There are fifteen books on the first shelf, twenty-one on the second, that makes thirty-six in all.

According to a scientific research, forming a habit takes twenty-one days.

一项科学调查显示，养成好的习惯需要用21天的时间。

A class of fifth system with one twenty-one order singularity

一类有21阶奇点的五次系统

Yet only twenty-one percent of their population is online.

然而，上网的总人数仅占总人口的21%。

A study on primary culture in vitro of twenty-one laryngeal squamous carcinoma tissues

喉鳞状细胞癌癌细胞的原代培养

Nursing analysis and precaution strategy of twenty-one eclampsia patients with normal blood pressure

21例正常血压子痫患者护理分析及防范对策

Effects on Transmittance and Surface Characters of Thin Films Using O2 Plasma Treatment

氧等离子体清洗对sol-gel薄膜透过率和表面性质的影响

Our products include temperature controller, industrial controller, O2 sensor, H2 sensor and visualisation software.

我们的产品包括，温度控制器、业控制器、探头，氢探头及上位机控制软件。

It is necessary to keep high concentration ratio of TEA/ O2 in order to achieve the accelerating effect.

体系中保持比较大的TEA/O2浓度比值，是实现氧加速作用的必要条件。

The air sample of the system can be also analyzed for concentration of CO2 and O2.

能测量系统中空气样本CO2和O2含量，并能根据需要自动补O2。系统实现了平衡吸入~（133）Xe。

But now, O2 is a place to cry for every love you people.

但是现在，O2是一个让每个爱你的人哭泣的地方。

Ag has a reasonably high catalytic activity for O2 reduction in alkaline electrolyte.

在碱性电解质中，银对氧还原具有很高的催化活性。

The production rate of O2 increased at early stage and then decreased.

O2~（？）产生速率在休眠前期上升，在休眠后期下降。

The changes in, O2 and CO2 pressure under different tidal volume and operation related time were investigated.

记录两组手术相关时间及TTS组在不同潮气量时氧分压和二氧化碳分压的改变。

In industrial production process, O2 concentration and temperature measurement has great significance.

工业生产过程中，对O2浓度和温度的测量具有十分重要的意义。

These results may be induced by O2 and other activated oxygen.

和其它活性氧作用的结果。

HE-C was lowest under the middle water, low CO2 and high O2;

HE和FA以中含水量低二氧化碳高氧气（W2C1O3）处理最小；

Compared with 20% O2, blastocyst rate and total cell number of cloned embryos were improved significantly.

与高氧（20%O2）的气相条件相比，克隆胚胎的囊胚率和囊胚细胞数得到了显著提高（P<0.05）。

Different Gs values might come from O2 effect in the radiation process.

不同的裂解G值表明，O2气在聚丙撑碳酸酯的辐射裂解过程中有重要影响。

A fuzzy self-optimizing control system for maintaining economic combustion based on co/ o2 coordinated control

基于CO／O2协调控制的燃烧经济性模糊寻优控制

But I did perform in the O2 Arena in London last week.

不过上周确实在伦敦的O2体育馆表演过了。