AAAS

Prestigious scientific journal of the American Association for the Advancement of Science (AAAS)
Science, with the impact factor (ISI) higher in their field, offers a scientific portal with multimedia, scientific events, resources for teaching, etc.
AAAS -- the American Association for the Advancement of Science -- is Science publisher, and a leading voice for the interests of scientists worldwide. It is the world's largest general-science society; through its primary membership and its affiliations with some 262 scientific societies and academies, it serves 10 million individuals. The organization's mission, simply stated, is to "advance science and serve society". This it does not only through publication of Science, but through annual meetings, public outreach, activities to boost international scientific cooperation and sustainable development, policy advocacy, educational programs, press relations, and efforts to boost the public understanding of -- and appreciation of -- the scientific enterprise. 

The webpage direction is: http://www.sciencemag.org/search.dtl