X线管阳极靶面的材料一般采用
A.铜B.铝C.铅D.锡E.钨
参考答案:E
解析:X线管阳极靶面一般都是用高原子序数,高熔点的钨制成。
Everybody dreams. Some people think dreams can tell us about the future. Other people think dreams can tell us about ourselves. It’s like our (11) is talking to us.
Why are dreams (12) strange and hard to understand Some people think our brain uses (13) to talk to us. When we fly, swim, or fall down in our dreams, it has a (14) meaning. Lots of doctors help people (15) their dreams. They find that dreams tell us about our (16) and fears.
These days, many scientists (17) that dreams are very important. During the day, we have many (18) , and our brain receives a lot of information. When we dream, our brain (19) information that is not important, and puts the most important information into our (20) . As we learn more about the brain, we may find answers to our questions about dreams.
18().
A.experiences
B.dreams
C.mistakes
D.inventions
以下哪一项不属于继发性免疫缺陷病的病因
A.营养紊乱B.免疫抑制药C.肿瘤D.感染E.以上都不是