We have databases that play the same role as Philsopher's Index and the ATLA Religion Database for almost every field of study. A few examples given below, but you can find more through our database listings (use the subject pull-down menu).
JSTOR and Project Muse are both journal repositories.
Strengths: Everything in there is full text. Interdisciplinary.
Weakness: They don't have the breadth of Philosopher's Index or the ATLA Religion Databases.