问题 问答题 简答题

射极输出器有哪些特点?

答案

参考答案:射极输出器的特点是:输入电阻大,输出电阻小,输出电压与输入入电压大小接近相等、相位相同,电压放大倍数近似为1。

阅读理解与欣赏

黄果树瀑布

       黄果树瀑布,一部大自然的杰作。车到黄果树风景区,便闻一阵“哗哗”之声自远处飘来,若微风拂过树梢,渐近渐响,最后潮水般涌漫过来,盖过了人喧马啸,天地间只存下一片奔泻的水声了。     

       透过树隙,便见一条白帘挂在岩壁上,上面折为三叠,似一阔幅白绢正从机杼上吐泻而下,那“哗哗”水声合成了千万架织布机的大合奏,响遏行云。     

       我们去时,正遇上枯水季节,瀑布的水势并不宏大,远不如徐霞客在游记中所描写的那般摄人心魄。所以游者甚为寥落,连街上的不少店铺都早早关门打烊了。据当地人介绍,盛水季节,瀑水激出的水花雨雾腾空而上,随风飘飞,漫天浮游,高迭数百米,落于瀑布右侧高岩上的黄果树小镇,造成“银雨洒金街”的奇景。可惜我们去得不是时候,无缘一睹其壮观,留下了一点遗憾。      

       黄果树瀑布落在一片群山环抱的谷地,我们自西面顺着石阶下行,山径寂寥无人,“哗哗”的瀑布声在山谷间震荡着、回响着,似千百架低音提琴在奏鸣、在轰响。     

       至谷底,我们坐在水边的一块岩石上,隔着一口小小的绿潭,那一幅白帘般的瀑布,仿佛一伸手便可撩过来拭脸似的,它跃入涧底激起的烟雾般的水珠,直扑到我们脸上,沁凉沁凉的。黄果树瀑布虽不如庐山瀑布挂得那么长,但远比它宽阔,所以气势十分雄壮。当年徐霞客描写道:“上溪悬捣,万练飞空,溪上石如莲叶下覆,中剜三门,水由叶上漫顶而下。”描写得准确形象,令人叹服。      

       瀑布如雷轰鸣,山回谷应,我们仿佛置身于圆形乐池中,四周乐声奏鸣,人若浮身于一片声浪,每个细胞都灌满了活力,让人真正感受到大自然的伟大与恢宏。

       我们久坐岩上,任沁凉的飞珠扑上火热的脸庞,沾湿薄薄的衣衫。我们聆听着訇然作响的瀑声,只觉得自己的胸臆在扩展,似张开的山谷,那瀑布便直跃而进,挟来大自然生生不息的活力,回荡着大自然纯正清脆的音响。     

       离开潭边,我们循着石径登上溪旁的一个平台。绿树掩映间,有一座徐霞客塑像,他正遥对瀑布,作凝神谛听状,他完全沉醉了,如痴,如迷。此时此地此刻, 我们也完全沉醉了,如痴,如迷。 

1.查字典小能手。

   “訇”字用部首查字法应先查部首(    ),再查 (    )画,读音是(    )。“訇然”一词的意思是 (         )。 

2.用“        ”画出文中的一个比喻句。 

3.文章第____自然段都是描写瀑布声音的。 

4.作者是从         和____两个角度来写黄果树瀑布的。

填空题

Holidays are special times of (1) from work and other routines. Holidays are often times for celebration, (2) , eating, drinking, travel, and family (3) . In most cultures the scheduling of holidays originally was related to the (4) , the (5) cycle, and (6) . Christmas, December 25, celebrates the (7) of Jesus, but it is not actually known whether Jesus was (8) in the wintertime Over the years Christmas has come to symbolize goodwill and (9) for both Christians and non-Christians, and the (10) of Christmas threatens to replace generosity with greed. Other important holidays in America are Valentine’s Day, St. Patrick’s Day, April Fools’ Day, and (11) . On Valentine’s Day, people give cards, chocolates, flowers, and kisses to their (12) and sweethearts. During Easter Week in late March or early April, Christians remember the death and (13) of Jesus. Although not actually a holiday and has no religious (14) , April Fools’ Day, celebrated on April 1, is a day when people play embarrassing (15) on their fiends and (16) and even on their teachers. In (17) , Labor Day is celebrated on May 1, whereas in (18) and the United States, labor and laborers are honored by a (19) holiday on the first (20) in September.

Holidays are special times of (1) from work and other routines. Holidays are often times for celebration, (2) , eating, drinking, travel, and family (3) . In most cultures the scheduling of holidays originally was related to the (4) , the (5) cycle, and (6) . Christmas, December 25, celebrates the (7) of Jesus, but it is not actually known whether Jesus was (8) in the wintertime Over the years Christmas has come to symbolize goodwill and (9) for both Christians and non-Christians, and the (10) of Christmas threatens to replace generosity with greed. Other important holidays in America are Valentine’s Day, St. Patrick’s Day, April Fools’ Day, and (11) . On Valentine’s Day, people give cards, chocolates, flowers, and kisses to their (12) and sweethearts. During Easter Week in late March or early April, Christians remember the death and (13) of Jesus. Although not actually a holiday and has no religious (14) , April Fools’ Day, celebrated on April 1, is a day when people play embarrassing (15) on their fiends and (16) and even on their teachers. In (17) , Labor Day is celebrated on May 1, whereas in (18) and the United States, labor and laborers are honored by a (19) holiday on the first (20) in September.