Internet Library of Early Journals (http://www.bodley.ox.ac.uk/ilej/)
"A Digital Library of 18th and 19th Century Journals." Includes the titles Annual Register (1758-1778), Blackwood's Edinburgh Magazine (1843-1863), Gentleman's Magazine (1731-1750), Notes and Queries (1849-1869), Philosophical Transactions of the Royal Society (1757-1777), and The Builder (1843-1852).
The Nineteenth Century in Print: The Making of America in Books and Periodicals (http://memory.loc.gov/ammem/ndlpcoop/moahtml/ncphome.html)
"This collection comprises 1,500 books and 23 popular periodical titles published in the United States during the nineteenth century, primarily during the second half of the century. The materials selected illuminate the subject areas of education, psychology, American history, sociology, religion, and science and technology. Also included are volumes of American poetry."
See also the original Making of America pages from Cornell University and University of Michigan.
Science in the Nineteenth-Century Periodical (http://www.sciper.org/)
"A searchable electronic index to the science content of sixteen nineteenth-century general periodicals. Contains entries for over 14,000 articles and references to more than 6000 individuals and 2500 publications."
Undergraduate Victorian Studies Online Teaching Anthology (http://etrc.lib.umn.edu/uvsota/index.htm)
A project from the University of Minnesota Libraries. Includes a digital collection of Victorian periodical articles grouped into three thematic areas: Condition of Women, Empire, and Science, Evolution and Eugenics.
The Victorian Web (http://www.victorianweb.org/): "Literature, history and culture in the age of Victoria," from Brown University. Particularly, see the section on Victorian Science.