Results 21 to 30 of about 1,217 (166)
取代基上官能团位置对苄基壳聚糖衍生物液晶性的影响 [PDF]
, 2009 合成了4种N-苄基化壳聚糖衍生物,即N-(2-羟基苄基)壳聚糖、N-(3-羟基苄基)壳聚糖、N-(4-羟基苄基)壳聚糖和N-(3-甲氧基-4-羟基苄基)壳聚糖(分别简写为NOCS、NMCS、NPCS和NMPCS),它们的取代基上官能团的数目和位置不同.N-取代度相近,分别为0.72,0.62,0.71和0.68.衍生物溶解在甲酸溶液中均呈现胆甾型溶致液晶相.用偏光显微镜法和折射率法测得各衍生物的液晶临界浓度w分别为28%,37%,24%和27%,均比纯壳聚糖的12%有很大提高 ...
曾志群, 曾海涛, 董炎明
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How much biotic nativeness matters across human demographic groups
Conservation Biology, EarlyView.Abstract Many central concepts of conservation biology—such as nativeness—are structured by ecological and social factors. However, the social consequences of using these concepts to make conservation decisions remain inadequately understood. Some researchers argue that nativeness, rather than acting as an objective proxy for important ecological ...
Harold N. Eyster, Rachelle K. Gould
wiley +1 more source
, 1996 用偏光显微术、平均折射率法和富立叶红外光谱法研究了壳聚糖的溶致液晶行为。在二氯乙酸、甲酸、丙烯酸和３６％乙酸等溶剂中测得的临界浓度都是８％（体积比）或４％～６％（重量比），与根据Ｆｌｏｒｙ理论得到的计算值相符 ...
张璟, 董炎明
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Informing spatial conservation prioritization with species’ traits
Conservation Biology, EarlyView.Abstract New Guinea, the most botanically diverse island on the planet, is the location for one of the boldest conservation initiatives. The Manokwari Declaration aims to achieve 70% conservation designation for the Bird's Head Peninsula. This is 40% higher than the 2022 Global Biodiversity Framework target.
Liam A. Trethowan +27 more
wiley +1 more source
, 2011 通过圆环试验,研究了4种常用减水剂和UEA膨胀剂对混凝土收缩开裂的影响。结果发现:聚羧酸系和萘系高效减水剂对净浆开裂龄期均有延缓作用,但影响规律却不尽相同。随着聚羧酸系减水剂掺量的增多,试件开裂龄期逐渐缩短,抗裂性能下降;而随着萘系减水剂掺量的增多,试件开裂龄期逐渐增长,抗裂性能提高。UEA膨胀剂在6%～12%范围的等量内掺 ...
余彬彬, 刘冬冬, 胡红梅
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Conservation Biology, EarlyView.Abstract In the western United States, conservation practitioners are increasingly working with private landowners to restore habitat for North American beavers (Castor canadensis) and to use nonlethal mitigation techniques when beavers damage crops and infrastructure.
Brian D. Erickson, Megan S. Jones
wiley +1 more source
, 2004 从N 乙基壳聚糖的35%(重量百分比)甲酸溶液浇铸膜制备片状单晶.单晶呈矩形,最大单晶长度达800μm.片状单晶生长在球晶微纤的顶端或没有球晶的地方.片状单晶中分子链方向取矩形的长边方向.单晶中裂纹的方向也是这一方向.由于浇铸膜吸潮,形成片状单晶的实际高分子浓度为83%左右,在此浓溶液中结晶非常缓慢 ...
毕丹霞 +4 more
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Geographic risks to functional groups of mammals and birds from habitat loss in Mexico
Conservation Biology, EarlyView.Abstract There is a need to quantify the impact of habitat loss due to anthropogenic factors on different aspects of biodiversity, such as functional trait diversity represented by functional groups (FGs). We developed a metric to assess the weighted risk of loss of habitat for 33 FGs of mammals and 36 FGs of birds in Mexico based on potential ...
Fernando Mayani‐Parás +4 more
wiley +1 more source
Analysis on the Elastic Lateral Stiffness under Seismic Action for Palace Structure in the Building Standards of Song Dynasty [PDF]
, 2015 中国古代木构架房屋具有良好的抗震性能，其中凝结了长达数千年间古代的建筑工程经验与智慧。这种“干架”结构有别于现代刚接杆系结构，其结构受力分析尚不能直接套用现代框架结构计算方法。已有的研究，通过缩尺模型试验，回归分析，拟合出类似于现代钢筋混凝土框架结构的动力学方程，尚未能揭示出符合古代设计思想及技术水平的基本原理。从古代房屋结构的设计、建造方法入手，探寻其本源的科学原理，一方面可以为古代建筑的安全性能评价找到一般性的方法，另一方面，古为今用，可以为现代工程建设带来新的启迪。 本文在深入研读《营造法式 ...
黄燕萍
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Changes in Key Biodiversity Area networks following national comprehensive assessments
Conservation Biology, Volume 40, Issue 1, February 2026.Making comprehensive assessments of Key Biodiversity Area (KBA) networks in a country greatly increases their number and area. Countries that have not yet done so will be missing about half of these globally significant sites and missing the opportunity to get 30 × 30 conservation in the right places. Abstract Key Biodiversity Areas (KBAs) are sites of
Andrew J. Plumptre +46 more
wiley +1 more source