The NEHGR is a journal, and as such each issue has a number of articles (some frequently being serialized due to length) by different authors. A proper citation needs to include the author, title, and the volume information (name of journal, volume. Number, date, page(s), and so on). The Ancestry citation does not conform to the standard format for journal articles.
Collections of this journal, some complete and some not, exist in a number of genealogical libraries in the US and elsewhere. Electronic versions exist as well, also some complete and some not, such as Ancestry or American Ancestors. All of these are simply respositories and are not necessary for the citation. However, they may be included as a convenience for the reader. Personally, I have used the physical bound volumes, the older ones bring fragile, in places such as the Sutro Library in San Francisco, as well as electronic versions (online data bases, CDs, and digitized volumes).
Thus, if I were to cite an article from NEHGR, I would cite the actual article, and may or may not cite where I actually found it. If I thought it was rare and difficult to find, and NEHGR is not, I would identify a respository.