质谱的bottom up和top down 有什么区别

bottom up_百度翻译
bottom up 英[ˈbɔtəm ʌp] 美[ˈbɑtəm ʌp]
[词典] 颠倒，<俗>干杯！;
[例句]It struck me that lasting change came from the bottom up and not from the top down.
top down_百度翻译
top down 英[tɔp daun] 美[tɑp daʊn]
[词典] 严密的;
[例句]It struck me that lasting change came from the bottom up and not from the top down.

两种工作模式。bottom up是自下而上，拿蛋白质来说，就是先将蛋白质消化成多个小的肽段再进行质谱分析。top down就是 自上而下，直接对整体进行分析。