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   57篇
  免费   3篇
  2024年   1篇
  2023年   3篇
  2021年   1篇
  2020年   1篇
  2019年   4篇
  2018年   1篇
  2017年   2篇
  2016年   4篇
  2015年   2篇
  2014年   2篇
  2013年   5篇
  2012年   1篇
  2011年   1篇
  2010年   2篇
  2009年   3篇
  2007年   2篇
  2004年   2篇
  2003年   1篇
  2002年   2篇
  1999年   1篇
  1997年   1篇
  1995年   1篇
  1993年   1篇
  1987年   1篇
  1986年   2篇
  1983年   2篇
  1982年   1篇
  1981年   4篇
  1978年   1篇
  1976年   2篇
  1969年   1篇
  1967年   1篇
  1961年   1篇
排序方式: 共有60条查询结果,搜索用时 265 毫秒
11.
Two analytical models for unreinforced masonry (URM) buildings are proposed with the aim to simulate their seismic response and to estimate corresponding vulnerability functions. The proposed models are implemented in SAP 2000 nonlinear software to obtain capacity curve parameters for representative Indian URM buildings, based on a field survey and statistical analysis. Vulnerability functions are estimated using the obtained capacity curves. Damage Probability Matrices (DPMs) are obtained using the approximate PGA-intensity correlation relationship as per Indian seismic building code and are compared with the commonly used intensity scales and empirical damage data observed after the 2001 Bhuj earthquake.  相似文献   
12.
Abstract. The nationalisms faced by Gorbachev after 1985 were an outcome of Soviet policies, and most of them were not secessionist. Why, then, couldn't the Soviet state accommodate them? This article puts Soviet attempts to manage ethnic diversity into a comparative perspective, and looks at some of the ways in which the ideology and political structures of the USSR contributed to its failure to overcome its ethnic problems. Like other authoritarian states, the Soviet state was not based on consensus, and some of its policies exacerbated rather than diminished differences between ethnic groups. Moreover, the absence of intellectual and political pluralism, and the inflexibility of Soviet political structures made it difficult for the Soviet leadership to reconcile differences between the centre and the union republics and between ethnic groups, and this rigidity contributed to the disintegration of the USSR.  相似文献   
13.
Iron has been one of the most critical technotraditions that had lasting impact on social formation throughout the Iron Age and historical period. Iron was used in warfare and subsistence economy. Our knowledge on ancient iron smelting and working have generally been derived from ethnography and ethnohistory, which is by all means, time, region, and raw material specific. Scientific analyses of ancient iron have contributed in understanding this heritage to a respectable extent, yet a comprehensive knowledge about the evolution of iron making through time and space in India eludes us. In this work, a comparative study of iron artefacts from two Iron Age/Megalithic-Early Historic sites of Tamil Nadu, south India, that is, Mangadu (burial site) and Ambal (habitation-cum-burial site) is carried out to understand the iron thermal-processing capabilities. The retrieved artefacts were examined using X-ray fluorescence (XRF) for elemental composition. The imaging of the artefacts was done using Scanning Electron Microscopy (SEM), Electron Backscatter Diffraction (EBSD), and Optical Microscopy (OM). In addition, phase identification was performed using X-ray diffraction (XRD) and Energy Dispersive X-ray Spectroscopy (EDS). Combination of these analyses illustrates that inhabitants of Mangadu and Ambal were aware of the iron alloy manufacturing/processing techniques such as forging and hammering.  相似文献   
14.
In farming communities dependent on the cultivation of pollinator-dependent crops, the livelihoods of farmers are inextricably linked with pollinator health. A global pollination crisis interlinked with a crisis of food production and farmer livelihoods, exacerbated by processes of socio-environmental change, is emblematic of the Anthropocene and of the kinds of ecosocial problems with which critical physical geography (CPG) engages. We propose examining the farmer-pollinator system in the Indian Himalayas through an ecological livelihoods approach using a range of collaborative citizen science methods including bloom observations to document pollinator visits, plant phenological observations to document year-round floral resource availability, and farm diaries to document orchard management practices. An ecological livelihoods approach draws on posthumanist theory, which has remained largely disengaged with methodological questions that are of concern to CPG. Citizen science, although widely used across a range of disciplines, has seen limited engagement in CPG. After elaborating some of the opportunities and challenges that an engagement between CPG, posthumanist theory, and citizen science opens up, we propose a methodology that would be simultaneously epistemological (understanding interdependence between livelihoods of farmers and pollinators) and ontological (imagining and building worlds where farmer and pollinator habitats are recomposed).  相似文献   
15.
