What professional chemistry websites are there at present?

It is recommended to use the competition database, the contents of which can be read by anyone, and the chemicals are relatively complete. The spectrograms of many other websites are copied from it, and there are few advertisements.

If possible, it is best to use scifinder, which requires a certain level of foreign language.

Second, think about chemical engines, chemical books and Moby. These contents are random and worthless. Moby is better, especially Moby's summary of the synthetic route is better, but there are more advertisements and valuable content needs to be logged in. Actually, I may not show it to you.

Finally, consider Wikipedia, which is generally free, and Wikipedia is the best. Secondly, consider Baidu, the non-characteristic entries are similar, and others are barely ok. Encyclopedias such as sogou and 360 are even worse in the field of professional knowledge, and many of them are just copies of the history of Baidu version.