Previewable Chapters of Science Resources
The NSTA has created a space called the Learning Center. Registration is free (although paid members get more features.) By logging in, you get access to a number of lesson plans and free resources, as well as the opportunity to create a "library" of articles and previewable chapters you can download as PDFs to read on what ever device/platform you like. While some chapters have a cost, you can view the list of free offerings by using the "filter by price" option.
For example: here's a link to "The First Week" by Teirney and Dorroh. Simply log in, add it to your library, then you can download and read it.