the api can not query an alts researches but there are plenty of addons that will track your researches across all characters, it does require to log in each char you wish to track.
Probably the most popular one is AI Research Grid
http://www.esoui.com/downloads/info2...earchGrid.html
I am working on an Addon/ Application / website that will let you track monitor and even notify you in regards to your researches while offline as well called IGOR that is still in Beta as i am finishing it up, would probably be done already if it wasn't for Dragon Age...
http://www.esoui.com/downloads/info8...Assistant.html