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   121篇
  免费   19篇
  国内免费   26篇
测绘学   24篇
大气科学   38篇
地球物理   19篇
地质学   34篇
海洋学   17篇
天文学   7篇
综合类   16篇
自然地理   11篇
  2023年   1篇
  2022年   1篇
  2021年   1篇
  2020年   2篇
  2019年   4篇
  2018年   3篇
  2017年   7篇
  2016年   5篇
  2015年   3篇
  2014年   7篇
  2013年   14篇
  2012年   9篇
  2011年   13篇
  2010年   12篇
  2009年   6篇
  2008年   9篇
  2007年   11篇
  2006年   14篇
  2005年   6篇
  2004年   5篇
  2003年   5篇
  2002年   6篇
  2001年   5篇
  2000年   10篇
  1999年   2篇
  1998年   3篇
  1997年   2篇
排序方式: 共有166条查询结果,搜索用时 187 毫秒
21.
杨逊  赵静 《四川测绘》2012,(1):35-38
本文从建筑设计企业ISO贯标信息化工作实际需求,针对行业ISO贯标特点,探讨了在GIS支持下建筑设计企业ISO贯标信息化的可能性和可行性,并在此基础上开发了一个ISO贯标信息管理系统。实践表明,将GIS集成到ISO贯标工作是切实可行和有效的。  相似文献   
22.
副热带北太平洋大气季节内振荡时空特征的诊断研究   总被引:5,自引:1,他引:4  
韩荣青  李维京  董敏 《气象学报》2010,68(4):520-528
用时空谱分析和小波变换方法,对1958—2002年NCEP/NCAR再分析资料经、纬向风速和位势高度的年时间序列进行了波谱分析,并重点研究了北太平洋副热带区域经向风30—60天振荡(ISO)的时空特征。研究结果表明,北半球经向风与纬向风和位势高度的30—60天振荡特征迥然不同,代表风场经向低频扰动的经向风ISO在副热带和中高纬度最为活跃,而在热带地区的活动十分微弱;北半球副热带850 hPa高度场和纬向风在10—90天内(季节内)振荡的主要能量集中在纬圈波数为1、周期为30—60天的波动上,而850 hPa经向风季节内振荡的主要能量集中在纬圈波数为4—6、周期为30—60天以及70—90天的波动上,上述3个物理量30—60天振荡向西传播的能量都强于向东传播的能量。一年当中,东亚到北太平洋的副热带地区,经向风ISO在东亚—西北太平洋与东北太平洋两个区域的活动最强,且在这两个区域存在明显的季节振荡,即东北太平洋的ISO在冬季最强在夏季最弱,而东亚—西北太平洋区域的ISO在夏季最强冬季最弱。850 hPa经向风ISO的年际和年代际变化分析表明,在东亚副热带区域其活动1958—1975年较强,1976—1990年明显减弱,而1991—2000年最强;其在ENSO发生期间有较为明显的异常活动,但其强弱变化没有显著的定势,然而2—7年的带通滤波分析表明西北太平洋ISO的年际活动含有较显著的ENSO信号,9年的低通滤波分析表明,年代际时间尺度上,西北太平洋ISO的活动与ENSO循环有较为显著的反相关特征,而东北太平洋区域ISO与ENSO循环有较为显著的正相关关系。  相似文献   
23.
Recommendations for the certification of reference materials, as published by the International Organisation for Standardisation (ISO), are reviewed and proposals made as to how they can be adapted for the certification of new geological reference materials. Whilst acknowledging the important contribution made by the large number of existing matrix-matched geological reference materials, it is recommended that future characterisation programmes should follow the ISO guidelines for certification, not the least so that laboratories can readily use the resultant samples to establish the traceability of geoanalytical results.  相似文献   
24.
