This is a network security protection mechanism of Google. Because the computer network is unstable and abnormal at some point, Google verifies whether it is a real person or an automatic computer program. Generally, it can be used normally as long as it passes man-machine verification. The specific steps are as follows:

1. Enter any search keyword in Google Academic Search, and then click the search button to search, as shown in the figure.

2. After that, man-machine verification is needed. You can see the explanation of why man-machine verification is needed from the "About this webpage" below, as shown in the figure.

3. Click the box on the left of "Conduct man-machine identity authentication" to start man-machine authentication, as shown in the figure.

4. After that, a verification question will pop up, asking to search for items in a picture according to keywords. Select a picture, and a blue checkmark icon will appear in the upper left corner, as shown in the figure.

5. Carefully observe the drawing group, select all parts that meet the requirements, and pass the verification, as shown in the figure.

6. If it passes the verification, the icon in the original box will turn into a green check mark, as shown in the figure.

7. After waiting for a very short time, the page will automatically jump to the result page of keyword search, which can be used normally. As shown in the figure.

Precautions:

Generally speaking, the frequency of man-machine verification interface is not very high, but if this verification interface appears every search, it may be a network quality problem, so it is best to contact the network operator to deal with it.