REVERE-Revere police are investigating two armed robberies that occurred over the past weekend, including one that left a store clerk recovering from a stab wound.A city woman who just left her job at the Tedeschi’s at the corner of Beach Street and Winthrop Avenue was sliced once in the abdomen after she was unable to re-open the convenience store after closing time, police said.At about 12:20 a.m. Sunday, after the employee closed the store for the night, a man wielding a long knife allegedly approached her. She was ordered to re-open the store and open the ATM machine, but the victim told the suspect she didn’t have any keys, police said.At the same moment, the victim’s cell phone began ringing and that irritated the suspect, according to police.The victim reported the suspect then swung the knife at her, striking her once.Police are hoping a store surveillance tape might trigger leads as no arrests have been made.Another robbery was reported about two hours earlier at a gas station parking lot on Squire Road at the Malden city line, police said.The incident started when two people begging for money approached two other people in the parking lot. The pair gave the beggars a couple of bucks and went on their way, police said.The victims, on their way to catch a movie, were followed by the suspect who approached them again and demanded they hand over their wallets.The victims reported one of the suspects made a threatening motion as if to retrieve a weapon, but none was displayed.The suspects were described as men in their mid to late 20s.They were last seen getting into a red Ford Taurus, driven away by a third person, in the parking lot of The Squire Lounge.