当磁极对为2对时,对四极三相异步电动机而言,其旋转磁场的转速等于()r/min。
A.3000
B.1500
C.1000
D.750
参考答案:B
女性,25岁,低热,便秘腹泻交替3年。查体:右下腹5cmx5cm肿块,质中等,较固定,轻压痛。
最具诊断意义的检查是()
A.血沉
B.血常规
C.结肠镜检查
D.X线钡剂透视
E.诊断性腹腔穿刺
When I was young, there was an amazing publication called The Whole Earth Catalog, which was one of the bibles of my generation. It was created by a fellow named Stewart Brand not far from here in Menlo Park, and he brought it to life with his poetic touch. This was in the late 1960′s, before personal computers and desktop publishing, so it was all made with typewriters, scissors, and Polaroid cameras. It was sort of like Google in paperback form, 35 years before Google came along: it was idealistic, and overflowing with neat tools and great notions. Stewart and his team put out several issues of The Whole Earth Catalog, and then when it had run its course, they put out a final issue. It was the mid-1970s, and I was your age. On the back cover of their final issue was a photograph of an early morning country road, the kind you might find yourself hitchhiking on if you were so adventurous. Beneath it were the words: "Stay Hungry. Stay Foolish." It was their farewell message as they signed off. Stay Hungry. Stay Foolish. And I have always wished that for myself. And now, as you graduate to begin anew, I wish that for you.