A scientific journal somewhere between the National Geographics and Nature.  I find the level to be around a bachelor degree.  For your own field, the articles are too simple, for the other fields, the articles are very difficult.

Example: Zoology and Molecular Biology seem overly simplistic, Physics seem overly complicated.  Guess my field. -- AlexSchroeder

* http://sciam.com/

You can download articles for a fee at their archive:

* http://www.sciamarchive.com/