Silicon nitride is known as Si3N4 powder, it's a super-hard substance, which has lubricity itself, and is resistant to wear and oxidation at high temperatures.…
How serious are fertility problems today? People don't want to give birth,can't afford it, and can't give birth that has become the "three mountains". The problem of childbirth is related to the people's livelihood. Whether a country can prosper or n…
Recently, covid 19 outbreak spreads in Shanghai, China. There are more than 25,000 new asymptomatic domestic infections every day. China is implementing a dynamic zero-out policy. A leading respiratory expert said the key to COVID-19 prevention and c…
Under the spread of the new crown epidemic, after Americans experienced life and death, they set off the largest "resignation wave" in history, and the number of resignations broke the highest record since statistics began in 2000. Since April this y…