Depends on the Date mostly

first Research only become available to be researched at specific dates in the game.

in later campaigns research is already complete and upgrades should already be available at port.

the intent is the not allow specific items to be acquired during the early years of the war ,where many players can cheese the mechanic to complete all research by 1939/40. This ensures research and equipment become available slowly throughout the campaign.

So in summary , depending on date/campaign, different research for the period may be available. Other equipment may already be provided in port (pre-researched) if the date is late enough.