查询词典 ring

Androstenedione and dehydroepiandrosterone as a new steroid material attracts people's attention because of the shortage of diosgenin resource and successful synthesis of AD by degradation of sterols. The followings were included in this thesis: 1. 24 new oxime-ether and oxime-ester compounds from AD were synthesized by cleavage of A-ring through NaIO_4/KMnO_4 oxidation, ring closure by amination, oximation with hydroxylaminechloride in C-17 position.

甾体药物的合成原料一般为薯蓣皂素、剑麻皂素、番麻皂素等，随着薯蓣资源日渐枯竭，使得甾体药物工业不得不寻求新的原料，而微生物降解胆固醇和植物甾醇合成雄烯二酮获得成功，使得AD成为新兴的甾体原料吸引了人们的注意。

Parasternal short axis view showed two ring echoes,which was named 2DE ＂double-ring sign＂.

2DE胸骨旁大动脉短轴观显示两条大动脉呈两个环状回声，称2DE&双环征&。

This result again showed that in the process of the reaction of flavonoidswith α-hydroxy ethyl peroxyl radicals, 2,3-double bond in the C ring of flavonoidsplays a more important role than o-dihydroxy in the B ring.

这进一步说明了黄酮类化合物与有机过氧自由基反应的过程中C环2，3双键比B环邻二羟基起着更重要的作用。

It can beconcluded from the experimental results that in the reaction of flavonoids withα-hydroxy ethyl peroxyl radicals, 2,3-double bond in the C ring plays a moreimportant role than o-dihydroxy in the B ring.

从实验结果来看，在黄酮类化合物与有机过氧自由基反应的过程中，其分子结构中起主要作用的是C环2，3双键，而不是B环的邻二羟基。

The synthetic route starts from penicillin G, peroxyacetic acid(8.5%) as Oxidizing Agent to get penicillin G sulfoxide; esterifided with p-nitrobenzyl bromine to synthesize penicillin G sulfoxide ester; we synthesize 3-exomethylenecepham sulfoxide ester with phthalimide potassium and 4A molecular sieve as acid scavenger to open the ring, SnCl_4 as catalyzation to close the ring. The yield is over 60%.

本研究采用的合成路线为：以青霉素G钾盐为原料，选用工业过氧化氢制备的过氧乙酸(22.3%)稀释至8.5%为氧化剂，氧化得青霉素亚砜；采用对硝基溴苄为酯化试剂，制备青霉素亚砜酯；以NCP(N-氯代邻苯二甲酰亚胺)为开环试剂，酞酰亚胺钾和4A型分子筛为酸清除剂，顺利开环；再经无水SnCl_4催化闭环得3-环外亚甲基头孢亚砜酯，最终产率在60%以上。

The substituents on 2 and 4 position of furan ring were derived from the propargylic part of homopropargylic alcohol, and the substituent on 5 position of furan ring was derived from the

其呋喃环上2号及4号位置的取代基乃源自於高炔丙基醇之炔丙基，5号位置的取代基乃源自於醇之偕位，故藉此方法合成之碘化呋喃化合物具有高度的位向选择性。

From the photophysical behaviors of 1, 3, 4-triaryl-2pyrazoline compound (TPP16) at low temperature, it can be considered that the twisted configuration between pyrazoline ring and the non-substituted phenyl group on the position 1 is the fluorescence configuration of conjugated system Ⅰ, and the twisted configuration between pyrazoline ring and P-nitrobenzene group is fluorescence configuration of conjugated system Ⅱ.

研究了1，3，4-三芳基-2-吡唑啉化合物TPP16在低温时的发光情况，发现：在低温77K下，共轭体系Ⅰ(苯基-N1-N2＝C3-苯基)在非极性溶剂中不发荧光，在极性溶剂中有较强荧光发射；而共轭体系Ⅱ(N1-N2＝C3-C4＝对硝基苄叉)在非极性溶剂或极性溶剂中均有荧光发射，表明N1所联取代基与吡唑啉环相扭曲的构象是共轭体系Ⅰ的发光构象，而对硝基苄叉与吡唑啉环相扭曲的构象是共轭体系Ⅱ的发光构象。

The structure characters of this kind of molecules were discussed. The results show that the phenyl group located in the 4- or 5- position of pyrryl ring are not coplanar with the pyrryl ring.

对这类吡咯环上4或5-位有芳环取代基时化合物的晶体结构特征进行了扼要讨论，晶体衍射实验结果表明，4， 5-位上的芳环与吡咯环本身处于非共平面结构。

The contrast experiment shows that the d90 temporary plugging technology presents the best pretection effect,which shield ring intensity is more than 25MPa, the flowback recuperability of the permeability can attain 97.2%, and the shield ring intensity is more than 15 MPa.

进行的对比实验表明，运用&理想充填&理论和&d90&暂堵技术与传统屏蔽暂堵技术相比，&d90&技术对储层有更好的保护效果。该技术对于孔隙性储层屏蔽环强度大于25MPa，渗透率返排恢复率最高能达到97.2%；裂缝性储层屏蔽环强度大于15MPa。

Before reinstallation of Checks, thoroughly clean O-ring groove and lubricate O-ring with FDA approved lubricant.

在重新安装止回阀之前，要彻底清洗O形环沟槽，并用通过美国食品及药物管理局认证的润滑剂对O形环进行润滑。

For a big chunk of credit-card losses; the number of filings (and thus charge-off rates) would be rising again, whether

年美国个人破产法的一个改动使得破产登记急速下降，而后引起了信用卡大规模的亏损。

Eph. 4:23 And that you be renewed in the spirit of your mind

弗四23 而在你们心思的灵里得以更新