General overview
For a general overview on Japanese standards and various resources see the description under Legal & Regulatory Issues » Standards.
Practical Information
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
An alternative is a website called kikakurui.com where JIS documentation is searchable by number. It is searchable, even if you do not read Japanese, and gives the English title of the standard (if present). It is however less complete (does not included drawings) than the JISC database.
Link: kikakurui.com
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)