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排序方式: 共有144条查询结果,搜索用时 15 毫秒
1.
为解决高等师范院校物理专业学生的知识结构和实际能力与社会需要明显不相适应的矛盾,我们对四年制物理专业的课程结构进行了全面改革。改革后,毕业生不仅能胜任普通中学或职业中学(职业中专)的教学,而且有能力参与厂矿企业的技术工作,具有更广泛的适应性和更强的竞争力。 相似文献
2.
红磷增效Al(OH)3/Mg(OH)2阻燃的聚丙烯结晶形态 总被引:2,自引:0,他引:2
借助宽角X-射线衍射、差热分析、偏光显微镜对红磷增效Al(OH)a和Mg(OH)2混合填充的阻燃聚丙烯体系的结晶形态进行了研究。发现这种体系中不仅出现a型而且还出现β型聚丙烯晶体。β型晶体可能是由于Al(OH)a和Mg(OH)a协同诱发而生成的。 相似文献
3.
4.
5.
The crystallization processes of hydrated Mg-borates, boric, magnesium hydroxide and Mg-oxychloride from MgO-B2O3-18%MgCl2-H2O supersaturated solution at 20°C have been studied by kinetic method. The crystallization solid phases were characterized
by X-ray powder diffraction, IR spectra, thermal analysis and chemical analysis. The liquid-solid phase diagram of thermodynamic
nonequilibrium state has been given. In this phase diagram, there exist eight crystallization fields, boric acid(H3BO3), trigomagneborite(MgO · 3B2O3 · 7.5H2O, MgO · 3B2O3 · 7H2O), hungchaoite(MgO · 2B2O3 · 9H2O), inderite(2MgO · 3B2O3 · 15H2O), chloropinnoite(2MgO · 2B2O3 · MgCl2 · 14H2O), magnesium hydroxide(Mg(OH)2) and magnesium oxychloride (5Mg(OH)2 · MgCl2 · 8H2O). 相似文献
6.
四(对三甲铵苯基)卟啉,在乙二胺存在下与Zn(Ⅱ)形成络合物。据此提出了用分光光度法测定微量锌的方法,该络合物最大吸收波长为425nm表观摩尔吸光系数为3.42×10^5,锌量在0~4.5μg/25mL范围内符合比尔定律,本法可用于稻米中微量锌的测定。 相似文献
7.
Zhixian Zhou Yuzhong Wang Jingchao Tao Yaoting Fan Yangjie Wu 《Journal of inclusion phenomena and macrocyclic chemistry》1998,32(1):69-80
A novel anion-selective electrode has been prepared by usingtetraazaporphyrinogen as the electroactive component and o-nitrophenyloctylether as the plasticizer. The electrode exhibits almost Nernstian responsecharacteristics for Pic-, ReO
4
-
,SCN-, ClO
4
-
and TPB-. The linearresponse ranges towards the above-mentioned anions are 10-6 10-2, 10-5 10-2,10-5 10-2, 10-5 10-1, and 10-5 10-2mol/Land the corresponding slopes are -56.8, -57.1, -56.3, -56.1, and -59.9mV/decade with correlation coefficients of -0.99978, -0.99987, -0.99999,-0.99998, and -0.99998, respectively. The electrode shows an anti-Hofmeisterselectivity sequence: Pic- > SCN- >ReO
4
-
> ClO
4
-
> I- >Br- > BF
4
-
> Sal->NO
3
-
> Cl-. The unusual responsemechanism of the novel anion-selective electrode was investigated byexperimental observations and calculation with the MNDO method. Theelectrode was used as a TPB- and a Pic-sensitiveelectrode, respectively, and applied to the assay of levamisolehydrochloride tablets by potentiometric titration and Gran's methods. Theresults obtained are in excellent agreement with that determined by thestandard pharmacopoeia method based on nonaqueous titration. 相似文献
8.
