全文获取类型
收费全文 | 52篇 |
免费 | 7篇 |
国内免费 | 2篇 |
出版年
2022年 | 1篇 |
2021年 | 1篇 |
2020年 | 1篇 |
2019年 | 1篇 |
2018年 | 1篇 |
2015年 | 1篇 |
2014年 | 2篇 |
2013年 | 1篇 |
2012年 | 1篇 |
2011年 | 2篇 |
2010年 | 1篇 |
2009年 | 1篇 |
2008年 | 3篇 |
2007年 | 4篇 |
2006年 | 5篇 |
2005年 | 3篇 |
2004年 | 5篇 |
2003年 | 3篇 |
2002年 | 1篇 |
2001年 | 1篇 |
2000年 | 4篇 |
1999年 | 1篇 |
1997年 | 1篇 |
1996年 | 2篇 |
1995年 | 1篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1978年 | 2篇 |
1976年 | 1篇 |
排序方式: 共有61条查询结果,搜索用时 14 毫秒
1.
Molecular evolution of pteridophytes and their relationship to seed plants: Evidence from complete 18S rRNA gene sequences 总被引:1,自引:0,他引:1
Complete 18S ribosomal RNA sequence data from representatives of all extant pteridophyte lineages together with RNA sequences from different seed plants were used to infer a molecular phylogeny of vascular plants that included all major land plant lineages. The molecular data indicate that lycopsids are monophyletic and are the earliest diverging group within the vascular land plants, whereasPsilotum nudum is more closely related to the seed plants than to other pteridophyte lineages. The phylogenetic trees based on maximum likelihood, parsimony and distance analyses show substantial agreement with the evolutionary relationships of land plants as interpreted from the fossil record. 相似文献
2.
3.
4.
Five altitudinal pteridophyte zones are established along the northeastern altitudinal slopes of Mt. Banahaw de Lucban, Quezon,
Luzon Is., Philippines using cluster- and ordination analyses, namely: Zone 1, Cyathea contaminans – Dicranopteris–Nephrolepis–Diplazium patches at 700–800 m a.s.l.; Zone 2, Sphaerostephanos hirsutus var. hirsutus – Selaginella delicatula patches at 750–900 m a.s.l.; Zone 3, Cyathea philippinensis – Selaginella patches at 900–1200 m a.s.l.; Zone 4, Cyathea philippinensis – Cyathea callosa–Asplenium cymbifolium–Selaginella cumingiana patches at 1200–1550 m a.s.l. and; Zone 5 which is further divided into Sub-zone 5A, Cyathea callosa – Cyathea loheri-Hymenophyllaceae patches at 1550–1800 m a.s.l. and Sub-zone 5B, Cyathea loheri – Cephalomanes apiifolia patches at 1800–1875 m a.s.l. These pteridophyte zones coincide with the woody species zones of Mt. Banahaw de Lucban but
differ significantly with the altitudinal fern zones of Mt. Makiling. Stepwise multiple regression analysis reveals that altitude
exhibits a linear relationship with pteridophyte species distribution. Altitude and soil pH influence 65% of the variation
in principal component 1 [PC1 = 0.0839 + 0.0010(altitude) − 0.2072(soil pH); r = 0.8058] and 27% of the variation in principal component 2 [PC2 = 2.0453 − 0.0005(altitude) − 0.2560(soil pH); r = 0.5206]. Thirty-three (33) species are preferential to specific microenvironments along the altitudinal gradient, making
them effective altitudinal zone markers and biodiversity conservation indicators for the forest ecosystem of Mt. Banahaw de
Lucban. 相似文献
5.
Noncoding DNA sequences from numerous regions of the chloroplast genome have provided a significant source of characters for phylogenetic studies in seed plants. In lycophytes and monilophytes (leptosporangiate ferns, eusporangiate ferns, Psilotaceae, and Equisetaceae), on the other hand, relatively few noncoding chloroplast DNA regions have been explored. We screened 30 lycophyte and monilophyte species to determine the potential utility of PCR amplification primers for 18 noncoding chloroplast DNA regions that have previously been used in seed plant studies. Of these primer sets eight appear to be nearly universally capable of amplifying lycophyte and monilophyte DNAs, and an additional six are useful in at least some groups. To further explore the application of noncoding chloroplast DNA, we analyzed the relative phylogenetic utility of five cpDNA regions for resolving relationships in Botrychium s.l. (Ophioglossaceae). Previous studies have evaluated both the gene rbcL and the trnL(UAA)-trnF(GAA) intergenic spacer in this group. To these published data we added sequences of the trnS(GCU)-trnG(UUC) intergenic spacer + the trnG(UUC) intron region, the trnS(GGA)-rpS4 intergenic spacer+rpS4 gene, and the rpL16 intron. Both the trnS(GCU)-trnG(UUC) and rpL16 regions are highly variable in angiosperms and the trnS(GGA)-rpS4 region has been widely used in monilophyte phylogenetic studies. Phylogenetic resolution was equivalent across regions, but the strength of support for the phylogenies varied among regions. Of the five sampled regions the trnS(GCU)-trnG(UUC) spacer+trnG(UUC) intron region provided the strongest support for the inferred phylogeny. 相似文献
6.
