共查询到19条相似文献，搜索用时 880 毫秒
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本文研究在ＰＨ５．５的六次甲基四胺缓冲体系中，以５－Ｂｒ－ＰＡＤＡＰ作为指示剂，用ＥＤＴＡ滴定铅精矿中铅含量。试验结果表明，终点变色敏锐，测定结果变异系数为０．２７％（ｎ＝５）。 相似文献
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《中学数学教学参考》1999,(9)
第一试一、选择题１．在△ＡＢＣ中,若ｃｔｇＡｔｇＡ２＋ｃｔｇＢｔｇＢ２＋ｃｔｇＣｔｇＣ２≥１,则△ＡＢＣ的形状是（ ）．Ａ．任意三角形 Ｂ．直角三角形Ｃ．钝角三角形 Ｄ．等边三角形２．已知ｘ,ｙ∈Ｒ,且３ｘ＋５ｙ≥３－ｙ＋５－ｘ,则ｘ与ｙ满足（ ）．Ａ．ｘ＋ｙ＞０ Ｂ．ｘ＋ｙ≥０Ｃ．ｘ＋ｙ＜０ Ｄ．ｘ＋ｙ≤０３．已知Ｐ是正方形ＡＢＣＤ所在空间任一点,则ＰＡ２－ＰＤ２与ＰＢ２－ＰＣ２的大小关系是（ ）．Ａ．ＰＡ２－ＰＤ２＞ＰＢ２－ＰＣ２Ｂ．ＰＡ２－ＰＤ２＜ＰＢ２－ＰＣ２Ｃ．ＰＡ２－Ｐ… 相似文献
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范闽光 《南宁职业技术学院学报》1999,(2)
本文用热重法考察了三种不同孔道结构的分子筛（ＳＡＰＯ－３４,ＳＡＰＯ－５,ＨＺＳＭ－５）在乙醇转化为低碳烯反应过程中的积炭行为,以及经钾、镁的化合物改质的ＳＡＰＯ－３４分子筛在该反应过程中的抗积炭能力。用氨程序升温脱附法（ＴＰＤ）研究了它们在积炭前后的酸性变化。 相似文献
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PVA渗调对线椒种子活力及芽期酶活性的影响 总被引：5，自引：0，他引：5
巩振辉 《河南职业技术师范学院学报》1995,23(2):29-32,56
在１８℃条件下，线椒种子经０．５％～２．０％ＰＶＡ渗调处理１２～４８ｈ发芽率，发芽势，发芽指数均有所提高，种子浸出液相对电导率降低，芽期ＰＯＤ，ＳＯＤ活性增强，ＳＯＤ活性的峰值提前，其中以１．５％ＰＶＡ渗调１２ｈ效果最好。 相似文献
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一、填空题 １．ＡＢ是Ｏ的直径，弦ＣＤ⊥ＡＢ，垂足为Ｐ．若ＡＰ：ＰＢ＝３：１，，则ＣＤ等于 ２．如图１，ＣＤ是Ｏ的直径，ＡＢ是弦，ＡＢ⊥ＣＤ，垂足为Ｅ，如果ＣＥ＝２，ＡＢ＝８，那么ＥＤ＝＿，Ｏ的半径ｒ＝＿．（江苏省徐州市） ３．如果Ｏ的半径为５ｃｍ，一条弦长为８ ｃｍ，那么这条弦的弦心距为 ｃｍ（安徽省） ４．在圆内接四边形ＡＢＣＤ中，如果∠Ａ：∠Ｂ：∠Ｃ＝２：３：４，那么∠Ｄ＝ （吉林省） ５．如图 ２，ＢＡ是半圆Ｏ的直径，点Ｃ在Ｏ上．若∠ＡＢＣ＝５０°，则∠Ａ＝ （吉林省） ６．如图３，ＡＢ是Ｏ的直径… 相似文献
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黄严生 《中学数学教学参考》1996,(3)
一道高考题的推广及其应用中国科大附中黄严生如图，三棱锥Ｐ－ＡＢＣ中，已知ＰＡ⊥ＢＣ，ＰＡ＝ＢＣ＝ｌ，ＰＡ与ＢＣ的公垂线段ＥＤ＝ｈ．求证：三校锥Ｐ－ＡＢＣ的体积这是１９８７年的一道高考题，此题可以推广成下面的命题。如图，三校推Ｐ－ＡＢＣ中，ＰＡ与ＢＣ所... 相似文献
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基于用ＨＮＯ_３－ＨＣｌＯ_４法消化样品、用α，α’－联吡啶法测定铁、用５—Ｂｒ—ＰＡＤＡＰ法测定锰、用Ｚｎ（ＨＤｚ）２一次萃取混色法测定锌、用Ｃｕ（ＤＤＴＣ）２一次萃取法测定铜，建立了测定生物材料中铁、锰、锌、铜的快速分光光度法．不计样品消化时间，一次测定一般２—３小时即可完成。关键词： 相似文献
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ＡＭＯＤＩＦＩＥＤＣＲＡＮＫ－ＮＩＣＯＬＳＯＮＳＣＨＥＭＥＦＯＲＴＨＥＩＮＩＴＩＡＬ－ＢＯＵＮＤＡＲＹＶＡＬＵＥＰＲＯＢＬＥＭＯＦＳＵＰＥＲＴＨＥＲＭＡＬＥＬＥＣＴＲＯＮＴＲＡＮＳＰＯＲＴＥＱＵＡＴＩＯＮＳｕｎＺｈｉｚｈｏｎｇ（孙志忠）（Ｄｅｐａｒｔ... 相似文献
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JIANGYouyi TANMingshu LIUXuefei 《重庆大学学报(英文版)》2004,3(1):105-107
This work deals with the power exponent r1 and r2 respectively of the maximal and second-maximal prime factors ofthe order of simple K4-group, and the classification for simple {5,7}′-K4-group G (i.e. ｜G｜ can not be divided by 5 nor by 7 or ｜π(G)｜ = 4 ), simple 5′ -K4-group G (i.e. ｜G｜ can not divided by 5 and ｜π(G)｜ =4) and simple 7′-Ea-group G (i.e. ｜G｜ can notdivided by 7 and ｜π(G)｜ =4). It is derived that r1 =1, 2 and 4, and r2 is not greater than 4. All the simple K4-groups with order 2^a3^b5^cp^d, 2^a3^b7^cp^d and 2^a3^b5^c7^d are obtained. 相似文献
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Yong-zheng Guo Kai-jin Xu Yong-tao Li Jia-dan Fu Min Xu Ling Yu Ji-fang Sheng Biao Zhu 《Journal of Zhejiang University. Science. B》2020,21(12):948
