Yes, you can select “deduplicate” when uploading references. You can select deduplication by: Title, Journal, and/or Year.
After uploading references, you will see a message indicating the total number of references uploaded. For example, the image below shows that out of 8,773 references, 8,759 were imported (14 duplicates were removed since I had selected deduplication by Title, Journal, and Year before uploading).
