Perhaps you should try some spelling variations:
"article and nuclear material" » "article and nuclear materials", "article and nuclear matrix", "article and nuclear matter"
"article and nuclear medical" » "article and nuclear medicine"

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• The words AND, OR and NOT may confuse the search; try adding quotes: "((\"article and nuclear medical\") OR (\"article and nuclear material\"))".
• Removing quotes may allow a broader search: (( article and nuclear medical ) OR ( article and nuclear material )).
• Adding a wildcard symbol may retrieve word variants: (("article and nuclear medical") OR ("article and nuclear material"))*.