Results 51 to 60 of about 1,133,740 (188)
托卡马克中凯尔文-亥姆霍尔茨不稳定性与密度分布及速度分布的关系 [PDF]
, 1985 近年来,在托卡马克装置实验中观察到等离子体环的密度及环向速度沿半径都有变化。当反平行中性束注入时,密度分布对应空洞型温度(即中心温度低而外侧高),等离子体的稳定性变坏。本文对密变分布和速度分布对等离子体环的凯尔文-亥姆霍尔茨稳定性的影响分别进行了研究,得出,在托卡马克实验参数范围内,密度沿半径的分布会使凯尔文-亥姆霍尔茨稳定性变坏 ...
唐福林
core +2 more sources
, 1999 对攀枝花苏铁（Ｃｙｃａｓｐａｎｚｈｉｈｕａｅｎｓｉｓ）种群的地理分布、数量特征、空间分布格局和毁坏历史进行了野外调查和研究。结果表明：攀枝花苏铁种群的自然栖息地是相互隔离和片断化的。已发现的１３个自然种群中，８个分布在金沙江河谷，５个种群分布在金沙江支流河谷；最大的种群位于攀枝花市郊，占有面积约３８０ｋｍ２。７９年以来的商业采挖使８个种群灭绝，种群分布区从３０７００ｋｍ２减少到８８００ｋｍ２，种群占有面积从１１５０ｋｍ２减少到６３０ｋｍ２。３个被研究种群的分布格局为集群分布，以幼苗聚集程度最大 ...
何永华,李朝銮, 李朝銮
core
Policy Studies Journal, EarlyView.ABSTRACT The examination of policy evolution has important practical implications, but current literature often only evaluates changing policy goals and instruments at the macro‐level, overlooking changes that occur at the more granular, micro‐level of policy text.
Graham Ambrose +1 more
wiley +1 more source
, 2004 本文以尾流振子模型为基础,通过改进Lyong的半经验公式法,研究了张力腿的张力变化以及流场分布对张力腿涡激振动响应的影响.计算结果表明,张力腿的张力改变,使各阶模态的锁频区域分布发生变化,从而改变了结构的涡激振动响应;流场分布的响应计算表明,同样的流场分布对不同阶模态的激励作用的效果不同 ...
王艺, 陈伟民
core +2 more sources
野生动物学报, 2010 根据2008～2009年实地考察研究结果,着重就该区2种有蹄类动物的分布、种群数量以及有关问题作概要性探讨。调查研究结果表明:（1）老虎台盘羊分布区盘羊平均密度=8.49/8=1.06只/km2,黑英山盘羊分布区盘羊平均密度=5.34/3=1.78只/km2。整个分布区盘羊种群数量1 488只,其中,老虎台分布区种群数量=480×1.06=509只,黑英山分布区种群数量=550×1.78=979只。（2）老虎台北山羊分布区北山羊平均密度=14.59/5=2.92只/km2 ...
阿布力米提·阿布都卡迪尔 +5 more
doaj
Local Public Goods Provision in the Post-Agricultural Tax Era in Rural China [PDF]
This paper investigates regional differences in local public goods provision in rural area in the 2000s, using large village sample surveys (CHIP 2002 and 2007 surveys, a survey in Ningxia).
Hiroshi Sato, Sai Ding
core
World Food Policy, Volume 12, Issue 2, November 2026.ABSTRACT Household food expenditure continues to be a key factor in ensuring the realization of the Human Right to Adequate Food. Particularly in Brazil, access to food can be limited by economic constraints in vulnerable families, especially among farming families, who have been more vulnerable to food insecurity in recent years in the country.
Lucas de Almeida Moura +3 more
wiley +1 more source
, 2015 沙冬青属(Ammopiptanthus Cheng f.) 隶属豆科(Leguminosae)蝶形花亚科(Papilionaceae)黄华族(Thermosideae)，是亚洲荒漠唯一的常绿阔叶灌木，属下有2个种：新疆沙冬青(Ammopiptanthus.nanus)和蒙古沙冬青(Ammopiptanthus.
刘美
core
Beyond Evidence: How Framing Shapes Public Health Policies During Health Crises
Policy Studies Journal, Volume 54, Issue 4, November 2026.ABSTRACT Does the level of evidence that accompanies policy action depend on how a problem is framed, and on who frames it? This article examines these questions in the context of health crises. Bridging sociological and equivalence framing theories, it treats frames as preexisting interpretive schemes shared within communities of actors, whose ...
Antoine Claude Lemor, Eric Montpetit
wiley +1 more source
Gaoya dianqi, 2009 笔者提出应用ART算法根据测量得到的两个垂直方向上的弧根线性电流分布重建弧根电流密度分布的方法。对Drouet M G实验测量的弧根在2个互相垂直方向的电流分布进行计算,获得了2-D弧根电流密度分布并加以讨论。结果表明,ART重建算法结合分离极板法所测的弧根电流分布是获得其电流密度分布的一个切实可行而有效的途径。
徐铁军, 荣命哲, 吴翊, 马强
doaj