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   29篇
  免费   1篇
  2022年   1篇
  2021年   1篇
  2019年   1篇
  2018年   2篇
  2017年   4篇
  2016年   1篇
  2013年   4篇
  2010年   2篇
  2009年   3篇
  2008年   1篇
  2007年   2篇
  2006年   1篇
  2005年   2篇
  2004年   1篇
  1982年   1篇
  1980年   2篇
  1979年   1篇
排序方式: 共有30条查询结果,搜索用时 203 毫秒
1.
2.
The geologic section of the Torrente Scrivia in 061 the vicinity of Rigoroso is generally reported as an conformable sequence in Oligocene and Miocene strata.In fact, it has suffered important reworkingsduring Lower Miocene and this event is not only evident in sedimentology but also in paleontology. Locally, these events reflect tectonic motions more strongly marked in the north-eastern part of the ligurian piemontese basin.Consequently, the result is that the geologicsection concerned could not be satisfactory referring to Lower Miocene.  相似文献   
3.
AIMS: Verify the presence and the molecular identity of phytoplasmas in Northern and Central Italy vineyards where yellows diseases are widespread. METHODS AND RESULTS: Phytoplasma presence and identity were determined by PCR/RFLP analyses on 16S ribosomal gene testing 1424 symptomatic samples. The 65% of samples resulted phytoplasma infected; in particular 256 samples were found positive to phytoplasmas belonging to group 16SrV (mainly Flavescence dorée associated), and the remaining 37% was infected by phytoplasmas belonging to ribosomal subgroup 16SrXII-A (Stolbur or Bois Noir associated). 16SrV ribosomal group representative strains were further typed for variability in SecY and rpS3 genes. The results showed the presence of phytoplasmas belonging to 16SrV-C, 16SrV-D and to a lesser extent, 16SrV-A subgroup. CONCLUSIONS: Possible relationships between genetic polymorphisms of phytoplasma strains belonging to subgroup 16SrV-C and their geographic distribution and/or epidemic situations were detected. SIGNIFICANCE AND IMPACT OF THE STUDY: Bois Noir and Flavescence dorée phytoplasmas are present in significant percentages in the areas under investigation. Molecular tools allowed to identify phytoplasma-infected plants and the genes employed as polymorphism markers resulted useful in distinguishing and monitoring the spreading of the diseases associated with diverse phytoplasmas belonging to 16SrV subgroup in vineyards.  相似文献   
4.
A search for phytoplasma-associated diseases was conducted for the first time in the main grapevine-growing localities of the Dukagjini plain in Kosovo. A total of 144 samples were collected from grapevine cultivars displaying leaf yellowing, reddening, discolouration and irregular wood ripening, and analysed using nested and quantitative PCR assays. These assays showed that 35.4% of samples belonging to eight cultivars were positive to the presence of phytoplasmas in the 16SrXII group. The 16S rDNA phytoplasma sequences obtained from 15 samples shared identity greater than 99.5% with ‘Candidatus Phytoplasma solani’. Sequence analysis of the tuf gene showed that the strains found in Kosovar grapevines are in the tuf-type b1 group, sharing 99.6% to 99.8% identity with ‘Ca. P. solani'-related strains associated with the “bois noir” grapevine disease in many European countries; the secY gene sequences, on the other hand, shared 100% identity with ‘Ca. P. solani' strains from Bosnia and Herzegovina, Serbia, Croatia and Turkey. This study constitutes the first report on the presence and molecular characterization of phytoplasmas in Kosovar vineyards. Based on these results, it is recommended that testing for phytoplasma be included in the certification program for grapevine in Kosovo.  相似文献   
5.
《Comptes Rendus Palevol》2018,17(6):351-356
Fossils belonging to Ripidiinae are rare. Here, we describe and figure a remarkable new genus and species of Ripidiinae, Protoripidius burmiticus gen. et sp. nov., from the Upper Cretaceous amber of Myanmar. Protoripidius can be placed in the extant subfamily Ripidiinae based on the widely separated and abbreviated elytra (in male), unfolded hind wings, simple claws and the absence of tibial spurs. Protoripidius bears many transitional features shedding new light on the relationships of the two extant tribes of Ripidiinae. The discovery also highlights the palaeodiversity of the subfamily Ripidiinae in the mid-Cretaceous.  相似文献   
6.
The opening of the Deux-Ouvertures cave is on the left bank of the Ardèche River, just before the canyon exit on the land of the village of Saint-Martin d’Ardèche in the Southwest of France. Although it has been known since 1896, the deep part of one of the galleries was not discovered until 1985. The surface of this gallery was covered by animal bones, 90% of which belonged to Ursus spelaeus. In 2007, two osseous human fragments were discovered: the distal part of an adult humerus and the diaphysis of a radius belonging to a young individual. These two specimens are the topic of the present paper. Although the date of the humerus (34,440–33,730 cal BP) corresponds to the period when bears frequented the caves, the dates of the diaphysis of the radius (4410–4570 cal BP), found at the heart of the “decorated Paleolithic sector”, lead us to assume that it was transported there, perhaps deliberately. The study of the two human bones originating in the Deux-Ouvertures cave illustrates that the diaphysis of the radius, belonging to a young individual of the Neolithic period, does not exhibit any differences in comparison to modern radii. By contrast, the distal part of the adult humerus, although it is incomplete and altered, is the first example that has been dated in the Ardèche of adult human remains associated with a decorated Paleolithic cave. This specimen, aside perhaps from the width of its median column, is rather slender and does not present any significant difference in relation to other upper Paleolithic humeri.  相似文献   
7.
