排序方式: 共有66条查询结果,搜索用时 15 毫秒
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密度是海冰资源的一个重要物理参数,它受许多因素的影响,有着较大的变动范围。本文以渤海沿岸连续两个年份的平整冰和堆积冰为研究对象,将海冰密度分为实密度和表观密度两种类型,并给出了相应的定义、实验和计算方法;通过一系列的实验和数据分析,得出渤海湾和辽东湾沿岸的海冰在密度分布方面具有一定的规律性。研究结果表明平整冰密度介于0.633-0.918g/cm3之间,堆积冰的密度变化范围为0.615-0.906g/cm3。在同一地点,不同年份的海冰密度大小存在差异,但是平整冰的实密度和表观密度均高于堆积冰。利用两种密度值计算得出的海冰空气孔隙率对于了解海冰性质的空间分布规律以及指导渤海海冰资源的开发利用具有积极的意义。 相似文献
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渤海滨海重黏性盐渍土淋溶过程中的盐碱变化 总被引:2,自引:0,他引:2
本文对渤海西岸重黏质盐渍土进行土柱淋溶脱盐过程的研究,结果表明:在淋溶过程中,随着土壤含盐量的下降,在整个过程中,Na+、Cl-随土壤含盐量的下降而下降;由于土壤盐离子的初始含量和迁移能力的不同,K+、Ca2+、Mg2+、SO42-的含量随淋溶水增加而减小,在淋溶水接近土壤质量后含量稳定;而HCO3-与其它离子不同,出现随淋溶液增加而缓慢增加的趋势。随着土壤盐离子的迁移,土壤的pH值随土壤含盐量的的减小而呈现增大的趋势,从原土的8.50增加到土壤含盐量为1.6g/kg时的9.86,并在土壤含盐量小于1g/kg后又略有下降,但仍保持在一个较高的水平上。淋溶实验表明,在滨海重黏性盐渍土的淋溶改良过程中,需要注意因脱盐而造成的土壤碱性增加的现象,控制淋溶水的数量和采取其他相应的降碱措施。 相似文献
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城市与乡村的教育资源配置上存在明显的差距,表现为优质教师资源配置和教育信息资源的非均衡发展."农远工程模式一"投入少、设备操作简单的特点适合于农村中小学教学点,但其缺乏人机交互和信息反馈的缺点也十分明显.树立正确观念,立足自身,正确运用"农远工程模式一"的光盘教学资源,探寻不同层次的光盘教学模式,缩小城乡教师资源差距,促进乡村教师专业化发展. 相似文献
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城市与乡村的教育资源配置上存在明显的差距,表现为优质教师资源配置和教育信息资源的非均衡发展"。农远工程模式一"投入少、设备操作简单的特点适合于农村中小学教学点,但其缺乏人机交互和信息反馈的缺点也十分明显。树立正确观念,立足自身,正确运用"农远工程模式一"的光盘教学资源,探寻不同层次的光盘教学模式,缩小城乡教师资源差距,促进乡村教师专业化发展。 相似文献
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传统模式的大学写作教学已经不能培养出适应社会需要的写作人才,其中一方面原因就是不注重对学生写作个性的培养,教学方法简单陈旧,不能激发学生的写作兴趣和创造力.要改变这一现状,必须革新教学理念,探寻适合学生个性的教学方法,培养学生个性化写作能力. 相似文献
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大学语文课程要在传授专业知识的同时,对学生进行思想政治教育,达到语文课程立德树人的目的。该文从语文课程思政建设的意义、语文课具备的德育功能和人文属性出发,对确定思想政治教育内容、明确语文课程思政教学目标、构建教学体系、创新教学手段和方法等方面进行了探讨。 相似文献
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体育教师如何开展课外体育活动 总被引:1,自引:0,他引:1
课外体育活动是体育课堂教学的一个重要延伸,搞好课外体育活动具有重要的意义。体育教师应争取学校领导的重视;争取班主任和其它授课老师的支持;加强对体育干部、骨干的培养,争取团、队、学生会等组织的协助和配合;培养学生的体育兴趣;努力提高自身修养和各方面的素质。 相似文献
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Peng-Fei Wu Hui Lu Xiaoting Zhou Xuchen Liang Ruizhuo Li Wan Zhang Danyang Li Kun Xia 《运动与健康科学(英文)》2021,10(4):454-461
BackgroundPhysical activity has been hypothesized to play a protective role in neurodegenerative diseases. However, effect estimates previously derived from observational studies were prone to confounding or reverse causation.MethodsWe performed a two-sample Mendelian randomization (MR) analysis to explore the causal association of accelerometer-measured physical activity with 3 common neurodegenerative diseases: Alzheimer''s disease (AD), Parkinson''s disease (PD), and amyotrophic lateral sclerosis (ALS). We selected genetic instrumental variants reaching genome-wide significance (p < 5 × 10−8) from 2 largest meta-analyses of about 91,100 UK Biobank participants. Summary statistics for AD, PD, and ALS were retrieved from the up-to-date studies in European ancestry led by the international consortia. The random-effect, inverse-variance weighted MR was employed as the primary method, while MR pleiotropy residual sum and outlier (MR-PRESSO), weighted median, and MR-Egger were implemented as sensitivity tests. All statistical analyses were performed using the R programming language (Version 3.6.1; R Foundation for Statistical Computing, Vienna, Austria).ResultsPrimary MR analysis and replication analysis utilized 5 and 8 instrumental variables, which explained 0.2% and 0.4% variance in physical activity, respectively. In each set, one variant at 17q21 was significantly associated with PD, and MR sensitivity analyses indicated them it as an outlier and source of heterogeneity and pleiotropy. Primary results with the removal of outlier variants suggested odds ratios (ORs) of neurodegenerative diseases per unit increase in objectively measured physical activity were 1.52 for AD (95% confidence interval (95%CI): 0.88–2.63, p = 0.13) and 3.35 for PD (95%CI: 1.32–8.48, p = 0.01), while inconsistent results were shown in the replication set for AD (OR = 1.06, 95%CI: 1.01–1.12, p = 0.02) and PD (OR = 0.99, 95%CI: 0.88–0.12, p = 0.97). Similarly, the beneficial effect of physical activity on ALS (OR = 0.51, 95%CI: 0.29–0.91, p = 0.02) was not confirmed in the replication analysis (OR = 0.96, 95%CI: 0.91–1.02, p = 0.22).ConclusionGenetically predicted physical activity was not robustly associated with risk of neurodegenerative disorders. Triangulating evidence across other studies is necessary in order to elucidate whether enhancing physical activity is an effective approach in preventing the onset of AD, PD, or ALS. 相似文献