The d-p back bonding formed between Cu () and 5-substituted phenanthroline, and Hammett parameters of substituents were discussed.

So would you expect this to be a pi bond or a sigma bond her PROFESSOR: OK, so I'm hearing some mixed answers.

你们觉得这是一个π键还是sigma键？，我听到有不同的答案。

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So that's exactly what our definition of a pi bond is, so we have one sigma bond, and one pi bond.

这是我们对π键的定义，我们有一个sigma键，和一个π键。

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The electron in the π bond of S-ylide-like radical appears mainly near the C atom. It has π( C → S) bond character, therefore it is weaker than the C-S bond in the corresponding product.

类硫叶立德自由基（·CHSH2）中单电子π键中的电子主要在碳原子附近运动，属于单电子π（C→S）配键，所以其C&S键的强度比相应的产物要弱。

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But once you have a double bond here, we have our pi bond, as well as our sigma bond.

但一旦你有了双键，我们有π键，也有sigma键。

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So if we have a single bond here, would you consider that a sigma bond or a pi bond?

如果这里有个单键，你觉得这是sigma键还是π键？

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Monomers used include the acrylic, the-bond, the Si-OR silicone in bifunctional structures and the straight ( or ring-like) silicone.

所用单位有丙烯酸类A，和既有π键又有硅氧烷基的双官能结构硅氧烷单体B，以及直链（或环状）硅氧烷D；

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We want to discuss sigma bonds and pi bonds.

我们要讨论sigma键和π键。

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They generally consist of a flat, rigid and large conjugated aromatic structure.

作为DNA嵌入剂，它们一般都具有平面刚性结构和大共轭π键。

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Is that a sigma or a pi bond?

这是sigma键还是π键？

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So we can kind of flip it this way this will be one pi bond, this will be another interacting between these p orbitals.

我们可以把它这样翻一下，这是一个π键，这是另外一个p轨道之间，相互作用的π键。

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It's like an executive I once knew who confided that he was not fulfilled.

我曾经认识一位主管,他透露说他很不满意他的现状.

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For high head pressure, the operation of conventional adding sand fracture treatment tech can not fulfilled.

由于施工井口压力高, 常规加砂压裂工艺无法实施作业.

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But I was not accomplished ; because it's really too long to go.

未遂 因为它真的太长了.

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You never can tell.

谁也说不准.

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But you never can tell.

可是谁也说不准.

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And you never can tell how close you are.

你永远不能确定距离成功有多么近.

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The two teams are evenly matched, and It's hard to say who will win.

两队实力势均力敌, 输赢一时难说.

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It's hard to say. Everyone is different.

很难说. 每个人都不一样.

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It's hard to say hello because it might be goodbye.

也许在离别的时候,要说你好很困难.

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It's hard to say . Language isn't like other studies.

很难说. 语言不同于其它的学问.

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