Now that I have graduated I don’t have access to the same resources I did when a student. I find this frustrating, as I enjoy the deeper insight that they provide on topics that interest me. Technical papers are also useful or adding depth to my journal entries. There are search facilities and open access journals available on the internet . Be aware though, that the quality of papers found using search facilities and open access journals listed cannot be guaranteed and the majority have not been peer reviewed.
The following is a list of resources that I have used in the past to search for technical papers.
INFOMINE. Not to be confused with InfoMine, a resource for mining and mineral exploration technology. INFOMINE is an virtual library of internet resources. Typically the results from the search are good but you have to ensure that you specify the resource access as free on the search page and not to include UC subscription eJournals and eBooks on the results page.
Intute. Intute is a free online service. All material returned by Inture is evaluated and selected by a network of subject specialists. Intute does not make it clear whether this involves peer review of the material. Regardless of that technicality, the seems to work as the quality of the results are good.
The University of Glasgow, Enlighten. Enlighten offers access to the University’s Institutional Repository. Despite this being only a fraction of the university research output, this is still a valuable resource. In the future the university aims make available where possible, the full text, for all peer-reviewed, published research outputs produced by university staff.
CiteSeerx. CiteSeerx is a scientific literature digital library and search engine that focuses primarily on the literature in computer and information science. CiteSeerx is loosely based on the previous CiteSeer search engine.
Directory of Open Access Journals. The Directory of Open Access Journals lists open access journals, that is, scientific and scholarly journals that meet high quality standards by exercising peer review or editorial quality control and are free to all from the time of publication.
Open J-Gate. Open J-Gate is another directory of open access journals. Open J-Gate claims to be the largest list of open access journals available but it is important to note that unlike The Directory of Open Access Journals the majority are not peer reviewed or exposed to editorial quality control.
arXiv. arXiv is an directory service in the fields of physics, mathematics, non-linear science, computer science, quantitative biology and statistics. The contents of arXiv conform to Cornell University academic standards.
Tags: Academic Database, CiteSeerx, Directory of Open Access Journals, DOAJ, Engineering, Enlighten, INFOMINE, Intute, Open Access Journal, Open J-Gate, Peer Review, Search Engine

You missed out JURN, although it’s not science – it indexes over 1200 mostly free ejournals in the arts and humanities
http://www.jurn.org/