How do I create gated content that is still crawled by Google for SEO?

Discussion:
I am building a gated content site where only registered members get access to full blog posts. I am not charging for membership, I just collect their emails and users would then use those emails to login to the site to see the content. Similar to a lot of the mainstream news sites like New York Times, The Atlantic or Washington Post.

What are you trying to achieve:
I want blog posts to be indexed by Google for SEO so it shows up in search results. But non-registered users would only see the first few paragraphs of the blog post, but to see the full blog post they would either need to login or register.

How do I accomplish this with Wix?

Additional information:
The site’s main business model is a newsletter business and I would be emailing people via something like MailChimp. So I’d prefer to only have one email registration system (MailChimp) rather than juggling two places where people would be registering (MailChimp & Wix)…but it’s not a showstopper.