If a technology is researched to reveal a resource, will the new resource be shown automatically on the maps? or does it required a new/special survey of the entire empire?
If you've already surveyed the system a new resource is in, then it shows up right away. If you've already built a mining station there, then you have access to it right away.
I can't find a good citation for these facts, but I've played the game for dozens of hours and can assure you that it is the case. I believe there's also an in-game tip to this effect.
At the top of the screen, to the right of your technology income, there is a white diamond-shaped icon.
Next to the icon are numbers representing how many total resources you have access to, and how many of those are currently available for use. Hovering over the icon shows you those same numbers, but for each individual type of resource. Thanks to @toolkitxx for pointing out the icon, and @Sjoerd for providing a picture.
When you are trying to build something that requires one of these strategic resources, a red X on the thing that you're trying to build indicates that you don't have the resource available in the same sector.