题干

5月14﹣15日“一带一路”论坛峰会在北京隆重召开,促进了我国与世界各国的互联互通互惠,“一带一路”地区覆盖总人数约为44亿人,44亿这个数用科学记数法表示为(   )

A:  4.4×108

B:4.4×109

C:4×109

D:44×108

上一题 下一题 0.0难度 选择题 更新时间:2019-10-17 10:10:54

答案(点此获取答案解析)

B

同类题1

阅读下面的文言文,完成文后小题。

程千里列传

    程千里,京兆人。身长七尺,骨相魁岸,有勇力。本碛西募人,累以戎勋,官至安西副都护。天宝十一载,授御史中丞。十二载,兼北庭都护充安西北庭节度使。突厥首领阿布思先率众内附隶朔方军玄宗赐姓名曰李献忠李林甫遥领朔方节度用献忠为副将后有诏移献忠部落隶幽州,献忠素与禄山有隙,惧不奉诏,乃叛归碛北,数为边患。玄宗愤之,命千里将兵讨之。

    十二载十一月,千里兵至碛西,以书喻葛禄,令其相应。献忠势穷,归葛禄部。葛禄缚献忠并其妻子及帐下数千人,送之千里,飞表献捷,天子壮之。十三载三月,千里献俘于勤政楼,斩之于朱雀街,以功授右金吾卫大将军同正,仍留佐羽林军。禄山之乱,诏千里于河东召募,充河东节度副使、云中太守。

    十五载正月,迁上党郡长史、特进,摄御史中丞,以兵守上党。贼来攻城,屡为千里所败,以功累加开府仪同三司、礼部尚书、兼御史大夫。

    至德二年九月,贼将蔡希德围城,数以轻骑挑战。千里恃其骁果,开悬门,率百骑,欲生擒希德。劲骑搏之,垂将擒而希德救兵至,千里敛骑而退,桥坏坠坑,反为希德所执。仰首告诸骑曰:“非吾战之过,此天也!为我报诸将士,乍可失帅,不可失城。”军人闻之泣下,昼夜严兵城守,贼竞不能拔。千里至东都。

    安庆绪舍之,伪署特进,囚之客省。及庆绪败走,为严庄所害。其年十二月,上御丹凤楼大赦,节文曰:“忠臣事君,有死无贰;烈士徇义,虽殁如存。其李橙、卢奕、袁履谦、张巡、许远、张介然、蒋清、庞坚等,即与追赠,访其子孙,厚其官爵,家口深加优恤。”自是赦恩,无不该于节义,而程千里终以生执贼庭,不沾褒赠。

(选自《旧唐书》卷一百八十七下列传第一百三十七下)

同类题3

阅读理解

    Elizabeth Bishop, who was famous for the poetry AProdigal, FillingStation , Sandpiper, Manuelzinho and so on, was an influential(有影响的) American poet of the 20th century. Her poetry often shows things that concerned her throughout her life, such as her search for a sense of home. Her troubled childhood and feelings of loneliness from this time affected her character and poetry.

    Bishop's painful childhood is apparent(显面易见的) in some of her poems. Her father died when she was eight months old and her mother was mad when she was five. Bishop was raised firstly by her mother's parents and then by her father's parents. This experience left her confused about belonging. She had no home and this was shown in her poetry. In “AProdigal”, when the character in the poem makes up his mind to go home, there is a sense of pessimism for Bishop who has no home. The lack of a sense of home has contributed to her depression(消沉) all her life.

    Bishop attempts(企图) to make small, everyday experiences extraordinary in her poems such as “FillingStation”. In “FillingStation”, Bishop describes the beauty of a family filling station. Although it is “dirty” there is order in it. Simple family life is celebrated in it. She recognizes the value of home and beauty in everyday life, but she is only an observer of these. Distance remains between her and the family at the filling station.

