共查询到20条相似文献,搜索用时 687 毫秒
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<正>传统植物纹样作为装饰图案伴随着人类文化的发展逐步由简单到丰富,由朴素到华丽,其在我国的发展历史是一个漫长的过程。此外,传统植物纹样的渐进性和阶段性特征也使得服饰设计艺术更加丰富多彩,备受东西方设计师的喜爱与追崇。传统植物纹样的构成形式主要包括3类。一是团花式,亦称“团窠”, 相似文献
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蛇,在中国传统文化中占有重要地位,与人们的生活关系十分密切。东汉许慎的《说文解字》中这样解释"蛇"字:"蛇,它或从虫。"本义指会摆尾游行之虫。更早的《左传·襄公二十八年》则道出了蛇的两面性:"蛇,元武之宿,虚危之星。"确实,每每提起蛇总让人又爱又怕。爱它,因为它有着优美的身形、玲珑的曲 相似文献
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Yuri I Arshavsky Tatiana G Deliagina Grigori N Orlovsky 《Current opinion in neurobiology》1997,7(6):781-789
Central pattern generators are neuronal ensembles capable of producing the basic spatiotemporal patterns underlying ‘automatic’ movements (e.g. locomotion, respiration, swallowing and defense reactions), in the absence of peripheral feedback. Different experimental approaches, from classical electrophysiological and pharmacological methods to molecular and genetic ones, have been used to understand the cellular and synaptic bases of central pattern generator organization and reconfiguration of generator operation in behaviorally relevant contexts. Recently, it has been shown that the high reliability and flexibility of central pattern generators is determined by their redundant organization. Everything that is crucial for generator operation is determined by a number of complementary mechanisms acting in concert; however, various mechanisms are weighted differently in determining different aspects of central pattern generator operation. 相似文献
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A I Selverston 《Current opinion in neurobiology》1992,2(6):776-780
The study of rhythmic motor pattern generation continues to be dominated by preparations in which cellular and circuit mechanisms can be bridged. Using these preparations, basic questions such as how circuits can be modified in order to generate a large number of patterns have begun to be answered. The action of neuromodulators on second messengers and channel proteins can provide a link between molecular studies and behavior. There has been a large increase in the use of computer simulations, and their usefulness as a way of studying pattern generation is growing. 相似文献
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从成熟中华猕猴桃果实中克隆到了一个 β 半乳糖苷酶基因cDNA片段 ,其长度为 747bp ,有一由 2 49个氨基酸组成的开放阅读框架 ,它与苹果、芦笋、绿花椰菜、番茄中 β 半乳糖苷酶基因cDNA相应区段的核苷酸同源性为 6 7.3 %~ 70 .3 %,氨基酸同源性为6 9.1%~ 72 .7%。用该片段为探针进行Northern分析表明 ,果实采收时 ,β 半乳糖苷酶mRNA水平最高 ,随后呈下降变化 ,同时 β 半乳糖苷酶基因的表达可为外源乙烯所诱导 ,但在果实乙烯跃变期间 β 半乳糖苷酶基因的表达信号无显著变化。文中对 β 半乳糖苷酶在猕猴桃果实成熟衰老过程的作用进行了讨论 相似文献
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SYNOPSIS. The embryonic chick limb bud is a growing organ rudimentwhose undifferentiated cells give rise to a precise spatialpattern of differentiated structures. The establishment of positionalvalues of chick limb bud cells (pattern specification) and theresponse of limb bud cells with established positional valuesto experimental perturbations (pattern regulation) are the majortopics considered in this paper. The results of recent experimentswith developing chick limb buds analyzing pattern specificationand pattern regulation are presented. These studies with thechick limb are described in light of the postulates of a modelthat was originally formulated from experiments performed onregenerating amphibian and insect appendages. 相似文献