An abstract of each publication is available which makes it relatively easy to judge whether a publication is relevant to your project. Use the list of references of publications already available to you. Often, you can judge from the way some publication has been cited whether the publication is useful for you. Repeating this process will lead you backward in time. Another important and useful data base is the Science Citation Index .
Abstracts are sometimes available.
Apart from the possibility to search on title words, author, etc., it also has the possibility of the cited reference search . The latter is quite interesting. Suppose that you know of some key papers that are sufficiently old, then the cited reference search will present you the articles that have cited those papers and may report about progress on the specific topics. So, this search will lead you forward in time. An on-line data base that is quite interesting is the The NECI Scientific Literature Digital Library .