I am writing a text for a website where I'm going to sell nootropics.
I was wondering if it is illegal/fraudulent to copy the text directly from the scientific papers onto my website without directly referencing the papers? (I will reference the papers at the end of the text).
You must quote copied text and cite it where it is quoted.
Citations at the end are vague and can be misleadingly general. Specifically, it can give the impression that the cited works support all of the text on the page as a whole. Specific citations are honest in that they clearly delimit what is being cited from the rest of the content of the page.
In the scientific community, doing such a thing is frowned upon. In short, one can do it, but the negatives clearly outweigh the positives.
If you're appealing to the scientific community with evidence, scientists like to vet the supporting evidence by reading the citations. If your appealing to non-scientists, your evidence can quickly get mistaken for opinion if not presented as supporting evidence.
Journalists sometimes hide their sources with the hackney phrase, "an anonymous source says". Even in journalistic circles, this is poor practice as it basically advertises that you can't find a person who's willing to say it with a proper citation. That, or you made up the statement and the fake source.
If you are concerned that the citation will break up the flow of the writing, then work the citation into the writing.
In 1996, Prof. John Doe at the University of Elbonia found that flatworms dance to the tune of a polka best.
The effort you spent writing this question exceeds the effort you would spend citing your source.
So just cite it more clearly and don't bother to worry about whether you can avoid it or not. There's no downside to citation. If you're worried about the space this would take up, then link to the bottom of your text instead of citing in some long form.
It is both unethical and illegal to copy text if you don't acknowledge the source. If the amount of text is substantial, copying usually is illegal even you do acknowledge the source.
If your operation is small, and you don't care about your reputation, you may be able to fly under the radar and not get caught. But first ask yourself the Dirty Harry question.
You can eather use Edwin Buck format or put the name of author and publication year in parantesies at the and of the sentence. or you can put a number at the end of the sentence that coinsides with the number on your reference list. in this way people can look where you are taking the sentence from and check it. as sessej said only references is vary vaigue and I just might want to check where a particular sentence or idea come from.
When you quote something exactly, turn it into a quotation and include a citation next to the quote. You're using words somebody else went to the effort to create, and you need to give the credit to them. A references list at the end is not specific enough to give the specific credit where it is due for the quotes you're including.
As someone who has written scientific papers, I would think it very unethical, fraudulent, and disingenuous to find text that I had written copy-pasted onto a website without a note that is was a direct quote and an attribution back to my paper. And as others have pointed out, it's illegal.
[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.
<sup>1</sup>for the text you're supporting by the citation and then have an ordered, or unordered, list at the end of the page with the numbered reference information. OTOH, if you're quoting a larger portion, it's normal to have something inline to indicate the source.