It is not likely that you will find all the articles you want in one database. For most research, it will be necessary to look in two or three databases to be sure you have found the appropriate materials.
Each database has its own search terms so it may be necessary to use different words to search for the same idea each time you start researching in a new database.
Example: Revolution or Rebellion can be used to refer to the same type of uprising, depending on the author's choice.
Language changes over time and it might be helpful to use synonyms when searching a large period of time.
Example: Consumption and Tuberculosis are the same illness, but different words were used to refer to it in different centuries.
Nations and regions change names regularly. Keep in mind that the name we use for a nation today might not be what is was called only 50 years ago.
Example: Bruma and Myanmar are the same geographic nation, but the name has changed depending on the leadership of the country.
The following two options are not really indexes to journal articles. They are enormous collections of journals with full text access to the articles included in each journal. They do not offer searching options that are as focused as those above so the results lists can be very large. It is highly recommended that you use them with caution and very focused search terms.