核门槛

nuclear threshold

pit / stone / nucleus / nuclear / to examine / to check / to verify

variant of 核[he2] / to investigate

gate / door / CL:扇[shan4] / gateway / doorway / CL:個|个[ge4] / opening / valve / switch / way to do something / knack / family / house / (religious) sect / school (of thought) / class / category / phylum or division (taxonomy) / classifier for large guns / classifier for lessons, subjects, branches of technology / (suffix) -gate (i.e. scandal; derived from Watergate)

doorstep / sill / threshold / fig. knack or trick (esp. scheme to get sth cheaper)

banister / balustrade / cage for animal or prisoner / to transport caged prisoner on a cart

door sill / threshold