It's helpful to know that scientific information follows a pretty consistent "communication lifecycle" – use this knowledge to get an understanding of what kind of information you are likely to find about any given topic.
The "Lifecycle of Scientific Information" begins with an initial research idea - "what if?" or "why does that happen?" From that point, experiments explore the idea and the hypotheses developed by the investigator. Discussion with colleagues and presentations at conferences follow the initial results, and pre-print articles may be archived in digital repositories or published in "letters journals" or preprint journals.
Following the preprint and conference stage, articles are submitted for publication in scholarly, peer-reviewed journals. These articles typically undergo rigorous review by experts in the field before being accepted for publication.
In the months following publication, services that create indexes of journal contents, as well as services that index articles in various subjects, will include the new publication in their indexes (these indexes are frequently electronic databases of articles). These services provide access to other researchers to the information discovered by the original researcher, and will frequently touch off new areas of inquiry.
Between one and three years (usually) following publication, if the article is deemed important in its field, it may be included in a review article, which will synthesize recent, important research in a particular field to provide an overview of new discoveries, research trends, and the overall impact of current research.
Finally - usually several years after initial publication - information discovered during the initial research may be included in "common" or "accepted knowledge" sources like encyclopedias, dictionaries, and handbook.