Because different mixings of coins had different amounts of gold and silver, even though they bore the same face value, some coins were worth more than others as commodities. 因为不同成分比例的硬币所含的金银量不同,即使它们面值相同,有些硬币的商品价值高于另外一些硬币。
The Competition between Two-Photon Resonance Four Wave Frequency Difference and Sum Mixings 波差导数;四波混频过程中差频与和频的竞争研究