A few personal favorites from the list of alternatives to the popular Web of Science (WoS) index reviewed by Dana L. Roth (for details, see the RMIMR post or the full PDF file). In accordance with my personal research interests, these are the tools useful for literature and citation searches in Physics and Chemistry.

Web of Science
WoS and other databases from Thomson Scientific like ISI Web of Knowledge and the ISI journal impact factor are the tools that I personally use the most. One feature in WoS that I find increasingly useful is the system of citation alerts, whereby I am notified (by e-mail) every time a particular paper has been cited. By selectively “tagging” in this manner several important and specialized papers in a given field (e.g., immobilization of DNA on surfaces), the resulting alerts effectively notify me about most of the new papers on the subject. WoS also happens to provide the easiest way I know to check a Hirsch index.

Google Scholar
In a previous post I already mentioned the updated recent articles option, which attempts to enhance the relevance of the search results. Also very useful are direct links to PDF files of the papers hosted on authors’ websites, in addition to the publishers’ versions, of course.

Search results are displayed according to relevance based on the full text of each article, the article’s author, the publication source and how often it has been cited. Google Scholar also automatically analyses and extracts citations and presents them as separate results, even if the documents they refer to are not online.

Chemical Abstracts/SciFinder/SciFinder Scholar
Many chemists prefer SciFinder over WoS for searches in Chemistry journals, which is not surprising, because SciFinder is based on Chemical Abstracts (CA). On several occasions, SciFinder indeed helped me to find useful references on topics not covered by WoS, but in general the features are very similar between these two major subscription-based services.

[The ‘Get Citing References’] feature is similar to the ‘Times Cited’ link appearing on the full record for individual articles in WoS, which retrieves ‘exact’ citation matches but not citations with minor errors. There are some examples (J. Chem. Soc. Chem. Commun./Chem. Commun.) where citations in CA are algorithmically corrected. In contrast with CA, WoS also indexes articles from journals published in non-Roman alphabets which, by definition, are excluded from the CAplus file.

Scopus and Scirus
Scopus is a comprehensive subscription-based indexing service from Elsevier, which directly competes against SciFinder and WoS. Scirus, is the often-overlooked free version of the same index. Perhaps the most unique functionality of Scirus is an automatically-generated list of suggested search refinements, based on keyword frequency in the current set of results. This is a very convenient option for initial broad searches on an unfamiliar topic, because it helps to quickly identify the relevant search terms. Oddly enough, this option is only offered in Scirus, but not in Scopus. Update: see a more extended discussion of the differences between Scopus and Scirus in the comments to this post.

Scopus is a ‘work in progress’ that is based on a variety of sources which result in some interesting retrievals. A ‘Basic’ search for Marcus, R. A. as an author retrieves 56 items including an article authored by Marcus A. R. Several articles are listed twice, suggesting incomplete editing of overlapping sources for the article references. The results list displays the article title, authors source and the number of ‘cited by’ references in the
Scopus database.

CiteSeer is, perhaps, the most Web 2.0 tool from the list, with a lot of useful features, like citation analysis and direct links to PDFs. Unfortunately, it only indexes computer and information science literature. So for now I can only hope that a similar index will be created for other sciences, or at least some of the features will be adopted by the existing indices.