Two new species of ferns and a hybrid horsetail are described from Mexico:Diplazium wendtii, Polypodium microgrammoides, andEquisetum × haukeanum. 相似文献
7.
Diversity and distribution of ferns in sub-Saharan Africa, Madagascar and some islands of the South Atlantic 总被引:2,自引:0,他引:2
Aim This paper reports the diversity and endemism patterns of African ferns, and explores the potential role of diversity refuges and environmental and historical factors in the shaping of these patterns. Material and locations The extant fern taxa occupying Africa south of the Sahara, Madagascar and some islands of the South Atlantic. Methods The number of taxa in each area or operational geographical unit (OGU) was scored, and the correlation between this number and physical and climatic variables analysed by standard pairwise and stepwise multiple regression analysis (SPR and SMR). The effects of biological factors such as dispersal capacity, reproductive biology, genetic features and certain physiological adaptations were evaluated by comparing the number of species in each OGU. Floral affinities among OGUs were analysed using non‐metric multi‐dimensional scaling (NMS) and parsimonic analysis of dispersion (PAD), and compared with β‐turnover and inter‐OGU distances. Results OGU area, elevation and the distance between refuges determined the composition of local floras, but only greater OGU area and the existence of higher maximum elevations increased species richness. The distance between refuges also affected the number of endemic species, especially on islands. The biological features studied only slightly influenced fern distribution. The main climatic predictor of species number was humidity. SPR and SMR revealed three main groups of ferns with different ecological trends. NMS and PAD analyses separated the four areas of highest diversity in Africa, three of which are inhabited by ferns with distinct ecological requirements. The fourth area was Madagascar, which shows an accumulation of endemic and relict diversity that is not easy to explain. Main conclusions The distribution of ferns in Africa has been influenced by refuges. These probably allowed many species to recolonize the neighbouring areas after the extinctions of the Pleistocene. Three major components were detected in the African flora: Guinea‐Congolian thermophilous, cold‐tolerant Afro‐montane, and Southern drought‐tolerant elements. These are related to the three main refuge areas, i.e. the Gulf of Guinea area, the eastern tropical region, and the Cape region. Endemicity in ferns was found to be lower than that of seed plants due to the higher dispersability of fern spores. The distance between OGUs seems to be the main predictor of the number of endemic fern species these areas contain. 相似文献
8.
滇东南老君山自然保护区蕨类物种多样性研究 总被引:5,自引:0,他引:5
本文在分类和区系的基础上,对老君山自然保护区蕨类物种进行多样性研究。结果如下:(1)蕨类物种丰富,物种多样性指数较高;(2)物种密度及个体密度均较大;(3)频度最大的物种为中华桫椤等;(4)相对多度最多者为斑点毛鳞蕨;(5)物种形态各异,大小差别悬殊;(6)分类群比较齐全而且其系统演化的位置多样;(7)地理成分复杂但以北部湾或滇东南山地特有成分最突出;(8)各种生态类型兼备。 相似文献
9.
浙江北雁荡山野生蕨类植物资源 总被引:4,自引:0,他引:4
对浙江北雁荡山的蕨类植物进行专题研究。浙江乐清北雁荡山共有蕨类植物147种,隶属于37科70属。蕨类植物物种密度为42.13/100 km2。比西双版纳的密度1.71/100 km2要高。远大于全国蕨类植物密度0.027/1 000 km2,是我国东南沿海蕨类植物物种密度较高的地区之一。按照用途分为药用、食用、观赏和其他用途4大类型。并记录本地常用蕨类的俗名,统计草药市场药用蕨类资源销售量,为进一步开发利用蕨类植物资源提出建议。 相似文献
10.