@media (min-width: 700px) {
    .Imagen1 {
        content: url("../PROPLANbig.jpg");
    }

    .Imagen2 {
        content: url("../MARSbig.jpg");
    }

    .Imagen3 {
        content: url("../LAVECCSBig.jpg");
    }

    .Imagen4 {
        content: url("../AMONCOVETbig.jpg");
    }

    .Imagen5 {
        content: url("../BOEHRINGERbig.jpg");
    }

    .Imagen6 {
        content: url("../SANJERONIMObig.jpg");
    }
}

@media (max-width: 700px) {
    .Imagen1 {
        content: url("../PROPLANsmall.jpg");
    }

    .Imagen2 {
        content: url("../MARSsmall.jpg");
    }

    .Imagen3 {
        content: url("../LAVECCSsmall.jpg");
    }

    .Imagen4 {
        content: url("../AMONCOVETsmall.jpg");
    }

    .Imagen5 {
        content: url("../BOEHRINGERsmall.jpg");
    }

    .Imagen6 {
        content: url("../SANJERONIMOsmall.jpg");
    }
}