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   433篇
  免费   7篇
  2024年   4篇
  2023年   4篇
  2022年   5篇
  2021年   16篇
  2020年   12篇
  2019年   10篇
  2018年   6篇
  2017年   14篇
  2016年   11篇
  2015年   9篇
  2014年   6篇
  2013年   22篇
  2012年   23篇
  2011年   29篇
  2010年   28篇
  2009年   44篇
  2008年   29篇
  2007年   30篇
  2006年   20篇
  2005年   24篇
  2004年   10篇
  2003年   18篇
  2002年   20篇
  2001年   17篇
  2000年   13篇
  1999年   4篇
  1998年   4篇
  1997年   3篇
  1996年   2篇
  1994年   3篇
排序方式: 共有440条查询结果,搜索用时 15 毫秒
1.
明墓出土的历书,粘连固结成块,脆硬易于折断。通过实验分析研究,探明其主要原因可能是木质素选择性地吸附的钙铁离子与蛋白质的分解物形成复杂物质,沉积在纸上,渗入书内所致。故揭取该历书的关键是去除钙离子,EDTA二钢,碱性过氧化氢、气相二氧化硅等的分步处理,使脆硬的纸张软化,再逐页分离揭取,然后再去除色素沉淀物,终于恢复了书的原貌。  相似文献   
2.
Pan, Z., Zhu, M., Zhu, Y. &; Jia, L., August 2017. A new antiarch placoderm from the Emsian (Early Devonian) of Wuding, Yunnan, China. Alcheringa 42, 10–21. ISSN 0311-5518.

Wufengshania magniforaminis, a new genus and species of the Euantiarcha (Placodermi: Antiarcha), is described from the late Emsian (Early Devonian) of Wuding, Yunnan, southwestern China. The referred specimens were three-dimensionally preserved in black shales, allowing a high-resolution computed tomography reconstruction of anatomical details. The new euantiarch is characterized by a large orbital fenestra, an arched exoskeletal band around the orbital fenestra and a developed obtected nuchal area of the skull roof. Maximum parsimony analysis, using a revised data-set of antiarchs with 44 taxa and 66 characters, resolves Wufengshania gen. nov. as a member of the Bothriolepididae, which is characterized by the presence of the infraorbital sensory canal diverging on the lateral plate, and the nuchal plate with orbital facets. New analysis supports a sister group relationship between Dianolepis and the Bothriolepididae. Luquanolepis, a coeval euantiarch from the neighboring site of the new form, is referred to the Asterolepidoidei and represents the basalmost and earliest member of the Asterolepidoidei.

Zhaohui Pan* [], Min Zhu* [], You’an Zhu? [] and Liantao Jia [] Key Laboratory of Vertebrate Evolution and Human Origins of Chinese Academy of Sciences, Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences, PO Box 643, Beijing 100044, PR China. *Also affiliated with University of Chinese Academy of Sciences, Beijing, 100049, PR China. ?Also affiliated with Uppsala University, PO Box 256, 751 05 Uppsala, Sweden.  相似文献   
3.
In Chinese traditional timber buildings, stitching is very common. When the bearing capacity or the rigidity is inadequate, a timber beam is often strengthened with another beam using the stitching method. The timber stitching beams are mainly of two types—the small-top/big-bottom type and the big-top/small-bottom type. To study the bending behavior of these two types of timber stitching beams, including the failure mode, the flexural capacity, the strain distribution at mid-span section, and the maximum deflection, bending tests are carried out on 14 timber stitching beams with Chinese traditional conformation for seven pine beams and seven fir beams. The results show that the failure modes of the small-top/big-bottom type of stitching beams all show brittle fractures at the bottoms of the bottom beams. The failure modes of the big-top/small-bottom type of stitching beams all show brittle fractures at the bottoms of the top beams. The distribution of section strain along the height of each part of the beam basically obeys plane hypothesis. Based on the theoretical and experimental analysis, the calculation formulas of flexural capacity and maximum deflection of these two types of timber stitching beams made of pine and fir are presented.  相似文献   
4.
