全文获取类型
收费全文 | 299篇 |
免费 | 14篇 |
出版年
2021年 | 3篇 |
2020年 | 2篇 |
2018年 | 3篇 |
2017年 | 3篇 |
2016年 | 4篇 |
2015年 | 6篇 |
2014年 | 13篇 |
2013年 | 4篇 |
2012年 | 10篇 |
2011年 | 18篇 |
2010年 | 12篇 |
2009年 | 16篇 |
2008年 | 15篇 |
2007年 | 20篇 |
2006年 | 7篇 |
2005年 | 13篇 |
2004年 | 11篇 |
2003年 | 14篇 |
2002年 | 9篇 |
2001年 | 2篇 |
2000年 | 6篇 |
1999年 | 4篇 |
1998年 | 7篇 |
1997年 | 11篇 |
1996年 | 4篇 |
1995年 | 7篇 |
1994年 | 5篇 |
1993年 | 6篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1986年 | 3篇 |
1985年 | 2篇 |
1984年 | 5篇 |
1983年 | 2篇 |
1981年 | 3篇 |
1978年 | 1篇 |
1972年 | 1篇 |
1970年 | 1篇 |
1969年 | 3篇 |
1968年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
1959年 | 5篇 |
1958年 | 14篇 |
1957年 | 4篇 |
1956年 | 5篇 |
1955年 | 5篇 |
1954年 | 1篇 |
1953年 | 2篇 |
1952年 | 4篇 |
排序方式: 共有313条查询结果,搜索用时 140 毫秒
1.
2.
Phylogenetic systematics of the nymphaeales 总被引:2,自引:0,他引:2
Motomi Ito 《Journal of plant research》1987,100(1):17-35
A cladistic analysis was applied to reveal the phylogenetic relationships among the Nymphaeales. Seventeen out of twenty three
characters in gross morphology, anatomy and palynology were analyzed, for their evolutionary polarities. From the results
of the present analysis, the phylogenetic status of each genus and their relationships were clarified: 1)Nelumbo is a distinct taxon and is presumed to have originated from an ancestral stock of the Nymphaeales; 2)Ceratophyllum has a close phylogenetic relationship withCabomba; and 3) in the Nymphaeaceaesensu stricto, Nuphar and the remaining genral constitute a monophyletic group.
A conclusion obtained from the present analysis was that the following three families should be recognized in the Nymphaeales;
Nelumbonaceae Nymphaeaceae, and Ceratophyllaceae. The generaBrasenia andCabomba are traditionally classified in the Nymphaeaceae or in the independent family Cabombaceae. However, they should be included
in the family Ceratophyllaceae. 相似文献
3.
The genusCrepidiastrum is distributed in East Asia and includes 7 species. In the Bonin Islands, three species ofCrepidiastrum occur, and all of them are endemic to the islands. For detecting the origin and speciation of these endemic species, electrophoretic
studies have been done in three endemic species of the Bonin Islands as well as in the remaining four species ofCrepidiastrum, andYoungia denticulata which is considered to be closely related toCrepidiastrum.
A total of 386 individuals were sampled from 14 populations. As a result, 17 loci of 10 enzyme systems were resolved and gene
frequencies for each population were calculated. The genetic variability was low in island species, as reported in some oceanic
island plants. Four groups were recognized in the dendrogram generated by the UPGMA method. The Bonin endemics were clustered
together, suggesting a monophyletic origin.C. ameristophyllum andC. linguaefolium were found to be genetically very similar, and this may suggest recent and rapid speciation within the islands. 相似文献
4.
Mitsuyasu Hasebe Rumiko Kofuji Motomi Ito Mikio Kato Kunio Iwatsuki Kunihiko Ueda 《Journal of plant research》1992,105(4):673-679
Partial nucleotide sequences of the large subunit of ribulose-1,5-bisphosphate carboxylase (rubisco) gene (1333 base pairs:
about 90% of the gene) from several seed plants were determined. Phylogenetic trees based on amino acid sequences were inferred
by using the neighbor joining and maximum likelihood methods. The results indicate (1) monophyly of gnetum group (Ephedra, Gnetum, Welwitschia), (2) monophyly of extant gymnosperms containing gnetum group, which contradicts the results of morphological data. 相似文献
5.
