排序方式： 共有37条查询结果，搜索用时 171 毫秒
31.
秦九韶《数书九章》(1247)治历演纪等题,记载了行用44年(1207-1251)的开禧历推演积年过程,是行用上元积年的一千多年间,唯一流传至今的珍贵史料．着重剖析开禧历的上元条件、周期齐同原理、气元概念、求入元岁术理、大衍术和求元数算法原术自然思路,从而复原出开禧历上元积年数据的完整演算过程． 相似文献
32.
India's rapid population and economic growth leads to fast changing land use and management practices that have a major impact on the environment. Therefore, this study assesses spatio-temporal dynamics of land use and cropping frequencies using moderate resolution spaceborne data (Landsat 7 and LISS III). Based on a hierarchical knowledge-based classification approach, multi-temporal satellite data from the years 2000/2001 and 2010/2011 have been used to derive land use and cropping frequency maps. The approach adopted in this study resulted in a satisfactory classification quality as indicated by overall accuracies >90% for the individual classifications. A reduced land use pressure on mountainous areas was found, indicated by an increasing development of forests within the transition zones between cultivated land and steep slopes. Furthermore, an increase of tree plantations points to a shift from drought vulnerable plants to less risk prone perennial plants. We found a higher cropping frequency in 2010/11 related to both inter-annual precipitation differences over the course of the rainy season and long-term socio-economic changes. While low yield areas are left for natural succession or switched to tree plantations, the cultivation of high yield areas was intensified. 相似文献
33.
从实际预报出发 ,根据阴阳历之间的关系 ,用 Turbo C语言编写了一个能够灵活、快速自动确定指针的阴阳历叠加程序 ,为用阴阳历叠加法制作气候预测提供一个简便的方法 相似文献
34.
哈尼族原始的历法,是将一年分成10个月、每个月固定为36天,另外5～6天余日用于过新年,简称十月历。在受到汉族的农历影响、接受了一年分成12个月的概念后,十月历与十二月历被混淆在一起,出现了有月份重叠的现象,即在生活中,注重以十二生肖纪日,以物候指导生产,纪月相当模糊,相差几天也无所谓的局面。 据哈尼族的神话传说和云南绿春县的白氏家谱分析,哈尼族从使用十月历转向接受十二月历的概念,约开始于公元14世纪,而后逐渐扩展开来,十月历渐渐被淡忘。但是,转向完全使用农历,却经历了漫长的历史时期,直至1950年还没有完成这一转变过程,主要原因是经济发展极端缓慢,交通困难,很少与外部进行交流。 相似文献
35.
花信风与我国公元六世纪气候的重建 总被引：2，自引：1，他引：1
对宋朝程大昌的《二十四番花信风》的历史渊源进行了考征,认为它是出自六世纪(南朝梁时)的"荆楚岁时记".它也是一种重要的物候学文献和物候历,进而根据它推测了当时的气候。经对比分析显示,六世纪冬春季的开花现象比现在早1～2候,而晚春与初夏的开花现象与现在差不多,说明当时冬春季比现代温暖,而夏季温度与现代差不多。 相似文献
36.
Based on the Virtual Water Theory, the research analyzed the spatial and temporal distribution characteristics of major crops in China. Analysis results indicate that the unit virtual water content varies with the type of crop obviously as well as the distribution region. We also found irrational water utilization in some regions, which means that the renewable water sources could not meet the water demand for crop growth. With a view solving these problems found in the research, discussions on agricultural water-saving technology, comprehensive allocation of crops, selection of rational cropping pattern, full use of green water and trade of virtual water were carried out, which may result in some theoretical basis for the sustainable utilization of agricultural water resources in China. 相似文献
37.
竺可桢是中国物候学研究的开创者和领导者,他研究物候学可分为三个时期:(1)研究古今物候学,个人开始物候观测时期(1921—1931年);(2)领导组织中国物候观测时期(1931—1940年);(3)领导建立物候观测网,开展中国物候学研究,并完成北京24年物候观测记录时期(1950—1973年)。本文详述了他对物候学的贡献。 相似文献