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The ori region of an Erwinia stewartii plasmid, pSW1200 (106 kb), has been cloned and sequenced. This region consists of a gene encoding a protein which has 91% similarity and 73% identity with the RepA protein of bacteriophage P1. The ori region also consists of eight copies of 19-bp iterons which are highly homologous to the iterons of P1. Similar to plasmid P1, pSW1200 replicon has a copy number of approximately 1. On the other hand, the copy number increases about ninefold if three of the iterons located downstream from repA gene are deleted. We also demonstrate that pGEM-5Z consisting of a copy of P1 iteron is incompatible with a pSW1200 derivative, pSW1201, suggesting that pSW1200 and P1 DNA are incompatible and both belong to the IncY group.  相似文献   
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A novel wafer bonding process has been used to integrate high quality GaAs devices on quartz substrates. The method of adhesion by spin-on-dielectric temperature enhanced reflow (MASTER) uses a spin-on-dielectric as a bonding agent to achieve a robust bond that in no way degrades either high frequency performance or reliability. A 585 GHz integrated mixer fabricated using this process has achieved record double-sideband mixer noise temperatures of 1,150 K at room temperature and 880 K at 77 K. Furthermore, the integrated mixers require no mechanical tuning, are easy to assemble, and repeatable. Precise control of the circuit geometry, coupled with the reduction of parasitic elements, allows greater accuracy of computer simulations and will therefore lead to better high frequency performance and bandwidth. This new technology is easily extended to other circuit designs and will allow the development of a new generation of submillimeter-wave integrated circuits  相似文献   
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Young 2-yr-olds' interpretation of a novel noun was influenced by preexposure to similar-sounding words. In Exp 1, 16 children selected an unfamiliar rather than a familiar object as the noun's referent more often when they had just heard many words that sounded like it than when they had just heard many that did not. Exposure to repeated sounds was hypothesized to reduce the attentional resources needed to process a word made up of the sounds, permitting extra resources to be applied to the name mapping problem. In Exps 2 and 3, exposure had a similar effect on children's mapping of a novel noun that sounded similar to the name of the familiar choice object (e.g., their mapping of wog onto a stethoscope rather than dog). Exposure was hypothesized to cause differences perceived within the set of words to be magnified and those perceived outside of it to be reduced. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
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