I don't subscribe to any of the online journals as I prefer to do things the old fashioned way with books. If I need to I can usually google the full text of almost every study I'm interested in and on the rare occasions when I can't the abstract will usually tell me everything I need so I don't see much point in paying for anything.
Instead of recommending any journals then I'm going to suggest that you get hold of a copy of Exercise Physiology: Energy, Nutrition, and Human Performance by McArdle, Katch and Katch as it covers pretty much everything you need to know plus a ton of stuff you've probably haven't even thought of yet. There's a new 7th edition out now but any good library should have a copy of one of the earlier editions so I'd go that route before buying a copy.
"Eat food. Not too much. Mostly plants." - Michael Pollan.