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   408篇
  免费   20篇
  国内免费   25篇
  2023年   6篇
  2022年   6篇
  2021年   3篇
  2020年   7篇
  2019年   11篇
  2018年   6篇
  2017年   12篇
  2016年   10篇
  2015年   13篇
  2014年   11篇
  2013年   35篇
  2012年   16篇
  2011年   23篇
  2010年   14篇
  2009年   26篇
  2008年   22篇
  2007年   27篇
  2006年   20篇
  2005年   18篇
  2004年   24篇
  2003年   12篇
  2002年   13篇
  2001年   18篇
  2000年   10篇
  1999年   9篇
  1998年   14篇
  1997年   10篇
  1996年   9篇
  1995年   8篇
  1994年   9篇
  1993年   5篇
  1992年   3篇
  1991年   3篇
  1990年   7篇
  1989年   2篇
  1988年   1篇
  1986年   3篇
  1985年   1篇
  1983年   1篇
  1982年   1篇
  1980年   2篇
  1977年   1篇
  1972年   1篇
排序方式: 共有453条查询结果,搜索用时 978 毫秒
1.
Non-selected and sodium chloride selected callus lines of Vacdnium corymbosum L.cv Blue Crop and cv. Denise Blue were grown on media supplemented with 0–100 mM NaCl. For both cultivars, fresh weight and dry weight yields were greater in selected lines on all levels of NaCl. Selected lines of Blue Crop displayed better growth than selected lines of Denise Blue at most concentrations of NaCl. Internal Na+ and Cl concentrations in selected and non-selected lines of both cultivars increased as external concentration was raised. However, selected lines of Blue Crop and Denise Blue accumulated more Na+ and Cl than non-selected lines. Selected lines of both cultivars maintained higher levels of K+ than non-selected lines on all external NaCl levels. Selected lines of Blue Crop had higher levels of Na+ and Cl than that of Denise Blue. The results suggest Na+ and Cl accumulation could be a mechanism allowing better growth in selected lines at moderate salinity levels (50–75 mM NaCl).  相似文献   
2.
3.
越桔亚科植物化学成分研究进展   总被引:2,自引:0,他引:2  
本文综述了近年来越桔亚科植物的研究进展。分别介绍了越桔属,红梅苔子属等化学成分研究的概况。  相似文献   
4.
The effects of light on in vitro proliferation and subsequent in vivo rooting and acclimatisation of Vaccinium corymbosum were investigated. The shoots were exposed in vitro to different irradiances (total radiation ranging from 55 to 240 μmol m−2 s−1) for 7 to 60 days. In vitro growth and proliferation and the possible consequences on in vivo rooting were observed.
As compared to the control treatment (55 μmol m−2 s−1), higher irradiances improved proliferation and rooting ratios only with short applications (7 days). Short but high (210 μmol m−2 s−1) exposures applied at the end of the proliferation phase increased in vivo growth and rooting of the shoots. The shoots treated with strong light for longer times (14 and 28 days) showed both inhibition of growth and red colour of leaves and sprouts, and were less vigorous when transferred in vivo.  相似文献   
5.
不同产地苍术药材化学成分的比较   总被引:13,自引:2,他引:11  
江苏、安徽及湖北5个产地苍术(Atractylodeslancea(Thunb.)DC.)商品药材的化学分析结果表明:它们在某些药材性状、一些常规化学成分、挥发油成分和含量上存在显著差异。江苏茅苍术根茎挥发油的化学成分复杂,由此探讨了它作为地道药材的特殊性。同时对苍术的“断面暴露稍久可析出结晶”的性状和《药典》(1990年版)规定的“层析谱上应显有苍术素斑点”的鉴别实验进行讨论。  相似文献   
6.
金银花作为我国重要的中药材,具有消炎、抗菌、抗病毒、抗氧化、防癌等多种功效。随着金银花市场供需矛盾日益加剧,通过分子标记辅助选择育种方法来培育高产优质品种势在必行。通过NCBI的Blast工具扫描金银花蛋白组数据发掘花形候选基因,并执行候选基因的亲缘关系分析、结构域分析、表达模式分析、理化性质分析、蛋白质结构预测等一系列生物信息学分析。依据拟南芥调控花形的ABE类基因,通过NCBI-Blast工具扫描金银花氨基酸序列,筛选出包含MADS结构域的8个调控花形的金银花候选基因。经LjaFGD表达模式分析发现,金银花的花中GWHGAAZE016592和GWHGAAZE014905表达量显著高于其他部位,可能正向调控金银花花形。GWHGAAZE014905是一个包含MADS结构域的调控花器官发育的B类基因;GWHGAAZE016592是AP3同源基因。生物信息学分析发现,GWHGAAZE016592和GWHGAAZE014905均是稳定的亲水蛋白,属于非分泌蛋白,包括Motif1、Motif3、Motif4、Motif2、Motif6和Motif5,蛋白质三级结构模板为6byy.2.A和4ox0.2.C。GWHGAAZE014905被定位到细胞核上,而GWHGAAZE016592被定位到叶绿体上,且包含1个位于151~173 bp的跨膜螺旋区域,属于膜蛋白。研究结果为分子标记辅助选择方式培育道地高产优质金银花品种提供了基因资源和分子标记。  相似文献   
7.
