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   389篇
  免费   48篇
  437篇
  2021年   4篇
  2020年   15篇
  2019年   18篇
  2018年   25篇
  2017年   15篇
  2016年   28篇
  2015年   17篇
  2014年   10篇
  2013年   54篇
  2012年   16篇
  2011年   21篇
  2010年   22篇
  2009年   22篇
  2008年   11篇
  2007年   14篇
  2006年   20篇
  2005年   8篇
  2004年   9篇
  2003年   3篇
  2002年   7篇
  2001年   3篇
  2000年   5篇
  1999年   9篇
  1998年   4篇
  1996年   3篇
  1995年   3篇
  1994年   5篇
  1993年   7篇
  1992年   9篇
  1991年   4篇
  1989年   4篇
  1988年   3篇
  1987年   2篇
  1986年   2篇
  1985年   3篇
  1984年   2篇
  1983年   3篇
  1982年   4篇
  1981年   3篇
  1980年   3篇
  1978年   2篇
  1976年   4篇
  1974年   2篇
  1972年   1篇
  1970年   2篇
  1968年   1篇
  1967年   1篇
  1966年   1篇
  1963年   1篇
  1950年   1篇
排序方式: 共有437条查询结果,搜索用时 15 毫秒
21.
A human skull, buried about 2500 years ago in a Bronze Age cemetery at Jinggouzi, a site of an important ethnic group in ancient China, appeared to have characteristics of fibrous dysplasia. The CT images indicated a reduction in bone density and relatively homogeneous lesions. More features were revealed using CT reconstruction techniques. Lesions seen in low‐magnification images using a 3D deep‐field microscope had an irregular honeycomb‐like structure. At higher magnification, the trabeculae morphology and the gaps between the trabeculae were irregular and varied in size and shape. Paraffin‐embedded specimens stained with HE showed trabeculae with tortuous irregular arrangements varying in shape and width. The irregular trabeculae of woven bone has been described as having fibrous dysplasia. Molecular analysis of the GNAS gene indicated no mutation. This provides a non‐invasive approach for us to make more comprehensive diagnoses and to assist research into ancient human diseases.  相似文献   
22.
Yelang (夜郎), a mysterious state located in the south‐western area of early China and dating from the Bronze Age to the Early Iron Age (1300 bc – ad 25), is a cultural interactive junction between the Yunnan–Guizhou Plateau and the Yangtze River Basin. The Zhongshui Basin in Weining County, Guizhou Province, was one of the important distribution areas of the Yelang civilization. This area, which includes sites at Jigongshan (鸡公山; 1300 – 800 bc ), Hongyingpan (红营盘; 700 – 400 bc ) and Yinzitan (银子坛; 400 bc – ad 25), has provided a very integrated chronology, spanning from the Bronze Age to the Early Iron Age in the eastern Yunnan – western Guizhou area. To investigate human migration and horse‐trading at these Yelang sites, we conducted a strontium isotopic analysis on the teeth enamel of humans and horses unearthed from these three sites. The results indicated the following: (1) people at the earlier sites (Jigongshan and Hongyingpan) were all indigenous, whereas in the Yinzitan cemetery, there was a more immigrant population, and all the people who were buried in an upper limb flexed supine position were non‐local; and (2) most of the horses found at the Jigongshan and Yinzitan sites show different provenances, probably related to the famous Dian (滇) and Zuo (筰) horses recorded in historical documents, providing more clues for further study on horse‐trading in South‐West China during the Bronze Age and the Early Iron Age.  相似文献   
23.
Lead isotope compositions provide a direct means of assessing provenance. The lead contents in bronzes cannot be used to argue against lead isotopes. Any claim for the origin of the source material for the origin of Yin‐Shang bronzes must satisfy the measured lead isotope compositions. Thus far, only southern African sources are found to meet this criteria.  相似文献   
24.
This paper follows the form of that by Mazzarello that precedes it (Mazzarello, 2006) and presents an imaginary interview with Santiago Ramón y Cajal in December 1906. A few days earlier Cajal had been awarded the Nobel Prize for Physiology or Medicine, an award that he shared equally with Professor Camillo Golgi. Golgi had been recognized for his work as a pioneer into investigations of the nervous system, primarily on account of his discovery of the "black reaction" of silver chromate impregnation of whole nerve cells and their processes. Cajal had been recognized for his implementation of that method and for laying with it the foundations of what was to become modern neuroanatomical science. Paradoxically, the two awardees had been led by their researches to diametrically opposed views of the organization of the nervous system. Golgi believed in a continuous network of axons that formed the basis of all the integrative properties of the nervous system, while Cajal had provided the information that led to the formulation of the neuron doctrine that saw the nervous system as being made up of chains of discontinuous cells joined by polarized functional contacts that we now call synapses. The paper takes the form of an interview with Professor Cajal in the Grand Hotel Stockholm. His responses to questions posed by the imaginary interviewer are all taken from Cajal's own writings.  相似文献   
25.
