单选题视网膜上分布的感光细胞几乎全是视锥细胞的区域在

单选题No doll outshines Barbie's celebrity. If all the Barbies and her family members-Skipper, Francie and the rest-sold since 1959 were placed head to toe, they would circle the Earth more than seven times. And sales are sure to boom in 2009, when the fashion doll celebrates her 50th birthday on March 9th. Barbie will star at an array of global events honouring her milestone, possibly including a glitzy affair at New York's Fashion Week in February (most of the world's top fashion designers, from Givenchy to Alexander McQueen, have designed haute couture for her). On her birthday, Mattel, the company that makes her, will launch a souvenir doll honouring the original Barbie in her black-and-white striped swimsuit and perfect ponytail. It will be available for purchase only that one day. Another Golden Anniversary doll targets collectors. Barbie fans have planned hundreds of events, including the National Barbie Doll Collectors Convention in Washington, DC, which is already sold out. When Ruth Handler created Barbie in 1959, a post-war culture and economy thrived but girls still played with baby dolls. These toys limited the imagination; so Handler introduced Barbie the Teen-Age Fashion Model, named after her daughter, Barbara. Jackie Kennedy soon sashayed onto the world stage and Barbie already had a wardrobe fit for a first lady. Barbie bestowed on girls the opportunity to dream beyond suburbia, even if Ken at times tagged along. Barbie entranced Europe in 1961 and now sells in 150 countries. Every second three Barbies are sold around the world. Her careers are myriad-model, astronaut, Olympic swimmer, palaeontologist and rock star, along with 100 others, including president. Like any political candidate, controversy hit Barbie in 1992 when Teen Talk Barbie said "Math class is tough" and girls' education became a national issue. She has been banned (in Saudi Arabia), tortured (by pre-teen girls, according to researchers at the University of Bath's School of Management) and fattened (in 1997). Feminists continue to bash Barbie, claiming that her beauty and curves treat women as objects. But others see her as a pioneer trendsetter, crashing the glass ceiling long before Hillary Clinton cracked it. High-tech entertainment now attracts girls and Barbie also faces fierce competition from various copycats including the edgier, but less glare, Bratz dolls. The Bratz suffered a setback in 2008．Mattel sued MGA Entertainment, Bratz's producer, for copyright infringement. A judge awarded Mattel $100 million in damages. Mattel has smartly ensured that Barbie products reflect current trends. Through two Barbie websites, girls can design clothes, network and play games. The pink Barbie brand is licensed for products from DVDs and MP3 players to bicycles and even 24-carat gold and crystal jewellery. Barbie collectors fuel an entire global industry on eBay and at conventions. To entice collectors, Mattel regularly releases pricey limited-edition dolls based on characters in films and popular culture. Industry analysts believe Barbie will remain a bestselling and lasting icon regardless of competition. "Barbie's been out in the world and had fun, and she's ready for her second career," says Rachel Weingarten, a pop culture expert. "I don't see her adopting five children from five different countries, but I could see Barbie with a conscience, activist Barbie. " At 50 Barbie will also be a marvel of plastic surgery and eternal youth. And she still knows how to party.

单选题按控制论的观点，起纠正、减弱控制信息作用的是

单选题不属于肾分泌的物质是

单选题肾髓质渗透压梯度的维持主要依靠( ) A．小叶间动脉 B．弓形动脉 C．小叶间静脉 D．直小血管 E．弓形静脉

单选题伤寒病的潜伏期中，伤寒杆菌寄生、繁殖的细胞是

单选题原尿中葡萄糖的含量( ) A．高于血浆 B．低于血浆 C．与血浆的相同 D．低于终尿 E．与血浆不同

单选题在下列选项中，符合IgA肾病镜下特征的病变是

单选题下列选项中属于生理性钙化的是

单选题下列不符合伤寒临床表现的是

单选题A．髓袢升支和降支 B．近端小管和远端小管C．近端小管和集合管 D．远端小管和集合管

单选题参与形成黏液-碳酸氢盐屏障的成分是A．Cl-B．K+C．Na+D．

单选题 不称为玻璃样变的病变是 ( ) A、Aschoff小体 B、Councilman小体 C、Mallory小体 D、Rusell小体 E、Negri小体

单选题在消化期不能抑制胃液分泌的因素是

单选题骨骼肌细胞中横管的主要作用是

单选题近髓肾单位的主要功能是( ) A．释放肾素 B．排泄NaCl C．释放ADH D．浓缩和稀释尿液 E．分泌K+

单选题最常引起肺源性心脏病的是

单选题人类第二级记忆的机制可能与下列哪项有关( ) A．海马环路的活动 B．脑内蛋白质的合成 C．新的突触的建立 D．神经元作用的后作用 E．脂肪酸的合成

单选题男性，25岁，体重60kg。因高位小肠瘘1天入院，入院后经颈内静脉插管滴入肠外营养液，2周后突然出现寒战、高热．无咳嗽、咳痰，腹部无压痛和反跳痛。

单选题 引起硅肺病变最为严重的硅尘微粒直径是： A、＞5m B、＜5m C、1~2m D、＜1m E、＞2m