...

表明笔石详细构造的物质是利用氢氟酸从石灰岩中侵蚀出来.Material illustrating detailed structure of graptolites has been etched from limestone by means of hydrofluoric acid.从而为笔石反射率的正确测定和取值奠定了基础.These provide base for the correct measurement and val...

“笔石”的拼音为：bǐ shí...