万里长城是世界古代建筑的奇迹。早在春秋时期,楚国就修筑了长数百千米的非封闭性城墙,叫作方城。战国时,燕、赵、魏、韩、秦等都在边界筑起了长城。秦始皇统一天下后,把燕、赵、秦原有的北方长城连接起来,筑成西起临洮东至辽东的长城,长万余里。今山西大同北部,甘肃岷县城西等地均有秦长城遗址。
西汉沿河西走廊一带向西增筑朔方长城和河西长城,经玉门关延伸到今新疆境内,以保护河西走廊。北魏时西部柔然人满为患,又兴筑长城以防柔然人南侵。北齐也多次修筑长城。隋代为防御突厥、吐谷浑,数度修筑长城。明朝建立后,大将徐达曾18次在居庸关修筑长城。明长城西起甘肃嘉峪关,东至鸭绿江,这就是今天我们见到的万里长城。
明长城主体是城墙。山西东面至山海关一段,断面下宽上狭,平均底宽6米,高逾6.5米,外砌整齐条石和特大城砖,内部夯土。城墙顶部用三、四层砖铺砌,最上一层是方砖,用石灰勾缝,十分平正坚实,连野草也难以生根,平均宽5米,可容5马
并骑10人并进。墙顶两侧还砌有砖墙,内侧砌成约高1.5米的矮墙,外侧砌成约高1.5米的垛墙,每一垛牙上面有了望孔,下面有一射击眼。城墙上有排水沟、吐水嘴等设施,在关口和险要的地方还设有凸出的罗城。
修筑长城的工程浩大,筑长城所用土方如所来筑一道厚1米、高5米的墙,可绕地球一周有余。筑长城一般就地取材,大型城砖和石灰是就地烧制的。在高山峻岭,则开采石料,用石砌筑。在沙漠中,用红柳枝条和芦苇与砂石层层相间铺砌,可砌到6.5米以上。在黄土地区,大都取土垒筑,在重要地段的城墙一般用砖砌和条石镶砌
I have a great mother. She cares much about me in my life and study.
In the morning, she gets up early to make breakfast for me. When I was little, she prepared my schoolbag. But now, she tells me to do it by myself. Because she thinks I have been old enough to do it. Besides, she always checks my homework. When I finish my homework, she checks it and points out the mistakes. She is very careful and helps me a lot.
I love my mother.
响水湖长城位于怀柔慕田峪西部,距北京78公里,总占地面积18平方公里,是集长城、古洞、山川、泉潭、飞瀑于一体的天然锦绣谷,响水湖并不是一片很大的水域,而是在泉水的源头,泉涌如注,千米之外便可听到泉水的响声,系怀柔第一大泉,故得名\"响水湖\"。
金秋的响水湖长城秋高气爽,红叶满山,昔日长城内外郁郁葱葱的绿,如今已成片片红叶,把这大山装扮得如此美丽,在秋风微微吹动下,像一个青春少女穿着色彩斑斓的裙服在翩翩起舞。
而更引人注目的是景区内占地面积1700余亩、年产水果20余万斤的果园,果园内硕果累累,坠满枝头,品种有:苹果、红果、山栆、梨、核桃、板栗、山葡萄、山花椒、山野菜等品种,目前正值丰收季节,响水湖长城为感谢各界人士的厚爱,愿把这丰收喜悦与您一起分享,定于8月25日至10月底在景区举办\"庆金秋、游美景、送采摘\"活动。活动期间,游客购买门票进入景区游览,同时您可凭门票领取专用提袋,到景区指定的果园免费采摘时令水果,您也可在果园内先尝为快,然后带回去一袋,让您的朋友也一饱口福。请即刻行动吧!带上您的家人和朋友一起到响水湖长城当一天果民、亲身体验一次丰收的.喜悦!
November **, ****
To Whom It May Concern:
This is to confirm that Mr. Li Dashui has worked as a full-time system analyst in the NY University since Jun 1994(or This letter is to verify that Mr. Li Dashui worked as an chemist from July 1993 to Sept. 1994. Mr. Lis main duties and responsibilities are as follows:
Design, develop and install various computer hardware, software and network systems for banks.
Determine and analyze the requirements of each system project into related componets solved through the application of computer technology.
Write specifications for computer programs, and test and implement programs for network systems and control systems.
Supervise computer programmers and other system analysts for paticular system projects.
Mr. Li has mainly taken part in the following projects:
The first engineering design of city general business computer network system.
Upgrading banks system for IBM AS/400 E45 to IBM AS/400 320, IBM AS/400 530.
The design development and test of city general business computer network system.
The design and development network and database systems for the Golden Credit Card Project.
Mr. Li is well experienced with IBM AS/400 system analysis, TCP/IP protocol, SNA protocol and LAN; proficient in RPGIII, VB, C/C++ and DB2, and skilled in UNIX, Informix, Client/Server etc.
Mr. Li is a hard-working and talented analyst, and is highly respected member in our company. If you need further information, please feel free to contact me. Sincerely yours, Singature, Zhang Jianguo
Senior Engineer and Technical Manage Company Name, Address, Tex Fax
My mother
My mother is very kind and beautiful although she is not tall.She is 42 years old this year.She is a nurse,so she is always very busy day and night.But she loves her job,and she often takes care of her patients.Of course,she also likes singing,dancing,cooking and shopping,but she almost no time to do them.
Oh,I love my mother.
描写妈妈的英语作文:
© 2022 xuexicn.net,All Rights Reserved.