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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. 3. Beauty of a gemstone is especially in relation to the degree of transparency.
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正确
B.
错误
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【单选题】下列属于杭州西湖的是()
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三潭映月
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湖心岛
C.
阮公墩
D.
以上都是
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增加毛细血管通透性,减轻肿胀
B.
使神经末梢的敏感性降低
C.
降低痛觉神经的兴奋性
D.
降低细胞新陈代谢和微生物活力
E.
增强新陈代谢和白细胞的吞噬功能
【单选题】热疗法减轻疼痛的机制是
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增强新陈代谢和白细胞的吞噬功能
B.
降低痛觉神经的兴奋性
C.
降低细胞新陈代谢和微生物活力
D.
使神经末梢的敏感性降低
E.
增加毛细血管通透性减轻肿胀
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B.
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净水机
B.
机床
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配餐服务
D.
节水器
【单选题】热疗法减轻疼痛的机制是
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增强新陈代谢和白细胞的吞噬功能
B.
降低细胞新陈代谢和微生物活力
C.
降低痛觉神经的兴奋性
D.
使神经末梢的敏感性降低
E.
增加毛细血管通透性减轻肿胀
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