You cannot combine credit scores together to buy a house. However, lenders will look at both your credit scores if you put both names on the application. Even if one partner has a high score, a really low score from the other partner can disqualify you from getting a mortgage.
If one partner has a credit score and enough income to qualify for the mortgage themselves, you might want to consider only applying with one name on the application. This could improve your odds of being approved and getting the mortgage you need to buy a house.