## 3 Results  
### Annual Changes  
In accordance with the above standards for classification, a total of 368 relevant documents were finally screened out from the two databases. The hot terms of BCG/SCG technology and the year-by-year changes of the number of documents in the field of medical treatment and health management, and the proportion of research focus in different fields \begin{table}
\begin{tabular}{c c} \hline \hline
**Classification Standards** & **Description of Classification** \\ \hline \multirow{4}{*}{Research of technologies} & The papers contain research on development of BCG/SCG technology, such as exploration of the principle of signal generation, design of signal detection devices, optimization of signal processing methods, establishment of the models for monitoring body status. \\ \hline \multirow{4}{*}{Field of applications} & Exploration and attempt aimed at practical applications of BCG/SCG. \\ \cline{2-3}  & A branch of the category of “application”. The documents intuitively indicated the assessment of BCG/SCG technology in clinic medicine for such aspects as disease diagnosis, patient health status monitoring, and postoperative recovery status. \\ \cline{2-3}  & A branch of the category of “application”. The research of evaluation of human body health level by means of BCG/SCG technology, especially the important role in improving health level and preventing diseases. \\ \cline{2-3}  & A branch of the category of “medical treatment”. BCG/SCG technology is used for monitoring abnormal breathing information, mainly applied in apnea and asthma. \\ \hline \multirow{4}{*}{Field of cardiovascular health (medical)} & A branch of the category of “medical treatment”. This technology is mainly used for evaluation of cardiovascular status, assisting in the detection of cardiovascular diseases, such as hypertension, coronary heart disease, coronary atherosclerosis, and atrial fibrillation, etc. \\ \cline{2-3}  & A branch of the category of “medical treatment”. The study explored application of BCG/SCG technology in sleep monitoring, and laid emphasis on monitoring sleep-related diseases. \\ \cline{2-3}  & A branch of the category of “health”. The study mainly explored application of BCG/SCG technology in sleep monitoring, and laid emphasis on evaluation of the overall level of health during sleeping. \\ \hline \multirow{4}{*}{Environment for the study} & Laboratory environment & The experiment was conducted in a laboratory, and the experiment environment was strictly controlled. \\ \cline{2-3}  & Non-laboratory environment & The experiment was conducted out of a laboratory, and the real site was affected by certain environmental variables, including the experimental tests conducted in a hospital, clinic or at home. \\ \cline{2-3}  & Both of the above & The experiments were conducted in both the laboratory and non-laboratory environments. \\ \cline{2-3}  & Not mentioned & What environment the experiment was conducted in was not mentioned in the article. \\ \hline \multirow{4}{*}{Samples the study} & Complete experimental samples & The experimental samples included male/female/healthy/diseased subjects. \\ \cline{2-3}  & Sufficient experimental samples & The experimental samples did not cover the subjects of all types, but the candidates included in the samples were enough to provide the basis for experimental analysis. For example, in a study, which used BCG to monitor patients with heart failure, a group of samples, who were all patients with heart failure, were used. \\ \cline{2-3}  & Limited experimental samples & The experimental samples were not universal, and some types of experimental subjects were ignored. \\ \cline{2-3}  & Not mentioned & The composition of the experimental samples was not mentioned in the article. \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Standards for Classification of Documents. can be obtained from Figures 4-6. It can be seen that the scope of research and practice of this technology has been expanded, and the number of documents showed a trend of sharp increase.