Fluid chemistry and microbial community patterns in chimney habitats were investigated in two hydrothermal fields located at the Central Indian Ridge. Endmember hydrothermal fluid of the Solitaire field, located ~3 km away from the spreading center, was characterized by moderately high temperature (307°C), Cl depletion (489 mm ), mildly acidic pH (≥4.40), and low metal concentrations (Fe ≤ 105 μm and Mn = 78 μm ). Chloride depletion indicates that the subseafloor source fluid had undergone phase separation at temperatures higher than ~390°C while the metal depletion was likely attributable to fluid alteration occurring at a venting temperature of around 307°C. These different temperature conditions suggested from fluid chemistry might be associated with an off‐spreading center location of the field that allows subseafloor fluid cooling prior to seafloor discharge. The microbial community in the chimney habitat seemed comparable to previously known patterns in typical basalt‐hosted hydrothermal systems. Endmember hydrothermal fluid of the Dodo field, standing on center of the spreading axis, was characterized by high H2 concentration of 2.7 mm . The H2 enrichment was likely attributable to fresh basalt–fluid interaction, as suggested by the nondeformed sheet lava flow expansion around the vents. Thermodynamic calculation of the reducing pyrite–pyrrhotite–magnetite (PPM) redox buffer indeed reproduced the H2 enrichment. The quantitative cultivation test revealed that the microbial community associated with the hydrothermal fluid hosted abundant populations of (hyper)thermophilic hydrogenotrophic chemolithoautotrophs such as methanogens. The function of subseafloor hydrogenotrophic methanogenic populations dwelling around the H2‐enriched hydrothermal fluid flows was also inferred from the 13C‐ and D‐depleted signature of CH4 in the collected fluids. It was observed that the hydrothermal activity of the Dodo field had ceased until 2013.  相似文献   
16.
Vijaya, Prasad, G.V.R. & Singh, K., June, 2009. Late Triassic palynoflora from the Pranhita–Godavari Valley, India: evidence from vertebrate coprolites. Alcheringa 33, 91–111. ISSN 0311-5518.

The Upper Triassic Maleri Formation, represented by red clays and sandstones, has to date not produced any plant macrofossils or palynomorphs. Many spiral and non-spiral coprolites collected during this study from the Maleri Formation of the Pranhita-Godavari Valley were analysed for palynomorphs. Based on shape, nature of coiling and size, the Maleri coprolites are classified into seven groups. Of these, only Group-I, Type 5 (non-spiral) and amphipolar (spiral) types yielded diverse gymnospermous and pteridophytic spores, pollen, other plant debris and sparse fungal spores and algal remains. Occurrences of Antulsporites varigranulatus, Aratrisporites spp., Cadargasporites baculatus, Dubrajisporites isolatus, Enzonalasporites vigens, Foraminisporis coelatus, Grandispora spinosa, Kraeuselisporites saeptatus, Polycingulatisporites reduncus, Staurosaccites spp., Tethysispora unica and Tikisporites balmei confirm a Late Triassic age for the coprolite-bearing red clays. Records of Classopollis classoides and Callialasporites turbatus/dampieri in these assemblages more precisely suggest a Norian to Rhaetian age. The non-spiral coprolites were possibly produced by aquatic piscivorous animals whereas the spiral coprolites may have been produced by an as yet unidentified fish taxon. The coprolite-producing animals (spiral and non-spiral groups) possibly ingested gymnospermous and pteridophytic plant remains passively along with water or their herbivorous prey.  相似文献   
17.
18.
19.
20.
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