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   7387篇
  免费   289篇
  2020年   106篇
  2019年   111篇
  2018年   156篇
  2017年   173篇
  2016年   221篇
  2015年   152篇
  2014年   121篇
  2013年   2042篇
  2012年   182篇
  2011年   194篇
  2010年   189篇
  2009年   181篇
  2008年   181篇
  2007年   152篇
  2006年   137篇
  2005年   167篇
  2004年   107篇
  2003年   97篇
  2002年   101篇
  2001年   101篇
  2000年   103篇
  1999年   112篇
  1998年   89篇
  1997年   80篇
  1996年   81篇
  1995年   81篇
  1994年   70篇
  1993年   86篇
  1992年   81篇
  1991年   59篇
  1990年   48篇
  1989年   76篇
  1988年   61篇
  1987年   79篇
  1986年   70篇
  1985年   103篇
  1984年   122篇
  1983年   108篇
  1982年   91篇
  1981年   90篇
  1980年   107篇
  1979年   92篇
  1978年   90篇
  1977年   74篇
  1976年   92篇
  1975年   90篇
  1974年   60篇
  1973年   53篇
  1972年   52篇
  1971年   49篇
排序方式: 共有7676条查询结果,搜索用时 15 毫秒
991.
992.
Despite the existence of research conducted by geographers eschewing or professing religious faith, the influence of researchers and their methods have yet to receive critical attention within the study of religion. The experience of three geographers working on a three-year research project suggests that it is vital to reflect upon the inter-subjective relationships and methodologies used to reconstruct the religious past. How do different subject positions influence our selections from historical records? We also consider whether the spatialities of putatively 'religious' archives, whether formally or informally constituted, make a difference to the construction of historiographical knowledge. In attempting to answer these questions, the paper argues that developing an awareness of different types of positionality, vis-à-vis religious faith and practice, combined with reflexivity, vis-à-vis methodology, can enrich the interpretative reconstruction of the religious past.  相似文献   
993.
994.
A major aim of including the spatial component in ecological studies is to characterize the nature and intensity of spatial relationships between organisms and their environment. The growing awareness by ecologists of the importance of including spatial structure in ecological studies (for hypothesis development, experimental design, statistical analyses, and spatial modeling) is beneficial because it promotes more effective research. Unfortunately, as more researchers perform spatial analysis, some misconceptions about the virtues of spatial statistics have been carried through the process and years. Some of these statistical concepts and challenges were already presented by Cliff and Ord in 1969. Here, we classify the most common misconceptions about spatial autocorrelation into three categories of challenges: (1) those that have no solutions, (2) those where solutions exist but are not well known, and (3) those where solutions have been proposed but are incorrect. We conclude in stressing where new research is needed to address these challenges.  相似文献   
995.
The role of raw material quality in Oldowan technology has not been fully explored. There are numerous studies suggesting Oldowan hominins preferred certain types of stone for artifact manufacture. Previous studies of the artifact assemblage from the early Pliocene Oldowan locality of Kanjera South (South Rachuonyo District, Kenya) show that raw material selection and transport was an important aspect of Late Pliocene hominin adaptations. Yet the exact properties of stones that hominins were selecting remain enigmatic. Two potentially important features of artifact raw material are durability and fracture predictability. We investigate fracture predictability through mechanical tests of stone and investigations of the affect of stone properties on fracture patterns in archaeological collections. We investigate stone durability with actualistic studies of edge attrition combined with further mechanical tests of various lithologies. Oldowan hominins at Kanjera appear to have selected raw materials based on their durability. The ability for a stone to fracture consistently does not appear to be as important in hominin toolstone preference as previously assumed. Hominins that produced the assemblages at Kanjera South appear to have incorporated an extensive understanding of various attributes of raw material in the transport and production of stone artifacts. When combined with previous research on the transport patterns at Kanjera, the results of this study provide evidence for a more complex raw material acquisition strategy than has previously been suggested for Late Pliocene Oldowan hominins.  相似文献   
996.
