Measures, scales or instruments can be found in different ways. Research articles occasionally include the actual measure or scale used - sometimes at the end, as an appendix. Some measures are only available commercially - they must be purchased and might be restricted to qualified individuals.
The sources below are good places to start because they include the complete text of many measures.
Handbook of Clinical Rating Scales and Assessment in Psychiatry and Mental Health by 
Measures for Clinical Practice and Research: a Sourcebook