First, it's "accept", not "believe in".
Second, it differs greatly according to country and scientific field.
You really can't be a biologist or geologist without accepting it. Of the scientists and engineers in the United States, only about 5% are creationists, according to a 1991 Gallup poll (Robinson 1995, Witham 1997). However, this number includes those working in fields not related to life origins (such as computer scientists, mechanical engineers, etc.). Taking into account only those working in the relevant fields of earth and life sciences, there are about 480,000 scientists, but only about 700 believe in "creation-science" or consider it a valid theory (Robinson 1995). This means that less than 0.15 percent of relevant scientists believe in creationism. And that is just in the United States, which has more creationists than any other industrialized country. In other countries, the number of relevant scientists who accept creationism drops to less than one tenth of 1 percent.