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   1135篇
  免费   21篇
  2024年   1篇
  2023年   12篇
  2022年   14篇
  2021年   13篇
  2020年   45篇
  2019年   18篇
  2018年   15篇
  2017年   16篇
  2016年   16篇
  2015年   37篇
  2014年   21篇
  2013年   61篇
  2012年   67篇
  2011年   104篇
  2010年   90篇
  2009年   103篇
  2008年   91篇
  2007年   82篇
  2006年   97篇
  2005年   71篇
  2004年   13篇
  2003年   25篇
  2002年   25篇
  2001年   14篇
  2000年   20篇
  1999年   18篇
  1998年   18篇
  1997年   7篇
  1996年   12篇
  1995年   7篇
  1994年   5篇
  1993年   3篇
  1992年   2篇
  1991年   4篇
  1990年   2篇
  1989年   1篇
  1986年   1篇
  1984年   2篇
  1982年   2篇
  1981年   1篇
排序方式: 共有1156条查询结果,搜索用时 15 毫秒
961.
Li  Feng  Kuhn  Steven L.  Bar-Yosef  Ofer  Chen  Fu-you  Peng  Fei  Gao  Xing 《Journal of World Prehistory》2019,32(2):111-141

The timing and behavioral markers of the Upper Paleolithic in different parts of the world are of great importance to research on modern human dispersals. The pattern of behavioral developments in the Upper Paleolithic in northern China differs in important ways from the patterns observed in West Eurasia, Africa, and South Asia. Shuidonggou (SDG), a cluster of Paleolithic sites in northern China, contains several of the most important Upper Paleolithic sites in the region. Various localities yield evidence of three major cultural components dated by 14C, uranium-series, and optically stimulated luminescence (OSL) methods to between roughly 46 ka and 10 ka. The oldest component, blade assemblages with western Eurasian early Upper Paleolithic characteristics, appears to be intrusive from Siberia and/or Mongolia, beginning at least 41 ka (e.g., SDG 1 and SDG 9). Advanced core and flake assemblages may mark the appearance of an indigenous Late Paleolithic of North China beginning at around 33 ka (e.g., SDG 2 and SDG 8). Finally, around 10.5 ka, microblade technology arrived in the area (SDG 12), although we are not sure of its origins at present. Other typical Upper Paleolithic cultural remains, such as bone tools and body decorations, have been found at various localities in the SDG area as well (e.g., ostrich eggshell beads from SDG 2, 7, and 8). Information from this cluster of occupations increases our understanding of cultural variability, adaptation, and demographic dynamics of modern humans in Late Pleistocene northern Asia.

  相似文献   
962.
This article is built upon the author's previous attempt to review Sino–Israel relations from the Chinese perspective, where it is argued that the relationship is at a crossroads because China is increasingly more proactively involved in the international arena, which will inevitably lead to a more assertive role in trying to facilitate a solution to the Israel–Palestinian conflicts. The author also affirmed that China is more supportive of the Palestinians. In this article, the author will further analyze China's pro‐Palestine stance, give empirical evidence of this preference by Chinese intelligentsia, and provide insight into the decision‐making mechanisms of the Chinese government in terms of its diplomatic policies. The author also wants to demonstrate that, despite the evident pro‐Palestine tendency of Chinese scholars and consequently the government, little has been done to implement this preference. The Israelis still have a sizable time window to achieve a fair and just peace agreement with the Palestinians. In the long run, China's pro‐Palestine inclination will work more and more against Israel, in contrast to the strong pro‐Israel inclination of the United States.  相似文献   
963.
2003年3~6月,山东长清月庄遗址发掘期间,采集了一批以后李文化为主的土壤样品进行浮选。我们曾简单报道过月庄遗址H124浮选出的后李文化时期炭化稻,这是目前中国北方见到最早的稻谷遗存之一。本文将详细报道全部浮选结果,以期认识月庄遗址先民与植物之间的关系,对于理解全新世早期人类与植物的互动关系、植物的利用以及黄河流域早期食物生产等方面有重要意义。  相似文献   
964.
明清时期,通州是大运河北端的漕运枢纽,漕运物资悉经通州码头转运至北京。由于通州一带土质松软,水道迁徙频繁,对漕运码头影响巨大。在自然水道自身变化和人力整治的叠加作用下,通州运河水系格局屡有变迁,位于通州附近的运河码头分布和功能也随着水系格局改变而迁移和调整。本文从分析明清时期通州运河水系格局变迁入手,梳理通州码头兴衰起伏和迁移分布过程,以阐述河道变迁与通州漕运码头之间的依存关系。通州码头变迁实际上是人与自然之间互相作用,互相影响的结果。  相似文献   
965.
日本《杏雨书屋藏敦煌秘笈》新公布的敦煌文书有不少社会文书,本文对其中六件作了释录、考订。其中《敦煌县龙勒乡都乡里天宝六载籍》,是罗振玉旧藏13行天宝六载籍前面紧连的部分。对《仓史令狐良嗣状》作了重新释读和订名。对《癸未年史喜酥买马契》契文作出考释,指出咸通七年表奏朝廷的米怀玉是敦煌的米都头。对广顺二年的《赵盐久户状》作出考释,确定此文书是由县一级统一抄写成册拟呈报给归义军使衙的"都受田簿"。考订了《驿程记》产生的背景及沙州专使的进京路线。通过对开元年间的《沙州会计历》考订,发现本卷实属法藏敦煌卷P.3841号《唐开元廿三年(735)沙州会计历》尾部的接续部分。  相似文献   
966.
Taxonomic restudy of Early Darriwilian graptolites from the Yangtze region, Chiadam and Alxa, has enabled a precise correlation of the Undulograptus austrodentatus Zone (including two subzones) across the three regions, and with the Darriwilian GSSP at Huangnitang in the Jiangshan-Changshan-Yushan (JYC) area. Based on specimens from 17 localities in the Yangtze region, the Exigraptus clavus and Undulograptus austrodentatus zones are recognised as replacements respectively of the Undulograptus sinodentatus (Lower) and U. austrodentatus (Upper) zones of Mu et al. (1979). The U. sinicus Subzone, the upper subzone of the U. austrodentatus Zone, is also recognised from the Sichuan-Guizhou area of the Yangtze region. Two subzones of the U. austrodentatus Zone have also been identified from the Chiadam region with more diverse graptolite fauna. The U. austrodentatus Zone fauna also occurs in the Alxa region. A general pattern of changing graptolite diversity from platform through basinal slope to deep basin is proposed, based on early Darriwilian bio- and lithofacies changes from the Yangtze Platform through the Jiangnan belt to the Zhujiang basin. The graptolite diversity increased with water depth and more off-shore setting. Key graptolite species are illustrated.  相似文献   
967.
The Late Devonian (Famennian) brachiopod Yunnanella is reported from the western Junggar Basin, northern Xinjiang, on the basis of Yunnanella hanburii (Davidson) and Yunnanella sp.  相似文献   
968.
O’Gorman, J.P. &; Gasparini, Z., 2013. Revision of Sulcusuchus erraini (Sauropterygia, Polycotylidae) from the Upper Cretaceous of Patagonia, Argentina. Alcheringa 37, 161–174. ISSN 0311-5518.