ITO OSAMU; OKANO KUNIO; KUROIWA MIYOKO; TOTSUKA TSUMUGU 《Journal of experimental botany》1985,36(4):652-662
Ten-day old kidney bean plants (Phaseolus vulgaris L. cv. Shin-edogawa)were exposed to 2.0 and 40 parts 106 NO2, and0.1, 0.2, and 0.4 parts 106 O3 alone or in combinationfor 2, 4, and 7 d. The effects of these air pollutants wereexamined with respect to the growth, partitioning of assimilates,nitrogen uptake, soluble sugar content, and root respiration. Decreased dry matter production was significant with all treatmentsexcept 2.0 parts 106 NO2 and 0.1 parts 106 O3.Exposure to mixtures of the gases produced more severe suppressionof growth than exposure to the single gases. Root/shoot ratiowas significantly lowered at 7 d by the gas treatments otherthan 2.0 parts 106 NO2 and 0.1 parts 106 O3. Thetotal nitrogen content of plants was increased by all treatments;the higher percent of nitrogen found with O3 exposure will resultfrom the growth retardation which increases the concentrationof nitrogen in the plants because the absorption of nitrogenby roots was unaffected. The combination of O3 with NO2 significantlydecreased the assimilation of NO2 by the plants. The concentration of soluble sugars in roots was decreased bythe gas treatments. There was a strong positive correlationbetween soluble sugar content and dry weight of the roots harvestedat 7 d. Root respiration was relatively unchanged until 5 dand then decreased significantly at 7 d by 2.0 parts 106NO2 and 02 parts 106 O3. Retarded growth of theroots and the decreased root respiration may be due to diminishedtranslocation of sugars from leaves to roots caused by exposureto air pollutants. The uptake of soil nitrogen was not closelyrelated with root respiration in the case of O3 exposure. Key words: NO2, O3, Phaseolus vulgaris, Growth, Sugars, Root respiration 相似文献
6.
Motomi Ito 《Journal of plant research》1986,99(2):169-184
Floral morphology ofBrasenia schreberi Gmel. andCabomba caroliniana A. Gray was observed chiefly from an anatomical point of view. The receptacle ofB. schreberi is rather flat and a vascular plexus is observable in the mature flower. The vasculature in this plexus is so complex taht
it is not easy to trace its structure in detail. by observation on small buds, it can be seen that the receptacular vasculature
consists of a girdling bundle in the basal area and usually nine receptacular strands from which traces to the petals and
stamens branch off. The vasculature in the receptacle is reconstructed and diagramatically shown as though split longitudinally
and spread out in one plane.
Floral vasculature inCabomba caroliniana is simpler, and is probably related to the smaller number of stamens and carpels. It also has a girdling bundle at the bottom
of receptacle and this vasculature is suggested to be derived by simplification from aBrasenia-type vasculature.
Evidence from floral anatomy suggests that these two genera are closely related. InNymphaea, a vascular plexus in the receptacle is also observed (Moseley, 1961; Ito 1983). The plexus ofBrasenia andNymphaea are not the same in their construction. Nevertheless, their fundamental floral vasculature is comparable and it is preferable
to place them in the same family or same order. 相似文献
7.
The percentage of pectic substances in the cell wall of riceleaf decreased with the ageing of the leaf but other componentsin the cell wall changed little during leaf growth. Cell wallcomponents were not affected by a nutritional deficiency ofcalcium. At the beginning of the growth of rice leaf, calciumin the cell wall existed only in the pectic substance fractionboth in the calcium sufficient and deficient leaves. However,in the cell wall of the mature leaf, a considerable amount ofcalcium was found in the lignin fraction. The amount of calciumin this form was larger in calcium sufficient leaves than indeficient leaves. Calcium seems to occur in two forms in the cell wall, combinedwith pectic substances and with ligneous substances. This assumptionwas further supported by calcium distribution in enzymaticallydegradated fractions of the cell wall. Calcium seems to be combined with pectic substances by a strongerchemical bond than with the ligneous substances.
