Searching the Identifying Codes Field

Enter Identifying Codes to search the following fields within a record:

  • PubMed ID
  • Date Revised
  • NLM Unique ID
  • ISSN (both print and electronic)
  • Molecular Sequence Databank Name
  • Molecular Sequence Databank Accession Number

Enter one or more codes connected with search operators (AND, OR, NOT). Enter complete codes or partial codes using wildcards.


Left- and Right-hand Truncation

Both left- and right-hand truncation are allowed when using wildcards (* $ ?) when searching for Identifying Codes. You must enter at least one characters after a wildcard when used at the beginning of a word.


Identifying Codes Examples

  • 12953261 finds the record with the PubMed ID 12953261.

  • *295326* finds all records that contain these six numbers in the PubMed ID number (for example, 21295326, 12953267, and 20295326) because both left-hand and right-hand truncation is used in the query.

  • 9416830 finds records with the NLM unique ID 9416830.

  • 0022-0345 finds records that have the ISSN 0022-0345.

  • 0022* finds records that have ISSNs beginning with 0022.

  • 1REK finds records containing the accession number 1REK from a databank of molecular sequence data.



The International Standard Serial Number is a unique eight-digit number that identifies periodical publications such as journals and electronic publications. If a journal has both a print ISSN and an electronic ISSN, then both display. The format is four numbers, a hyphen (-), three numbers, and then a check character that may be a number or X. Example: 1367-4803


PubMed ID and NLM Unique ID

The difference between the PubMed ID and the NLM Unique ID is that the PubMed ID is a unique identifier for the record. The NLM Unique ID is a unique identifier for the source journal. Searching by NLM Unique ID is like searching by ISSN.