Six kinds of benzo-15-crown-5 (L) adducts having the stoichiometric formula M(Pic)2 · L · xH2O (M=Mn, Cu, x=2; M=Co, Ni, Zn, Cd, x=4; Pic means picrate anion) have been synthesized and characterized by EA, IR, UV and molar conductance. The X-ray crystal structural analysis of the benzo-15-crown-5 adduct with hydrated copper(II) picrate revealed that the benzo-15-crown-5 molecule virtually acts as a second-sphere ligand, which associates with the copper(II) ion by hydrogen bonding of the coordinating water molecule. By the comparison of the IR, UV spectra and molar conductance of the new adducts prepared, it can be deduced that the other adducts exhibit the similar coordination environment to that of the copper adduct. 相似文献
9.
生晒参、全须生晒参中19种有机氯残留农药的毛细管气相色谱测定 总被引:2,自引:0,他引:2
建立了生晒参、全须生晒参中19种有机氯农药残留的毛细管气相色谱分析方法。对样品中六六六的4种异构体、滴滴涕的5种异构体、四氯苯胺、六氯苯、五氯硝基苯、七氯、五氯苯胺、艾氏剂、百菌清、环氧七氯、狄氏剂及异狄氏剂共19种有机氯农药的残留量进行了测定。以石油醚-丙酮混合物作为提取剂,样品采用索氏提取,提取液用弗罗里硅土柱层析净化。采用OV-1701石英毛细管气相色谱柱分离样品,ECD检测器进行检测。在3个水平添加时的回收率(n=5)分别为75.7%~96.1%、78.8%~111.6%和81.7%~115·2%;相对标准偏差分别为2.4%~10.6%、2.1%~9.8%和1.4~10.0%。方法用于生晒参和全须生晒参样品中农药残留的测定,结果满意。 相似文献
10.
Zhixian Zhou Hongna Han Tiesheng Li Yanjun Xing Yangjie Wu Xian Xin Zhang Reed M. Izatt N. Kent Dalley Jerald S. Bradshaw Weijie Chai Cunheng He 《Structural chemistry》1999,10(3):177-185
Reactions of CsI and HgI2 with benzo-15-crown-5 (B15C5) and 15-crown-5 (15C5) in an ethanol-acetone mixture produced [Cs(B15C5)2]2[Hg2I6] (1) and {[Cs(15C5)]2[Hg2I6]}n (2), respectively. The structures of the two complexes are quite different. Molar ratios of Cs+ : crown ether are 1 : 2 in 1 and 1 : 1 in 2. Complex 1 consists of two Cs(B15C5)
2
+
cations and a Hg2I
6
2-
anion. Cs+ lies between the two crown-5 ligands, resulting in a sandwich-type cation. Cationic Cs(B15C5)
2
+
and anionic Hg2I
6
2-
are linked together by electrostatic interactions and the complex 1 is an ion pair compound. Complex 2 consists of infinite [Cs(15C5)]2[Hg2I6] units. Each structural unit contains two Cs(15C5)+ cations and a Hg2I
6
2-
anion. Cs+ is coordinated by five oxygen atoms of 15C5, three iodine atoms of Hg2I
6
2-
, and an iodine atom of Hg2I
6
2-
in an adjacent structural unit. The interactions between the Cs+ of Cs(15C5)+ and an I– in Hg2I
6
2-
from adjacent structural units polymerize the complex 2, resulting in a one-dimensional network structure. The anions of Hg2I
6
2-
in both complexes are similar. The two mercury atoms are linked through two bridging iodine atoms and each mercury is also coordinated by two terminal iodines. Crystal data for 1: space group P21/c (No. 14), a = 12.253(4), b = 20.945(7), c = 16.110(6) Å, = 111.0(1)°, V = 3860 Å3, Z = 4, R = 0.082 (R
w = 0.089). Crystal data for 2: space group P21/c (No. 14), a = 12.157(4), b = 8.546(4), c = 20.666(6) Å, = 91.54(3)°, V = 2146 Å3, Z = 4, R = 0.034 (R
w = 0.048). 相似文献