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   622篇
  免费   34篇
  2024年   5篇
  2023年   17篇
  2022年   13篇
  2021年   21篇
  2020年   20篇
  2019年   23篇
  2018年   26篇
  2017年   32篇
  2016年   27篇
  2015年   22篇
  2014年   28篇
  2013年   59篇
  2012年   31篇
  2011年   34篇
  2010年   55篇
  2009年   23篇
  2008年   33篇
  2007年   27篇
  2006年   27篇
  2005年   24篇
  2004年   22篇
  2003年   13篇
  2002年   13篇
  2001年   9篇
  2000年   5篇
  1999年   7篇
  1998年   6篇
  1997年   1篇
  1996年   1篇
  1995年   1篇
  1994年   2篇
  1993年   5篇
  1992年   5篇
  1991年   2篇
  1990年   3篇
  1989年   1篇
  1988年   1篇
  1986年   1篇
  1985年   2篇
  1983年   1篇
  1977年   1篇
  1974年   5篇
  1973年   1篇
  1972年   1篇
排序方式: 共有656条查询结果,搜索用时 15 毫秒
71.
黄河流域区域经济差异的时空动态分析   总被引:4,自引:0,他引:4  
以黄河流域的各地级市为研究单元,人均GDP为测度指标,综合运用不同时空动态分析方法,在Open Geoda和Pysal2.7软件支持下,对1990-2013年黄河流域73个地级市经济发展水平空间格局和演变过程进行分析。研究表明:黄河流域整体区域经济差异呈现先扩大后减小的趋势,东部地区内部差异最显著对整体差异贡献最大,中部、西部区域经济差异相对稳定;流域经济空间异质性明显,存在显著的空间正相关,区域经济格局两极化明显且东部经济水平明显高于中西部地区,流域经济发展的热点区主要分布在山东省内,冷点区主要分布在甘肃、陕西、青海等部分州市;通过分析黄河流域73个地级市经济发展类型时空演变特征,反映出黄河流域经济发展存在俱乐部趋同趋势,初始状态对区域经济发展具有重要作用,区域背景亦具有一定作用,区域经济水平的跨越式发展基本不存在。  相似文献   
72.
过渡金属离子与有机物对钢铁的缓蚀协同效应   总被引:1,自引:0,他引:1  
从过渡金属离子的特点、过渡金属离子对钢铁的缓释作用机理、及其与有机物对钢铁的缓释协同等方面,较全面地综述了过渡金属离子与有机物缓蚀体系应用于钢铁的研究现状,并结合铁质文物保护技术要求,提出了模拟制作铁质文物试片,选择合适的过渡金属离子与有机物,借鉴现代钢铁缓释剂研究的分析技术,开展铁质文物保护研究课题的技术路线.  相似文献   
73.
自宋代以来,《汉书》所载元王诗多被人目为《鲁诗》,但其证据存在诸多疑点。因此,考察《元王诗》的归属是进一步地弄清汉代《诗经》传承版图的一个重要内容。本文从《元王诗》被看作《鲁诗》的过程出发,具体分析了《元王诗》非《鲁诗》的原因,并比对了刘向《诗》学观点与楚元王封地附近的汉代《诗》简,从而最终判定《元王诗》是汉代《诗经》传授中的独立一支,刘向所习主要是《元王诗》而非《鲁诗》。所以从刘向《诗》学中辑考的鲁诗也非《鲁诗》。  相似文献   
74.
在跨文化语境下,色彩词是怎样命名的?相近意义的色彩词有没有语义流变或焦点?同音异字的汉语色彩词组与色彩词的语义比较是怎样的?本文将探讨色彩词的建构与文化影响,使人们在不同文化语境下了解和探讨瓷釉色彩的深层含义,以便合理应用。  相似文献   
75.
We conducted experiments to compare the micromorphological signatures of modern burnt sedge and grass bedding to laminated layers of carbonized material and phytoliths in Middle Stone Age deposits at the shelter, Sibudu. The experiments were designed to clarify the formation processes associated with the laminated layers and to investigate whether these previously identified layers of bedding were deliberately burned or not. The results indicate that the laminated layers were most likely produced by human activity related to the construction, maintenance and burning of bedding. Furthermore, our experiments demonstrate that large volumes of vegetal material could have produced the relatively thin, archaeological deposits of burnt bedding.  相似文献   
76.
