For evaluation purposes, you can use the trial version. Download the distribution from Doctor Web's site at download.drweb.com/demoreq. The period of a demo license is 30 days.
You can also use the free scanner Dr.Web Light for OS X. The scanner incorporates state-of-the-art technologies to detect and eliminate viruses. You can use it to check your system, whenever you need to. However, Dr.Web for OS X is a more feature-packed product as compared with Dr.Web Light for OS X. It includes Dr.Web SpIDer Guard file monitor to scan files in real time.