简析19世纪社会民主主义的思想主张。

As one works with color in a practical, or experimental way, one is impressed by two apparently unrelated facts. Color as seen is a mobile, changeable thing (1) to a large extent on the relationship of the color (2) other colors (3) simultaneously. It is not (4) in its relation to the direct stimulus which (5) it. On the other hand, the properties of surfaces that give (6) to color do not seem to change greatly under a wide variety of illumination color, usually (but not always) looking much the same in artificial light as in daylight. Both of these effects seem to be (7) in large part to the mechanism of color (8) .

When the eye is (9) to a colored area, there is an immediate readjustment of the (10) of the eye to color in and around the area (11) . This readjustment does not promptly affect the color seen but usually does affect the next area to which the (12) is shifted. The longer the time of viewing, the higher the (13) , and the larger the area, the greater the effect will be (14) its persistence in the (15) viewing situation. As indicated by the work of Wright and Schouten, it appears that, at (16) for a first approximation, full adaptation takes place over (17) time if the adapting source is moderately bright and the eye has been in (18) darkness just previously. Also, (19) of the persistence of the effect if the eye is shifted around from one object to another, all of which are at similar brightness or have similar colors, the adaptation will tend to become (20) over the whole eye.

18（）

A.efficient

B.parallel

C.relative

D.respective

下列说法哪项不妥（）

A.DSA为介入治疗提供了及时的诊断

B.DSA能监测栓塞物的灌注

C.DSA能指导介入的操作

D.DSA为急诊病人的抢救和介入治疗赢得时间

E.DSA提高了血管显示的清晰度

简答购买过程模式的四个阶段

分层桥架安装，先安装上层，后安装下层。（）

社区服务的属性有哪些？