Organic fertilizers have the capacity to alter the nitrogen isotopic composition of plants. Camelid dung and seabird guano are two potentially important fertilizers in the agricultural systems of western South America, particularly Peru and Chile. This paper presents isotopic data (δ13C and δ15N) from field grown plants (maize, Zea mays) fertilized with the following four treatments: CO (control, no fertilizer applied), AS (ammonium sulfate, a chemical fertilizer), DU (camelid dung), and SG (seabird guano). Plants were grown in experimental plots in the Virú Valley, northern Peru. Plants fertilized with the chemical fertilizer presented very similar isotopic compositions compared to the control. Conversely, the camelid dung fertilized plants were characterized by higher δ15N values compared to the control plants (by 1.8 to 4.2‰ depending on the plant part). The seabird guano fertilized plants were greatly enriched in 15N in comparison to the control plants (by 11.3 to 20.0‰). The results of this study have important implications for the reconstruction of human diet using isotopic data derived from bone collagen and related tissues, particularly in the prehispanic Andes, but also in Europe and North America during the 19th century, when Peruvian seabird guano was used extensively. Specifically, the interpretation of the relative contributions of plant and animal protein to the diet on the basis of bulk isotopic compositions of bone collagen (or similar tissues) may be confounded by camelid dung fertilization if the carbon isotopic compositions of the two sources are similar. Likewise, the interpretation of the relative contributions of maize and marine protein may be confounded by seabird guano fertilization.  相似文献   
77.
On September 1, 1969, a group of junior Libyan Army officers took control of the Libyan government in a bloodless coup d'état. After the coup, the group formed the Revolutionary Command Council (RCC), chaired by Muammar al‐Qadhafi. In the four decades following, Libya faced numerous foreign policy challenges. The Qadhafi regime took on a distinctly anticolonial flavor that mirrored the revolutionary political trends of Egypt under of Gamal Abdul Nasser. This change in foreign policy posture shook Libya's relations with the United States and the United Kingdom and initiated the degradation of Libyan–Western ties. Under Qadhafi's leadership, Libya chose an ideological path for that focused on the strengthening of sovereignty while pursuing policies of unity and anti‐imperialism. This often put Libya at loggerheads with the West, and at times with its neighbors. Nevertheless, Qadhafi maintained popularity among his constituency. 1 His domestic fame was the product of a carefully constructed persona that gave him the charismatic appeal necessary to maintain leadership during the latter quarter of the twentieth century and into the new millennium. Publicly, Qadhafi highlighted the similarities between himself and Libya's rural working class. He lived in a tent, and wore modest clothing. He fancied himself a devout Muslim, and praised the wisdom of the Libyan masses. He connected with his constituency through rhetoric that illustrated the stability of his policies over time, and their connection to the ideas that originally made him popular. This argues that the source of Qadhafi's charismatic power lay in his rhetoric, which connected Libya's foreign policy decisions to his foreign policy vision, the basis of his charismatic leadership. Qadhafi articulated his foreign policy vision during his first major speech to the Libyan people in September 1969, and he referred to it time and again when speaking about major Libyan foreign policy decisions. To demonstrate, this article describes the basis of Qadhafi's leadership authority and defines the parameters of his vision. Then Qadhafi's rhetoric surrounding major shifts in Libyan foreign policy is analyzed to show its congruence with his foreign policy vision. The rhetoric surrounding the Libya–Egypt war, the end of Libya's Chad intervention, Libya's surrendering of the two Lockerbie bombing suspects to be tried under Western authority, and Qadhafi's denunciation of the weapons of mass destruction programs—all major shifts in Libyan foreign policy—demonstrate how Qadhafi was able to maintain a single message, and thus his authority, over his first 35 years in power based on values established in the early days of his revolution. The flexibility of his vision enabled Qadhafi to maintain authority, while tactically adjusting Libyan foreign policy positions.  相似文献   
78.
79.
浙江瓯海出土一件西周青铜器腐蚀成因研究   总被引:4,自引:3,他引:1  
为研究浙江温州瓯海M24墓出土的一件青铜器的腐蚀成因,采用扫描电镜(SEM)、X射线荧光光谱仪(XRF)、X射线衍射仪(XRD)、离子色谱分析仪(HPIC)等,对青铜剑腐蚀产物及其埋藏土壤进行了分析。结果表明,青铜剑已严重腐蚀,铜元素大量流失形成以锡元素为主的腐蚀产物。通过测量模拟瓯海土壤环境下的自腐蚀电位并参照CuH2O体系的电位-pH图,推导出了浙江瓯海出土一件西周青铜器腐蚀反应历程。研究结果对类似出土文物有参考价值。  相似文献   
80.
吴琦  马俊 《安徽史学》2012,(2):14-24
在明代君臣关系中,君权一直处于强势地位,并左右着官员进退。明中后期,这种情况出现了微妙的变化。时值万历朝出现大范围缺官,以京官为首的文官群体以此为契机,引发了群体性的致仕乞休现象,不惜以影响政府的正常运作为代价,孤立皇帝,从而扭转了在致仕问题上长期处于被动的局面,并由此引发了官员对于君臣关系、权力分配及仕隐哲学的再思考,影响了主流舆论的变化以及政治力量在中央与地方之间的转移等。这种主动弃官的现象所折射出的理性精神和反传统思想在一定程度上催生了晚明政治文化的进步因子,并为中国日后具有近代意义的民主政治发展奠定了基础。  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