问题 单项选择题

首关消除(首过效应)主要是指

A.舌下含化的药物,自口腔黏膜吸收后,经肝代谢药物降低
B.肌内注射吸收后,经肝药酶代谢,血中药物浓度下降
C.药物口服后胃酸破坏,使吸收入血的药量减少
D.药物口服吸收后经肝代谢而进入体循环的药量减少
E.静脉给药后通过血-脑屏障减少

答案

参考答案:D

单项选择题
阅读理解

     At the beginning of the twentieth century,many people thought that the American family

was falling apart.A century later,we know that this was not the case.However,although the

family is still alive in the United States,its size and shape were very different from 100 years

ago.

     In the late 1800s and early 1900s,there were mainly two types of families in the United

States:the extended and the nuclear.The extended family usually includes grandparents,

parents,and children living under the same roof.The nuclear family consists of only parents

and children.

     Today there are many different kinds of families.Some people live in “traditional” families,

that is,a stay?home mother,a working father,and their own biological children.Others live in

two?paycheck families,single-parent families,adoptive or foster families,blended families

(where men and women who were married before marry again and combine the children

from previous marriages into the new families),child less families,and so on.

     What caused the structure of the family to change?In the early 1900s the birthrate began

to fall and the divorce rate began to rise.Women were suddenly choosing to go to college

and take jobs outside the home.In the 1930s and 1940s,many families faced serious financial,

or money problems during the Great Depression,when many people lost their jobs.During

World War Ⅱ(1939-1945),5 million women were left alone to take care of their homes and

their children.Because many men were at war,thousands of these “war widows” had to go to

work outside their home.

     During the next ten years,the situation changed.There were fewer divorces,and people

married at a younger age and had more children than the previous generation.It was unusual

for a mother to work outside the home during the years whenher children were growing up.

Families began leaving cities and moving into single-family homes in the suburbs.The traditional

family seemed to be returning.

     In the years between 1960s and 1990s,there were many important changes in the structure

of the family.From the 1960s to the early 1970s,the divorce rate doubled and the birthrate fell

by half.The number of single-parent families tripled,and the number of couples living together

without ?being? married doubled again.In fact,the single?parent household,once unusual,has

replaced the “traditional” family as the typical family in the States.If we can judge from history,

however,this will probably change again in the twenty-first century.

The Changes of the American Family