A.S. Leskov Al’manac of Modern Metrology № 1 (17) 2019, pages 35–43 The work presents the method of electron paramagnetic resonance, possibilities of EPR spectroscopy, its demand in a number of areas of science. The State primary standard for the unit of the number of paramagnetic centers (NPC) of GET 83-2017 is described, the history … Continue reading The state primary standard of the unit of the number of paramagnetic centers: yesterday, today, tomorrow