Karakterisasi Siklus Estrus Tikus Betina dan Analisis Pengaruh Induksi Hidroksiurea-Adrenalin Terhadap Ketebalan Endometrium Tikus Betina Model Gangguan Reseptivitas Endometrium = Characterization of the Estrus Cycle of Female Rats and Analysis of the Effect of Hydroxyurea-Adrenaline Induction on Endometrial Thickness of Female Rats Model of Impaired Endometrial Receptivity