When one says scholasticism, one means Aquinas and the Summa Theologica, and vice versa, so great was the impact of Aquinas's work. Rigorously systematic and logical and heavily influenced by Aristotelean thinking, the Summa Theologica is the epitome of scholastic theology and learning more generally, especially that done in the burgeoning university communities like those in Paris.
Full text of Summa Theologica in Latin and English