Scientists obtain information from multiple sources, and as science tries to be as objective as possible, is important to use reliable sources.
Scientific journals are one of the main means where the scientists share their discoverings, so they are a reliable source, as well as books, another media where the information is collected.
Opinions are not a reliable source of information, as they are subjective and reflect the belief of the person giving the opinion, and are NEVER used by scientists to obtain information.
The Internet can be a great source of information, but this depends on the reliability of each website, as there are many useful resources for scientists available online, but also websites that don't have a reliable source to back up the information they are displaying.