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   104篇
  免费   23篇
  国内免费   41篇
  168篇
  2023年   1篇
  2022年   1篇
  2021年   2篇
  2020年   3篇
  2018年   5篇
  2017年   4篇
  2016年   6篇
  2015年   8篇
  2014年   5篇
  2013年   5篇
  2012年   4篇
  2011年   12篇
  2010年   8篇
  2009年   7篇
  2008年   12篇
  2007年   17篇
  2006年   10篇
  2005年   15篇
  2004年   8篇
  2003年   2篇
  2002年   2篇
  2001年   6篇
  2000年   4篇
  1999年   3篇
  1998年   2篇
  1997年   4篇
  1996年   1篇
  1993年   1篇
  1992年   1篇
  1991年   2篇
  1989年   1篇
  1988年   1篇
  1986年   1篇
  1984年   1篇
  1982年   1篇
  1978年   1篇
  1972年   1篇
排序方式: 共有168条查询结果,搜索用时 15 毫秒
91.
Introduction – The aerial part Eupatorium lindleyanum is commonly used as an antipyretic and detoxicant clinically in traditional Chinese medicine. Our previous research showed that germacrane sesquiterpene lactones were its main active constituents, so the development of rapid and accurate methods for the identification of the sesquiterpene lactones is of great significance. Objective – To develop an HPLC‐PDA‐ESI‐MS/MS method capable for simple and rapid analysis of germacrane sesquiterpene lactones in the aerial part E. lindleyanum. Methodology – High‐performance liquid chromatography‐photodiode array detection‐electrospray ionization‐tandem mass spectrometry was used to analyze germacrane sesquiterpene lactones of Eupatorium lindleyanum. The fragmentation behavior of germacrane sesquiterpene lactones in a Micromass Q/TOF Mass Spectrometer was discussed, and 9 germacrane sesquiterpene lactones were identified by comparison of their characteristic data of HPLC and MS analyses with those obtained from reference compounds. Results – The investigated germacrane sesquiterpene lactones were identified as eupalinolides C (1), 3β‐acetoxy‐8β‐(4′‐hydroxy‐tigloyloxy)‐14‐hydroxy‐costunolide (2), eupalinolides A (3), eupalinolides B (4), eupalinolides E (5), 3β‐acetoxy‐8β‐(4′‐oxo‐tigloyloxy)‐14‐hydroxy‐heliangolide (6), 3β‐acetoxy‐8β‐(4′‐oxo‐ tigloyloxy)‐14‐hydroxy‐costunolide (7), hiyodorilactone B (8), and 3β‐acetoxy‐8β‐(4′‐hydroxy‐tigloyloxy)‐ costunolide (9). Compounds 6, 7 and 9 were reported for the first time. Conclusion – HPLC‐PDA‐ESI‐MS/MS provides a new powerful approach to identify germacrane sesquiterpene lactones in E. lindleyanum rapidly and accurately. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   
92.
世界性恶性杂草──紫茎泽兰研究的历史及现状   总被引:145,自引:0,他引:145  
紫茎泽兰又名破坏草,其学名为Eupalo,。u。。ade;;opho;、。nSprengel,[Age。t。naade。;opho;a(Spreng.)K.&R,E.glandulosumH.B.K.nonMichx.j,英文名为Croftonweed或Pamakani,菊科泽兰属多年生杂草。原产美洲的墨西哥至哥斯达黎加一带,后作为观赏植物被引种到欧洲"',后再引到澳洲和亚洲'"。显然,长距离的传播是借助于人的力量。不过,短距离传播扩散都是由其自身的瘦果扩散能力,经风力完成的'"。现已广泛分布在世界热带、亚热带地区30多个国家和地区。除中美洲原产地外,其中还包括美国'"'、澳大利亚","…  相似文献   
93.
