题干

关于半导体,以下说法错误的是(       )

A:半导体的导电性能受温度、光照等外界因素的影响远比导体、绝缘体大得多

B:楼道自动开关中的光敏电阻就是半导体

C:盐水的浓度对导电性能有很大的影响,调节盐水的浓度就可以使盐水成为半导体

D:集成电路是用半导体材料制作的

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答案(点此获取答案解析)

C

同类题1

阅读下面的文字,完成下列小题。

    王羲之字逸少,司徒导之从子也。父旷,淮南太守。元帝之过江也,旷首创其议。羲之幼讷于言,人未之奇。及长,辩赡,以骨鲠称。尤善隶书,为古今之冠,论者称其笔势,以为飘若浮云,矫若惊龙。深为从伯敦、导所器重。时陈留阮裕有重名,亦目羲之与王承、王悦为王氏三少。时太尉郗鉴使门生求女婿于导,导令就东厢遍观子弟。门生归,谓鉴曰:“王氏诸少并佳,然闻信至,咸自矜持。惟一人在东床坦腹食,独若不闻。”鉴曰:“正此佳婿邪!”访之,乃羲之也,遂以女妻之。

    羲之雅好服食养性,不乐在京师,初渡浙江,便有终焉之志。会稽有佳山水,名士多居之,谢安未仕时亦居焉。孙绰、李充等皆以文义冠世,并筑室东土,与羲之同好。尝与同志宴集于会稽山阴之兰亭,羲之自为之序以申其志。

    尝诣门生家,见棐几滑净,因书之,真草相半。后为其父误刮去之,门生惊懊者累日。又尝在蕺山见一老姥持六角竹扇卖之羲之书其扇各为五字姥初有愠色因谓姥曰但言是王右军书以求百钱邪姥如其言人竞买之。他日,姥又持扇来,羲之笑而不答。其书为世所重,皆此类也。每自称“我书比钟繇,当抗行;比张芝草,犹当雁行也”。曾与人书云:“张芝临池学书,池水尽黑,使人耽之若是,未必后之也。

    时骠骑将军王述少有名誉,与羲之齐名,而羲之甚轻之,由是情好不协。述先为会稽,以母忧居郡境,羲之代述,止一吊,遂不重诣。述每闻角声,谓羲之当候己,辄洒扫而待之。如此者累年,而羲之竟不顾,述深以为恨。及述为扬州刺史,将就征,周行郡界,而不过羲之。及述蒙显授,羲之耻为之下,遣使诣阙,求分会稽为越州。行人失辞,大为时贤所笑。述后检察会稽郡,辩其刑政,主者疲于简对。羲之深耻之,遂称病去郡。

(选自《晋书·王羲之传》,有删改)

同类题5

阅读下列短文,从每题所给的四个选项中,选出最佳选项。

The health-care economy is filled with unusual and even unique economic relationships. One of the least understood involves the peculiar roles of producer or “provider” and purchaser or “consumer” in the typical doctor-patient relationship. In most sectors of the economy, it is the seller who attempts to attract a potential buyer with various appealing factors of price, quality, and use, and it is the buyer who makes the decision. Such condition, however, is not common in most of the health-care industry.

In the health-care industry, the doctor-patient relationship is the mirror image of the ordinary relationship between producer and consumer. Once an individual has chosen to see a physician — and even then there may be no real choice — it is the physician who usually makes all significant purchasing decisions: whether the patient should return “next Wednesday”, whether X-rays are needed, whether drugs should be prescribed, etc. It is rare that a patient will challenge such professional decisions or raise in advance questions about price, especially when the disease is regarded as serious.

This is particularly significant in relation to hospital care. The physician must certify the need for hospitalization, determine what procedures will be performed, and announce when the patient may be discharged. The patient may be consulted about some of the decisions, but in general it is the doctor's judgments that are final. Little wonder then that in the eye of the hospital it is the physician who is the real “consumer”. As a consequence, the medical staff represents the “power center” in hospital policy and decision-making, not the administration.

Although usually there are in this situation four identifiable participants— the physician, the hospital, the patient, and the payer (generally an insurance carrier or government) — the physician makes the essential decisions for all of them. The hospital becomes an extension of the physician; the payer generally meets most of the bills generated by the physician/hospital, and for the most part the patient plays a passive role. We estimate that about 75-80 percent of health-care choices are determined by physicians, not patients. For this reason, the economy directed at patients or the general is relatively ineffective.