Developing approaches to automate the analysis of the massive amounts of data sent back from the Moon will generate significant benefits for the field of lunar geomorphology. In this paper, we outline an automated method for mapping lunar landforms that is based on digital terrain analysis. An iterative self-organizing (ISO) cluster unsupervised classification enables the automatic mapping of landforms via a series of input raster bands that utilize six geomorphometric parameters. These parameters divide landforms into a number of spatially extended, topographically homogeneous segments that exhibit similar terrain attributes and neighborhood properties. To illustrate the applicability of our approach, we apply it to three representative test sites on the Moon, automatically presenting our results as a thematic landform map. We also quantitatively evaluated this approach using a series of confusion matrices, achieving overall accuracies as high as 83.34% and Kappa coefficients (K) as high as 0.77. An immediate version of our algorithm can also be applied for automatically mapping large-scale lunar landforms and for the quantitative comparison of lunar surface morphologies.  相似文献   
25.
This paper presents a comparison between the Chinese Code GB50011-2001 and the International Standard ISO3010: 2001(E), emphasizing the similarities and differences related to design requirements, seismic actions and analytical approaches. Similarities include: earthquake return period, conceptual design, site classification, structural strength and ductility requirements, deformation limits, response spectra, seismic analysis procedures, isolation and energy dissipation, and nonstructural elements. Differences exist in the following areas: seismic levels, earthquake loading, mode damping factors and structural control.  相似文献   
26.
The stability of river channels and their suitability as habitat for aqueous organisms is strongly controlled by the rate of bedload transport. Quantification of bedload transport rates in rivers is difficult, not only because of the temporal variation in transport, but also because of the cross‐channel variation in transport. The objectives of this study were: (i) to determine the effect of cross‐channel variation in bedload transport on the uncertainty of width‐integrated transport rates; and to use this knowledge (ii) to improve guidelines for bedload sampling. This was done through a thorough statistical evaluation of stochastic and systematic uncertainties involved in bed‐load transport measurements. Based on this evaluation, new guidelines are presented for determination of the number of samples and sampling positions across the channel that are required for bedload measurements in several types of sand‐bed rivers and gravel‐bed rivers. The guidelines relate to bedload measurements made with pressure‐difference (Helley‐Smith type) samplers that require numerous bedload samples of short duration at several positions across the channel. The results show that generally more sampling positions across the channel are required in gravel‐bed rivers than in sand‐bed rivers. For gravel‐bed rivers with unknown cross‐channel distribution of transport, at least 10 sampling positions are recommended, whereas for most sand‐bed rivers five positions suffice. In addition, at least 12 short‐duration samples are required at each position to obtain bedload estimates with uncertainties below 20%. If the same level of uncertainty is desired in the case of high spatial and temporal variation in transport rates, the number of short‐duration samples needed per sampling position increases to 40.  相似文献   
27.
从商业策划的角度介绍了朝阳天马集团卫生学校地块商住综合体设计的总体构思和特点,该项目欲在朝阳最重要的朝阳大街上建造地产的新标志,使之成为城市的重要节点。  相似文献   
28.
The heavy metal inventory and the ecological risk of the tidal flat sediments in Haizhou Bay were investigated. Results show that the average concentrations of heavy metals in the surface sediments exceeded the environment background values of Jiangsu Province coastal soil, suggesting that the surface sediments were mainly polluted by heavy metals (Cd, Cr, Cu, Mn, Pb and Zn). In addition, the profiles of heavy metals fluxes can reflect the socio-economic development of Lianyungang City, and heavy metals inputs were attributed to anthropogenic activities. Cr, Cu, Pb and Zn were mainly present in the non-bioavailable residual form in surface sediments, whereas Cd and Mn were predominantly in the highly mobile acid soluble and reducible fractions. The ecological risk of the polluted sediments stemmed mainly from Cd and Pb. According to the Sediment quality guidelines (SQGs), however, the adverse biological effects caused by the heavy metals occasionally occurred in tidal flat.  相似文献   
29.
30.
介绍质量管理体系在我院运行的概况,阐述了根据ISO 900 1∶2008的要求对原有质量管理体系文件进行修改的情况,根据多年来实际工作经验探讨了在质量管理体系运行过程中的体会及改进方向。  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