Open Access repositories

Apart from institutional repositories, like DTU's research database DTU Orbit, there are many subject repositories available.
PilDTU Orbit

Here are some examples of Open Access repositories:

ADS
The NASA Astrophysics Data System
http://adswww.harvard.edu/
arXiv.org
E-prints in e.g. physics, mathematics, computer science and statistics
http://arxiv.org/
CiteSeer
Primarily computer science and informatics
http://citeseer.ist.psu.edu/
PhilPapers
Online Research in Philosophy
http://philpapers.org/
PMC
PubMed Central
http://www.ncbi.nlm.nih.gov/pmc/
RePEc
Research Papers in Economics
http://repec.org/
SPIRES
High Energy Physics Literature Database
http://www.slac.stanford.edu/spires
SSRN
Social Sciences Research Network
https://www.ssrn.com/



More repositories
For more repositories please consult opendoar.org