Why do some academic papers have sentence-cased titles? I noticed that many academic papers that I cited in my thesis have sentence-cased titles, for example, this one "Comparative analysis using K-mer and K-flank patterns provides evidence for CpG island sequence evolution in mammalian genomes."

I was just wondering why and if this is correct?

I was about to manually fix all of them so that they will appear with the proper title-cased titles on the Bibliography.
Many journals prefer sentence-case to title-case - in this case, a quick glance at the contents list for that particular journal shows they use sentence case for all titles. Neither is "proper" or "correct" in all circumstances.

If you are trying to conform to a particular style, check if it has guidelines on preferred capitalisation for citations. For example, the ACS style guide recommends:


  In [articles from] ACS journals, capitalization follows that of the original publication;
  in other publications, the main words are capitalized


If there is no firm guidance in your particular style, then you can either leave them in the original capitalisation, or standardise them all in whichever form you prefer. (Personally, I default to sentence case...)