This looks like a FAQ page, but there is a search engine link at the top.
CIA reading room
CREST is search engine that finds the titles of documents, but the documents are not online. You need to go to the National Archives (NARA) in College
Park Maryland. Third floor in the library. You are monitored via overhead camera. What you print out is noted. Hey, these people are spies, what else
would you expect.
CIA CREST
CREST data just shows up. Usually quarterley, but NARA gets no notice. The CIA just shows up and puts new data into their servers, which are in a
steel cage bolted to the floor. There is no electronic retrieval of documents, just a laser printer. I have well over a foot of printed pages, and I
assure you I'm not scanning and uploading that much information.
With CREST, you can at least do the search at the leisure of your PC, then when you show up to NARA, you can plug and chug the documents. Every time
the word "secret" appears, you need to cross it out. This is usually twice on every page. This gets very tedious. The only good news in all this is
the CIA provided the paper and toner.
DOE search
There is also a "reading room" in Las Vegas at the Atomic Testing Museum. Access to the reading room is free. I've only gone their to look at
sanitized and declassified videos. I don't know if they have more documents there than can be found on line.
The DOE used to run a website call graylit. The documents aren't in the black, but rather they are gray. This vanished for some reason. This link is
what you get if you look for the old graylit website. It seems similar to the other OSTI search, but I haven't investigated that aspect fully.
something like graylit
old Groom Lake security manual
new security manual
Happy searching.