No, you cannot screw into end grain plywood. The fibers in the plywood are oriented perpendicular to the surface of the plywood, making it very difficult to drive a screw into the wood. Additionally, the glue that holds the layers of plywood together is not as strong at the edges of the sheets, so screws tend to pull out more easily. If you need to attach something to end grain plywood, try using nails or brads instead.