import re
p = re.compile(r'@article.*(?:\n(?![ \t]*}[ \t]*(?:\n|$)).*)*\s*}')
s = "@article{Fu_2007_ssr,\ndoi = {10.1016/j.surfrep.2007.07.001}\n}\n\n@article{Shibuya_2007_apl,\n doi = {10.1063/1.2816907}\n}"
print(p.findall(s))
aW1wb3J0IHJlCnAgPSByZS5jb21waWxlKHInQGFydGljbGUuKig/OlxuKD8hWyBcdF0qfVsgXHRdKig/OlxufCQpKS4qKSpccyp9JykKcyA9ICJAYXJ0aWNsZXtGdV8yMDA3X3NzcixcbmRvaSA9IHsxMC4xMDE2L2ouc3VyZnJlcC4yMDA3LjA3LjAwMX1cbn1cblxuQGFydGljbGV7U2hpYnV5YV8yMDA3X2FwbCxcbiBkb2kgPSB7MTAuMTA2My8xLjI4MTY5MDd9XG59IgpwcmludChwLmZpbmRhbGwocykp