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Gemology and Gemstone Instruction Gemology is the study of gemstones, which includes gem properties, locations and origins. Gemology is often studied by people in the jewelry business, including business owners, buyers, designers and appraisers. Others studying gemology include antique dealers and auction house catalogers. A gemstone is a mineral, rock or organic material that is used for jewelry, ornamentation, or art. A gem, such as a diamond, is a type of gemstone that must be cut and polished for its beauty to be visible. A gemstone can be valued for its natural growth having the traditionally quoted “three cardinal virtues” of beauty, durability and rarity. Acceptability and portability are other factors decided by the society for valuation of gemstones. Beauty is related to the results of the visible light by interaction with the gemstone. These effects are different for different types of gem materials, especially in relation to the degree of transparency. Durability is related to the structure, which depends on hardness against scratching, toughness against breaking and stability against external forces such as heat, pressure, shock and chemical action etc. Rarity of a gemstone depends on its availability, and the valuation is decided by the supply and demand theory in economics. 2. There are no differences between gemstone and gem.
A.
正确
B.
错误
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【单选题】神经细胞动作电位的特点是( )
A.
没有不应期
B.
动作电位值可以总和
C.
衰减性传导
D.
动作电位形成过程中有Na+通道激活
【简答题】两类细颗粒土中()的液化和冻胀问题更严重些,因为土颗粒连接弱和毛细现象和其它土都不同,相比粗颗粒土其质量轻而不能密实,相比粘性土其颗粒连接弱,且毛细现象又最显著。
【单选题】味觉感受器是:
A.
舌乳头
B.
味蕾
C.
舌界沟
D.
舌苔
【多选题】神经细胞动作电位的特点是
A.
属于峰电位
B.
全或无式的
C.
去极化幅度为100mV
D.
时程为0.5-2.0ms
E.
呈非衰减性传导
【单选题】下列关于味觉的叙述,正确的是(    )
A.
味觉感受器是味毛
B.
一个味感受器一般并不只对一种味质起反应
C.
味觉的敏感度随年龄的增长而增长
D.
甜味感受器多分布在舌两侧面
E.
酸味感受器多分布在舌尖部
【单选题】神经细胞动作电位的特点是
A.
电位幅度高低与刺激强度有关
B.
具有全或无性质
C.
有总合现象
D.
由Na+外流形成
E.
呈衰减性传导
【单选题】神经细胞动作电位的特点是( )
A.
没有不应期
B.
动作电位值可以总和
C.
衰减性传导
D.
Na十通道激活产生去极相
【单选题】神经细胞动作电位的特点是
A.
电位幅度高低与刺激强度有关
B.
具有全与无性质
C.
有总合现象
D.
由Na+外流形成
E.
呈衰减性传导
【单选题】中国人腰围的标准上限是女性、男性不超过( )厘米。
A.
80 90
B.
90 80
C.
85 75
D.
100 90
【简答题】味觉感受器是 查看材料
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