Results 51 to 60 of about 37,085 (167)

海南坡地芒果园间作体系水土流失养分损失初步研究

open access: yesShuitu Baochi Xuebao, 2004
通过对4龄芒果园间作体系前期水土流失研究表明,热带地区坡地芒果园水土流失严重,在试验条件下,果园不同间作生态系统中,芒果 柱花草间作模式的径流量和泥沙流失量分别为13747.9m3/hm2,6881.0kg/hm2;芒果 木薯间作模式的径流量和泥沙流失量分别为11199.3m3/hm2,5105.6kg/hm2,单作芒果的径流量和泥沙流失量分别为10590.5m3/hm2,4440.3kg/hm2,芒果 蕃薯-花生间作模式的径流量和泥沙流失量分别为8701.5m3/hm2,3741.3kg/hm2 ...
易小平 唐树梅 余雪标 漆智平
doaj   +2 more sources

滇池流域坡耕地土壤氮磷流失效应

open access: yesShuitu Baochi Xuebao, 2018
为了揭示间作对坡耕地上不同类型土壤径流和侧渗氮(N)、磷(P)浓度的削减及作用机制,通过径流和淋溶模拟试验,设置不同类型土壤(红壤和紫色土)、坡度(8°和15°)和玉米(Zea mays L.)/大豆(Glycine max L.)间作及各自单作对照,比较分析了各因素影响下径流和侧渗N、P浓度的变化情况。结果表明:(1)径流总氮(TN)、总磷(TP)在红壤不同坡度条件下,与单作大豆处理相比较,间作处理对径流TN浓度有不同程度的削减作用,分别降低27.5%和30.8%,且间作处理下TN浓度在坡度为8 ...
钟雄   +6 more
doaj  

Twelve principles for successful governance of community‐based coastal marine restoration

open access: yesConservation Biology, EarlyView.
Abstract Global agreements, such as the Global Biodiversity Framework, call for urgent, large‐scale action to halt biodiversity loss through a whole‐of‐society approach. Community‐based restoration can play a crucial role in achieving this goal, yet there remains limited understanding of what makes these projects effective and sustainable.
Michelle M. Holian   +2 more
wiley   +1 more source

操作冲击电压下空间电荷对棒—线间隙放电的影响

open access: yesGaoya dianqi, 2014
绕击是造成超特高压输电线路雷击跳闸的主要原因,而在绕击事故中,空间电荷的作用不容忽视。为研究空间电荷对雷电绕击输电线路的影响,笔者对150 cm棒—线间隙施加正负操作冲击电压,采用高速摄像系统对放电发展过程进行观测并对外径不同的线电极上的击中次数进行了统计分析,测量了棒对不同外径线电极的预放电电流,采用积分电流法得到线电极周围的空间电荷量,通过ANSYS仿真得到空间电荷对电场的影响。实验结果发现:正操作冲击电压下空间电荷的屏蔽作用对放电击中点的影响较大,而负操作冲击电压下 ...
詹花茂   +4 more
doaj  

Psychometric framework for coexistence with large carnivores

open access: yesConservation Biology, EarlyView.
Abstract Human–carnivore coexistence is essential for biodiversity conservation, yet measuring the attitudes and behaviors that support it remains methodologically challenging. We developed psychometric scales to assess willingness to coexist with carnivores and the underlying beliefs of this coexistence through an iterative expert elicitation process ...
Benjamin Ghasemi   +14 more
wiley   +1 more source

Self-assembly of biomimetic electron-rich foldamers and tetracationic cyclophane(仿生体系的富电子折叠体与四价离子环番的自组装)

open access: yesZhejiang Daxue xuebao. Lixue ban, 2010
合成仿生体系的含1, 5-二氧萘基的富电子折叠体2N、3N、4N和含1, 4-二氧苯基的富电子折叠体2B、3B和4B.用紫外光谱研究了富电子折叠体与缺电子四价离子环番(CBPQT)之间的吸收光谱.结果显示折叠体中的1, 5-二氧萘基的个数越多,其吸收越大,供受体之间的作用越强.随着分子中1, 4-二氧苯基个数的增加,供受体之间的作用由微小到弱相互作用.含1, 5-二氧萘基的富电子折叠体和CBPQT之间的相互作用要远远大于含1, 4-二氧苯基的折叠体和CBPQT之间的相互作用 ...
LIUShi-yong(刘诗咏)   +5 more
doaj   +1 more source

Behavioral interventions to reduce demand for threatened freshwater turtles as pets

open access: yesConservation Biology, EarlyView.
Abstract Growing demand for freshwater turtles as pets has fueled illegal trade and accelerated wild population declines, underscoring the need for theory‐based demand‐reduction interventions. We conducted a three‐part randomized controlled trial with active turtle keepers (n = 1800) in China to test conservation‐ and legality‐framed messages by ...
Wuji Zheng   +9 more
wiley   +1 more source

110 kV同塔四回线路带电更换悬垂绝缘子串作业方法研究

open access: yesGaoya dianqi
针对110 kV同塔四回输电线路相间净空距离与横担间距离较近,带电更换悬垂绝缘子串存在一定的难度以及危险性的问题,文中基于有限元仿真从带电作业危险率以及作业人员体表场强两个方面,对比分析了采用等电位作业、地电位作业以及中间电位作业3种不同作业方式时带电作业的安全性。研究表明:等电位、地电位作业方式均存在危险率大于1×10-5的情况,不符合安规;而采用中间电位作业法进入电场时的组合间隙以及带电作业危险率均符合安规;且采用中间电位作业法时作业人员体表场强也远小于另外两种作业方式 ...
陈鑫涛   +3 more
doaj  

Motivation, Self‐Regulated R2W Strategy Use, and Their Relationship Patterns Among Different Writing Performance Groups

open access: yesInternational Journal of Applied Linguistics, EarlyView.
ABSTRACT The study investigated how writing motivation and self‐regulated read‐to‐write (SRL‐R2W) strategy use was related to writing performance and how the relationship between motivation and SRL‐R2W strategy use varied among different writing performance groups.
Huixuan Zhou   +3 more
wiley   +1 more source

偏头痛患者血浆中过氧化物酶体增殖物激活受体水平的研究

open access: yesZhongguo shiyan zhenduanxue, 2015
目的观察不同时期、不同亚型偏头痛患者血浆中过氧化物酶体增殖物激活受体(PPARs)的变化,探讨偏头痛的发病机制。方法将227例偏头痛患者分成偏头痛发作期组(A组,n=98)和发作间期组(B组,n=129);同时根据患者先兆症状的不同又分为四个亚组,即A1组-无先兆的偏头痛发作期患者(n=71),A2组-有先兆的偏头痛发作期患者(n=27);B1组-无先兆的偏头痛发作间期患者(n=94),B2组-有先兆的偏头痛发作间期患者(n=35);以年龄、性别相匹配的100例健康者作为对照组。搜集患者的临床资料(性别、
张贺敏   +4 more
doaj  

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