While science textbooks and popular science texts are written for non-experts, scientific literature as a whole is written by experts for experts. In fact, experts in one subfield of physics will find it challenging to read and understand literature in another physics subfield. Texts are dense with information, and expect to spend hours reading through a small section of text. Read actively to increase your comprehension. Ask questions of the text before, during, and after you've read the text; draw connections between what you're learning and what you've already learned. It will also help to know what kind of text you are reading.
Rather than reading from beginning to end, recognize and use standard conventions of science articles to maximize your comprehension, reading in this order:
To aid comprehension, ask professors and peers questions about the text, but also use those opportunities to explain your current understanding of the content.
Follow this quick tutorial to learn