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建构主义是当代最为流行的学习理论,它为教师反思教学行为提供了一个全新的视角。本文介绍了建构主义的基本观点和主要教学模式,提出了在化学教学中促进学生意义建构的指导思想和具体做法。 相似文献
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在预混甲烷/空气燃烧的平面火焰炉上,采用脉冲式光腔衰荡光谱技术(cavity ring-down spectroscopy, CRDS)实现了对OH分子浓度的定量测量。根据光腔衰荡吸收光谱理论,选取OH的A2Σ+-X2Π(0,0)电子跃迁带中的P1(2)吸收谱线构搭建了一套激光波长在308.6 nm的脉冲CRDS实验装置。脉冲CRDS装置中的衰荡光腔是由一对反射率为99.7%的高反射镜组成且其衰荡腔的腔长为270 cm,并测量空腔(光腔中无火焰)的衰荡时间为2.33μs。通过理论分析影响浓度精确测量的实验参数,分别采用平面激光诱导荧光(planar laser induced fluorescence, PLIF)、相干反斯托克斯拉曼散射(coherent anti-stokes Raman scattering, CARS)和脉冲CRDS三种技术精确测量OH的有效吸收长度、高温火焰的温度和有效的光腔衰荡时间。当在平面火焰炉上燃烧预混的甲烷(1.1 L·min-1)和空气(15... 相似文献
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研究了盐析剂浓度和水相PH值对分配比D的影响。研究了烷基膦酸萃取剂P507和喹吉林 类萃取剂N601协萃锗的机理,并对萃取平衡常数和热效应进行了估算。 相似文献
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The reaction of an aqueous solution of sodium molybdate with iron powder at low pH (-0.184) gives rise to the formation of a six-member Mo ring-shape cluster with an Fe (II) encapsulated at the center, [Na4(H2O)7][Fe(OH)6Mo6O18](1), which is further linked to a remarkable three-dimensional network via sodium ions. 相似文献
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1 INTRODUCTION Polyoxometallates are of great interest not only for their structural variety but also for their un- expected properties[1, 2]. These inorganic anions had been widely investigated in catalysis, biology, me- dicine, magnetochemistry and materials science[3~6]. Especially, the studies on the organic ligands coor- dinated by polyoxometallates might help to under- stand the catalytic mechanism of polyoxometallates. In recent years, several octamolybdates containing organic l… 相似文献
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1 INTRODUCTION The polyoxometalates have aroused extensive in-terest due to their alluring topologies and potentialapplications in various fields (e.g. catalysis, biology,medicine and materials science)[1]. A variety of po-lyoxometalate anions and related fragments withoxygen-rich compositions can serve as inorganic li-gands to coordinate secondary transition metal ions(so-called heterometals, such as Cu2 , Ni2 , Co2 andMn2 )[2]. Thus, larger discrete species and infinitelyextending ar… 相似文献