  Objective: Translational science aims at "translating" basic scientific
discoveries into clinical applications. The identification of translational
science has practicality such as evaluating the effectiveness of investments
made into large programs like the Clinical and Translational Science Awards.
Despite several proposed methods that group publications---the primary unit of
research output---into some categories, we still lack a quantitative way to
place papers onto the full, continuous spectrum from basic research to clinical
medicine. Methods: Here we learn vector-representations of controlled
vocabularies assigned to MEDLINE papers to obtain a Translational Axis (TA)
that points from basic science to clinical medicine. The projected position of
a term on the TA, expressed by a continuous quantity, indicates the term's
"appliedness." The position of a paper, determined by the average location over
its terms, quantifies the degree of its "appliedness," which we term as "level
score." Results: We validate our method by comparing with previous techniques,
showing excellent agreement yet uncovering significant variations of scores of
papers in previously defined categories. The measure allows us to characterize
the standing of journals, disciplines, and the entire biomedical literature
along the basic-applied spectrum. Analysis on large-scale citation network
reveals two main findings. First, direct citations mainly occurred between
papers with similar scores. Second, shortest paths are more likely ended up
with a paper closer to the basic end of the spectrum, regardless of where the
starting paper is on the spectrum. Conclusions: The proposed method provides a
quantitative way to identify translational science.
