已知非零向量a,b,c满足a•b=a•c,则b与c的关系是( ) A.相等 B.共线

题型:选择题

问题:

已知非零向量
a
b
c
满足
a
b
=
a
c
,则
b
c
的关系是(  )
A.相等B.共线C.垂直D.不确定
考点:向量数量积的运算
题型:选择题

动物在生态系统中的重要作用是 [ ]

A.促进生态系统的物质循环

B.把水和二氧化碳等无机物合成有机物

C.分解动植物的尸体或残骸,把有机物转变为无机物

D.吸收空气中的二氧化碳

题型:选择题

东风4B型内燃机车两台冷却风扇的驱动采用静液压传动。

题型:选择题

FAT32文件管理系统比FATl6系统缺点是( )。

A.磁盘碎片少

B.文件操作速度慢

C.需长文件名

D.寻址能力低

题型:选择题

FOR the past two years in Silicon Valley, the centre of America’s technology industry, conference-goers have entertained themselves playing a guessing game: how many times will a speaker mention the phrase "long tail" It is usually a high number, thanks to the influence of the long tail theory, which was first developed by Chris Anderson, the editor of Wired magazine, in an article in 2004. Though technologists and bloggers chuckle at how every business presentation now has to have its long-tail section, most are envious of Mr Anderson, whose brainwave quickly became the most fashionable business idea around.

Whether a blockbuster film, a bestselling novel, or a chart-topping rap song, popular culture idolizes the hit. Companies devote themselves to creating them because the cost of distribution and the limits of shelf space in physical shops mean that profitability depends on a high volume of sales. But around the beginning of this century a group of internet companies realized that with endless shelves and a national or even international audience online they could offer a huge range of products—and make money at the same time.

The niche, the obscure and the specialist, Mr Anderson argues, will gain ground at the expense of the hit. As evidence, he points to a drop in the number of companies that traditionally calculate their revenue/sales ratio according to the 80/20 rule—where the top fifth of products contribute four-fifths of revenues. Ecast, a San Francisco digital jukebox company, found that 98% of its 10,000 albums sold at least one track every three months. Expressed in the language of statistics, the experiences of Ecast and other companies such as Amazon, an online bookseller, suggest that products down in the long tail of a statistical distribution, added together, can be highly profitable. The internet helps people find their way to relatively obscure material with recommendations and reviews by other people and (for those willing to have their artistic tastes predicted by a piece of software) computer programs which analyze past selections.

Long-tail enthusiasts argue that the whole of culture will benefit, not just commercial enterprises. Television, film and music are such bewitching media in their own right that many people are quite happy to watch and listen to what the mainstream provides. But if individuals have the opportunity to pick better, more ideally suited entertainment from a far wider selection, they will take it, according to the theory of the long tail. Some analysts reckon that entire populations might become happier and wiser once they have access to thousands of documentaries, independent films and sub-genres of every kind of music, instead of being subjected to what Mr Anderson calls the tyranny of lowest-common-denominator fare. That might be taking things a bit far. But the long tail is certainly one of the internet’s better gifts to humanity.

The 80/20 rule is used to()

A. prove the long tail theory

B. figure out financial ratio

C. select profitable products

D. design procedures

题型:选择题

患者男性,7l岁,上下颌牙列缺失,行全口义齿修复

临床上一般调整下列哪两个因素来达到前伸平衡()

A.切导斜度、补偿曲线曲度

B.牙尖斜度、髁导斜度

C.切导斜度、髁导斜度

D.牙尖斜度、定位平面斜度

E.切导斜度、定位平面斜度

更多题库