。
She has very little knowledge of science.
Literal
She [topic-は] a-little [only-しか] science [possessive-の] knowledge [subject-が] doesn't-exist.
しか~ない is a restrictive negative pattern: 'only X, nothing but X (and it's not enough).' Unlike だけ which is neutral, しか always pairs with a negative and implies the amount is insufficient. Here, her science knowledge is limited and notably so.