对分布式有毒污染物模型ESSI-2进行参数率定,并基于模拟结果,对临沂流域的甲基异柳磷负荷及其输移的空间分布特征进行了分析。结果表明,分布式非点源有毒污染物模型是研究农药输移过程的首选工具。临沂流域在农药施用初期,其空间分布主要与农药的施用相关,随着时间的推移,在水流的作用下,农药逐渐向河道汇聚,从而流向下游流域,在这一阶段中,地表径流是影响农药输移的主要因素。
活血补肾周期治疗子宫内膜异位症相关不孕症临床观察
,
中国中医药信息杂志 , 2014, DOI: 10.3969/j.issn.1005-5304.2014.04.029
Abstract:
我国一流大学的入学机会及其地区差异:2008-2015
曹妍,
- , 2016, DOI: 10.16382/j.cnki.1000-5560.2016.04.008
Abstract: 摘要 近来,各地区一流大学招生公平性问题引起了社会各界的关注。本研究运用主成分分析的方法构建了一流大学入学机会指数,并对2008年至2015年间31个省市地区一流大学的相关数据进行实证研究。研究发现:我国一流大学总体的入学机会有所提高;西部地区获得了较多的招生名额,但由于当地高考报名人数的增加,入学机会的实际增长幅度并不大;此外,受到各地区适龄人口数和高考报名人数差异扩大的影响,地区间入学机会的差异呈现出逐年扩大的趋势。研究进一步采用固定效应模型对入学机会的影响因素进行回归分析。结果表明,目前招生名额的调整对入学机会的改善贡献较弱,而经济发展的变化成为入学机会提高的重要原因,进而导致地区差异的进一步扩大。
Abstract: In recent years, access to top universities and its regional disparity have become a major concern. With government initiatives launched to improve the quality of higher education through building world class universities, the research focus is shifting from access to higher education to access to high quality top universities. This paper first defines the criteria for top universities in China. According to three Chinese universities rankings and four international universities rankings from 2011 to 2015, 34 Chinese universities are regarded as top universities in China. In addition, considering several factors in the enrollment procedures in college entrance examinations, this paper employs the Principle Component Analysis method to construct the index of the access to top universities. Based on province level descriptive statistics analysis of the access index from both longitudinal trends and horizontal regional differences, three empirical results were produced. First, the access to the 34 top universities has been increasing year by year at a moderate race, i.e. by about 4.57%. It is true that an increasing quota has been allocated to west China. However, as more and more students from west China participate in the college entrance examination, the increased access to top universities was attenuated. Therefore, the effectiveness of quota policy on bridging the regional gap is relatively weak. Moreover, as the relevant compensatory policies target some provinces in the middle and western area, provinces in other area, like Guangdong, Hainan, Chongqing and Sichuan, have less support from the central government. Compared with the increasing number of students entering for the college entrance exam, the access to top universities in these provinces is decreasing. Secondly, while in 2015 the regional disparity was reduced, it has been greater in the other years. The phenomenon is most obvious in east China, where the widening gaps in school age population, the number of examinees and enrollment quotas have aggravated the regional disparity. In terms of the access to top universities throughout the years, cities like Shanghai, Beijing and Tianjin have their comparative advantages, while in some other provinces like Guangdong and
海洋生物抗氧化活性物质的研究进展
,崇禧
北方园艺 , 2010, DOI: 10.11937/bfyy.201009080
Abstract:
农田土壤表层粗糙度信息解析
,孙宇
农业机械学报 , 2010,
Abstract: 耕作后农田土壤地貌属于具有趋向性的随机表面。由随机过程角度看,它随时间的变异满足各态遍历性质。揭示它的时空变异特征对于客观评价农田耕作质量、探讨表层土壤水运移规律、优化农田管理具有较高的实用价值。因此,基于各种粗糙指数的信息解析是精细农业技术体系研究热点之一。本文从不同尺度数学模型、时空变异多因素分析、直接与潜在应用价值等方面作了系统性分析。
低介电常数介质薄膜的研究进展*
,,冯坚
化学进展 , 2005,
Abstract: 用低介电常数介质薄膜作金属线间和层间介质可以降低超大规模集成电路(ULSI)的互连延迟、串扰和能耗。从介质极化的原理出发,揭示了开发低介电常数介质薄膜的可能途径;综述了低介电常数介质薄膜的制备方法、结构与性能表征、工艺兼容性等领域的最新进展。
DOI:10.7524/j.issn.0254-6108.2014.01.021
,
环境化学 , 2015,
Abstract: 持久性有机污染物(POPs)因具有半挥发性和持久性,可随大气迁移到偏远的高山地区甚至人迹罕至的两极地区,对当地生态环境带来严重威胁,因而受到大量关注.苔藓和地衣在偏远高山地区分布广泛,通常被用作高山地区大气POPs分析的天然被动采样器.本文首先介绍了苔藓/地衣用于指示POPs污染的特点,然后分别阐述了苔藓/地衣在指示偏远地区POPs时间变化和空间分布两方面的应用,最后本文对苔藓/地衣用于指示大气POPs污染所存在的问题提出了几点建议,并分析了未来研究的发展趋势.
三甲基氯硅烷对纳米多孔二氧化硅薄膜的修饰
,,冯坚
物理化学学报 , 2004,
Abstract:
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