Those people who think they know everything are a great annoyance to those of us who do.

Isaac Asimov (1920-1992) Russian-American author, polymath, biochemist

(Spurious)

Sometimes quoted without the initial "Those".

The citationless attribution of this quip to Asimov cannot be traced back further than 2001, several years after his death. The earliest version found is a filler item in The Saturday Evening Post (6 May 1961), attributed to humor columnist Harold Coffin: "The fellow who thinks he knows it all is especially annoying to those of us who do."

More discussion here: The Fellow Who Thinks He Knows It All Is Especially Annoying To Those of Us Who Do – Quote Investigator.