The aim of this study was to evaluate the safety of an antiviral regimen of protease inhibitors combined with Arbidol (umifenovir) for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pneumonia patients. The genomic sequence of SARS-CoV-2 is highly homologous to that of SARS-CoV (Zhou et al., 2020). Previously published basic and clinical research on anti-SARS-CoV treatment found that lopinavir/ritonavir (LPV/r) could improve the prognosis of SARS patients (Chan et al., 2003; Chu et al., 2004). Darunavir (DRV) is another protease inhibitor that blocks the binding of SARS-CoV-2 to human angiotensin-converting enzyme 2 (Omotuyi et al., 2020). The broad-spectrum antiviral drug Arbidol (umifenovir) also shows in vitro anti-SARS-CoV activity (Khamitov et al., 2008). 相似文献
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本文报道了14种新的固态稀上元素配合物(除C_e,P_m,L_u外),它们是用稀土的硝酸盐与1,4—双(1′—苯基—3′—甲基—5′—氧代吡唑—4′—基)—1,4苯二酮(简写为H_2L)在乙醇—水溶液中,于PH=5.8～6.0条件下反应而制得的.配合物的分子式为RE_2L_3·nH_2O(RE=La,Nd,n=8,RE=Pr,Sm,n=6.RE=Eu,Gd,Tb,Dy,Ho,Er,Tm,Yb,Sc,Y,n=5).用化学分析,元素分析,紫外,红外、质子核磁共振,热分析和荧光谱对配合物进行了研究.根据以上研究,认为配合物具有双核结构. 相似文献
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测定维生素A的三种方法比较 总被引：4，自引：0，他引：4
目的:比较测定维生素A含量的3种不同方法,为维生素A及其制剂的质量研究提供参考。方法:分别采用紫外(UV)三点校正法与正、反相高效液相色谱法(HPLC)测定维生素A含量。UV三点校正法以环己烷为溶剂,按照三点校正法测定;NP-HPLC采用Hypersil SiO2柱(250mm×4.6mm,5μm),流动相为正己烷-异丙醇(99.8∶0.2);RP-HPLC采用C18柱(150mm×4.6mm,5μm),流动相为甲醇-水(97∶3)。结果:UV三点校正法测得VA含量为95.5%,RSD=1.3%(n=5);NP-HPLC为112.5%,RSD=3.2%(n=5);RP-HPLC为102.3%,RSD=1.0%(n=5)。结论:UV三点校正法和RP-HPLC法操作简单易行,NP-HPLC法能较好地控制杂质,但系统稳定性相对较差。 相似文献
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[目的]探讨腹膜、腹膜后间质瘤的临床病理特点.[方法]对大连大学附属医院近3a收治11例腹膜、腹膜后间质瘤患者的临床病理特点及用免疫组织化学方法检测CD117、CD34、SMA、S100蛋白表达的情况进行回顾性分析.[结果]11例患者中发生于结肠(横结肠)上区3例,结肠(横结肠)下区8例.肿瘤未能完整切除者4例.肿瘤大小≤2cm者2例,>2～5cm者1例,>5～10cm者3例,>10cm者5例.细胞形态以梭形细胞为主9例,以上皮样细胞为主2例.11例患者CD117全部阳性,CD34阳性7例,SMA阳性5例,S100全阴性.[结论]结果提示腹膜、腹膜后间质瘤作为GIST的一种特殊类型,有着其自身的临床病理特点. 相似文献
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郭纪昌叶一舵 《宁波大学学报(教育科学版)》2016,(2):15-019
Nine hundred and forty-four effective participants from middle schools are enrolled in this research and divided into two subgroups: sample 1 (N=472) is used in the exploratory factor analysis (EFA), and sample 2 (N=472) in the certified factor analysis (CFA). Results show that an Adolescents’ Personal Growth Initiative Scale contains 24 items in 5 factors, with expected indices of reliability and validity. 相似文献
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本文对协青早Ａ播种至始穗期天数（ｙ：播始历期）,与相应的日均活动积温（ｘ１）、日均有效积温（ｘ２）、日均实效积温（ｘ３）、平均日照时数（ｘ４）、降水量（ｘ５）和日均相对湿度（ｘ６）等气象因子进行多元线性逐步回归分析。结果表明：播始历期与其相应的各气象因子无明显的回归关系;与幼穗分化至始穗期的ｘ２、ｘ３、ｘ４和ｘ５有极显著的回归关系：ｙ＝－１２２．１８２８－８．６７２２５８ｘ２＋２１．８１９２３ｘ３＋０．７７５２９７ｘ４＋０．０２０１１２６８ｘ５;与穗分化中期至始穗期的ｘ５有显著的回归关系：ｙ＝５９．６７８９＋０．０４１１５８７３ｘ５。 相似文献