本文主要目的为重新对元代初期之书画鉴赏家及收藏家汤生平之考证及与其同时文人往来之情形。因此,本文除了藉用地方志、文集、诗集及书画题跋等为佐证之外,同时也将汤父亲汤炳龙之背景,与其他宋末元初文人、画家之交往,及对汤仕途之影响作进一步研究。本论文之结论则定汤约生于1250年代中期,而卒于1310年代中期;乃确定汤活跃于元代初期,且旅居杭州多年,最后移居且卒于北京。汤撰有二书,现仅存《画鉴》一书。此书对了解元初绘画发展及收藏品味具有重要贡献。  相似文献   
26.
27.
The study of technology transfer in pottery production to the periphery of the Mycenaean world has been addressed by considering two different areas, southern Italy and central Macedonia. Technological features such as ceramic paste, decoration and firing have been determined for different ceramic groups established according to provenance criteria. The studies of technology and provenance have been performed following an archaeometric approach, using neutron activation analysis, petrographic analysis, X‐ray diffraction and scanning electron microscopy. The results have revealed the existence of two different models. On the one hand, southern Italy seems to exhibit a more organized pottery production, which follows a Mycenaean‐like technology, while in central Macedonia production is probably more varied, being based in part on the technology of the local tradition.  相似文献   
28.
抗战初期的南调命令是国民党在发展和维护它的华中敌后利益,尤其是大别山根据地利益的过程中提出来的.由于抗战的新形势,国民党对在失去大举"剿共"手段之后的策略选择和反共部署,其实并没有多少及时而深入的考虑,尤其因为共产国际五月指示以来共产党在华中采取攻势策略,国民党更显缺乏心理和策略准备,南调命令最终在国民党内外重重阻力下不了了之.但是,这并不意味着它在国共关系史上没有产生实际的影响.在皖南,国共都因为南调命令而发生了策略变化,两党由此不可避免地开始积累矛盾,直至事变发生.  相似文献   
29.
Y. LIU  G. CHI  K. M. BETHUNE  B. DUBÉ 《Geofluids》2011,11(3):260-279
The Red Lake mine trend, a deformation zone in the Archean Red Lake greenstone belt that hosts the world‐class Campbell‐Red Lake gold deposit, is characterized by abundant foliation‐parallel iron‐carbonate ± quartz veins with banded colloform‐crustiform structures and cockade breccias overprinted by silicification and gold mineralization. There is an apparent incompatibility between the cavity‐fill structures of the veins and breccias (typically developed at shallow crustal depths) and the upper greenschist to lower amphibole facies metamorphic conditions recorded in the host rocks (indicating relatively deep environments). This, together with the development of veins along the foliation plane, represents an enigmatic problem that may be related to the interplay between fluid dynamics and stress field. We approach this problem through systematic study of fluid inclusion planes (FIPs) in the vein minerals, including the orientations of the FIPs and the pressure–temperature conditions inferred from fluid inclusion microthermometry. We find that fluid inclusions in the main stage vein minerals (pregold mineralization ankerite and quartz and syn‐ore quartz) are predominantly carbonic without a visible aqueous phase, whereas many inclusions in the postore stage contain an aqueous phase. Most FIPs are subvertical, and many are subparallel to the foliation. High fluid pressure coupled with the high wetting angles of the water‐poor, carbonic fluids may have been responsible for the abundance of brittle deformation features. The development of subvertical FIPs is interpreted to indicate episodic switching of the maximum principal compressive stress (σ1) from subhorizontal (perpendicular to the foliation) to subvertical (parallel to the foliation) orientation. The subvertical σ1 is favorable for the formation of foliation‐parallel veins, as fractures are preferentially opened along the foliation in such a stress regime, the origin of which may be linked to the fluid source.  相似文献   
30.
In this study, trepanations in ancient Anatolia were discussed from a historical perspective. Trepanations were studied in respect to temporal and spatial distribution, sex and age distribution, techniques and reasons, completeness, healing and number of holes. Forty individuals from 23 different Anatolian settlements are identified to have undergone trepanations. Cranial trepanations in Anatolia show a distribution over a period of 10 000 years ranging from the Aceramic Neolithic period to the Late Ottoman period and spread to whole Anatolia. The greater majority of the individuals had single trepanation orifices while only four individuals were identified with multiple holes. It is observed that the surgical procedure was predominantly carried out on males in Anatolia. Main techniques of trepanations used in Anatolia are drilling and cutting. Early cases of trepanation were made by drilling; however, this technique has been used for cranial surgery until the Ottoman period. Scraping and rectangular sawing techniques first applied in the Early Bronze Age. The boring‐and‐cutting technique was only applied in the Iron Age. More than half of the trepanations practiced due to cranial trauma. Training and treatment besides of cranial trauma are also considered as likely causes of trepanations in Anatolia. It is concluded that trepanation techniques are similar to South America and the Mediterranean region rather than Europe. Copyright © 2010 John Wiley & Sons, Ltd.  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