Where to get Review articles? I am wondering about review articles. Where to get them? Google scholar or Researchgate or other such sites does not provide any option to separate out the review articles. It is very hard to look into all the articles and separate out.

Is there any way to separate out the review articles only?
If you're looking for biomedical reviews, Pubmed allows you to filter reviews after searching for keywords. This option is available in the sidebar, under "Article Types". Depending on your field, there might be other search engines that allow this type of filtering.

On Google Scholar, you can refine your searches by using Google search operators. For example, if you search for insubject:"obstructive lung disease" intext:"review", Google Scholar will return results that have "Obstructive Lung Disease" in the title and the word "review" somewhere in the text.