http://scholar.google.com/ 
1. Syntax
" ", "lifespan extension"
-, testosterone -doping
OR, rats OR mice
2. Age can be limited by pressing "Recent articles". Then the exact cut-off year can be selected from the drop-off menu.
3. If finding an interesting article, then articles that have cited it can be found by pressing "Cited by xxx".
4. Now and then Google will find a complete copy of the article and not just the abstract. If so, it can be read by pressing the link to right of the green arrow to the right of the usual article abstract link. Even if not, you can still try pressing "All xxx versions" which sometimes will find a complete article. If you are interested in a subject and what an overview, it can be worthwile to just read the introduction of a full article which will provide a literature overview, even if the experiment itself is not interesting to you.
5. Sometimes you are not allowed to read even abstract if you follow the given link. For example some publishers want you to pay even for that. Then you can still try pressing "All xxx versions" and look for "ncbi.nlm.nih.gov" which will usually provide the abstract, if any.
