Selecting an appropriate set of scientific journals which best meets the users' needs and the dynamics of science requires usage of weight parameters by which journals can be ranked. Previous methods are based on the simple counting of relevant articles, or hits in SDI runs. The new method proposed combines hit numbers in SDI runs and journals' impact factors to a weight parameter called Selective Impact. The experimental results obtained show that ranking by Selective Impact leads to a higher quality of the conclusions to be drawn from journal rank distributions.