Plants of the blueberry cultivar Bluecrop were pollinated with pollen from the cultivars Sierra and Duke under controlled conditions. After pollination, styles were removed at 6 h intervals from 1.25 days to 4.00 days. An increase in the number of developed seed was seen across time, ranging from 1 seed per fruit (s/f) at 1.25 days, to a peak of 63.4 s/f at 3.25 days in 1992, and from 0.1 s/f at 1.25 days to 56.0 s/f at 3.75 days in 1993. Germination tests of 200-seed seedlots of Bluecrop×Sierra exhibited a significant trend toward earlier germination by seed from earlier style removal times. Seed weight measured in the cross Bluecrop×Duke, however, showed decreasing weights with longer style removal times, suggesting that seed size may time of germination. A multiple regression of seed size and stylar removal time against time of germination showed that style removal time was the only significant source of variation for germination time. Results suggest that pollen vigor, as reflected in the speed of growth down the style, may have a direct bearing on characteristics of the seed and subsequent plant.  相似文献   
8.
Hymenoscyphus ericae survived in liquid media containing up to 500 g/ml iron (Fe), Mycorrhizal seedlings of Vaccinium macrocarpon showed higher yields and lower shoot Fe levels and exhibited less severe toxicity symptoms than nonmycorrhizal seedlings.  相似文献   
9.
10.
Laboratory experiments tested whether two economically-important sibling species of tephritid fruit flies have evolved distinct egg-laying responses to chemical stimuli on the fruits of their respective hostplants. The egg-laying preferences displayed by apple maggot flies, R. pomonella, and blueberry maggot flies, R. mendax, on artificial fruits treated with apple and blueberry extract paralleled their egg-laying responses to whole apples and blueberries. R. pomonella flies laid more eggs than R. mendax flies in artificial fruits treated with extract from ripe McIntosh apples, and vice versa for artificial fruits treated with extract from ripe Bluehaven blueberries. Furthermore, both species laid more eggs in artificial fruits treated with extract from their respective host fruits than control artificial fruits which were not treated with fruit extract. Prior electroantennogram recordings from R. mendax and R. pomonella flies exposed to volatiles from pentane extracts of apples and blueberries indicate that the antennal sensitivity of both species is selectively tuned to their respective host fruit odors. This differentiation in their olfactory responses to fruit odors could be important in mediating their distinct ovipositional responses to blueberry and apple fruits. Extract from unripe McIntosh apples also elicited egg laying by R. pomonella flies, however, artificial fruits treated with unripe apple extract received 1.9 times fewer eggs than those treated with ripe apple extract. Moreover, the numbers of R. pomonella ovipositor punctures and eggs placed in wax artificial fruits were increased when the artificial fruits were treated with a blend of 7 identified apple esters. Black coloration on these artificial fruits and the presence of apple esters had a synergistic effect on the egg-laying behavior of R. pomonella flies, which caused them to lay substantially more eggs per black fruit than white fruit treated with the same concentration of apple esters. In summary, our results indicate that the egg-laying responses of R. pomonella flies are mediated by the integration of information from fruit chemical and visual cues, and that R. mendax and R. pomonella flies have evolved divergent egg-laying responses to chemical stimuli on the fruits of their respective hostplants. These findings are discussed in the context of other studies on plant compounds which influence the ovipositional behavior of phytophagous Diptera.
Stimuli chimiques des pommes et des myrtilles induisant la ponte des espèces jumelles, Rhagoletis pomonella et R. mendax
Résumé Des fruits artificiels en cire traités avec des extraits de fruits ont provoqué chez les espèces jumelles de R. mendax (Curran) et R. pomonella (Walsh) des réactions de ponte différentes suivant les stimulations chimiques par les fruits. Le comportement de ponte sur des fruits artificiels traités avec des extraits au pentane des myrtilles mûres (Vaccinium corymbosum L.) et de pommes mûres (Malus pumila Miller = Pyrus malus L.), est le même que sur des fruits naturels, ce qui montre que la réponse aux stimulations chimiques provenant du fruit constitue un aspect important de la reconnaissance de l'hôte. R. pomonella pond plus d'ufs que R. mendax sur les fruits artificiels traités à l'extrait de pommes mûres; c'est l'inverse pour les fruits traités aux extraits de myrtille. Les fruits artificiels traités avec des pommes ou des myrtilles provoquent la ponte de R. pomonella, tandis que les myrtilles mûres seules provoquent la ponte de R. mendax. Les extraits de pommes vertes stimulent la ponte de R. pomonella mais elle est alors 2 fois plus faible qu'avec des extraits de pommes mûres. Un mélange de 7 esters identifiés dans l'extrait de pomme induit aussi la ponte de R. pomonella. Le nombre de piqûres de tarièresfli dans les fruits artificiels en cire et le nombre d'ufs par fruit ont été augmentés par addition d'esters de pommes à des fruits blancs ou noirs. La couleur des fruits artificiels influence aussi la réaction de ponte de R. pomonella; la fréquence des piqûres de tarière contenant un uf et le nombre d'ufs par fruit étaient significativement plus élevés sur les fruits noirs que sur les fruits blancs traités avec la même concentration d'esters de pomme. Les fruits artificiels noirs traités avec la concentration la plus stimulante d'esters de pommes ont reçu 2, 3 fois plus d'ufs que les fruits blancs avec les mêmes concentrations en esters. Ces résultats montrent que les esters de pomme et la couleur noire stimulent synergiquement la ponte de R. pomonella sur des fruits artificiels.
  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