VE型不育－保持系
VE type male sterile-maitainble line
σ-闭包保持闭加细
clousure-preserving closed refinements
σ内部保持开膨胀
interior preserving of open expansions
安全车距保持系统
Safety distance keeping system
安全壳负压保持系统
containment subatmospheric pressure (maintenance) system
保持原状
background of feeling
background of globalization