The detection and identification of protein residues from archaeological artefacts has been the subject of considerable controversy over the past two decades, this controversy spurring the application of a range of different analytical methods. Part of the debate surrounds the ability of the methods to uniquely identify original proteins. Another is the apparent contradiction between the ease of extraction in the laboratory of residues that have managed to survive in sediment over millennia; some studies use simple solvents including water, whilst others claim that efficient extraction requires the destruction of the artefact.Desorption electrospray ionisation mass spectrometry (DESI-MS) offers the potential to directly analyse proteins bound to the surface of artefacts. The method permits desorption of analytes under ambient conditions directly from a wide range of surfaces with little or no sample preparation. This has already led to its application in a range of areas, including forensic analysis of trace levels of narcotic drugs. It does not require destruction of the artefact (e.g. by drilling or dissolution) and can work in concert with other methods (for instance it could be used as a screening tool prior to lipid extraction).Here we report the construction of a DESI-MS interface and consider the potential of the method to contribute to the debate surrounding the preservation of proteins on artefacts. The DESI-MS interface was fitted to a conventional ion trap mass spectrometer and tested using peptides and proteins artificially applied to the surface of flint flakes and potsherd samples. A range of intact proteins was analysed; the DESI interface identified test proteins up to a maximum molecular weight of approximately 20 kDa. Peptides generated from these and larger proteins could be detected using DESI-MS following tryptic digestion in situ. The collected data allowed identification of the originating proteins. The potential applications to archaeological science of this new analytical tool are discussed.  相似文献   
997.
The remains of Henry V's flagship, the Grace Dieu, currently lie buried within the inter-tidal sediments of the River Hamble (S. England). Previous archaeological investigations have been hindered by difficult excavation conditions resulting in a poor understanding of the dimensions, shape and degradation state of the hull's deeper structure. This study therefore aimed to image, characterize and reconstruct the buried remains of this vessel using a high-resolution 3D acoustic sub-bottom Chirp system with RTK-GPS positioning capability. The accurate navigation and high-resolution data that were acquired enabled the construction of a full 3D image of the site that not only identified the remains of the wooden hull, but also features buried within it. In addition, the degradation state of these buried wooden remains were investigated by calculating reflection coefficients while a hypothetical larger reconstruction of the Grace Dieu's hull was achieved, through the use of the ShipShape ship design software package.  相似文献   
998.
El Mirón is a large cave in the Cantabrian Cordillera of northern Spain that presents a long archaeostratigraphic sequence radiocarbon-dated by over 60 assays to between 41,000 and 2000 BP. The sediments, collected from four areas within the cave and sieved-washed with fine wire meshes, contain microvertebrate remains of fish, frogs, lizards, birds and mammals, of which the latter are most abundant. Preliminary taphonomic analysis suggests that the microvertebrates were naturally collected by owls and (less) small carnivores. Small mammal assemblages are useful for palaeoenvironmental reconstruction because they are linked to particular habitats and are sensitive to environmental changes. The small mammals from El Mirón are ideal for this because sample sizes are large, bone preservation is good, and the stratigraphic sequence is long. In this paper we reconstruct the late Quaternary environments in the Cantabrian region of Spain using small-mammal assemblages from El Mirón Cave. On the basis of the ecologic adaptations of this suite of fauna, the majority still extant, we have identified seven habitat types, which are plotted through time. The evolution of the small mammal assemblages at El Mirón reveals seven major climatic shifts that correspond closely to the climatic changes recognized in the Iberian Peninsula during the last 41 kyr.  相似文献   
999.
In the investigation of the dispersal of maize (Zea mays ssp. mays) from south-central Mexico to the northern and southern limits of agriculture in the Western Hemisphere archaeologists and paleoethnobotanists are increasingly turning to the microbotanical record. Recent analysis of phytolith assemblages from charred cooking residues on pottery sherds in central New York recovered using 209 rondel phytolith variables has identified maize as early as 2270 ± 35 B.P. In this article we use discriminant analysis to re-classify these rondel phytolith assemblages resulting in only seven variables. The results are consistent with those achieved earlier using many more variables and a less formal statistical approach in terms of classification and in similarity of the original and reduced data matrix as seen by the Mantel test and cluster analyses.  相似文献   
1000.
A methodology is described by which spatial patterns of land use were reconstructed from pollen analyses on anthropogenic sediments at a recently excavated early Neolithic timber ‘hall’ in north east Scotland. The anthropogenic sediments were from a deep, small diameter pit within the building. They present numerous taphonomic and interpretative challenges to the analyst, but from this type of deposit, the power to estimate quantitatively the vegetation structure around the archaeological site makes such difficult deposits very significant. A rigorous methodology is firstly described, therefore, by which confidence in ecological interpretation can be established. Secondly, the source of pollen in the deposit is evaluated. Thirdly, the possible pollen source area and structure of the surrounding vegetation are estimated by quantitative simulation modelling. Finally, these analyses are compared with region-scale pollen analyses from nearby conventional wetland deposits with much larger pollen source areas. The pollen assemblages recovered probably reflect land uses adjacent to the ‘hall’ and up to 2.5 km around. Cereal cultivation was the most important land use immediately around the ‘hall’, possibly grown between stands of scrub Corylus (hazel) woodland. These intensive but local-scale land uses cannot be discerned in region-scale pollen analyses.  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