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   53篇
  免费   7篇
  2020年   4篇
  2019年   2篇
  2018年   4篇
  2017年   3篇
  2016年   1篇
  2015年   5篇
  2014年   4篇
  2013年   6篇
  2012年   7篇
  2011年   2篇
  2009年   2篇
  2008年   4篇
  2003年   1篇
  2002年   2篇
  1995年   2篇
  1994年   1篇
  1991年   3篇
  1987年   2篇
  1985年   2篇
  1984年   2篇
  1982年   1篇
排序方式: 共有60条查询结果,搜索用时 15 毫秒
31.
Molecular analysis of coprolites from Hinds Cave, Texas recovered chloroplast DNA sequences. The sequences were interpreted as evidence of diet. We analyzed 19 Hinds Cave coprolites to evaluate the potential sources of the chloroplast DNA (cpDNA) and compared our results to previous studies. This review shows that some cpDNA sequences could be from well-known prehistoric plants foods. Some other sequences could have come from ambient plant material in the guts of small animals eaten by humans in antiquity. Using pollen concentration analysis, we identify sources of ambient plant material which could have been inhaled or imbibed. It is even possible that cpDNA sequences are from proplastids within ambient pollen grains themselves. However, three sequence types cannot be explained as resulting from only dietary or ambient sources. We suggest instead that these might be from medicinal or hallucinogenic plants. We compared these three sequences to existing sequences in the GenBank. We found that these sequences are 100% matches for Rhamnus, Fouquieria, and Solanum.  相似文献   
32.
What are useful quantitative approaches in situations with highly variable data quantities, contexts, and sampling strategies? How can paleoethnobotanical findings be interpreted without over-representing data or selling results short? Described here are several major issues and potential solutions. The four sites of the study are located northwestern Honduras, a region with fairly hostile environments for paleoethnobotanical preservation. For this reason, several types of botanical residues are combined to provide a more holistic picture of past ethnobotanical practices. In some cases, these data prove to be complementary, while in others, they are corroborative. This article includes tactics for integrating multiple sample protocols, multiple and overlapping diagnostic elements, multiple and overlapping clade categories, multiple and overlapping samples in a single locus, multiple and overlapping formation processes, and multiple and overlapping cultural practices. In each section, the issue, sampling strategies, quantitative approaches, and a few results are described.  相似文献   
33.
The determination of the antifungal activities of nine kinds of powdered plant extracts and five essential oils was studied in vitro against four of the most common fungal species (Aspergillus flavus, A. versicolor, Penicillium sp. and P. purpurogenum), which were isolated from different organic materials from archaeological artefacts such as papyrus and linen. The essential oils showed greater efficacy than the powdered plant extracts, where thyme and lemongrass oils were the most potent. Also, the minimum inhibitory concentration and minimum fungicidal concentration of these oils were determined. Furthermore, their chemical components were identified using gas chromatography-mass spectrometry (GC-MS) analysis. In vivo, studies were performed using biodeteriorated samples for applying treatment, in which the microbiological test revealed that both oils can eradicate both tested fungi completely after exposure time, ranging from two weeks for papyrus samples to 14 weeks for linen. A scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR) and colorimeter were used to assess the treatment process, leading to the final results, which suggest that the essential oils could be useful sources of fungicidal preparations for the disinfection of biodeteriorated linen and papyrus artefacts. Nevertheless, further studies are strongly recommended to introduce these sources into practical use in preventive conservation.  相似文献   
34.
本文主要依据2001年北京老山汉墓中出土的植物遗存(果实、种子)的鉴定,提出在西汉时期的燕国(北京)食用和种植的旱生农作物为黍、粟、大豆和大麻,至少在当时小麦和水稻并未成为先民们的经济生活中的重要组成.参考墓中"黄肠题凑"用材属种和地处西山前缘,其时段大致可以对应的颐和园昆明湖底沉积物中较高时间分辨率的孢粉分析、炭屑资料的统计,可以大体得知,在西汉时期的北京西山地区的自然植被虽遭到砍伐或火烧(薪柴)的人为性影响,但就总体上看,当时西山地区仍覆盖着主要由栎、椴、梣、栗、胡桃、榆、朴等组成的暖温带落叶阔叶林和油松林,当时的历史气候应是北京地区3000年以来最为温暖和湿润的气候期,在山前湿地(湖泊、沼泽)发育,水生植物丰富.因此,本文资料有助于讨论北京地区自然环境的变化和人为活动的影响.  相似文献   
35.
Xu, H.-H., Wang, Y., Tang, P. & Wang, Y., May 2017. A new diminutive euphyllophyte from the Middle Devonian of West Junggar, Xinjiang, China and its evolutionary implications. Alcheringa 41, 524–531. ISSN 0311-5518.

