A year cannot be the only criterion in a search; it must always be used in the context of a query specifying (at least) an author, subject, region or free text. (If you are interested in everything published in a given year, choose the browse option at the top of this page.)
When the year of publication is not clear, we either deduce it from other information in the publication, thus , or make a guess, which produces [1994?]; both examples will appear if you search for 1994 publications. Rarely, publications are given more than one year of publication, as in 1994-1995. These cases will match your search if any of the possible years is in the range you specified.
Example 1:You just searched for "fertility" in the "United States" and got 1,671 hits. To restrict the search to publications in the nineties, you enter 1990 in the from field and 99 in the to field. You get 1020 hits. Since the listing is in reverse chronological order, you can focus on the most recent publications.