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内部过电压的数值一般可达相电压的()倍。
惊蛰是二十四节气之一,惊蛰之后气温回升较快,渐有春雷萌动。( )
简易呼吸器测试
项目信息管理的目的旨在通过有效的项目信息( )的组织和控制为项目建设的增值服务。
Passage 1People often complained about not getting"a good night's sleep", but sleep patterns differ from person to person. Most adults require six to eight hours of sleep to function well, while others survive on only a few hours. Still, most people today think of sleep as one continuous period of downtime. This is not the way people used to sleep. According to researchers in earlier times, people divided sleep by first sleep a few hours, waking up, then going back to sleep.Before the 18th century, people had no gas or electricity in their homes. Fire, candles, or oil lamps were the common forms of lighting. This lack of artificial lighting in homes contributed to people's sleep patterns. It made sense for people to go to bed early. If you live in this time period, you might be a hard-working farmer, and you would come home, eat and quickly fall into bed exhausted. You would probably go to sleep at 9:00 or 10:00 P.M. In this first period of sleep-called first sleep-you would typically sleep until midnight or shortly afterwards.Halfway through the night during a period some call the watch, or watching period. When you came out of first sleep, you would stay in bed and relax quietly. You might talk with a bedfellow, meditate on the day's events or the meaning of a dream, or just let your mind wander. If you enjoyed writing or drawing, you might get out of bed to write a poem or story or draw a picture.Then you would start to feel sleepy, so would return to bed and fall asleep again for your second sleep. This period would continue until early morning when daylight arrived. Again, with no artificial lighting in homes, people naturally woke up early to take advantage of sunlight.Today, human may consider divided sleep a strange habit, but sleep researchers say that it is actually a more natural sleep pattern. Dr. Thomas Wehr of the U.S. National Institute of Mental Health has studied human sleep. He thinks that modern sleep problems occur because the orderly, natural way of sleep is breaking through the more recent continuous sleep pattern. Wehr and other scientists believe that artificial lighting has altered the way people sleep. In a research study, he asked 15 adults to rest and sleep in darkness for 14 hours(from 6:00 P.M. to 8:00 A.M.). At first, the subjects took a few hours to get to sleep, and then slept 11 hours a night. Then overtime, they switched to divided sleep. They fell asleep for about 3 or 5 hours in the evening, stay awake for an hour of two and the slept again for four hours till early morning.Unlike the people in the study, we modern humans generally do not practice divided sleep. However, many of us have the experience of waking up in the middle of the night. We usually consider this a sleeping "problem", but perhaps we should look at it as natural behavior. Divided sleep may be the way we should all be sleeping.A first sleep followed by a relation period and a second period of sleep could help all of us to beat the stress of our fast-paced lives.What is the main purpose of paragraph 2~4?
船舶识别号应在船舶内部的机器处所、泵舱或滚装处所的舱壁上标注()编号。
男,58岁,右颈部肿块3个月,CT示右咽隐窝和耳咽管闭塞,局部有软组织密度肿块,颈部淋巴结肿大,诊断( )。
()就是对信息进行组织、控制、加工、规划等,并将其引向预定的目标。
饮白兰地酒的最佳温度为摄氏10度以上。
以下哪一个不是心理健康的标准()
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CDMA2000接收机结构是()。
CDMA2000 1x终端的rake接收机能够同时解调()路信号。
因为自整角机的接收机和发送机在结构上有差异,如果调错,将使自整角机()。
因为自整角机的接收机和发送机在结构上有差异,如果调错,将使自整角机()
CDMA2000系统结构与IS-95相比,有哪些不同?
画出GPS接收机的基本功能结构图。
接收机的标准输入信号是指加在接收机输入端频率为接收机的标称工作频率,经过标准试验调制,电平为()的射频信号。
按照同时能接收的()可将接收机分为双频接收机和单频接收机两类。
接收机的标准输入信号是指加在接收机输入端频率为接收机的标称工作频率,经过标准试验调制,电平为()的射频信号。
使用接收机空间分集时,BTS可安装一个()来实现发信机和接收机合用一根天线。