If you wrote a diploma yourself and are confident in your work, you should talk with the teacher and find out what material was unique. Some terms cannot be rewritten in your own words, as well as excerpts from journals or scientific papers. More unique are the formulas, conventional expressions, and lists of references.
It is also possible to validate the entire diploma through a special program for checking for plagiarism, such as Etkht anti-plagiarism, anti-plagiarism Advego. Checker looks for similarities of the texts and give the percentage of occurrences of non-unique phrases. Or analyze the text in the system Antiplagiat. By results of check in the system Antiplagiat it turns out the overall result of the borrowing and the original text as a percentage.
Before sending work to a teacher, you need to look for similar phrases in search engines such as Google, Yandex. For that copied pieces of text or articles, which Express the General sense of the content and contain the keys and are inserted into the search string. Gets a list of sites where you can find the entry of this text.