A diminutive euphyllophyte, Douaphyton levigata gen. et sp. nov., is described from the upper Middle Devonian (Givetian) Hujiersite Formation of West Junggar, Xinjiang, China. The plant consists of more than three orders of axis branching, each axis being less than 2 mm wide. The second-order axes are short, laterally and alternately attached to the main axis. The third-order axes are paired and anisotomously divided, bearing the vegetative appendages or the fertile units. The fertile unit consists of a short recurved axis giving off up to four short pedicels along one side, each of which bears one to four pairs of terminal sporangia. Douaphyton has a three-dimensional branching system that has an intermediate form in the evolutionary context of euphyllophytes and lignophytes. It is also proposed that complex branching developed in multiple groups in the Middle Devonian.

*Hong-He Xu [], Yao Wang [], Peng Tang [], Yi Wang [] State Key Laboratory of Palaeobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, Nanjing 210,008, PR China. Yao Wang [] University of Science and Technology of China. 96 Jinzhai Road, Hefei, Anhui Province, 230,026, PR China.  相似文献   

36.
McLoughlin, S. & Prevec, R. 20 September 2019. The architecture of Permian glossopterid ovuliferous reproductive organs. Alcheringa XX, xxx–xxx. ISSN 0311-5518

A historical account of research on glossopterid ovuliferous reproductive structures reveals starkly contrasting interpretations of their architecture and homologies from the earliest investigations. The diversity of interpretations has led to the establishment of a multitude of genera for these fossil organs, many of the taxa being synonymous. We identify a need for taxonomic revision of these genera to clearly demarcate taxa before they can be used effectively as palaeobiogeographic or biostratigraphic indices. Our assessment of fructification features based on extensive studies of adpression and permineralized fossils reveals that many of the character states for glossopterids used in previous phylogenetic analyses are erroneous. We interpret glossopterid fertiligers to have been borne in loose strobili in which individual polysperms represent fertile cladodes of diverse morphologies subtended by a vegetative leaf or bract. Polysperms within the group are variously branched or condensed with ovule placement ranging from marginal to abaxial, in some cases occurring on recurved branchlets or in cupule-like structures. Glossopterid polysperms of all types are fringed by one or two ranks of wing-like structures that may represent the remnants of megasporophylls that were, ancestrally, developed on the fertile axillary shoot. Glossopterid fertiligers have similarities to the condensed bract/ovuliferous scale complexes of conifer cones, but comparisons with Mesozoic seed-ferns are hindered by insufficient data on the arrangement and homologies of the ovule-bearing organs of the latter group. Nevertheless, glossopterid polysperms differ from the ovuliferous organs of Mesozoic seed-ferns by longitudinal versus transverse folding, respectively.

