首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   71篇
  免费   8篇
  国内免费   10篇
  2021年   1篇
  2020年   3篇
  2017年   1篇
  2016年   2篇
  2015年   3篇
  2014年   2篇
  2013年   1篇
  2012年   1篇
  2011年   2篇
  2010年   3篇
  2009年   5篇
  2008年   9篇
  2007年   10篇
  2006年   2篇
  2005年   5篇
  2004年   1篇
  2003年   1篇
  2002年   7篇
  2001年   2篇
  2000年   4篇
  1999年   4篇
  1998年   1篇
  1997年   2篇
  1996年   1篇
  1995年   2篇
  1994年   4篇
  1993年   2篇
  1992年   2篇
  1991年   1篇
  1990年   2篇
  1989年   1篇
  1985年   1篇
  1984年   1篇
排序方式: 共有89条查询结果,搜索用时 46 毫秒
81.
A new triterpenoid, 11a.O.trans-p-coumaroyltaraxerol (1), along with 11 known triterpenoids, taraxerone (2), taraxerol (3), 2α,3β,23,24-tetrahydroxyolean-12-en-28-oic acid (4), oleanolic acid (5), β-amyrin (6), 3β,23-dihydroxylursan-12-en- 28-oic acid (7), 2α,3β-dihydroxyursan-12-en-28-oic acid (8), 2α,3β,23-trihydroxyursan-12-en-28-oic acid (9), 2α,3β,24- trihydroxyursan-12-en-28-oic acid (10), u rsolic acid (11), and 3-O-acetylursolic acid (12), was isolated from Craibiodendron henryi W. W. Smith (Ericaceae). The structures of these compounds were elucidated on the basis of spectral evidence. Antioxidant activity and vasodilator effect of compound 1 were assessed.  相似文献   
82.
洪森荣  尹明华 《植物研究》2010,30(2):191-196
以香果树(Emmenopterys henryiOliv.)带芽茎段为外植体,以MS为基本培养基,采用正交实验和单因子实验方法研究了培养温度、无机盐水平、蔗糖、甘露醇和植物生长抑制剂PP333对香果树试管苗离体保存的影响。结果表明,香果树带芽茎段在9℃低温下保存于附加2.0 mg.L-1KT、2.0 mg.L-16-BA、0.1 mg.L-1NAA、50 g.L-1蔗糖和10 g.L-1甘露醇的1/2MS培养基上,180 d后其成活率可达80%。PP333对香果树的离体保存也有显著影响,其中最适合的PP333浓度为6 mg.L-1,180 d后其成活率可达95%以上。离体保存后的试管苗经形态指标和生理生化指标测定以及RAPD分析检测没有发生遗传变异。本实验结果为珍稀濒危植物香果树的种质保存提供了一条简单有效的途径。  相似文献   
83.
女贞苦丁茶挥发油成分分析   总被引:13,自引:0,他引:13  
苦丁茶是我国南方各民族长期饮用的茶代用品之一,其基原植物种类较多,据调查苦丁茶原植物有9科15种植物,其中木犀科(Oleaceae)女贞属(Ligustrum L.)有粗壮女贞[L. robustum (Roxb.) Bl.]、紫茎女贞(L. purpurascens Y.C.Yang)、序梗女贞(L. pedunculare Rehd)、日本毛女贞(L. japonicum Thunb. var. pubescens Koidz.)等[1~8].  相似文献   
84.
首次报道福建锥栗疫病调查及病原鉴定结果。此病在福建的发生期为4~10月,为害严重,是锥栗重要病害之一。其发生与树龄、品种和其他病虫病的发生有关。病原菌为Cryphonectriaparasitica(Murr,)Barr[Endothiaparasitica(Murr,)And.&And.]  相似文献   
85.
86.
鄂西香茶菜中挥发油成分分析   总被引:3,自引:0,他引:3  
采用水蒸汽蒸馏法分别从鄂西香茶菜的叶、花和果实中提取挥发油,并用气相色谱-质谱联用技术(GC-MS)对其挥发油中的化学成分进行分离和结构鉴定,运用气相色谱峰面积归一化法确定各成分的相对百分含量。从鄂西香茶菜的3种挥发油中共鉴定出39种成分,分别从叶、花及果实中鉴定出18、19和23种成分,其中只有6种成分在这3个部位都被鉴出,3种不同部位得到的挥发油成分差异较大。它们的挥发油中主要成分为单萜、倍半萜和二萜类化合物。  相似文献   
87.
The distribution of immature Culicoides Latreille (Diptera: Ceratopogonidae) in the intertidal zone was investigated at Redland Bay near Brisbane, southeast Queensland. The aims of this study were to determine the distribution of Culicoides immatures and to identify environmental factors influencing these distributions. Light trapping of adult midges indicated that C.subimmaculatus Lee & Reye, C.marmoratus (Skuse), C.longior Hagan & Reye, C.henryi Lee & Reye, C.cordiger Macfie, may have been breeding in the study site. Soil sampling on six transects traversing mangrove and salt-marsh revealed the breeding habitats from which immature stages of the first four species were obtained. The elevation, vegetation and soils of positive sites were recorded and analysed for each species of Culicoides. The distribution of intertidal vegetation (mangroves and salt-marsh plants) was compared to MacNae's (1966) system of mangrove zonation for eastern Australia. The distribution of immature Culicoides did not correspond with mangrove zones, but was related to the presence or absence of intertidal vegetation. C.subimmaculatus was closely associated with a particular substrate and the presence of burrowing crabs.  相似文献   
88.
Intense sexual selection in the form of mate choice can facilitate the evolution of different alternative reproductive strategies, which can be condition-dependent. Tree cricket males produce long-distance acoustic signals which are used by conspecific females for mate localization and mate choice. Our study shows that baffling, an acoustic call amplification strategy employed by male tree crickets using self-made tools, is a classic example of a condition-dependent alternative strategy. We show that though most males can baffle, less preferred males, such as smaller and lower-amplitude callers, predominantly use this alternative strategy. Baffling allows these males to increase their call amplitude and advertisement range, which attracts a higher number of females. Baffling also gives these males a mating benefit because females mate for longer durations with them. Our results suggest that the advantage of baffling in terms of gain in the number of sperm cells transferred while mating is primarily limited to less preferred males, thus maintaining the polymorphism of calling strategies in the population. We summarize that baffling is a condition-dependent strategy used by less preferred tree cricket males to obtain mating benefits.  相似文献   
89.
Emmenopterys henryi , an endemic species in China , being one of the grade Ⅱ national key conservation rare and endangered plants . Based on the data collected from sample plots, the community structure features in Dapanshan National Natural Reserve of Zhejiang Province were analysed. The results showed that the companion species of E . henryi were evergreen and from Lauraceae and Camelliaceae . The richness index , species diversity index and evenness index in the E. henryi community were low, but ecological dominance index was high . In the community , dominant life form, dominant leaf size , dominant leaf form, dominant leaf texture was phanerophytes, mesophyll , single leaves, herbaceous leaves respectively and whose percentage was 75.9%, 53.97%, 74.70%, 63.86% respectively. The second leaf sizewas microphyll, whose percentage was 36.51%. The spatial patterns of E. henryi population mostly conformed to clump distribution, and the tree layer could be easily divided into 3 sublayers in terms of height. The regeneration of population of E. henryi was poor and the population size was declining.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号