DE Descriptors

acid-rain in de

usa in de

The DE field lists subject terms, including regional and organism terms, that describe the content of the original document. Descriptors are drawn from a controlled as well as non-controlled vocabulary. Beginning with the 1997/12 update, data contain descriptors drawn from a controlled vocabulary only. Descriptors in data contained in the database prior to the 1997/12 update were drawn from a non-controlled vocabulary. From the 1997/12 update onward, any non-controlled subject terms assigned to data are available in the Keywords (KW) field.

The subject terms for this database are available in a textual format as well as a numeric format and are divided between two fields: the DE field and the Subject Description Codes (SC) field.

The DE field contains the most specific portion of the textual subject description; the numeric format of this specific classification appears in the Subject Description Codes (SC) field. The SC field also contains the broad portion of the textual subject description.

Descriptors are hyphenated for more efficient searching. The most efficient way to search a multi-word descriptor is as a hyphenated, "bound" phrase. Use without hyphens to enlarge your search. For example, acid in de retrieves records containing the descriptor terms amino-acid as well as acid-rain.

Use a hyphenated descriptor term to retrieve only records with occurrences of that exact term in the DE field. The search acid-rain in de retrieves only records indexed with the descriptor acid-rain.