1. Open database: This is the main source of empirical data, including various statistical data and research reports published by government statistical departments, international organizations and research institutions. For example, the statistical database of the United Nations, the public data of the World Bank and the data of the National Bureau of Statistics.

2. Self-collection: For some specific research problems, researchers may need to collect data by themselves. This may include first-hand data obtained through questionnaires, interviews and observations.

3. Literature: Historical literature, newspapers, magazines and books are also important sources of empirical data. Through the analysis of these materials, we can get information about past events and phenomena.

4. Experimental research: In some scientific and social science research, researchers may conduct experiments to obtain empirical data. For example, in psychological research, researchers may test hypotheses through laboratory experiments.

5. Network data: With the development of the Internet, network data has become an important source of empirical data. This includes user-generated content on social media, website logs, search engine queries, etc.

6. Patents and business reports: These resources can provide empirical data on technological innovation and market competition.

7. Reports of non-profit organizations and research institutions: These reports usually contain a lot of empirical data and are important resources for academic research.

Generally speaking, the acquisition of empirical data requires researchers to have certain information retrieval ability and data processing ability, and also to abide by relevant ethical norms and legal provisions.