We use several sources to collect and evaluate academic scientific publication on a country scale, and we apply it to the case of France for the years 2015-2020, while presenting a more detailed analysis focused on the reference year 2019. These sources are diverse: databases available by subscription (Scopus, Web of Science) or open to the scientific community (Microsoft Academic Graph), the national open archive HAL, and databases serving thematic communities (ADS and PUBMED). We show the contribution of the different sources to the final corpus. These results are then compared to those obtained with another approach, that of the French Open Science Barometer (Jeangirard, 2019) for monitoring open access at the national level. We show that both approaches provide a convergent estimate of the open access rate. We also present and discuss the definitions of the concepts used, and list the main difficulties encountered in processing the data. The results of this study contribute to a better understanding of the respective contributions of the main databases and their complementarity in the broad framework of a country-wide corpus. They also shed light on the calculation of open access rates and thus contribute to a better understanding of current developments in the field of open science.