Sulcusuchus erraini, from the upper Campanian–lower Maastrichtian of Patagonia, Argentina, is the only polycotylid from the Southern Hemisphere for which the skull and mandible are known. The diagnosis of the species and genus is emended based on new observations. Sulcusuchus is characterized by the following autapomorphies: (1) deep and broad rostral and mandibular grooves and (2) a wide notch on the posterior margin of the pterygoids that are combined with a part of the body of the basioccipital, forming a wide plate. Several hypotheses about the identity of the structures that could have been housed in the rostral and mandibular grooves are evaluated. Only two of several hypotheses were not discarded. The first is that the grooves may have accommodated oral glands (supralabial and sublabial), but the biological role of such glands could not be inferred. The second hypothesis is the presence of special structures of an electrosensitive and/or mechanosensitive nature, which might allow the detection of infaunal or semi-infaunal food in soft substrates, as is represented in modern analogues, such as dolphins.

José P. O’Gorman [joseogorman@fcnym.unlp.edu.ar] and Zulma Gasparini [zgaspari@fcnym.unlp.edu.ar], División Paleontología Vertebrados, Museo de La Plata, Universidad Nacional de La Plata, Paseo del Bosque s/n., B1900FWA La Plata, Argentina. Also affiliated with Consejo Nacional de Investigaciones Científicas y Técnicas, Av. Rivadavia 1917 (C1033AAJ), Ciudad Autónoma de Buenos Aires, Argentina and CONICET: Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina Received 5.6.2012; revised 31.7.2012; accepted 4.9.2012.  相似文献   
969.
This article investigates the ductility reduction factors for RC eccentric frame structures subjected to pulse-like ground motions. The structural models are with the strength eccentricities which are much disadvantageous than the stiffness eccentricities during the inelastic response range. A method to determine the ductility reduction factors of the strength eccentric structures is suggested by modifying those of reference symmetric structures through an eccentricity modification factor. The four factors of strength eccentricity ratio, ductility ratio, story number and velocity pulse of ground motions, are investigated to gain insight into this modification factor. It shows that the ductility reduction factors of the eccentric structures are clearly smaller than those of the symmetric structures. The eccentricity modification factor is mainly affected by the strength eccentricity and the ductility ratio, decreasing with the increment of the eccentricity or the decrement of the ductility ratio in a medium eccentricity range. The earthquake pulse-like effect and the eccentricity have coupling influence on the modification factor, while the effect of story number is not apparent. Based on the results of a comprehensive statistical study a simplified expression is suggested, which can estimate the eccentricity modification factors for both pulse-like and nonpulse-like ground motion cases.  相似文献   
970.
Ground motions recorded in the epicentral region of an earthquake often have a strong vertical component with dominant high frequencies. Damage to bridges in near-source regions due to strong vertical ground motion has been reported. The beneficial effects of footing uplift on structural performance in form of reduction of seismic response of structural members have been confirmed in previous research. The uplift of bridge piers has been utilised in a very limited number of bridge structures, e.g., the South Rangitikei railway bridge in New Zealand. However, the near-fault seismic behaviour of bridges with footing uplift has been even less addressed. In this study shake table investigations were carried out on the response of a single-span bridge model with footing uplift subjected to simultaneous vertical and horizontal excitations. Near-fault ground motions recorded in the Canterbury earthquake sequences of 2010 and 2011 were used. The experimental results show that inclusion of vertical ground motions produce stronger axial force in the pier and larger bending moment in the deck. Concurrent horizontal and vertical excitations may also cause more frequent footing uplift than the solely horizontal excitations.  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