I found a 2013 article from geoscientists who had tested Google Scholar: “Literature searches with Google Scholar: Knowing what you are and are not getting”. Although the body of the paper states that their test phrase was “wildfire-related debris flows”, the data shows they actually tested Scholar with the keywords wildfire-related debris flows. They reportedly found that…
“free articles were available in PDF format for 88% of citations returned by Google Scholar. They were available from open-access journals or via links to organizational sites where authors had posted their publications.”
However if you actually look at their linked search-results data file, then the above statement needs additional clarification. Since it’s clear that paywall articles from Elsevier, Springer and the like, appearing in their Scholar results, were being counted toward those “free articles”. It turns out that many of these were “free” only via a DigiTop proxy overlay for Scholar that is, in the words of DigiTop, “available to USDA employees only”. Nice if you work under the U.S. Department of Agriculture umbrella, but it seems that those outside have to pay.
Does Google Scholar perhaps need to add some kind of “paywall box detector” to its scraper bots? Then perhaps something like [PDF] [-||-] could be added on the right-hand column of the Scholar results, to indicate a PDF that’s “available maybe” — but which will prove to have a paywall that needs to be either backed out from or negotiated? And perhaps [PDF] [-~-] could indicate a genuine direct link to a bona fide PDF file?
Anyway… this is what geoscientists are talking about when they refer to wildfire-related debris flows. Seems like it might be a geological process that intelligent farmers, hiker-campers, and treeline homesteaders around the world would like to learn some precise details about…
Giant mudslides, basically.
Incidentally, the same wildfire-related debris flows search in JURN needs to be tightened up just a little for strong results. Using wildfire-related “debris flows” works better, though the first six pages of good results do stray just a little (to pick up what seem to be three articles about prehistoric ‘dinosaur-era’ debris flow events). Yet even on this test JURN appears to be doing about twice as well as Google Scholar in terms of getting open articles, once Scholar’s ‘false-positive’ paywall PDFs from Elsevier & co. are subtracted from Scholar’s results.