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Two remarkable reducing agents NaBH_4 (or NaBD_4)/SnCl_2(orSnCl_4·2Et_2O) with chiral ligands are applied to the asymmetricreduction of carbonyl compounds with excellent chemical yieldsand enantioselective excesses. 相似文献
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可持续能源的迅速发展,使绿色清洁的氢能源成为热点。质子交换膜(PEM)水电解是一项很有前途的技术,可高效生产高纯度氢气。IrO_(2)作为质子交换膜(PEM)水电解槽阳极氧析出反应(OER)的商用电催化剂,既能在强酸性、高强度腐蚀条件下保持稳定,又表现出优异的催化性能。然而,由于Ir的稀缺性和昂贵的价格,提高Ir基催化剂的OER活性,开发低Ir催化剂就显得至关重要。对其反应机理的认知是当前的研究热点之一,也是设计优异的OER催化剂的关键所在。因此,首先从OER机理出发,对目前被广泛认可的吸附物逸出机理(AEM)和晶格氧逸出机理(LOER)两种反应机理进行了研究。随后,根据所提出的这两种机理,介绍了OER催化剂设计的基本准则,即调控Ir基催化剂的电子结构,改善反应中间物种在催化活性位点上的吸附能,从而提高OER催化活性。并从催化剂的结构设计、形貌控制、载体材料3个方面简单概述了最近OER催化剂的研究进展。最后,在已有研究的基础上,提出了目前OER催化剂面临的困难与挑战,这为以后相关的研究指明了方向。 相似文献
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新型含噻唑和三唑环的亚胺类化合物的合成及生物活性研究 总被引:5,自引:0,他引:5
设计合成了一系列新型含有噻唑和三唑环的亚胺类化合物, 其结构经元素分析、1H NMR和X射线晶体衍射确证. 生物活性测试结果表明, 部分化合物在50 μg/L浓度下对苹果轮纹菌具有一定的杀菌活性. 相似文献
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本工作观察了重复刺激传入神经对由伤害性刺激引起的猫脊髓腰段背外侧索纤维(可能是脊颈束纤维)活动的抑制效应。 重复刺激前后肢的皮肤或肌肉神经、电针或手针刺激穴位都可产生抑制效应,抑制作用在重复刺激开始时较强,以后逐渐减弱消失,当伤害性刺激施加于后肢时,重复刺激后肢神经的抑制作用显著地较刺激前肢神经强, 我们还刺激了传递由强电脉冲刺激引起的“伤害性”传入信号的同一神经,观察对背外侧索纤维的抑制效应,大多数背外侧索纤维的反应受到抑制,其抑制效应比刺激其他传入神经引起的为强,刺激传入神经中全部A纤维的抑制效应比只刺激Aβγ纤维的要强。 对这两种刺激引起抑制效应的可能不同的机制作了推测,讨论了脊髓的整合机制在针刺镇痛中可能有的意义,认为本文所描述的各种传入冲动在脊髓中的相互作用可能在针刺镇痛中起一定作用。 相似文献
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A 30-MeV femto-second electron linac is built at the Shanghai Institute of Applied Physics, which can produce high power, coherent THz undulator radiation. We report the experimental facility and measurement of the power, frequency spectrum. First experiments show the averaged power at THz to be about 20mW. 相似文献
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Jian-Bing Zeng Yi-Dong Li Shao-Long Li Yu-Zhong Wang Ke-Ke Yang 《Journal of Macromolecular Science: Physics》2013,52(3):635-649
A novel biodegradable poly(ester urethane; PEU) was synthesized by chain extension reaction of dihydroxylated poly(L-lactic acid; PLLA) and poly(butylene succinate; PBS) using diisocyanate as a chain extender. The kinetics of thermal and thermo-oxidative degradation of PEU containing PLLA and PBS blocks were studied by thermogravimetric analysis (TGA). TGA results indicated that PEU was more stable in air than in nitrogen and went through a two-stage degradation process irrespective of the experimental atmosphere. Activation energy of each stage was calculated by means of Kissinger, Kim-Park, Friedman, Flynn-Wall-Ozawa, and Kissinger-Akahira-Sunose methods. For the first stage, the activation energy value obtained in air was slightly higher than the corresponding value obtained in nitrogen; and for the second stage, the activation energy showed a much higher value in air than in nitrogen. The Coats-Redfern method was employed to study the degradation mechanism of each stage. The results indicated that the degradation of the first stage follows the P3/4 mechanism irrespective of the experimental atmosphere; the degradation of the second stage of PEU obeys the P1 mechanism in nitrogen while P3/2 in air. 相似文献
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