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51.
52.
J. Mazumdar 《South African Journal of Botany》2011,77(1):10-19
Study of phytoliths of pteridophytes is an emerging area of research. Literature on this aspect is limited but increasing. Some recent findings have shown that phytoliths may have systematic and phylogenetic utility in pteridophytes. Phytoliths are functionally significant for the development and survival of pteridophytes. Experiments with some pteridophytes have revealed various aspects of silica uptake, deposition and biological effects. 相似文献
53.
Rhizome fragments (referred to as “fragments”) and tubers of Equisetum arvense L. were cultured in order to investigate their competence with respect to vegetative reproduction. The starch concentration of the fragments was lower than that of the tubers, but the initial growth of new individuals from these fragments was superior to that from tubers obtained from the same dry mass. This superior growth was due to the large number of buds (grown from nodes) and aerial shoots on the fragments. The competence for vegetative reproduction depended on the relationship between the stored starch and the number of buds. 相似文献
54.
At an early stage of growth gametophytes support the sporophytes of ferns. Young sporophytes become independent of gametophytes
when the first leaves develop. Although large fern gametophytes produce multiple archegonia simultaneously, only one sporophyte
is typically established on one gametophyte. The number of sporophytes is believed to be controlled in two possible directions,
from gametophyte to sporophyte or from preceding sporophyte to another sporophyte. To investigate the effects of gametophytes
on their sporophytes, we studied the relationship between organic matter production by gametophytes and the growth of young
sporophytes of Thelypteris palustris. We cut gametophytes in half (CGs) to reduce the gametophytes’ production of matter. There was no significant difference
between the growth of sporophytes on intact gametophytes (IGs) and that on CGs. According to our estimates, based on the rate
of organic matter production, the large gametophyte was able to produce two or more sporophytes. The resources required for
CGs to make similar-sized sporophytes was twice that for IGs. In polyembryony each of the multiple sporophytes was similar
in size to the single sporophytes. Resource limitation does not seem to explain why fern gametophytes establish single sporophytes. 相似文献
55.
海南岛及中国蕨类植物分布新记录 总被引:7,自引:1,他引:6
报道了海南岛蕨类植物分布新记录2属(即毛边蕨属Didymoglossum Desv.,凸轴蕨属MetathelypterisChing)、28种,其中毛边蕨属和8个种在中国也属首次发现。 相似文献
56.
四种蕨类植物根际土壤中VA菌根真菌孢子种群组成和季相变化 总被引:4,自引:0,他引:4
对4 种移栽到温室中的蕨类植物根际土壤中的VA 菌根真菌孢子种群组成和季相变化进行了研究, 结果发现, VA菌根真菌孢子的产生具有明显的宿主依赖性和季相变化。在相同气候条件下, 不同植物根际土壤中的VA菌根真菌种群组成不同; 同种VA 菌根真菌在不同宿主植物根际土壤中, 孢子的丰富度有很大的差异。本文对影响VA菌根真菌孢子种群组成和季相变化的因素进行了讨论。 相似文献
57.
为了解蕨类植物多样性及种群分布对环境因子的响应,建立元江干热河谷不同海拔气温和降水的分布模式,对蕨类植物在元江干热河谷内的自然分布进行了研究。结果表明,元江干热河谷从低海拔到高海拔,气温逐渐下降,但降水量却逐渐增加;河谷内蕨类植物多样性及种群分布呈现差异化;干热河谷内蕨类分布受气温影响不大,但与生境水分条件密切相关。元江干热河谷水热条件分布不均,生态环境破碎,气温和降水分布不均,差异化显著,促进了小生境发育。蕨类植物可以指示生态环境的完整性和连续性,某些种群可以指示和监测环境因子尤其是水因子的变化。 相似文献
58.
Ecology of the Pteridophytes on the Southern Slopes of Mt. Kilimanjaro. Part II: Habitat Selection 总被引:2,自引:0,他引:2
A. Hemp 《Plant biology (Stuttgart, Germany)》2001,3(5):493-523
Abstract: Based on the evalutation of 957 vegetation plots on the southern slope of Mt. Kilimanjaro, habitat preferences for 140 species of pteridophytes were evaluated. Using the average percentage cover value, and taking into account the pteridophyte flora's composition, life form spectra and its spectra of seasonal growth pattern, eight vegetation formations were recognized. Ferns contributed less than 1 % of the vegetation cover of salt marshes, ruderal vegetation, grasslands and (sub-)alpine heathlands. In contrast, pteridophytes constituted the most important vascular plant group on rocks, where 64 species were found, forming about two-thirds of the vegetation cover. With respect to alpha and beta diversity and fern biomass, luxuriant montane forest was the main habitat for pteridophytes on Mt. Kilimanjaro. Here 130 pteridophyte species (93 % of the whole pteridophyte flora of the study area), on average, contributed 16 % of the total vegetation cover. Epiphytic ferns, tree ferns and filmy ferns had their main distribution between 1900 and 2400 m, in a zone coinciding with the maximum rainfall on Mt. Kilimanjaro's southern slope.
Poikilohydrous species were typical of dry habitats, such as on rocks, in meadows or along roadsides, but they also occurred in the often sun-exposed epiphyte layer in moist montane forests. Deciduous species, which were in many cases fire resistant, had a similar distribution; however, inside the forest belt they were restricted to the lower and upper parts, where fires are a common phenomenon. Evergreen species were the dominant group in swamps, forests and forest clearings.
Compared to other volcanoes in East Africa, Mt. Kilimanjaro is distinctly richer in fern species in general and in filmy ferns, tree ferns and epiphytic ferns in particular, suggesting that the forest belt of the southern slope of Mt. Kilimanjaro is wetter than those of other high mountains in East Africa. 相似文献
Poikilohydrous species were typical of dry habitats, such as on rocks, in meadows or along roadsides, but they also occurred in the often sun-exposed epiphyte layer in moist montane forests. Deciduous species, which were in many cases fire resistant, had a similar distribution; however, inside the forest belt they were restricted to the lower and upper parts, where fires are a common phenomenon. Evergreen species were the dominant group in swamps, forests and forest clearings.
Compared to other volcanoes in East Africa, Mt. Kilimanjaro is distinctly richer in fern species in general and in filmy ferns, tree ferns and epiphytic ferns in particular, suggesting that the forest belt of the southern slope of Mt. Kilimanjaro is wetter than those of other high mountains in East Africa. 相似文献
59.
60.
Gar W. Rothwell 《Journal of plant research》1994,107(4):411-416
Ferns and gymnosperms are two of the most important traditionally recognized groups of vascular plants, but both are unnatural
when viewed in terms of phylogenetic systematics. That is to say that neither consists of a monophyletic group. Nevertheless,
both continue to be recognized as informal groupings of plants because representatives of each have similar grades of structural
and reproductive features, and because many aspects of their natural relationships remain equivocal. Monophylesis for some
traditionally recognized groups of pteridophytes and gymnosperms is fairly well established, but is unresolved or highly suspect
for others. The latter include fernssensu lato, filicalean ferns, seed ferns and coniferophytes. Some recent studies also question whether conifers represent an unnatural
assemblage. However, a taxon that includes the Marsileales and Salviniales recently has been interpreted to be monophyletic.
Comparisons of results from phylogenetic analyses using either morphological or molecular characters provide a basis for assessing
the strengths of systematic hypotheses and suggest fruitful avenues for future study. It is clear from all approaches that
the greatest impediment to resolution of phylogenetic relationships in the inadequate rate at which new data are being developed. 相似文献