1. When searching for the first time, in order to ensure the recall, you can not limit the segmentation. When we want to get the accuracy in the later stage, we should narrow the search scope by limiting the target field (whether in the title of the paper, keywords or content).

2. Search words can be written like this, AAA & amp； BBB&CCC, some can do this aaa+bbb+ccc.

3. The result of 3.AA * test may contain aaing instead of AAING, so make sure what you are searching for first.