1Present address: Tohoku Agricultural Experiment Station, Omagari,Akita. 相似文献
8.
A cladistic analysis was used to deduce the phylogenetic relationships within the colonial Volvocales. Forty-one pairs of characters related to gross morphology and ultrastructure of vegetative colonies as well as asexual and sexual reproduction were analyzed based on parsimony, using the PAUP 3.0 computer program, for 25 species belonging to nine volvocacean and goniacean genera of the colonial Volvocales. Chlamydomonas reinhardtii Dangeard was the outgroup. The strict consensus tree indicated the presence of two monophyletic groups, one composed of all the volvocacean species analyzed in this study and the other containing the goniacean species except for the four-celled species Gonium sociale (Dujardin) Warming. In addition, these two groups constitute a large monophyletic group, to which G. sociale is a sister group. A new combination Tetrabaena socialis (Dujardin) Nozaki et Itoh and a new family Tetrabaenaceae Nozaki et Itoh are thus proposed for G. sociale. In addition, the analysis suggests that the volvocacean genera Eudorina and Pleodorina are paraphyletic groups, respectively, and that the monotypic genus Yamagishiella has no autapomorphic characters and represents primitive features of the anisogamous and oogamous genera of the Volvocaceae. Phylogenetic relationships within the Volvocaceae and the Goniaceae, as well as the various modes of sexual reproduction exhibited by these organisms, are discussed on the basis of the analysis. 相似文献
9.
Chloroplast DNA phylogeny of Asian Bamboos (Bambusoideae,Poaceae) and its systematic implication 总被引:1,自引:0,他引:1
The bamboo is usually classified as a subfamily Bambusoideae of Poaceae, and includes approximately 20 genera and 300 species.
To estimate phylogenetic relationships among these genera, we examined restriction site mutations of cpDNA for 16 Asian genera.
In the cladogram obtained, the Bambosoideae was divided into two major lineages, one includingPleioblastus, Pseudosasa, Semiarundinaria, Shibataea, Phyllostachys, Sasa, Sinobambusa, Chimonobambusa, Arthrostylidium, andYushania, and the other consisting ofBambusa, Gigantochloa, Dendrocalamus, Thyrostachys, Melocanna, andSchizostachyum. Monophylly of each clade was supported by 83% and 98% bootstrap probability, respectively. The present result supports monophylly
of Arundinarieae of Potztal's (1964) classical system, but does not support his treatment to recognize Dendrocalameae. 相似文献
10.
DEREK TOBIN ANTHONY G. QUINN SHOSUKE ITO ANTHONY J. THODY 《Pigment cell & melanoma research》1994,7(4):204-209
The present study was carried out to investigate the abundance of tyrosinase and related proteins (TRP-1 and TRP-2) in human epidermis and their relationship to melanin type. Positive immunocytochemical staining was seen for all three proteins in epidermal melanocytes. For each protein the numbers of positively stained melanocytes were similar in all subjects studied irrespective of skin type. Following 5 daily suberythemal doses of UVB the melanocytes were larger, more dendritic, and increased in number. With TRP-1 and TRP-2 the increase in number in response to UVB was unrelated to skin type and, hence, with melanin type but with tyrosinase there was a much greater increase in skin types III and IV than in skin type I and II. The enhanced numbers of tyrosinase-positive melanocytes were accompanied by increased staining intensity, suggesting a greater expression of tyrosinase in the melanocytes from skin types III and IV compared with skin types I and II. This increase in tyrosinase could be related to the greater levels of eumelanin found in skin types III and IV, and this is in keeping with the view that higher levels of tyrosinase are associated with the production of eumelanin than phaeomelanin. 相似文献