[As suggested in a comment, I am adding a note that the following response is based on standards in the United States as far as I understand them. My experience is as an academic who has had to understand these issues in the course of my work. Much of this may be common throughout the world, but please confirm for the relevant jurisdictions.]
The question asks if it is legal "to copy the text" (emphasis mine). By that, I assume the questioner wants to copy the full (or nearly full) text of the original article.
No, you can't do this, even if you cite the source. Unless the source explicitly puts the article into the public domain (most journals do not do so).
You can quote (if you cite) parts of the article under Fair Use, but you cannot quote it substantially. Journals usually make money by charging a subscription or per-article access fees. To preserve this revenue stream, they do not want their articles to be available on the internet. In fact, even the original authors are usually barred from publishing their own articles on their web sites (depending on the journal and practices of the particular branch of academia), though they can share those articles with individuals if requested.
In the questioner's case, the content is probably from a clinical or biological journal. It's not likely these articles would be in the public domain (Math and Physics are more lenient), and since this would be using the text for commercial gain, you are in a poor spot. Large publishers would likely be pretty aggressive in enforcing copyright in such cases.
I can understand how coming from outside academia it is tempting to think that science is a free-for-all of information to benefit the public domain. There are indeed efforts to move in this direction. But in reality, academia is a pretty big business, and journals are often (not always) commercial ventures. A notable counterexample to all of this is PLOS. If your article happens to come from this journal, you might be in luck.