Can I copy text from a scientific paper onto my website without directly referencing? 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.