    Bishop's struggle to locate herself in the world is seen no more clearly than in “Sandpiper”. It deals with searching for something in a confusing world. She uses the metaphor(暗喻) of the bird which is “looking for something”. The “something” isn't specific(特殊的). It seems as if the bird doesn't know what he wants; the only certain thing is that he is searching.

    Bishop's poems are personal on a more subtle (巧妙的)level, especially when her childhood, travels, etc, are taken into consideration. It is believed that Bishop is a complex(复杂的)poet who uses her poetry to find this feeling of belonging.

同类题5

阅读下文,回答问题

为什么有些树木是空心的

刘光裕

    ①很多大树随着年岁增长,树心会慢慢腐烂,最后成为空心,威胁大树生长。在古树相对较多的北方,空心是个大问题,如曹雪芹纪念馆前的歪脖子老槐树,北京植物园龙王庙前的老槐树等。

    ②事实上,树木空心不止发生在北方我们所熟知的老槐树、大青树或常见大树中,在水热丰沛地区,树木的空心现象也很严重。研究发现,澳大利亚稀树草原上66%—89%的物种会发生空心,树干空心直径达50%;亚马逊热带雨林中有37%的空心率;云南哀牢山原始森林的空心树木也相当多。

    ③从树木生长环境与自身生长特征看,潮湿的原始森林中空心树最多,老粗矮的树木容易空心,主干比侧枝容易空心。那么,有些树木为什么会空心了呢?

    ④1976年,生态学家丹尼尔·扎森发表了一篇文章《为什么热带树木的心会腐烂掉》,认为树木空心是一种适应策略,空心乃自然界“无用之用”的体现。树木在闪电、火烧或真菌侵扰、动物啃噬之后,会形成空心。树木内心慢慢腐烂,营养逐步流到植物根部,被循环利用。扎森对树木空心“无用之用”的解释,听起来合乎逻辑,但长期缺乏证据,尚未被生态学家证实。

    ⑤细细思之,当树木中心在微生物或动物作用下慢慢腐败的时候,营养首先被白蚁等昆虫大量获取,枯木中最重要的部分被雨水冲刷到地表的土壤里,这些到达地表的营养则会被地表浅根的草本植物获取,而不能到达大树的深根。树木空心后渗入土壤中的营养实际上是被大树的竞争者草本植物获取了。此外,若树木空心是一种适应性策略,理论上空心木应该吸引很多分解者和啃噬者,而现实是啃噬倒木的动物多样性和真菌多样性高于空心木。所以,营养循环利用的理论是站不住脚的。

    ⑥英国科学家最近在《生物学快报》上发表一篇文章《为什么那么多树是空心的》,认为植物空心可能是选择性地牺牲一部分化学防御来节省能量,并非如扎森所言的促进能量循环。

    ⑦植物通常依靠化学物质来防御微生物或动物。对于长新叶新枝条、掉落老叶老枝的树木来说,像保护嫩叶嫩枝一样保护树心可能并不是一种经济的选择。对于较大的树木来说,树干外周的树皮通常是活的,用来运输水分、矿物质,树木要维持外周树皮通常每年要耗费5%—13%光合获取的能量。为了节约能量,很多树木的心实已死去,它既不储存能量也不传输物质。所以,树心一旦形成,化学防御物质没法更新,因此抵抗能力降低了。缺乏化学物质更新的树心自然容易受到真菌和动物的侵蚀,造成树木空心。

    ⑧从树木物理稳定性考量,高大树木的水平侧枝通常比直立的枝干更能忍受高强度的拉升力。因此,水平侧枝通常生长更加强壮,物理性强,更耐真菌和动物腐蚀一些。硕大的侧枝同时会将拉力施加在空心树木的外周,对树皮形成选择,树木空心的现象或许还能合理解释为什么树皮外周比树心结构复杂的现象。

    ⑨不过,树木为何会出现空心现象,这个问题仍然没有最好的解释。有人可能还会问,为何有的植物(如伞树或竹子)的茎干生来便是空心的呢?想要回答这个问题,那还得等待新的科研结果。