For a general overview on Japanese standards and various resources see the description under Legal & Regulatory Issues » Standards.
The Japan Industrial Standards Committee (JISC), a body attached to METI and in charge of surveying and deliberating on industrial standards, offers searchable databases on its website. They are however in Japanese.
Link: JISC database Search page
The Japan Standards Association (JSA) used to be attached to METI as well, is presently independent foundation. It has a wide scope of activities with regard to Japanese and international standards. What makes the JSA interesting is that they sell English translations of JIS documentation and a searchable database in English to obtain information. The database is also useful to determine whether a particular JIS standard has equivalency with international standards such as ISO. (Example)