darboux tangent是什么意思

用法例句

In the paper,a plenty of graptolite fossils are collected in a carbon-bearing slate at Daptar area.

本次工作在达布达尔乡沙依地库拉沟该套地层中首次发现了大量保存较完整的笔石化石,经鉴定,主要分子有Monograptus xizangensis,Pristiograptuselegans,Demirastrites raitzhainiensis,Oktavites planus,Rastrites hybridus,Diplograptus cartatus,Glyptograptus gracilis,Climacograptus bidongensis等8属20种,且均为早志留世早中期分子,它可为该套地层时代的确定提供确切的化石依据。