This can sometimes cause frustration when you're trying to isolate records very carefully. It is not designed to be a highly precise search tool for expert searchers. SciFinder's topic search was designed to maximize retrieval, so some of its imprecision is intentional. SciFinder uses a proprietary, complex (and somewhat mysterious) natural language query algorithm that breaks your query into a set of discrete concepts, searches them against the database indexes, and then presents you with a selection of result options.
The Explore by Research Topic option presents a single text box that looks like Google's, but SciFinder's search algorithm functions very differently from those of standard web search-engines.
