I understand that books and articles are scattered everywhere but is there a data base where you can find a lot of articles?
If you have access to it, I use JSTOR very often when I look for publications. I also use google scholars, but I might be using it wrong because I have a hard time getting interesting papers out of it.
What I also do is read bibliographies at the end of (good) general history books related to the subject that interests me. It is a goldmine when it comes to finding sources. Usually you will find more specialized sources in the bibliography that have been summed up in the book, then in the specialized book you will find even more specialized sources, etc. I don't know if that's really a "database", but a good bibliography and the access to a library seems close to it.
I use my library. Literature is on the 6th floor, history on the 4th. The catalog is online. If I have one reference number I know where to go and can shelf read.
There are also a number of sites online that have translations or the original text like Perseus or Livius or The Latin Library.
For medieval history, RI-Opac is the best database I've used so far. Just type in the relevant keywords and it will find the articles/monographs related to that topic, even various PhD/MA theses. It also arranges them by date of publication, so it is super useful for finding recently published stuff. I use Google Scholar sometimes too, but it often brings up irrelevant hits in my experience. Another good way to look for recent scholarship is to find the most recent book on the topic you are interested in and look through the bibliography; this is especially useful for finding articles written in other languages.
When I'm looking for an introduction to something I know pretty much nothing about, I like to google for a relevant, preferably grad-level, syllabus at a top tier university, and look through the class reading list. From there you can leaf through the bibliography and follow citations backwards, or use google scholar to follow citations forwards.
On Google Scholar you can see lots of articles plus you can see articles that cite a certain article on the list so you can find a bunch of articles about related things that are connected through citations.