核心素养视域下数学命题课的教学研究——以“一元二次方程根与系数的关系”为例

数学命题教学是学生学习和教师教学的重难点,也是发展学生数学核心素养的重要教学载体.研究从数学命题教学的现状出发,提出基于核心素养数学命题课的设计原则,在此基础上以“一元二次方程根与系数的关系”为支点,展示核心素养视域下命题教学的实践探索.     

A STUDY ON THE PLEISTOCENE STRATA AND THEIR DEPOSITIONAL ENVIRONMENT ON THE SONGLIAO PLAIN OF NORTHEAST CHINA

This paper deals with the Pleistocene strata and their depositional environment on theSongliao Plain of Northeast China by applying determinative and analytic techniques of spore-pollen, magnetic stratigraphy, clay minerals, isotopic dating, sedimentary facies, etc. Resultsshow that the underlying sand gravel layer below 75-80 m in depth in the central plain belongsto the alluvial-lacustrine deposits with a time range of 2.48-1.87 Ma, known as the lowerlimit of the Quaternary. As to the massive clay layer, its lower part, 40-30 m thick, belongsto the middle late period of the early Pleistocene, ranging from 2.01-0.73 Ma, while its upperpart, 25-21 m thick, belongs to the middle Pleistocene, ranging from 0.73-20 Ma, with amean sedimentation rate of 3-4 mm/1000a under the big lake, long-range gentle and steadydepositional environment.