The Altmetric Advanced search allows you to search for multiple identifiers at once. There is a list here of all the identifiers Altmetric supports.
To start you will need to click on the "Edit Search" button.
Once in the Advanced Search you can click on Add Scholarly Identifiers. This should open a new window.
You can then add up to 25,000 of any type of identifier tracked by Altmetric. You can search by multiple types of identifiers (e.g DOI and arXiv) or just by one (e.g PMID). The text at the bottom of the box will tell you how many identifiers you have. N.B the search box does not recognise duplicates, so if you add 10 identifiers but 2 are duplicates it will still say 10 identifiers.
You can now click Search to see the relevant search results.
You can now see the top segment of the Highlights that shows how many outputs Altmetric knows about and how many of those outputs have mentions.
Research outputs: Items in the Explorer to which Altmetric has tracked attention or for which we've created a transparent citation. We have more information here about transparent donuts.
Outputs with mentions: Items in the Explorer to which Altmetric has tracked attention
To suggest a journal to be tracked you can email firstname.lastname@example.org.