共查询到20条相似文献，搜索用时 218 毫秒
1.
《时代数学学习》2006,(4)
1·B.2·D.3·D.4·B.5·B.6·A.7·C.8·B.9·1.10·52.11·3y或6x.12·bb+-aa.13·M=N.14·100,1n.15·2-1x.16·2(x+2),值为22+2.17·由1a+1b=a1+b,知(a+b)2=ab,而ab+ab=a2a+bb2=(a+b)ab2-2ab,所以原式=ab-ab2ab=-1.18·x=0.19·设去年水价为x元/m3,根据题意,得(1+3256%)x-1x8=6,解得x=1.8.20·(1)x1=c,x2=cm.(2)x1=a,x2=aa+-11.原方程可变为x+x2-1=a+a-21.故x-1=a-1,x1=a;或x-1=a-a1,所以x2=aa+-11上期《“分式”测试卷》参考答案… 相似文献
2.
3.
Fe(Ⅲ)系络合物显色反应虽已有过很多研究〔1,2,3〕。 Fe(Ⅱ)—HAA 系显色反应的研究迄今未见有报导。本文研究了 HAA—Fe(Ⅲ)络合体系的显色反应。研究表明:络合物最佳显色酸度为 pH=3;λ_(max)为47δnm:ε=1.6×10~2l·mol~(-1)·cm~(-1)。Fe(Ⅲ)含量在0—20ug·ml~(-1)范围内遵从 Lambert-Beer 定律。络合物组成比为 Fe(Ⅲ):HAA=1:1,也存在1:5型的络合物,体系稳定,灵敏度、选择性高,五十多种常见离子试验都没有干扰。方法简便迅速,是用于微量铁测定的一个新方法。 相似文献
4.
复数中 ,由 | z| 2 =z· z极易推导出两个复数积的性质 :性质 1 设 z1 ,z2 ∈C,| z1 | =r1 ≠ 0 ,| z2 |= r2 ≠ 0 ,且 r2 z1 + r1 z2 =z0 ≠ 0 ,则有 z1 · z2 =r1 · r2 · z20| z0 | 2 .证明 ∵ r2 z1 + r1 z2 =1r1 r2( r1 · r22 · z1 +r21 ·r2 ·z2 )= 1r1 r2( r1 ·z2 ·z2 ·z1 + r2 ·z1 ·z1 ·z2 )=z1 · z2r1 · r2( r1 ·z2 + r2 ·z1 )=z1 · z2r1 · r2·r1 ·z2 + r2 · z1 ,∴z1 ·z2 =r1 · r2 ( r2 z1 + r1 z2 )r1 · z2 + r2 · z1=r1 · r2 · z0z0=r1 · r2 · z20| z0 | 2 .推论 1 若 | z1 | =| z2 | =r≠ 0 ,… 相似文献
5.
6.
杨水平 《赣南师范学院学报》2001,(6):49-51
本文研究了哌啶荒酸哌淀 (PDPC)与Co(Ⅱ )最佳显色反应的条件 ,在 pH =5 .5的条件下 ,Co(Ⅱ )与PDPC形成稳定的黄色络合物 ,络合物组成比为M∶R =1∶2 ,可见光区最大吸收波长λmax=4 0 0nm ,表现摩尔吸光系数ε=2 .2 9× 10 4L·mol- 1·cm- 1.该体系显色速度快 ,稳定性好 .应用拟定方法测定合成水样中Co(Ⅱ )含量 ,结果满意 . 相似文献
7.
在Nd3+、Yb3+共存的RE-XO-CPC弱酸性介质体系中,加入F-可有效地掩蔽Nd3+.选用L16(45)正交表进行试验,得到最佳实验条件为[XO]=1.31×10-4mol·L-1,[CPC]=4×10-4mo·L-1,[F-]=8×10-4md·L-1.二阶导数峰(+617.5 nm)-零法、零-谷(-592.8nm)法、峰(+617.5 nm)-谷(-592.8 nm)法测定Yb3+时,3倍量的Nd3+不干扰测定,直线回归方程分别为y=9.47×10-3+2.47×10-3x(峰-零法,相关系数p=0.9990);y=1.70×10-3+6.56×10-3x(零-谷法,p=0.9998);y=2.64×10-3+1.07×10-2x(峰-谷法,p=0.9949).用零-谷法对不同配比Nd3+、Yb3+混合物进行分析,平均偏差在12.0%-24.0%,变异系数在1.80%-6.98%. 相似文献
8.
