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A Comparative Study of the Usage of Synonyms Based on BNC-Taking Assessment and Evaluation as Examples
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作者 jiang tian-meng 《Journal of Literature and Art Studies》 2023年第1期29-35,共7页
The discrimination of synonyms has always been one of the great challenges for English learners.Taking assessment and evaluation as examples,this study analyses the similarities and differences of the two words,as wel... The discrimination of synonyms has always been one of the great challenges for English learners.Taking assessment and evaluation as examples,this study analyses the similarities and differences of the two words,as well as their usage from the perspectives of frequency,stylistics,collocation and semantic prosody with the help of British National Corpus,and demonstrates the importance of corpus retrieval tools in synonyms discrimination.Furthermore,this paper will give some suggestions for English learners and teachers in English vocabulary teaching. 展开更多
关键词 corpus linguistics SYNONYMS frequency STYLISTICS COLLOCATION semantic prosody
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一种异丙烷桥键液晶材料的合成与性能
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作者 杭德余 班全志 +2 位作者 姜天孟 田会强 储士红 《精细化工》 EI CAS CSCD 北大核心 2013年第11期1204-1207,1228,共5页
以3-氟溴苯、对溴苯腈、丙基环己基甲基氯等为原料,经过格氏反应、Suzuki反应、Witting反应、氢化反应等7步反应最终合成出化合物2,6-二氟-4-{3-氟_4’-[1-甲基-2-(4-丙基环己基)-乙基]联苯}苯基二氟甲氧基-3,4,5-三氟苯[化合物(Ⅶ)],... 以3-氟溴苯、对溴苯腈、丙基环己基甲基氯等为原料,经过格氏反应、Suzuki反应、Witting反应、氢化反应等7步反应最终合成出化合物2,6-二氟-4-{3-氟_4’-[1-甲基-2-(4-丙基环己基)-乙基]联苯}苯基二氟甲氧基-3,4,5-三氟苯[化合物(Ⅶ)],其中格氏试剂与对溴苯腈的反应中溶剂选择二甲苯;锂化反应制备硼酸中,锂化反应时间选择2h;纯化后目标产物气相色谱纯度为99.7%(熔点82.97-85.04℃),总收率约为30%,其结构经IR、HNMR及GC—MS确证。该化合物添加到液晶的基础配方中,能提高配方的双折射率(△凡),降低其阈值电压(Vth)。 展开更多
关键词 2 6-二氟-4-{3-氟-4’-[1-甲基-2-(4-丙基环己基)-乙基]联苯}苯基二氟甲氧基-3 4 5-三氟苯 1-(3’-氟联苯基)-2-(反式-4-丙基环己基)乙酮 光电性能 功能材料
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