为了解紫茎泽兰(Eupatorium adenophorum Spreng.)的化学成分,从其地上部分茎和叶中分离得到4个酚酸衍生物和5个甾体化合物。经光谱分析,分别鉴定为2-羟基苯丙醇(1)、香豆素(2)、去甲氧基英西卡林(3)、英西卡林(4)、3β-acetoxy-25-hydroxydammara-20,23-diene(5)、3β-acetoxy-24-hydroxydammara-20,25-diene(6)、豆甾-4,22-二烯-3-酮(7)、豆甾醇(8)和β-胡萝卜苷(9)。化合物1、2、5~7为首次从该植物中分离得到。  相似文献   
94.
两种入侵植物与三种本地植物根系特征的比较研究   总被引:1,自引:0,他引:1       下载免费PDF全文
以菊科2种入侵植物飞机草(Chromolaena odorata (L.)R. M. King & H. Rob)和紫茎泽兰( Eupatorium adenophorum Speng)以及生活型相似的3种本地植物异叶泽兰(Eupatorium heterophyllum DC.)、佩兰(Eupa-torium for...  相似文献   
95.
The fungus, Alternaria alternata (Fr.) Keissler Strain 501, has been evaluated as a bioherbicide for control of Eupatorium adenophorum Spreng., but the biology of the pathogen–host interaction and the optimal environmental conditions for disease development and effective weed control are unknown. Disease development of A. alternata Strain 501 mycelia on E. adenophorum was assessed under several factors including pathogen inoculum concentration, plant age, dew period duration, post-dew temperature, storage temperature and duration. The minimum inoculum concentration required to kill E. adenophorum seedlings was 3.2×106 mycelial fragment mL?1. E. adenophorum seedlings at the four-leaf-pair stage were more susceptible than the older plants, especially those at the older than seven-leaf-pair stage. With a dew period of at least 14 h, 100% mortality occurred. The optimal post-dew temperature for disease development was 18–25°C. Storage at <4°C maintained the infectivity of A. alternata strain 501 mycelia on E. adenophorum longer. Using light and scanning electron microscopy to examine the infection process of A. alternata Strain 501 mycelia, it was shown that the time from initiation to completion of infection with mycelia was much shorter (14 h) than with conidia (72 h). It was further shown that mycelial infection occurred predominately through direct penetration at intercellular junctions, while conidial infection occurred predominately through stomatal penetration. This suggests that mycelia are more suitable as infection propagules for A. alternata strain 501 in a bioherbicide for the control of E. adenophorum.  相似文献   
96.
广东土牛膝为菊科泽兰属植物华泽兰(Eupatorium chinense)的干燥根。从其甲醇提取物中共分离得到11个化合物,其中eupatorinA(1)为一新化合物,经波谱学方法鉴定为(threo)-3-O-acetyl-1-(4-hydroxy-3-methoxyphenyl)-2-[4-(3-hydroxy-1-(E)-propenyl)-2,6-dimethoxyphenoxy]propyl-β-D-glucopy-ranoside。已知化合物分别鉴定为(threo)-3-hydroxy-1-(4-hydroxy-3-methoxyphenyl)-2-[4-(3-hydroxy-1-(E)-propenyl)-2,6-dimethoxyphenox-y]-propyl-β-D-glucopyranoside(2),ardisiacrispinA(3),ardisiac-rispinB(4),euparone(5),3-(2,3-dihydroxy-isopen-tyl)-4-hydroxyacetophenone(6),12,13-di-hydroxy-euparin(7),gymnastone(8),N-(2′-hydroxy-tetracosanosyl)-2-amino-1,3,4-trihydroxy-octa-dec-8-(E)-ene(9),stigmasterol(10)和stigmasterol-3-O-β-D-glucopyranoside(11)。化合物2-4为首次从菊科植物,5-8为首次从泽兰属植物中分离得到。  相似文献   
97.
98.
