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   165篇
  免费   38篇
  国内免费   15篇
测绘学   37篇
地球物理   13篇
地质学   128篇
海洋学   10篇
天文学   3篇
综合类   8篇
自然地理   19篇
  2024年   1篇
  2023年   2篇
  2022年   5篇
  2021年   14篇
  2020年   4篇
  2019年   10篇
  2018年   3篇
  2017年   3篇
  2016年   9篇
  2015年   9篇
  2014年   11篇
  2013年   7篇
  2012年   7篇
  2011年   11篇
  2010年   11篇
  2009年   21篇
  2008年   27篇
  2007年   19篇
  2006年   7篇
  2005年   7篇
  2004年   5篇
  2003年   8篇
  2002年   7篇
  2001年   2篇
  2000年   2篇
  1999年   2篇
  1998年   2篇
  1994年   1篇
  1993年   1篇
排序方式: 共有218条查询结果,搜索用时 24 毫秒
31.
While there are numerous thick loess–palaeosol sequences preserved across the Carpathian Basin, well dated sites that provide terrestrial palaeoenvironmental records extending beyond last glacial–interglacial cycle are scarce. Robust chronologies are essential for correlations of loess with other long-term Quaternary records and to further understanding of the palaeoenvironment and climate of this important region beyond the last 125 ka. Here a new geochronology based on 13 post-infrared infrared stimulated luminescence ages focused on the lower part of the loess–palaeosol sequence at Erdut is presented. The results show that the lower part of the Erdut profile spans the penultimate glacial cycle (MIS 7 to MIS 5). The considerable sediments overlaying the investigated part of the profile suggest that this section spans two glacial cycles, rather than the previously suggested one. The most likely source of the discrepancy is the use of uncorrected infrared stimulated luminescence signal, which can cause age underestimation if not accounted for. This study demonstrates the need to revisit sites such as Erdut, re-date them using updated measurement protocols, and update existing palaeoenvironmental interpretations.  相似文献   
32.
在分析山东省胶南市城市地下管线M IS的基础上,从两个方面论述了城市地下管线与城市规划管理的关系,认为城市地下管线M IS和城市规划管理之间相互作用、互为补充、关系密切。城市地下管线M IS为城市规划管理工作提供了准确而有现势性的基础资料,提高了规划管理的工作效能和城市规划管理水平;城市规划管理保障了城市地下管线M IS数据的动态更新和现势性,实现地下管线从规划设计审批竣工测量,到系统数据更新的全过程动态管理。  相似文献   
33.
选取位于中亚哈萨克斯坦中南部的VA剖面作为研究对象,剖面厚7 m,野外采样以及实验分析间距均为5 cm。在AMS 14C测年基础上,综合野外地层考察和实验室指标(包括磁化率、碳酸盐、有机质和粒度)分析,结果表明:I:该剖面过去~25 000 14C a BP以来地层主要可以分为五个地层单元:(1) ~26 000 14C a BP—~22 000 14C a BP,河流作用过的黄土层;(2) ~22 000 14C a BP—~19 000 14C a BP,潜育化的黄土层;(3) ~19 000 14C a BP—~10 000 14C aBP,弱土壤层;(4) ~10 000 14C a BP—~5 000 14C a BP,典型的黄土层;(5) 过去~5 000 14C a BP以来,土壤层。II:将VA剖面与欧洲区以及东亚区黄土沉积对比发现:研究区过去~25 000 14C a BP 以来地层沉积与欧洲黄土沉积类似,全新世地层序列与东亚区具有反相位关系:中亚区早全新世为黄土沉积,晚全新世发育土壤层,说明研究区过去25 000 14C a以来主要受西风带和地中海气候控制,具有西风区气候特征。III:VA剖面MIS2记录到的潜育化黄土层以及弱土壤层显示研究区在MIS2时段气候相比东亚区更为湿润。  相似文献   
34.
A cliff outcrop called Kluckow, in the Baltic Sea area, with a (glacio-) fluvial to (glacio-) lacustrine succession, provides a unique opportunity to resolve uncertainties in the timing and extent of several poorly constrained Weichselian ice advances. Based on a detailed lithofacies analysis, we selected four sampling horizons for luminescence dating to determine a depositional chronology. We measured both coarse-grain quartz and potassium-rich feldspar for age determination using optically stimulated luminescence (OSL) and post-IR infrared stimulated luminescence (pIRIR). Furthermore we addressed potential problems such as incomplete bleaching and quartz saturation effects. The resulting luminescence-chronology, supported by one radiocarbon age, illustrates a depositional time interval of the investigated sequence between ∼62 and ∼22 ka. Within this sequence a mussel-bearing fluvial sand indicate interstadial climate conditions at approximately 46 ka. The upper part of the section is composed of a 4 m thick glaciolacustrine silty clay and an overlying glaciofluvial sand; the latter yielded an OSL age of ∼22 ka. Shortly after these sequences formed, the subsequent ice advance (indicated by the overlying till sheet) reached the study area. Based on our new chronology and lithofacies analysis, we conclude that the Scandinavian Ice Sheet did not reach the study area between ∼62 and ∼22 ka.  相似文献   
35.
何义权 《安徽地质》2009,19(1):1-11,16
回顾了安徽省国土资源信息化建设。叙述了标准化、基础数据库建设、管理信息系统(MIS)和地理信息系统(GIS)开发应用、电子政务等方面的进展;探讨了国土资源信息化面临数据质量、信息共享、电子政务和技术方面的挑战,事实上这些挑战不仅仅局限于安徽、也不仅仅局限于国土资源部门,而是信息化面对的挑战。  相似文献   
36.