L. Jiang  W. Pan  C. Cai  L. Jia  L. Pan  T. Wang  H. Li  S. Chen  Y. Chen 《Geofluids》2015,15(3):483-498
Permian hydrothermal activity in the Tarim Basin may have been responsible for the invasion of hot brines into Ordovician carbonate reservoirs. Studies have been undertaken to explain the origin and geochemical characteristics of the diagenetic fluid present during this hydrothermal event although there is no consensus on it. We present a genetic model resulting from the study of δ13C, δ18O, δ34S, and 87Sr/86Sr isotope values and fluid inclusions (FIs) from fracture‐ and vug‐filling calcite, saddle dolomite, fluorite, barite, quartz, and anhydrite from Ordovician outcrops in northwest (NW) Tarim Basin and subsurface cores in Central Tarim Basin. The presence of hydrothermal fluid was confirmed by minerals with fluid inclusion homogenization temperatures being >10°C higher than the paleo‐formation burial temperatures both in the NW Tarim and in the Central Tarim areas. The mixing of hot (>200°C), high‐salinity (>24 wt% NaCl), 87Sr‐rich (up to 0.7104) hydrothermal fluid with cool (60–100°C), low‐salinity (0 to 3.5 wt% NaCl), also 87Sr‐rich (up to 0.7010) meteoric water in the Ordovician unit was supported by the salinity of fluid inclusions, and δ13C, δ18O, and 87Sr/86Sr isotopic values of the diagenetic minerals. Up‐migrated hydrothermal fluids from the deeper Cambrian strata may have contributed to the hot brine with high sulfate concentrations which promoted thermochemical sulfate reduction (TSR) in the Ordovician, resulting in the formation of 12C‐rich (δ13C as low as ?13.8‰) calcite and 34S‐rich (δ34S values from 21.4‰ to 29.7‰) H2S, pyrite, and elemental sulfur. Hydrothermal fluid mixing with fresh water in Ordovician strata in Tarim Basin was facilitated by deep‐seated faults and up‐reaching faults due to the pervasive Permian magmatic activity. Collectively, fluid mixing, hydrothermal dolomitization, TSR, and faulting may have locally dissolved the host carbonates and increased the reservoir porosity and permeability, which has significant implications for hydrocarbon exploration.  相似文献   
5.
A new artwork trading model emerged in China at the beginning of 2010s: the value of a piece of artwork was divided into equal shares, and investors could buy and sell these shares in the cultural artwork exchanges, in exactly the same way as investors trading stocks in the stock market. In China, this trading model, once available, was hotly pursued by investors. This rapid market growth quickly descended into trading market confusion and speculation, forcing the government to deal with this model and eventually putting a stop to it. In this paper, we take a closer look at the reasons for the artwork shares’ price booming and slumping, the disorder and speculation in the artwork share trading market, and the reasons why the Chinese government halted this kind of trade. Taking the Tianjin Cultural Artwork Exchange of China as an example, we found that artwork can be an alternative investment vehicle, but the share trading model, similar in function to the stocks and bonds market, is not fit for artwork. The lack of legal basis and supervision by governmental bodies, together with the changeable trading rules has also contributed to the failure of this artwork trading model in China.  相似文献   
6.
张剑 《史学月刊》2007,1(6):48-52
《钦定宪法大纲》是清末一个重要的宪法性文件,是各方政治势力博弈的结果。大纲的产生自有其合理的一面。虽然大纲带有浓厚的封建性,但诸多条文仍不乏合理性、进步性和民主性。大纲在中国宪政史上确立了根本法的地位,确立了二元制君主立宪政体,初步确立了分权模式,初步确立了权利义务观念,与西方宪政初步实现了形式上的对接。  相似文献   
7.
珍本《影山草堂学吟稿》考述   总被引:1,自引:0,他引:1  
张剑 《文献》2007,(1):125-130
"清诗三百年,王气在夜郎",这是钱仲联先生<论近代诗四十家>对晚清宋诗派代表郑珍(字子尹)和莫友芝(字子偲)的赞语,郑、莫两人虽处西南边陲,但学深诗雄,名动全国,不愧为贵州历史文化宝库中两颗极其璀璨的明珠.  相似文献   
8.
近代中国的领券制度   总被引:1,自引:1,他引:0  
银行业的领券制度,是近代中国货币发行史上一项独特的制度。笔者由于工作的关系,曾对领券制度产生的源流做了初步的梳理。然而,现存关于领券制度的资料比较缺乏,在这方面的研究有待深入。本文仅是提供一些基本情况,并谈点自己肤浅的看法。  相似文献   
9.
日本帝国主义通过日俄战争,在中国东北旅大地区建立了关东州殖民地。会是关东州最基本的地方行政机构,日本殖民政府对关东州殖民统治主要是通过会来进行的。但关东州的会只是一种行政上的辅助机关。1925年6月20日,日本政府以第238号敕令的形式公布《关东州会制》,正式赋予会以法人资格,以后又不断强化,确保其殖民统治的需要。  相似文献   
10.
首脑外交是第二次世界大战以来国家间交往的一种频繁使用的外交形式,随着国际格局多极化与世界经济全球化的发展,首脑外交也日益突显出其独特作用,并且为当今大多数国家的政治首脑所接受,冷战约束后,首脑外交更加趋向于公开化,制度化,全球化,在当今国际新秩序的构建过程中,资本主义世界的铁三角同盟(日美欧战略三角)也面临着战略性的结构调整,向着全球性战略伙伴关系发展,日本与欧盟及其成员国的关键日益密切,日欧间首脑的频繁互访无疑发挥了重大的作用。  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