How many famous buildings are there in this country? Twenty-one.

The Public Opinion about Twenty-one Treaties between China and Japan in 1915

1915年中日二十一条交涉的社会舆论

Be one of the main method for ceramic materials in the twenty-one century.

陶瓷材料的固溶强化将成为21世纪提高材料性能的主要方法之一。

The diet is chosen under a franchise that is universal for citizens aged twenty-one and over.

国会由年满二十一岁以上的公民普遍选举产生。

Twenty-one people were killed and four others missing as heavy rain lashed in the township, according to the announcement.

当地政府8月13日通报，8月11日至12日，湖北省随县柳林镇发生极端强降雨天气，已造成柳林镇8000余人受灾，21人死亡、4人失联。

Twenty-one patients received a placebo plus standard treatment.

21位患者在标准疗法的基础上服用了安慰剂。

Nanotechnology is one of the three high technologies in the twenty-one century.

纳米科技是21世纪的三大科技之一。

He said he was twenty-one years old and the employment agency took him on faith.

他说他21岁，职业介绍所毫不怀疑就相信了他。

The researchers tested the blood of all twenty-one people.

研究人员给所有参加测试的21名人员检查了血液。

This paper reports twenty-one normal results in 13 transplant renal allografts.

本文报道了13例移植肾进行的21次正常检查结果。

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

书架的第一层有15本书，第二层有21本，总共是36本。

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。