How to get academic search engines only search in open access journals?

I'm not sure, whether you really meant open access journals, because when I'm searching at home and I'm too lazy to use the VPN of our university, I'm usually interested in publications I can access.

I wouldn't rely on Google Scholar alone, because I'm not sure whether they filter the results. When you study the advanced search of google a bit, you'll see, that some of the switches are really nice. One really important switch is the -filetype option. If you search for instance for image segmentation in Google Scholar you get instantly only results with a downloadable pdf file if you use

image segmentation filetype:pdf

Even more handy becomes this approach in a two step method. As you know, when you "put something in quotes" in google, you search for the exact string. This can be used to do the following:

• find some preview of the article you want to download.
• choose a very specific part of a sentence there
• search for this part and use the filetype option

Non-scientific example: Sometimes I'm searching for piano notes of some popular songs and since everyone tries to make money with this, you often won't find a free, downloadable version. Therefore, I first search for something like "sheet music evanescence my immortal" and look at one of the first links, where you usually can see one sample page. Then I see, what's on the page and I use this information to adjust my search

"My immortal" "I'm so tired of" "Slowly and freely" filetype:pdf

and the first hit is a high-quality pdf with all pages.

The same approach sometimes works for scientific publications, because most scientists put their publication on their website. So while you have to pay on the journal website, you may get it for free somewhere else.

This exact question has been asked at Webapps Stack Exchange:

Is there a way to configure Google Scholar to only show results where the document is freely available?

Quoting from the (unaccepted) answer there:

Unfortunately there isn't an option to restrict results like that in Google Scholar (I appreciate the idea, running into paywalls is very frustrating). I guess the argument could be made that you are limiting the articles/knowledge you could be exposed to be only looking at the free things. That and Google's recognition of what is accessible isn't 100%.

See over there for more information.

No, there is no way to restrict google scholar searches to only open-access papers.

However, you have several options, to ensure that you can access pay-for-access journals that your institution has subscriptions for, even when you're off-campus. This neatly short-circuits the question of having to search only open-access journals. And see also the section below on "Hosting on servers other than the journal itself", which will allow you to find open-access copies of papers that are in pay-to-access journals, by looking on author's homepages and similar.

Shibboleth / Athens login

The login name and password you use for your campus network, may also serve as your login and password for one of the access aggregators, such as Shibboleth or Athens. So once you're at the online journal page of the paper you're after, look for "institutional login" or "login", and then search for the login details of your aggregator, and then for your institution. For example, most UK universities are part of the Shibboleth network, and get access via the UK Access Management Federation. So the login route is: - a link called something like institutional login on the journal page - a dropdown for UK Access Management Federation - a select-box to pick the specific university - university login and password

Hosting on servers other than the journal itself

Once you've done your usual search, and got the title of a potentially-interesting paper, then you can start looking for PDFs of it. First do a plain (not scholar) google search for the title, in double-quotes, and filetype:pdf. So if you were looking for the paper "Ninja Google skills", then you'd google for

"Ninja Google skills" filetype:pdf

If that doesn't work, check whether the paper is hosted on:

• the university homepages of any of the authors
• the preprint server at each of their universities
• any subject-wide preprint archive for your subject area

Or email the author on the paper who's nominated as first contact, asking them for a preprint copy of the paper. A couple of sentences about why you're interested, and how you'll use it, will help.

Remote access to the campus network

Some people with this problem will have one or more means to access their campus network (although you do not. This answer is to help others as well as you, and their circumstances will not be identical to yours); a quick chat with one of the librarians, and someone in the university IT support team, should help clarify:

• VPN into the campus network, then search; or
• SSH into the campus network, then search; or
• log in to the university library network web page, and search from there.

Failing all that, get creative

For some of the following, you'll need to check your university's terms and conditions, and official guidelines, to ensure that you play within the letter and the spirit of the rules:

• Set up an in-campus server process that will receive remotely-submitted requests, search for a paper, and download it, and make it available to you. You might do this via a web-page, email, or Dropbox.
• Share a Dropbox folder or similar with colleagues, and arrange that whenever one of you is on campus, and has a spare few minutes, you'll look for new requests in the shared folder, and if you find any, you'll download the paper and pop it in the Dropbox.
• Ask your supervisor / department head (as appropriate) to mention to a very senior administrator that the University is failing its staff and postgrads in a key area, and that some form of off-site access is just part of being a university in the 21st Century.