If you're looking for great dividends to anchor your portfolio, the health care sector's a great place to start. Big pharma's top stocks offer top dividend yields with a punch -- but not all dividend stocks are made the same.

Merck (NYSE:MRK) sports a solid 3.6% dividend yield, but is this high-paying pick as good as it looks? The company has struggled with declining sales in recent quarters as patent expirations on high-profile drugs have taken some of the shine off Merck's luster. Singulair, Merck's top-selling drug as recently as the first half of last year, has seen its first-half sales in 2013 plummet by more than 75% year-over-year. That's the kind of loss that no investor likes to see, from those watching Merck's dividend to those interested in great growth opportunities.

But Merck isn't one of big pharma's best for no reason. Is this stock's strong dividend worth it for your portfolio? Below, Motley Fool contributor Dan Carroll takes you through how Merck's declining results have affected its appeal for income investors -- and whether you should still believe in this pharmaceutical giant.