We report a novel observation about which scientific publications are cited more frequently: those that are more textually similar to pre-existing publications. Using word-vector based document embeddings, we analyze quantitative trends for a large sample of publication abstracts in the field of astrophysics (N ~ 300,000). When new publications are ranked by how many similar publications already exist in their neighborhood, the number of citations per year that the upper 50th percentile receives is ~ 2 times that of the lower 50tb percentile. When new publications are ranked by an alternative metric of dissimilarity to neighbors, citations per year decrease by a factor of ~ 1.5 from the lower to the upper 50th percentile. We discuss a number of hypotheses that could explain this citation-similarity relationship relevant to the science of science.