《时代数学学习》2005,(11)
1·51.提示:不难推得原式应为1234×56.2·44.提示:小长方形的长+3×小长方形的宽=14,小长方形的长-小长方形的宽=6.解得S小长方形=8×2=16.S大长方形=14×(6+2×2)=140,S阴影=140-6×16=44.3·55.提示:机器松鼠每跳12步就回到原来的位置.因为1949=162×12+5.故甲机器松鼠顺时针跳1949步时,跳到了标有数字5的圆圈,而2005=167×12+1,故乙机器松鼠递时针跳2005步时,跳到了标有数字11的圆圈.4·1.提示:272=3·1·42857·,循环节的长为6,而2005÷6=334……1,故小数点后第2005位上的数字是1.5·36154.提示:原式=(1+3+5+7+9+11)+16+112+210+310+… 相似文献
9.
10.
不久前 ,笔者为一所学校六年级数学计算能力测试命题 ,其中一道题是 ( 3÷ 1 1 +2÷ 7+1÷ 2 )× 1 54,学生计算情况如下 :1 .( 3÷ 1 1 +2÷ 7+1÷ 2 )× 1 54 =0 .2 ·7·+0 .2 ·8571 4 ·+0 .5)× 1 54=……2 ( 3÷ 1 1 +2÷ 7+1÷ 2 )× 1 54 =( 31 1 +27+12 )× 1 54 =( 421 54+4 41 54+771 54)× 1 54=1 631 54× 1 54 =1 633 .( 3÷ 1 1 +2÷ 7+1÷ 2 )× 1 54 =( 31 1 +27+12 )× 1 54 =31 1 × 1 54+27× 1 54+12 × 1 54 =42 +4 4 +77=1 63据统计 ,有 54%的学生采用方法 1。究其原因 ,是学生受四则混合运算的运算… 相似文献
11.
12.
《海外英语》2007,(4):36
There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love. 相似文献
13.
Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject. 相似文献
14.
Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities. 相似文献
15.
16.
RUZBEHANI Mohsen 《重庆大学学报(英文版)》2004,3(1):20-25
1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec… 相似文献
17.
Rajesh Kanoi 《海外英语》2007,(1):52
Today, Sunday morning, I sit thinking and typing at my computer. My thoughts are in my homeland, India and my body is in China. The body is here and mind there for a good reason. Mr. Hu is president and I am resident and both are in each other's countries (what a difference the absence of one small letter makes!). Mr. Hu will return in a few days and I will stay on longer. 相似文献
18.
正A One day a pig went to the stable(马棚)to see his good friend,an oldhorse,and was going to stay there forthenight.Night came and it was time forsleep.The pig went into the straw heap(稻草堆)and lay comfortably.A longtime passed,but the horse was stillstanding there and did not move.Thepig asked the horse why he did not go tosleep."Standing like this is the begin-ning ofsleeping,"answered the horse. 相似文献
19.
《今日中学生》2014,(9)
正1.Any fool can count the seeds in an apple.Only God can count all the apples in one seed.2.Happy families are all alike;every unhappy family is unhappy in its own way.3.Memories are the key not to the past,but to the future.4.Sometimes in the dark you see what you want to see.5.There is a great difference between 相似文献
20.
《重庆大学学报(英文版)》2014,(2)
正Scope and Policy The Journal of Chongqing University-English Edition(JCQU-E)is a peerreviewed journal publishing research articles in multiple disciplines of science and technology,covering civil and environmental engineering,chemical engineering,biotechnology,mechanical and electrical engineering,computer and data processing,mining,metallurgy,materials science,and interdisciplines thereof. 相似文献