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31.
32.
加强吉安市地方文献收集之管见 总被引:1,自引:0,他引:1
论述了图书馆应注重收集哪些方面文献,收集地方文献的作用,收集时存在的问题,对解决这些问题的策略。 相似文献
33.
Cheng Z Ventura M She X Khaitovich P Graves T Osoegawa K Church D DeJong P Wilson RK Pääbo S Rocchi M Eichler EE 《Nature》2005,437(7055):88-93
We present a global comparison of differences in content of segmental duplication between human and chimpanzee, and determine that 33% of human duplications (> 94% sequence identity) are not duplicated in chimpanzee, including some human disease-causing duplications. Combining experimental and computational approaches, we estimate a genomic duplication rate of 4-5 megabases per million years since divergence. These changes have resulted in gene expression differences between the species. In terms of numbers of base pairs affected, we determine that de novo duplication has contributed most significantly to differences between the species, followed by deletion of ancestral duplications. Post-speciation gene conversion accounts for less than 10% of recent segmental duplication. Chimpanzee-specific hyperexpansion (> 100 copies) of particular segments of DNA have resulted in marked quantitative differences and alterations in the genome landscape between chimpanzee and human. Almost all of the most extreme differences relate to changes in chromosome structure, including the emergence of African great ape subterminal heterochromatin. Nevertheless, base per base, large segmental duplication events have had a greater impact (2.7%) in altering the genomic landscape of these two species than single-base-pair substitution (1.2%). 相似文献
34.
分析了某大型散装货轮艉轴部异常尖叫声。采用噪声和振动信号的频谱分析和相关分析,指出这种现象出现的原因在于船体刚度欠佳,致使中垂过大,轴系不对中,导致艉轴前密封盖艉轴卡环发生撞击式摩擦,最后用分子机械摩擦理论揭示了摩擦尖叫声产生的特点及其原因。 相似文献
35.
文章主要剖析了当前计划性检修制度存在的问题,提出了实施状态检修的必要性以及具体的实践方法.说明做好发电厂的检修管理工作是保证发电设备安全、经济运行的重要措施之一. 相似文献
36.
SHEKun CHENShu-zhen 《武汉大学学报:自然科学英文版》2005,10(3):539-544
A pitch detector for application in query by humming (QBH) is implemented in this paper. This algorithm is made up of two parts: note segmentation and pitch detection. In the first part, voiced/silence decision is made on each segment of the input signal by a pattern recognition approach, and further, the preparatory note borders are obtained; then, via analysis of the instantaneous energy contour, the adjacent notes that adhere to each other are separated. In the second part, pitch is estimated for all frames contained in a note‘s duration by an autocorrelation method and the mean of these pitch values is taken as the average pitch of this note. Moreover, in order to remove the effect of formant structure, a nonlinear preprocessing is adopted in the pitch detection part and the autocorrelation function is properly weighted before peak picking. Finally, hummings of several experimenters with different voice characters are recorded to test this pitch detector, whose efficiency and reliability are proved by the result. 相似文献
37.
"成功体育"教育作为一种科学的体育教育方式,是通过对学生自信心、进取心的培养,让其不断获得成功的体验,从而使学生提高从事体育运动的兴趣、并激发其成功动机,养成锻炼身体的习惯,为终身体育在意识和能力上奠定良好的基础.本文从心理学的角度分析了"成功体育"教育思想及其特点,为"成功体育"教学的开展提供了较系统的心理学依据. 相似文献
38.
Structural insight into brassinosteroid perception by BRI1 总被引:1,自引:0,他引:1
She J Han Z Kim TW Wang J Cheng W Chang J Shi S Wang J Yang M Wang ZY Chai J 《Nature》2011,474(7352):472-476
Brassinosteroids are essential phytohormones that have crucial roles in plant growth and development. Perception of brassinosteroids requires an active complex of BRASSINOSTEROID-INSENSITIVE 1 (BRI1) and BRI1-ASSOCIATED KINASE 1 (BAK1). Recognized by the extracellular leucine-rich repeat (LRR) domain of BRI1, brassinosteroids induce a phosphorylation-mediated cascade to regulate gene expression. Here we present the crystal structures of BRI1(LRR) in free and brassinolide-bound forms. BRI1(LRR) exists as a monomer in crystals and solution independent of brassinolide. It comprises a helical solenoid structure that accommodates a separate insertion domain at its concave surface. Sandwiched between them, brassinolide binds to a hydrophobicity-dominating surface groove on BRI1(LRR). Brassinolide recognition by BRI1(LRR) is through an induced-fit mechanism involving stabilization of two interdomain loops that creates a pronounced non-polar surface groove for the hormone binding. Together, our results define the molecular mechanisms by which BRI1 recognizes brassinosteroids and provide insight into brassinosteroid-induced BRI1 activation. 相似文献
39.
40.
应用纳米金免疫层析技术(双抗夹心法)和柠檬酸三钠还原法建立一种对尿RBP的快速定量检测方法,并在此基础上研制出快速检测试纸条.该试纸条用纳米金免疫层析定量分析仪可在15 min内实现RBP定量检测,检测限为150μg/L(相当于150 ng/mL),检测范围为150~5000μg/L.与尿微量白蛋白(ALB)、转铁蛋白(TRF)、β2-微球蛋白(β2-MG)、尿纤维连接蛋白(FN)、溶菌酶(LZM)等肾脏疾病标志物无交叉反应.该方法特异性强、检测灵敏度高、范围广、简便快捷,在近端肾小管的损伤、糖尿病肾病等肾脏疾病的早期诊断及过程监控中具有较为广泛的临床应用. 相似文献