Increases in the concentration of atmospheric CO2 and plant invasion are two important problems that face humans worldwide. In some plants, exposure to a short term elevated concentration of CO2 (SE[CO2]) promotes photosynthesis, but the promotion of elevated [CO2] (E [CO2]) to photosynthesis might disappear after long term treatment (so called “CO2 acclimation”); this might result from the associated inhibition of nitrate assimilation. The present study investigated the physiological effects of short term (8 days) and long term (40 days) exposure to E[CO2] when these were combined with different forms of inorganic N (full N; nitrate (NO3-) N) in the invasive species Eupatorium adenophorum. Exposure to E[CO2] increased the biomass of Eadenophorum, regardless of the duration of exposure to E[CO2] and the type of inorganic N that was supplied. E[CO2] could promote the photosynthesis of Eadenophorum seedlings fertilised with non depleted Hoagland solutions (full N). For plants fertilised with NH4+ depleted Hoagland solution (NO3- N), LE[CO2] treatment promoted the photosynthesis of Eadenop horum, but the promotion of photosynthesis by E[CO2] disappeared under SE[CO2] conditions. Photosynthetic pigments contents were determined to estimate potential changes in the photosynthetic capacity of Eadenophorum. For plants fertilised with non depleted Hoagland solution, there were no significant differences in chlorophyll among the three [CO2] treatments, but the treatment of SE[CO2] increased the levels of chlorophyll in leaves. The apparent promotion of biomass accumulation and photosynthesis at LE[CO2] without a decrease in chlorophyll indicates that Eadenophorum might not acclimate to long term exposure to E[CO2]. NH4+ depletion did not affect the capacity of LE[CO2] to promote the photosynthesis of Eadenophorum. Thus, considering some plants fertilised with NO3- acclimating to LE[CO2], Eadenophorum might be more competitive in areas where the soils are relatively poor in NH4+ as levels of atmospheric CO2 continue to rise.  相似文献   
99.
紫茎泽兰提取物对四种储粮害虫的杀虫活性   总被引:26,自引:0,他引:26  
紫茎泽兰提取物对米象、玉米象、绿豆象和蚕豆象等 4种储粮害虫成虫具有强烈的熏杀活性 ,用 4 4.4 4mg L的浓度熏蒸处理 4 8小时后 ,每种成虫死亡率均达到 1 0 0 .0 0 %。熏蒸毒力测定结果表明 ,紫茎泽兰提取物对上述 4种成虫 2 4小时的LC50 分别为 1 4 .65,1 2 .80 ,2 5.0 7和 1 2 .2 0mg L ,4 8小时的LC50 分别为 1 1 .79,9.67,1 3 .2 9和 9.76mg L。  相似文献   
100.
紫茎泽兰与黑麦草苗期相对竞争力和生长特征的研究   总被引:2,自引:0,他引:2  
为探究替代物种黑麦草(Lolium perenne)抑制外来人侵杂草紫茎泽兰(Eupatorium adenophorum)的潜力,采用de Wit取代系列设计,在野外小区内设置3水平多年生黑麦草栽植时间、4水平种植密度以及3水平混种比例等不同种植处理,于12周后收获,分别测量黑麦草与紫茎泽兰的地上生物量和地下生物量,用单株相对产量分析其竞争力。结果表明,种植密度、混种比例和黑麦草栽植时间显著影响紫茎泽兰的地上生物量,紫茎泽兰的竞争力在低种植比例情况下,随黑麦草栽植时间的推迟而明显增强,随种植密度的降低而增强。种植密度、混种比例、黑麦草栽植时间以及这些因素的互作等对黑麦草的地上生物量与地下生物量均具有显著影响;栽植时间越晚、密度越大,黑麦草的竞争力就越弱(尽管不存在直线关系)。在大多数种植处理条件下,紫茎泽兰经历的种间竞争明显大于种内竞争,表现出较弱的竞争力;而黑麦草在与紫茎泽兰同时栽植的情况下,经历的种内竞争大于种间竞争,表现出较强的竞争力。  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