Stephen McLoughlin* [], Department of Palaeobiology, Swedish Museum of Natural History, Box 50007, 104 05 Stockholm, Sweden; Rose Prevec [], Department of Earth Sciences, Albany Museum, 40 Somerset Street, Makhanda, 6139, Eastern Cape, South Africa, and Department of Botany, Rhodes University, PO Box 94, Makhanda, 6140, Eastern Cape, South Africa.  相似文献   
37.
This paper investigates how to gain quantitative comparability of macroscopic plant remains by estimating sample sizes representative to each population. First, this study reviews taphonomic pathways of plant remains to clarify how far we can draw cultural implications from the retrieved remains. The target population is defined here as the deposited assemblage, that is, plants that were deposited into the soil matrix. Through time, the deposited assemblage becomes reduced to the fossil assemblage, which is subject to being sampled (sampled population). The relation between the sampled population and samples is a statistical issue. A systematic recovery and a well-designed sampling strategy can help maintaining the same degree of representativeness of samples to the sampled population. The paper thus focuses on a statistical measure that estimates the sample sizes, based on a relative error and a confidence level of a small number of pilot samples. Data for the test is the plant remains recovered from the Nam River sites in south-central Korea, dating to the Early and Middle Mumun periods (3400-2400 BP). This measure ensures that quantitative differences between the plant remains in the two samples were due to real differences between the populations from which they were drawn rather than due only to variation within a single population. Thus this method strengthens cultural interpretations on quantitative differences in plant remains.  相似文献   
38.
Starch granules are being successfully recovered from an increasing range of artefacts. Here we present the recovery of starches from carbonised ceramic ‘foodcrusts’ from late Mesolithic–early Neolithic residues at the site of Neustadt in northern Germany. A method for investigating background loading of residues with contaminant starches is proposed by comparing interior ‘foodcrusts’ versus exterior ‘sooting’, for the purposes of eliminating samples with insignificant quantities of grains from subsequent identification procedures. The classification of starches to plant taxon is traditionally achieved by manual observations and measurement of nominal and ratio morphological variables. Here, we present a method for the automated classification of granules, using software developed in-house. The results show that when multiple granules are considered, the species selected as modern reference examples can be classified to high levels of specificity. When applied to the archaeological samples we show that wild plant resources persist in importance across the transition to agriculture, with high proportions of granule forms consistent with acorn (Quercus sp.) occurring in all samples. Hazelnut (Corylus avellana) types are less well-represented suggesting it was not an important food in the context of pottery, and may have been over-represented in the repertoire of hunter–gatherer resources. Cereals are not represented in any of the samples, supporting the notion that their adoption may have been a slow process, occurring more gradually than for other domesticated foods, or that they were not initially processed in ceramic vessels.  相似文献   
39.
古城寨城址始建于龙山时代晚期,并且在二里头、二里岗、殷墟时期一直延用。我们在古城寨城址龙山到殷墟时期的土样中收集到了粟、黍、小麦和藜四种农作物炭化种子。通过种子数量的统计分析,认定当时的农业是典型的以粟为主的早期旱作农业,并且农业生产水平较为发达,农业在整个社会经济中占有重要的地位。  相似文献   
40.
Although carbon-14 dates prior to 13,000 B.P. have been obtained from several sites east and south of Amazonia, their reliability is uncertain. By about 11,000 B.P., however, two lithic traditions were widespread. The Uruguai tradition, characterized by bifacial stemmed projectile points, was associated with open vegetation in the south; the Itaparica tradition, emphasizing well-formed unifacial artifacts, had dispersed over the eastern tropical parklands. An enormous amount and variety of rock paintings and/or engravings are associated with the latter. Around 7000 B.P., two new traditions emerged to exploit new habitats. The Humaitá tradition, characterized by large bifacial tools and an absence of stone projectile points, expanded over the broad-leaved forests in the south, leaving the open landscapes dominated by the projectile point-using Umbu tradition. The sambaqui (shell midden) tradition, also emphasizing large bifaces, developed along rugged portions of the southern coast. By 4000 B.P., groups along the coast of Rio de Janeiro and Espírito Santo were using domesticated or semidomesticated plants, perhaps sweet manioc. Maize was being grown in Minas Gerais by about 3500 B.P. Carbon-14 dates from numerous sites indicate, however, that the hunter-gatherer way of life persisted in many places long after the advent of pottery-making horticulturalists. The existence of large temporal and spatial gaps even in regions with considerable investigation makes it difficult to reconstruct the process of evolution reflected in these archaeological complexes. Correlations between cultural traditions and environmental fluctuations indicate, however, that adaptation to changing conditions was a significant challenge faced by prehistoric Brazilian populations.  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