Preheat the oven to 350°F (175°C). In a mixing bowl, combine the sour cream, mayonnaise, cream cheese, spinach, artichoke hearts, garlic, and ¾ cup of the parmesan cheese. Mix until a creamy, even texture is achieved. Transfer the mixture into a lightly greased baking dish—an 8×8-inch pan or similar-sized dish, such as a glass pie plate, will suffice. Evenly sprinkle the remaining ¼ cup of parmesan cheese across the top. Place in the preheated oven and bake for approximately 20 minutes, or until the dip is hot and bubbling throughout. Serve immediately with your choice of crackers or sliced bread.