Parallel Search is available for monthly subscription as well as day-pass access. In both cases, your subscription gives you full access to Parallel Search and the results it returns to you.
$19 for 24 hours of access (beginning at the time of payment)
Free: If you would like to give Parallel Search a try before subscribing, you can receive 3 free days of access by posting about Parallel Search on Facebook or Twitter (use the link on the Parallel Search subscription page to ensure you are credited for your post. Your free access begins as soon as the post has been made!).