What is a DOI number in a journal article?

Related questions

1. How do you check how many times an article has been cited?
2. How do I find a citation for an article?
3. How do you determine the quality of a journal article?
4. How do I make Google Scholar private?
5. What is a Google Scholar profile?
6. Are journals articles?
7. Is ISBN the same as Doi?
8. How do I find the DOI of a journal article?
9. How do I create a Google Scholar profile?
10. How do I find the most cited articles?

Tags

1. #letters
2. #identifier
3. #object
4. #symbols
5. #citation
6. #document
7. #numbers
8. #string
9. #locate
10. #permanently
11. #article
12. #digital
13. #easily
14. #reader
15. #identify