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园林植物蚧虫及其天敌调查 总被引:1,自引:0,他引:1
调查结果表明为害园林植物的蚧虫隶属4科19属35种。发生普遍而严重的是咖啡盔蚧、龟蜡蚧、酱褐圆蚧、考氏白盾蚧、米兰白轮盾蚧和云南白轮盾蚧等。寄生性天敌以膜翅目蚜小蜂和跳小蜂为主;捕食性天敌主要有瓢虫、日本方头甲等。利用天敌昆虫防治园林植物蚧虫具有十分重要的意义。 相似文献
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Under stress, many crystalline materials exhibit irreversible plastic deformation caused by the motion of lattice dislocations. In plastically deformed microcrystals, internal dislocation avalanches lead to jumps in the stress-strain curves (strain bursts), whereas in macroscopic samples plasticity appears as a smooth process. By combining three-dimensional simulations of the dynamics of interacting dislocations with statistical analysis of the corresponding deformation behavior, we determined the distribution of strain changes during dislocation avalanches and established its dependence on microcrystal size. Our results suggest that for sample dimensions on the micrometer and submicrometer scale, large strain fluctuations may make it difficult to control the resulting shape in a plastic-forming process. 相似文献
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园林草坪发展概况及景观设计 总被引:8,自引:0,他引:8
草坪在园林中的应用至少已有了数千年的历史.从附属于林地到独立成景再发展到乔、灌、草或密林草地、疏林草坪和空旷草坪的结合使用走过了一个缓慢发展的过程.草坪学的发展已有近百年的历史,中国在20世纪80年代后才有了快速的发展.园林草坪设计时要注意科学性和艺术性的平衡.务必要做到因地制宜,适地适草.参10 相似文献
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运用城市景观生态学原理,选择郑东新区景观水体、林地、湿地、商建区和绿地、广场等不同景观属地的空气负离子含量与环境温、湿度3项生态因子检测数据,通过比较综合分析,结果显示:绿地优于广场;林地优于湿地优于商建区优于湖区。据此认为:新区城建规划开放空间景观配置应多植树,少种草,慎建水体;尽力保持原生态成年林地与湿地;依据城市新区自然风向、立地条件与景观属性,科学均衡布局,以谋求新区景观生态格局最大功效;多引种常绿与阔叶观赏类和耐力强的本地树种,创设优良环境,构建生态城市新区。 相似文献
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Using single-molecule DNA nanomanipulation, we show that abortive initiation involves DNA "scrunching"--in which RNA polymerase (RNAP) remains stationary and unwinds and pulls downstream DNA into itself--and that scrunching requires RNA synthesis and depends on RNA length. We show further that promoter escape involves scrunching, and that scrunching occurs in most or all instances of promoter escape. Our results support the existence of an obligatory stressed intermediate, with approximately one turn of additional DNA unwinding, in escape and are consistent with the proposal that stress in this intermediate provides the driving force to break RNAP-promoter and RNAP-initiation-factor interactions in escape. 相似文献
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Alfred H. Siemens 《Agriculture and Human Values》2004,21(2-3):243-254
Prolonged investigations of past and present use of wetland margins in various lowlands within Latin America have yielded a wealth of detail. It has become necessary to search out regularities in the natural environmental context and the human adaptations, all of which can be done advantageously in the context of the concept of landscape. Such a move in the direction of theory is attempted here by means of a heuristic model and an exploration of variations in its expression. The discussion of seasonal as well as longer termed change in the natural environment and human adaptation is easily accomodated. The essay includes a brief consideration of some of the recent directions in the investigation of the tropical wetland landscape. 相似文献
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以长丰汽车等经销商为样本,对渠道影响策略、满意度、绩效关系模型,进行实证分析发现:威胁与诉诸法规策略会降低经销商的经济与社会满意度;建议与信息交换策略会提升其经济与社会满意度;当经销商的经济满意度提升时,其绩效会随之改善,但社会满意度对绩效并无显著影响。 相似文献
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Bray JR 《Science (New York, N.Y.)》1977,197(4300):251-254
During the past 2 million years, major Northern Hemisphere eruptions occurred within 0.01 million years before 22 of 24 maximum-temperature dates which preceded the ten European glacial stages and 42 of 60 maximum-temperature dates which preceded the 22 cooling episodes. Massive eruptions were even more closely associated with the glacial stages and the cooling episodes. Within the errors of Pleistocene dating, major eruptions apparently occurred at the crucial moments to have triggered each of the ice ages. 相似文献
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The transcriptional landscape of the mammalian genome 总被引:1,自引:0,他引:1
Carninci P Kasukawa T Katayama S Gough J Frith MC Maeda N Oyama R Ravasi T Lenhard B Wells C Kodzius R Shimokawa K Bajic VB Brenner SE Batalov S Forrest AR Zavolan M Davis MJ Wilming LG Aidinis V Allen JE Ambesi-Impiombato A Apweiler R Aturaliya RN Bailey TL Bansal M Baxter L Beisel KW Bersano T Bono H Chalk AM Chiu KP Choudhary V Christoffels A Clutterbuck DR Crowe ML Dalla E Dalrymple BP de Bono B Della Gatta G di Bernardo D Down T Engstrom P Fagiolini M Faulkner G Fletcher CF Fukushima T 《Science (New York, N.Y.)》2005,309(5740):1559-1563
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在挖掘景观设计内涵的基础上,对居住区人性化设计的实质、可行性和设计方法进行探讨。 相似文献