What level is your English, Jin? Maybe you are going beyond your current abilities and you need more practice with intermediate vocabulary. What kind of journals are you interested in reading? Scientific American is about science but it isn't overly technical. People like it because it explains science on a level most people can understand. It covers a variety of topics, so it can't be too technical about any of them. It's readability is about the level of first- or second-year university-level reading. Other journals, like "The Journal of Virology", have a lot more specialized vocabulary, but I think the grammar is easier. The difficulty here is that you must have knowledge about the science to understand these studies. Have you looked at National Geographic? Their website has a daily news section. The articles aren't as long or as detailed. This is suitable reading for a second year high school student. http://www.nationalgeographic.com/ You can find useful vocabulary in the Academic Word List. There are a number of sites that have exercises for these words. http://www.academicvocabularyexercises.com/ Keep a notebook of the new vocabulary. You have to decide if the word is useful or not.

"English has the richest and most varied vocabulary in the world," I completely disagree. Aside from grammar, English is one of the simplest languages. 英文是个非常肤浅的语言。比中文肤浅的多了。

You are reading academic and technically specialised material. The number of new words you encounter will be huge. Unfortunately, English has the richest and most varied vocabulary in the world, which in my view makes it the most difficult language to speak well. The answer? Short of being a(n educated) native speaker, there isn't one.

Many English speakers would have the same problem reading that kind of magazine! Such specialized publications will of course have many words that are unknown to people not involved or educated in the subject.

I think you need to master basic English grammar before going on to specialised material like that one.