This is the 4877th most frequent Russian word.
исследовательских
"Research" or "investigative" (adjective form).
The word "исследовательскими" here is in its instrumental plural form, agreeing with "проектами", indicating projects concerned with research.
Этот университет известен своими исследовательскими проектами.
This university is known for its research projects.
The term "исследовательских" is in its genitive plural form, modifying "работ" to describe the type of works.
Мы изучали материалы на тему исследовательских работ.
We studied materials on the topic of research works.
"Исследовательских" here is an adjective in the genitive plural form, specifying the type of activities, i.e., those related to research.