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ABSTRACT: Nearly 90% of graduating seniors from the Food Science program at Purdue University gain employment in the food industry. Ensuring the program is meeting employers' needs is one mission of our curriculum committee with input from an Industrial Advisory Board (IAB). In light of the recent outcomes-based assessment requirements outlined by IFT, feedback from our IAB members regarding the relative importance of the core competencies was needed. The objective of this study was to survey the IAB members regarding relative importance of each of the 46 core competencies. Each competency was ranked using a Likert scale from 1 = not important to 5 = very important. Statistical analysis was conducted using the Mann-Whitney nonparametric test. Significant differences (P = 0.05) were found between several of the five content categories with Success Skills scoring highest (4.35 out of 5) on relative importance followed by Applied Food Science Knowledge (4.02 out of 5). Also, significant differences (P = 0.05) were found between competencies within each content category. Overall, the results suggest that the 46 core competencies should not be given the same instructional weight within a curriculum. One option for addressing the variation in importance could be to include some planned redundancy within the curriculum for those core competencies that were ranked the highest. In addition, part of the outcomes-based assessment process should include measures of the level of competency being achieved by graduates. By considering relative importance and competency achieved by graduates, important areas for improvement can be identified. 相似文献
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《教育实用测度》2013,26(4):301-309
The relevance of test content to practice is essential for credentialing examinations and one way to ensure it is to collect ratings of item relevance from job incumbents. This study analyzed ratings of the 132 single-best-answer items and 117 multiple true-false item sets that formed the pretest books in a single administration of a medical certifying examination. Ratings collected from 57 practitioners were high (an average of more than 4 on a 5-point scale) and correlated with item difficulty (r = .31 to .34). The relationship between ratings and item discrimination is less clear (r = -.04 to .31). Application of generalizability theory to the ratings shows that reasonable estimates of item, stem, and total test relevance can be obtained with about 10 raters. 相似文献