Major employers across the country, eager to curb fast-rising healthcare costs, are opening their own state-of-the-art health centers where doctors and nurses provide medical care to workers often just steps from their desks. The cost-cutting strategy has been embraced by dozens of companies—typically large employers that are self-insured and pay their own medical claims, including Walt Disney Co., Qualcomm Inc. and American Express Co. Many of the health centers are full-service medical offices equipped with exam rooms, X-ray machines and pharmacies. Some provide on-site appointments with dentists, dermatologists, psychiatrists and other specialists who treat life-threatening illnesses. Executives say providing in-house medical care keeps workers healthy and productive. But the clinics also help the bottom line by reducing absenteeism and slashing employers' medical bills for outside doctors and emergency rooms.