Switch to Anvanced Search by clicking the "詳細検索" (Advanced/Detailed Search) tab. (You can switch back to Basic Search by clicking the "基本検索" tab to the left). 

Advanced Search allows you to combine multiple search words using "AND," "OR" or "NOT" operators. You can also set other search and sorting criteria (explained in boxes to follow). Also see JapanKnowledge's English guide page for more information (you may be prompted to log in to JapanKnowledge first): http://www.jkn21.com/contents/howto_e/onelook_shousai/shousai02.html

This function works the same across Basic and Advanced searches.

The right-hand side column allows you to choose a database/databases to include in your search. Databases can be selected one by one or by category by checking respective boxes. The screen capture below shows English translation for buttons and category headings. For English translation of each encyclopedia/dictionary/database, see the Contents page of this Libguide or go to JapanKnowledge's English content guide page  (You may be prompted to log in to JapanKnowledge first): http://www.jkn21.com/contents/intro_e/cont_top.html

Titles with an  icon next to them can be switched to the individual database mode by clicking the icon. Depending on the content type, the individual database page shows an advanced single database search screen (most encyclopedia and dictionaries) or the table of contents (most journals and e-books). 

In Advanced Search, you can set a "search scope" ("範囲") and "search condition" ("条件") for each search term. 

Search scope ("範囲")

Default is set to "見出し."

見出し: search headwords (entry titles) of encyclopedia and dictionary entries (including variants and derivative words)
別名: restrict search to variant names
派生語: restrict search to derivative words
タイトル: restrict search to article titles
索引: restrict search to indexes
全文: search full text of articles and entries including headlines

Search condition ("条件")

Default is set to "完全一致."

完全一致: exact match
前方一致: beginning of the word match
後方一致: end of the word match
部分一致: partial match

See JapanKnowledge's English guide page for the detailed explanation of scope and conditions (you may be prompted to log in to JapanKnowledge first): http://www.jkn21.com/contents/howto_e/onelook_shousai/shousai02.html