PubMed can provide at least two flavors of "tags". 1) The author-supplied keywords are always in the record if the publisher includes them in the metadata. 2) Journals indexed in Medline will also eventually receive indexer-assigned MeSH terms for their article records. 3) The NLM allows some journals (JAMA, New England Journal of Medicine) to include preassigned MeSH terms -- these are available with new PubMed records. (The preassigned MeSH terms may change or expand after review by NLM indexers.)
The NLM has long allowed licensees to access the master database to collect updates (MeSH terms, volume, issue, pagination metadata) and a few years ago eliminated the annual license requirement. However, at least once a year, every year, large or small changes to the NLM system have required changes to user automated query systems that search for updated metadata. These system changes are usually announced long in advance with an effective change date. However, some "enhancements" are implemented without notice and these can affect automated user queries. (For example, although not relevant to Zotero users, there have been two separate recent changes to how author affiliations are handled. There have been a series of unannounced changes to article relatedness pointers -- comment on this article in; this item is a comment on; article erratum at; etc.)
The recommendation to re-import and merge will always work no matter what NLM system changes occur.
Is there a way to automagically re-import a collection of papers? I am at about 2K citations total right now, so doing it one at a time by hand is sort of a non-starterl Thanks!
Is it your desire to refresh your ahead-of-print records with volume, issue, pagination metadata? Some other purpose? are you asking about PubMed as the import source, other specific sources, or in general? Do your Zotero records have PMIDs or DOIs?
edit: the short answer is that at the current time there isn't a shortcut to updating metadata automatically.
Only Medline articles have MeSH terms. Other items in PubMed may have author-assigned (rarely editor-assigned) keywords. Articles from Medline journals can be added to the database (days or weeks) before the indexing with MeSH terms is complete. MeSH terms aren't assigned to articles in PubMed that are not from Medline journals. These PubMed articles will have complete keywords at the time they are added to the database. Many articles in PubMed do not have metadata that includes keywords. I find that in many or most cases author-assigned keywords are less useful for finding the article in a database query than doing a text-word search for words in the title or abstract.
That said, I look forward to Zotero adding a "fetch missing MeSH" tool even if it is entirely separate from a tool to fetch missing volume, issue, and pagination metadata.
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Pubmed keywords for many articles are first updated a certain time after publication. Hence You will have a lot of articles with no autotags
The NLM has long allowed licensees to access the master database to collect updates (MeSH terms, volume, issue, pagination metadata) and a few years ago eliminated the annual license requirement. However, at least once a year, every year, large or small changes to the NLM system have required changes to user automated query systems that search for updated metadata. These system changes are usually announced long in advance with an effective change date. However, some "enhancements" are implemented without notice and these can affect automated user queries. (For example, although not relevant to Zotero users, there have been two separate recent changes to how author affiliations are handled. There have been a series of unannounced changes to article relatedness pointers -- comment on this article in; this item is a comment on; article erratum at; etc.)
The recommendation to re-import and merge will always work no matter what NLM system changes occur.
edit: the short answer is that at the current time there isn't a shortcut to updating metadata automatically.
That said, I look forward to Zotero adding a "fetch missing MeSH" tool even if it is entirely separate from a tool to fetch missing volume, issue, and pagination metadata.