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【简答题】

A quick look at an e-reader
New, High-Contrast(高对比度) E-Ink Screen
50% better contrast than any other e-reader. The clearest text and sharpest images.
Read in Bright Sunlight
Unlike LCD screens, its screen reads like real paper, with no glare. Read as easily in bright sunlight as in your living room.
Lighter Than a Paperback
Weighing only 8.5 ounces and 1/3 of an inch thick, it is lighter than a paperback and thinner than a magazine.
Holds 3,500 Books
We doubled its storage so you can carry up to 3,500 books.
Battery Life of Up to One Month
A single charge lasts up to one month with wireless off. Keeping wireless always on, it can go for up to three weeks without recharging.
Books in 60 Seconds
With fast, free wireless delivery, you can start reading books in less than 60 seconds. No computer required.
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Over 670,000 books, including 107 of 111 New York Times Best Sellers, plus audiobooks, periodicals and blogs. For non-U.S. customers, content availability varies.
Free, Out-of-Copyright Books
Over 1.8 million free, out-of-copyright, pre-1923 books are available such as Pride and Prejudice.
Low Book Prices
Over 550,000 books are $9.99 or less, including 73 New York Times Best Sellers of the present time.
Free Book Samples (样品)
Download and read first chapters for free before you decide to buy.
小题1:If you want to use the e-reader longer, you should ______.A.charge it frequentlyB.keep wireless offC.use it in bright sunlightD.read in a quiet room小题2:Which of the following can best fill in the blank in the text?A.Large selection. B.Excellent service.C.Reasonable prices.D.Interesting content.小题3:What is this text,mainly about?A.What an e-reader is.B.Who needs an e-reader.C.How to use an e-reader.D.The advantages of an e-reader.

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【单选题】影响照片对比度的因素不包括()

A.
胶片γ值
B.
摄影距离
C.
X线量
D.
被照体因素
E.
X线管电压

【单选题】有关照片对比度的叙述,错误的是()

A.
使用r值大的胶片获得照片对比度大
B.
使用增感屏可提高照片对比度
C.
高千伏摄影可提高照片的对比度
D.
降低散射线可提高照片对比度
E.
冲洗技术可直接影响照片对比度

【单选题】X线对比度是指

A.
胶片对X线对比度的放大能力
B.
照片上组织影像的最大密度差
C.
X线透过被照体后,形成的X线强度的差异
D.
与X线相关的所有对比度的概念的总称
E.
X线对比度与照片对比度是完全相同的概念

【单选题】CT低对比度测试的目的是()

A.
观察空间分辨率
B.
观察密度分辨率
C.
检测层厚的准确性
D.
检测CT值的准确性
E.
测量噪声的大小

【单选题】有关X线对比度的叙述,错误的是

A.
X线对比度也称射线对比度
B.
X线对比度是按指数规律变化
C.
组织密度差异影响X线对比度
D.
照片上相邻组织影像密度差称X线对比度
E.
组织对X线吸收系数之差是形成X线对比度的原因

【单选题】影响照片对比度的因素不包括()

A.
胶片γ值
B.
摄影距离
C.
X线量
D.
被照体因素
E.
X线管电压

【单选题】影响照片对比度的因素不包括

A.
X线量
B.
X线质
C.
放大率
D.
胶片γ值
E.
使用增感屏