Step-Free Access,
Wheelchair Accessible (mostly),
Wheelchair Accessible Lift,
Wheelchair Accessible Cafe.
The older part of the Aberdeen Maritime Museum is housed in a building built in 1593 (one or two years before wheelchair-accessibility was even a consideration). So wheelchair access in this part of the Museum is limited.
See the Aberdeen Wheelchair Map for details of other wheelchair accessible attractions, restaurants and hotels in Aberdeen.
Photo credit: Aberdeen Archives, Gallery & Museums (Twitter)