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The version in Hartshorne requires $X$ has at most a finite number of singular points and that $X$ projective (or equivalently, projective with a finite number of points removed). Do you have a more general form in mind? Also, your answer leads to another question (probably a dumb one that I cannot think of): curves are parametrizable, i.e. any segment on a curve is an image of a non-singular curve?
@Alison Miller: Could you please elaborate on what you said: "I learned the material out of Cassels and Frohlich mostly, but if I had to choose a book for someone interested in taking the local-first route I'd probably suggest Neukirch's /Algebraic Number Theory/ instead."? Why do you think Neukirch is a better choice?
Dear Dan: thanks for your comment. I agree that the question is somewhat vague. I am of course not asking for an isomorphism between them. I am just wondering if there is any relationship between them.
Yes. I'm myself doing it (undergrad). After reading Atiyah & MacDonald carefully (doing most exercises), Hartshorne is kind of a revelation of what all these commutative algebra is for. I can't believe I got -2 for this!