Results 51 to 60 of about 352,796 (61)
Ｅｆｆｅｃｔｓ ｏｆ Ｓｔｒａｗ Ｍｕｌｃｈｉｎｇ ａｎｄ Ｓｔｕｂｂｌｅ ｏｎ Ｓｏｉｌ ａｎｄ
, 2013 通过人工模拟降雨试验,研究秸秆覆盖和留茬在玉米生育期的水土保持效应。结果表明:覆盖和留茬在玉米不同生育期均可有效减少土壤侵蚀,覆盖的效果更为明显,其产沙量最大可减少75%,留茬的产沙量最大可减少29%。相同秸秆用量下实行覆盖的水土保持效应较留茬明显。覆盖结合留茬减弱土壤侵蚀的效果明显,在玉米各生育期的产沙量均有大幅减少,低覆盖高留茬减幅最大为85%,高覆盖低留茬减幅最大为78%;在抽穗期对径流强度也有削弱,低覆盖高留茬的径流量减少23%,高覆盖低留茬减少15 ...
王安, 鲍艳杰, 臧逸飞, 郝明德
core
, 2000 根据振荡边界层理论和波流分解方法，导出了河口往复水流的流速垂向分布廓线，据此建立了河口垂向准二维水流、盐度、泥沙运动模型。对泥沙输运，完整地考虑了其对流、扩散、起动和沉降的动力学过程。模拟结果与实测资料进行了对比。应用该模型研究河口泥沙输运 ...
李家春, 周济福
core
, 2002 一、中国人口现状及特点人口问题是一个全球十分关注的大问题，对这个问题的认识、探索、研究、论述和争论已延续了数千年。人口问题的核心就是人口增长过快与生态、环境发展的关系不协调问题和严重制约中国经济的腾飞。中国是人类的发祥地之一，是个历史悠久的人口大国，建国５０年来，我国人口的发展出现了人口再生产类型迅速转变的景象。从１９５３年到１９７３年我国人口生育出现两次高峰，人口由１９５３年的５．８亿增长到１９７３年８．９亿，２４年的平均增长速度为２．１％，净增人口３．５亿，使我国的人口总量达到了难以承受的地步 ...
任燕
core
Some of the next articles are maybe not open access.
Related searches:
Related searches:
Noise Suppression Effect of Soft Magnetic Co-Pd-B-O Films with Large è¬Å and BS
INTERMAG 2006 - IEEE International Magnetics Conference, 2006Magnetic properties and noise suppression effect of Co85B15-Pd-O soft magnetic nano-granular thin films were investigated. Films with a wide compositional range were prepared by the reactive sputtering method. Soft magnetic films were obtained in the compositional range with the O content more than the Co-Pd-B2O3, where there can be simultaneously ...
S. Ohnuma +3 more
openaire +1 more source
Motorization, Vehicle Purchase and Use Behavior in China: A Shanghai Surveyä¸åœ‹ä¹‹æ©Ÿå‹•åŒ–æš¨äº¤é€šå·¥å…·è³¼è²·å Šä½¿ç”¨è¡Œç‚ºï¼šä¸Šæµ·èª¿ç ”å Šæ¡ˆä¾‹åˆ†æž [PDF]
, 2008 Motorization is the transition from non-motorized travel means (e.g., walk) to motorized travel means (e.g., car). China, as the most populous country in the world, has started the motorization process, and its results will have huge impact on the whole world in terms of transportation, energy, environment and automobile market.
openaire