As part of our ongoing effort to provide new experimental tools on CISTI Lab, I've recently made available an SRU based API to CISTI that was developed by Chris Fenwick - who has since left CISTI for new pastures.
The API is built upon our base SOA webservices used to - amongst other things - to power CISTI Discover. Essentially, the API provides REST-based access to CISTI's article-level metadata databases. Being CISTI - these databases mostly contain data on Scientific, Technical and Medical articles primarily.
Chris made an awesome effort in a short period of time to make the service compliant with the SRU standard - but we're not making any guarantees as to its accuracy or completeness.
Give it a try if you're so inclined. Note that it's experimental - and could move/change in future.