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The Structure and Distribution of the Flavonoids in Plants   总被引:15,自引:0,他引:15  
6 -C3-C6 skeleton, have been found in plants, and are divided into several classes, i.e., anthocyanins, flavones, flavonols, flavanones, dihydroflavonols, chalcones, aurones, flavan and proanthocyanidins, isoflavonoids, biflavonoids, etc. In this review, the chemical structures of the reported flavonoid classes are introduced and their distribution in nature are described. Additionally, some recent chemotaxonomical examples using the flavonoids are also given. Received 1 June 2000/ Accepted in revised form 1 July 2000  相似文献
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Evolution of epiphytes in Davalliaceae and related ferns   总被引:3,自引:0,他引:3  
The evolution of epiphytes in Davalliaceae was investigated by field observations and molecular phylogenetic analyses. Field studies revealed that in Davalliaceae and related ferns, epiphytes in a broad sense are classified into climber, secondary hemi-epiphyte, and obligate epiphyte, based on combinations of the places (ground vs. tree) of inferred spore germination and sporophyte growth. Some species of Davalliaceae have multiple life forms, i.e. secondary hemi-epiphyte and obligate epiphyte, whereas others are obligate epiphytes. Phylogenetic trees obtained from rbcL and accD gene sequences supported that secondary hemi-epiphytic Oleandra is sister to the epiphytic Davalliaceae and polygrammoid ferns. Analyses of life form evolution based on the phylogenetic relationships suggested that obligate epiphytes of the Davalliaceae and polygrammoid ferns evolved from secondary hemi-epiphytes, or less likely from climbers. We hypothesized a scenario for the evolution of life forms in Davalliaceae and related groups that involves successive changes in rhizome habit, root function, and germination place. Rhizome dorsiventrality and scale morphology, shared by climbers, secondary hemi-epiphytes, and obligate epiphytes examined, may be other innovations for the ferns to have evolved into epiphytes.  © 2006 The Linnean Society of London, Botanical Journal of the Linnean Society , 2006, 151 , 495–510.  相似文献
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UV-absorbing substances were isolated from the translucent bracts of Rheum nobile, which grows in the alpine zone of the eastern Himalayas. Nine kinds of the UV-absorbing substances were found by high performance liquid chromatography (HPLC) and paper chromatography (PC) surveys. All of the five major compounds are flavonoids, and were identified as quercetin 3-O-glucoside, quercetin 3-O-galactoside, quercetin 3-O-rutinoside, quercetin 3-O-arabinoside and quercetin 3-O-[6-(3-hydroxy-3-methylglutaroyl)-glucoside] by UV, 1H and 13C NMR, mass spectra, and acid hydrolysis of the original glycosides, and direct PC and HPLC comparisons with authentic specimens. The four minor compounds were characterised as quercetin itself, quercetin 7-O-glycoside, kaempferol glycoside and feruloyl ester. Of those compounds, quercetin 3-O-[6-(3-hydroxy-3-methylglutaroyl)-glucoside] was found in nature for the first time. The translucent bracts of R. nobile accumulate a substantial quantity of flavonoids (3.3–5 mg per g dry material for the major compounds). Moreover, it was clarified by quantitative HPLC survey that much more of the UV-absorbing substances is present in the bracts than in rosulate leaves. Although the flavonoid compounds have been presumed to be the important UV shields in higher plants, there has been little characterisation of these compounds. In this paper, the UV-absorbing substances of the Himalayan R. nobile were characterised as flavonol glycosides based on quercetin.  相似文献
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Branching Principles Governing the Architecture of Cornus kousa (Cornaceae)   总被引:1,自引:0,他引:1  
The complex structure of the crown of Cornus kousa, generallyfive-forked in vegetative branching and two-forked in reproductivebranching, is analysed quantitatively and described by two basicbranching principles: decussate phyllotaxy and the resettingrule for planes of branching. Most Cornus species have opposite,decussate phyllotaxis. The leaf pair (with axillary buds) definesthe branching plane of a node. Because of regular phyllotaxis,the fundamental branching pattern is that every branching planealong an axis is perpendicular to the preceding one. However,the first node of a lateral horizontal shoot always has a horizontalbranching plane; we term this the resetting rule. We observedthat resetting occurs when the first nodes initiated in thevertical plane are repositioned by a twisting of their firstinternodes. All later nodes alternate directions, i.e. showusual decussate alternation. Foliage leaf nodes usually producethree-forked branchings. When vegetative winter buds are formed,a foliar node and adjacent scale leaf node produce a five-forkedbranching. When reproductive winter buds with a terminal inflorescenceare formed, the last foliar node and two adjacent scale leafnodes can produce a variety of branchings but usually producean equal two-forked branching. To understand better the architecturein C. kousa, we contrast it with C. capitata which does notproduce buds with scale leaves and whose vegetative nodes areclearly separated. Copyright 1999 Annals of Botany Company Branching pattern, Cornaceae, Cornus kousa, decussate branching, dogwood, Japanese strawberry tree, tree architecture, tree geometry.  相似文献
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Lethal toxicity (intraperitoneal, mouse) was examined in relation to Species composition of samples containing bloom-forming Microcystis populations from natural waters and correlated with toxicity of laboratory strains of four Microcystis formas and species. Toxicity was not always associated with the presence of M. aeruginosa f . aeruginosa Elenkin. A sample with almost all cells of M. aeruginosa f . aeruginosa showed no toxicity, However samples comprised of a high percentage of M. viridis Lemmermann often showed lethal toxicity. Toxicity tests were done on culture strains M. aeruginosa f aeruginosa, M. aeruginosa f flos-aquae Elenkin , M. viridis and M. wesenbergii Kamárek. All five cultured strains of M. viridis were found to be toxic, while only one out of nine strains of M. aeruginosa f . aeruginosa was toxic. Six strains of M. wesenbergii showed no toxicity, It is recommended that attention should be paid to the occurrences and possibility of toxic bloom of M. viridis from the standpoint of water management and public health .  相似文献
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