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
四月,万物复苏,柳絮纷纷飘落了下来。我悠闲地走在灞河边上,慢慢地,享受这场一点也不寒冷的“鹅毛大雪”。
三月,柳絮还尚在孕育之中时,柳树上的绿叶像是在向你挥手,说:“你好呀!”向远处望去,那一条条树枝像是嵌上了翡翠一样,不禁让我想起贺知章的《咏柳》:碧玉妆成一树高,万条垂下绿丝绦。看,这碧绿的枝条就像垂下的万千条丝绦一样,那么美丽,那么柔软,让人忍不住想伸手摸一摸。再向前望去,有的柳树十分臭美,正对着镜子似的水面摆弄着自己的头发。
一阵风吹来,柳枝随风摇曳着,风姑娘静静地为柳姑娘梳着头,还为她那长长的秀发绑上蝴蝶结,真美啊!
当柳絮成熟时,一个个白色的降落伞从树上飘下来,多像飞舞的雪花啊!但有的柳絮比较调皮,在空中飞来飞去,迟迟不肯落下来。
瞧啊,灞桥的春天是如此的美啊!如果你春天来西安,一定不要忘了去灞桥春游呀!
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:
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
© 2022 xuexicn.net,All Rights Reserved.