A fossil tree was discovered during the 16th century at Jáchymov (Bohemia). The wood was first named by Unger, in 1842, Ulminium diluviale. But it belongs to the Lauraceae family and Felix, in 1883, named it Laurinoxylon diluviale. The authors give the history and the geological setting of the area and describe the anatomy of the wood. The diagnosis of the genus Laurinoxylon Felix, 1883. is emended as follows: heteroxylous fossil wood with average sized solitary vessels or in radial groups; perforation plates simple and sometimes scalariform; intervascular pits alternate and moderately large; thyloses present. Paratracheal parenchyma. Uni to five seriate rays, slightly heterocellular and less than 1 mm high; ray-vessel pits large often stretched. Libriform or with radial pits fibres. Oil cells or mucilage (idioblasts) present. The diagnosis of the species Laurinoxylon diluviale (Unger) Felix, 1883. is also emended. Heteroxylous fossil wood with distinct growth rings; late wood poorly developed with vessels of diameter distinctly smaller as compared to the early wood and with smaller diameter fibres. Diffuse to semiporous vessels, solitary or in radial groups of two to seven , nine to 16 pores/mm2; tangential diameter 100 to 154 μm in early wood and 44 to 72 μm in late wood; vessel length 300 to 550 μm; perforation plates simple and scalariforme (6–12 bars); intervascular pits alternate, rounded (diameter 7–10 μm) or elliptic (long axes × short axes: 10–15 μm × 7–10 μm); thylosis present. Paratracheal parenchyma in more or less complete rows (1–2 cells wide) around the vessels. Heterocellular rays (1–(3) rows of upright cells), of one to five, more frequently three to four cells wide (80%); two to 36 cells high (60 to 820 μm); six to seven rays per tangential millimetre; vessels-rays pits sometimes large, stretched horizontally to vertically. Fibres of 15 to 25 μm in diameter; cell walls of 2–3 μm thick; pits not seen. Oil cells (idioblasts) at the ray margins; 27–60 μm in tangential diameter; 50–80 μm in radial diameter; 72–140 μm high; density of zero to 18 per transversal square millimetres depending on the observed area.  相似文献   
8.
A fossil human femur of Homo heidelbergensis from the site of the Sima de los Huesos (Atapuerca, Spain) was reconstructed from two main proximal and distal portions and numerous smaller fragments from the diaphysis. The use of an evaporative process to separate the bone fragments during their restoration represents an innovative approach in restoring paleontological materials and the intervention has resulted in the reconstruction of a complete femur. To avoid excessive manipulation of the reconstructed femur, a mold (negative) and cast (positive) were made of the restored specimen. This case study provides general protocols which can be widely applied to the restoration of paleontological materials from the moment of their excavation until they are deposited in a research center.  相似文献   
9.
Evidence of fungal activity expressed as typical decay patterns is described from silicified podocarpaceous wood from the Eocene of Patagonia, Argentina. Decay features consist of tracheids of the secondary xylem that are degraded, resulting in thin-celled, lignin-free, translucent, circular to elliptical areas, some of which have cells devoid of all cell wall components including lignin, hemicellulose, and cellulose, and other areas that show only partial simultaneous decay of all cell wall layers. These patterns conform to the white rot and its variant white pocket rot decay patterns produced by basidiomycetes and ascomycetes in gymnosperm and angiosperm wood in modern terrestrial ecosystems. Coagulated opaque bodies in the lumen of some cells and enlarged secondary walls may represent host reactions to infection or remains of metabolic products of fungal enzymatic activity. Similar decay patterns and reaction features have been described from fossil woods ranging in age from the Devonian to the present. This record expands the fossil record of wood rot fungi and underscores their importance as drivers of biological cycles in ancient terrestrial ecosystems.  相似文献   
10.
The pieces of wood extracted by the Marquis of Cerralbo at the Acheulian site of Torralba constitute one of the few materials from this famous locality that have not been subjected to detailed study by researchers. Over a century after their extraction, the present paper provides the first anatomical results of these 34 woody remains. The results highlight the presence of the taxon Pinus sylvestrisnigra group (Pinus cf. sylvestris) at the site, thus constituting one of the few and oldest references attributable to the aforementioned taxon for the Iberian Peninsula. The anatomical diagnosis confirms the existence of Middle Pleistocene landscapes with pine woods at elevations at least 200 m lower than at present in the site area. From a taphonomic point of view, the wood samples exhibit the typical morphologies of woody macroremains preserved in continental sedimentary environments, and there was no evidence at all that they had previously been manipulated by man.  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