双语有声阅读：民间文化

Folk Cultures A folk culture is a small isolated, cohesive, conservative, nearly self-sufficient group that is homogeneous in custom and race with a strong family or clan structure and highly developed rituals. Order is maintained through sanctions b

双语有声阅读：睡眠的进化

Evolution of Sleep Sleep is very ancient. In the electroencephalographic sense we share it with all the primates and almost all the other mammals and birds: it may extend back as far as the reptiles. There is some evidence that the two types of sleep

双语有声阅读：进化与轮子

进化与轮子 从前，研究自然界没有轮子的进化论生物学家都同意不能用无此需要来解释这种现象：轮子对于动物会像对于我们人类一样有好处。 生物学家们推论，动物没有进化出轮子是由下述

双语有声阅读：电

Electricity The modern age is an age of electricity. People are so used to electric lights, radio, televisions, and telephones that it is hard to imagine what life would be like without them. When there is a power failure, people grope about in flick

双语有声阅读：创造颜色

Creating Colors There are two ways to create colors in a photograph. One method, called additive, starts with three basic colors and adds them together to produce some other colors. The second method, called subtractive, starts with white light (a mi

双语有声阅读：收藏品

Collectibles Collectibles have been a part of almost every culture since ancient times. Whereas some objects have been collected for their usefulness, others have been selected for their aesthetic beauty alone. In the United States, the kinds of coll

双语有声阅读：火力发电厂

Coal-fired Power Plants The invention of the incandescent light bulb by Thomas A. Edison in 1879 created a demand for a cheap, readily available fuel with which to generate large amounts of electric power. Coal seemed to fit the bill, and it fueled t

双语有声阅读：感冒与年龄

Colds and Age A critical factor that plays a part in susceptibility to colds is age. A study done by the University of ichigan School of Public Health revealed particulars that seem to hold true for the general population. Infants are the most cold r

双语有声阅读：黑猩猩

Chimpanzee The most striking single fact about chimpanzees is the flexibility of their social life, the lack of any rigid form of organization. It represents about as far a departure from the baboon type of organization as one can find among the high

双语有声阅读：儿童的数学能力

Children's Numerical Skills People appear to be born to compute. The numerical skills of children develop so early and so inexorably that it is easy to imagine an internal clock of mathematical maturity guiding their growth. Not long after learning t

双语有声阅读：公共教育的角色

Changing Roles of Public Education One of the most important social developments that helped to make possible a shift in thinking about the role of public education was the effect of the baby boom of the 1950's and 1960's on the schools. In the 1920'

双语有声阅读：细胞与温度

Cells and Temperature Cells cannot remain alive outside certain limits of temperature, and much narrower limits mark the boundaries of effective functioning. Enzyme systems of mammals and birds are most efficient only within a narrow range around 37 ℃

双语有声阅读：英属哥伦比亚

British Columbia British Columbia is the third largest Canadian province, both in area and population. It is nearly 1.5 times as large as Texas, and extends 800 miles (1,280km) north from the United States border. It includes Canada's entire west coa

双语有声阅读：植物学

Botany Botany, the study of plants, occupies a peculiar position in the history of human knowledge.For many thousands of years it was the one field of awareness about which humans had anything more than the vaguest of insights. It is impossible to kn

双语有声阅读：冰山

Icebergs Icebergs are among nature's most spectacular creations, and yet most people have never seen one. A vague air of mystery envelops them. They come into being -- somewhere -- in faraway, frigid waters, amid thunderous noise and splashing turbul

双语有声阅读：灯塔

Lighthouses The first navigational lights in the New World were probably lanterns hung at harbor entrances. The first lighthouse was put up by the Massachusetts Bay Colony in 1716 on Little Brewster Island at the entrance to Boston Harbor. Paid for a

双语有声阅读：海洋哺乳动物

Marine Mammals Since there is such an abundance of food in the sea,it is understandable that some of the efficient, highly adaptable, warm-blooded mammals that evolved on land should have returned to the sea.Those that did have flourished. Within abo

双语有声阅读：火星

MARS Mars According to the best evidence gathered by space probes and astronomers, Mars is an inhospitable planet, more similar to Earth's Moon than to Earth itself-a dry,stark,seemingly lifeless world. Mars' air pressure is equal to Earth's at an al

双语有声阅读：植物拟态

Mimicry in Plants Plant adaptations can be remarkably complex. Certain species of orchids, for instance, imitate female bees, other plants look and smell like dead animals, and still others have the appearance of stones. These strange adaptations to

双语有声阅读：现代美国大学

Modern American Universities Before the 1850's, the United States had a number of small colleges,most of them dating from colonial days. They were small, church connected institutions whose primary concern was to shape the moral character of their st