通过管理信息平台和图纸打印收集归档利用系统的综合信息化管理,改变了原先不能及时有效得到各专业的实际生产状况和信息不能及时共享的问题,实现了项目管理的每个环节都有可供查询的信息,项目管理人员可随时利用管理信息平台对相关信息和数据进行分析,并形成分析报表,辅助决策。同时通过图纸打印收集归档利用系统对电子图纸进行辅助管理,使设计人员高效快速地对于既往图纸查询、利用。浙江工业大学建筑规划设计研完院的管理信息系统与协同设计工具(图纸打印收集归档利用系统)通过近两年的综合运行,有效降低了设计成本和管理成本,提高了设计人员的生产效率和项目管理人员的管理水平,这种全新的综合应用方式和技术思路有广泛的实用价值和借鉴作用。  相似文献   
37.
An evolutionary model of sedimentary environments since late Marine Isotope Stage 3 (late MIS 3, i.e., ca. 39 cal ka BP) along the middle Jiangsu coast is presented based upon a reinterpretation of core 07SR01, new correlations between adjacent published cores, and shallow seismic profiles recovered in the Xiyang tidal channel and adjacent northern sea areas. Geomorphology, sedimentology, radiocarbon dating and seismic and sequence stratigraphy are combined to confirm that environmental changes since late MIS 3 in the study area were controlled primarily by sea-level fluctuations, sediment discharge of paleo-rivers into the South Yellow Sea (SYS), and minor tectonic subsidence, all of which impacted the progression of regional geomorphic and sedimentary environments (Le., coastal barrier island freshwater lacustrine swamp, river floodplain, coastal marsh, tidal sand ridge, and tidal channel). This resulted in the formation of a fifth-order sequence stratigraphy, comprised of the parasequence of the late stage of the last interstadial (Para-Sq2), including the highstand and forced regressive wedge system tracts (HST and FRWST), and the parasequence of the postglacial period (Para-Sql), including the transgressive and highstand system tracts (TST and HST). The tidal sand ridges likely began to develop during the postglacial transgression as sea-level rise covered the middle Jiangsu coast at ca. 9.0 cal ka BP. These initially submerged tidal sand ridges were constantly migrating until the southward migration of the Yellow River mouth to the northern Jiangsu coast during AD 1128 to 1855. The paleo-Xiyang tidal channel that was determined by the paleo-tidal current field and significantly different from the modern one, was in existence during the Holocene transgressive maxima and lasted until AD 1128. Following the capture of the Huaihe River in AD 1128 by the Yellow River, the paleo-Xiyang tidal channel was infilled with a large amount of river-derived sediments from AD 1128 to 1855, causing the emergence of some of the previously submerged tidal sand ridges. From AD 1855 to the present, the infilled paleo-Xiyang tidal channel has undergone scouring, resulting in its modern form. The modern Xiyang tidal channel continues to widen and deepen, due both to strong tidal current scouring and anthropogenic activities.  相似文献   
38.
城市化进程的快速发展对城市规划管理观念、方法和手段提出了更高的要求,通过科学技术手段尤其是信息化手段改进城市规划管理,提高城市规划水平已成为必然。本文以GIS为核心技术,采用SOA面向服务的体系结构设计思想,介绍了昆明市规划管理信息系统的逻辑框架、技术路线、数据库的设计和各个功能模块的实现,最后重点阐述了系统的关键技术及应用后可能取得的社会、经济效益。  相似文献   
39.
An interdisciplinary study of a small sedimentary basin at Neumark Nord 2 (NN2), Germany, has yielded a high-resolution record of the palaeomagnetic Blake Event, which we are able to place at the early part of the last interglacial pollen sequence documented from the same section. We use this data to calculate the duration of this stratigraphically important event at 3400 ± 350 yr. More importantly, the Neumark Nord 2 data enables precise terrestrial-marine correlation for the Eemian stage in central Europe. This shows a remarkably large time lag of ca. 5000 yr between the MIS 5e ‘peak’ in the marine record and the start of the last interglacial in this region.  相似文献   
40.
福建沿海地区第四系较为发育,是研究晚更新世以来相对海平面变化的理想区域。本文以福建宁德NDQK5岩芯中产出的高分辨率介形类化石为研究对象,结合加速器质谱法(accelerator mass spectrometry, AMS)14C和光释光测年技术建立岩芯年代框架,重建了中全新世期间福建沿海地区的相对海平面变化。结果显示,NDQK5岩芯中的介形类化石记录主要分布于4~17. 1 m段,对应年代约为8. 2~6. 9 ka BP。岩芯内共计识别出海相介形类23属26种,根据优势种以及特征种的相对丰度变化特征可将岩芯内的介形类动物群划分为3个组合:① 介形类组合A以Bicornucythere bisanensis和Sinocytheridea impressa为主,代表潮下带环境;② 介形类组合B以Sinocytheridea impressa和Neomonoceratina delicata为优势种,指示近岸内陆架的沉积环境;③ 介形类组合C以Sinocytheridea impressa和Loxoconcha ocellifera为主,代表潮间带的沉积环境。基于介形类组合的分布特征,本文推断福建沿海地区海平面约在8. 2~7. 4 ka BP期间持续上升,并在约7. 9~7. 4 ka BP区间达到最高;7. 4~7. 0 ka BP期间海平面下降,随后再次上升。因此,介形类化石记录指示福建沿海地区在全新世高海平面背景下依然存在相对海平面的次一级波动。同时,结合已有福建沿海地区海平面变化驱动机制的研究结果,本研究推断8. 2~7 ka BP期间福建沿海地区的海平面变化可能主要受控于冰盖融水;7 ka BP后该地区的海平面波动可能受控于“冰川- 水均衡调整”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