【解决办法】加载部分图层的用法和二维类似；
下面是示例代码
var imageryLayers = viewer.imageryLayers;
//利用服务url创建SuperMapImageryProvider实例
var provider_mec = new Cesium.SuperMapImageryProvider({
url:'http://localhost:8090/iserver/services/map-nanning/rest/maps/2d@nanning',
layersID:"[0]"
});
imageryLayers.addImageryProvider(provider_mec);
