The Research Information Network has produced a report looking at the connection between the use of e-journals and research outcomes. Among their findings it shows that high levels of expenditure on e-journals together with high levels of use can aid research success, although a subscription to a new journal can take about 3 years to make an impact. Spending on library budgets however, has not kept pace with other university spending.
The full report is available at: http://www.rin.ac.uk/system/files/attachments/Ejournals_part_II_for_screen_0.pdf