E. I. du Pont de Nemours & Co., the nation's largest chemicals company, drew mixed reviews yesterday for its $7 billion friendly takeover of Conoco.

"For the short term, it hurts the shareholder," said Paul Miles, a chemicals analyst with the New York securities firm C.J. Lawrence. "Energy stocks are out of favor, at least temporarily, and that's going to dilute Du Pont's earnings."

On the other hand, "there will be some synergy," said Paul C. Christopherson, a chemicals analyst with Kidder, Peabody & Co. Christopherson said the takeover would give Du Pont the oil and gas which it needs to feed its voracious chemicals production and which it didn't have during the oil shock of 1974.

Du Pont, based in Wilmington, Del., was the nation's 15th-largest industrial corporation in 1980, ranking just after its merger partner Conoco with $13.7 billion in sales. Net income for 1980 came to $716 million, and assets came to $9.6 billion at the end of the year.

Raw chemicals for industrial production have traditionally been the company's dominant product but have declined in importance in recent years. Last year, the chemicals branch accounted for 16 percent of sales as well as income, down from 19 percent of sales and 32 percent of earnings in 1976.

Most important for the company's income have been the products it makes from its sizable raw chemical production. Synthetic fibers accounted for 33 percent of sales and 27 percent of earnings in 1980, and plastics for 22 percent of sales and 21 percent of earnings. Such specialty products as electronics, photographic supplies and pharmaceuticals provided 29 percent of sales and 36 percent of net income for the year.

In recent years Du Pont has diversified into fields unrelated to chemicals production, buying the Remington Arms Co. in early 1980 and agreeing to acquire New England Nuclear Corp.

In a statement announcing the takeover agreement, Du Pont chairman Edward G. Jefferson said, "The Conoco merger will not alter Du Pont's, or Conoco's existing strategic directions," pointing especially to Du Pont's life sciences research. But analysts emphasized that the combined company will obtain more than half its sales from oil and gas.