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   1003篇
  免费   134篇
  国内免费   130篇
测绘学   39篇
大气科学   89篇
地球物理   167篇
地质学   696篇
海洋学   68篇
综合类   48篇
自然地理   160篇
  2024年   2篇
  2023年   7篇
  2022年   15篇
  2021年   32篇
  2020年   29篇
  2019年   30篇
  2018年   23篇
  2017年   27篇
  2016年   22篇
  2015年   32篇
  2014年   50篇
  2013年   45篇
  2012年   68篇
  2011年   61篇
  2010年   80篇
  2009年   93篇
  2008年   50篇
  2007年   83篇
  2006年   66篇
  2005年   57篇
  2004年   65篇
  2003年   69篇
  2002年   22篇
  2001年   34篇
  2000年   40篇
  1999年   36篇
  1998年   32篇
  1997年   20篇
  1996年   18篇
  1995年   27篇
  1994年   7篇
  1993年   6篇
  1992年   5篇
  1990年   4篇
  1989年   3篇
  1988年   2篇
  1986年   1篇
  1981年   2篇
  1980年   1篇
  1979年   1篇
排序方式: 共有1267条查询结果,搜索用时 15 毫秒
81.
世界一些大城市防灾减损的比较研究   总被引:2,自引:0,他引:2  
比较分析了一些大城市的防灾减损措施,提出了具体对策。  相似文献   
82.
Different models were developed for evaluating the probabilistic three-dimensional (3-D) stability analysis of earth slopes and embankments under earthquake loading using both the safety factor and the displacement criteria of slope failure.The probabilistic models evaluate the probability of failure under seismic loading considering the different sources of uncertainties involved in the problem. The models also take into consideration the spatial variabilities and correlations of soil properties. The developed models are incorporated in a computer program PTDDSSA.These analysis/design procedures are incorporated within a code named SARETL developed in this study for stability analysis and remediation of earthquake triggered landslides. In addition to the dynamic inertia forces, the system takes into consideration local site effects.The code is capable of assessing the landslide hazard affecting major transportation routes in the event of earthquakes and preparing earthquake induced landslide hazard maps (i.e., maps showing expected displacements and probability of slope/embankments failure) for different earthquake magnitudes and environmental conditions. It can also beused for proposing a mitigation strategy against landslides.  相似文献   
83.
谭承业 《地震研究》1996,19(1):85-94
本系统讨论了土木工程结构的主动控制和混合控制设备的构造和性能及其实际应用的效果;对一般非线性优化控制方法及其效用做了分析介绍;对当前土木工程结构控制研究中存在的困难和问题以及今后的发展趋势进行了分析讨论和展望。  相似文献   
84.
During and after the very wet 1991/1992 winter experienced in Jordan, significant slope failures occurred along several sections of the new Irbid-Amman highway in Jordan. The topography over most of the route is hilly, and significant amounts of cut and fill were used to construct the highway. One such slope failure lies at 44+800 km on the highway south of Jerash City at a distance of about 5.0 km from Wadi Zerqa bridge. A landslide occurred downslope of the highway embankment resulting in a collapse of the most of the gabbion wall supporting the embankment. This paper deals with the overall stability of the slope at 44+800 km. It presents the geological and geotechnical studies carried out at this site, identifies the causes and mechanism of instability, and presents appropriate remedial measures. The study concluded that the landslide movement occurred within the colluvium material. It resulted primarily from excess piezometric pressures generated within the slope as a direct consequence of inadequate drainage. It is recommended to reconstruct the entire gabbion wall with its foundation seated on the sandstone that underlies the colluvium and to install a surface drainage system at the site.  相似文献   
85.
针对目前中深斜井通风存在的问题,在风筒接头,风筒节长,风筒直径,风筒的布置及修补等方面作了阐述了,并对改进前,后系统的送风效果进行比较。  相似文献   
86.
我国"入世"后,外国跨国公司必然会进入我国的地质市场.对比,本文指出了国内地勘单位与跨国公司相比,在技术力量、资本和管理水平等方面存在的问题,以及它们的介入所带来的不利影响和机遇,针对这些问题提出了具体的对策及所采取的措施.  相似文献   
87.
在改革中求发展--《干旱气象》改革的基本思路与措施   总被引:1,自引:0,他引:1  
吴喜峰 《干旱气象》2006,24(2):60-62,77
以《甘肃气象》改为《干旱气象》后所采取的一系列思路和措施为重点,论述了由技术类期刊向学术类期刊发展的过程和改刊后的成果以及所存在的问题,提出了以干旱气象为中心,将期刊办出特色、办出新意的理念,同时也对该刊今后的努力方向提出要求。  相似文献   
88.
This paper examines the utility of a number of pattern measures for local exploratory analysis of binary spatial data. Based on a review of existing pattern measures in cartography, geography, image analysis, and landscape ecology, two fundamental classes of such measures, termed compositional and configurational, are identified. The paper focuses on configurational measures and it is suggested that as many as five such measures (join counts, patch numbers, patch sizes, patch proximity, and distribution of the classes relative to the focal cell of the window) are required to differentiate between all possible local categorical maps. This suggestion is explored by examining aspects of the statistical behaviour (probability distributions and correlations between extreme values of pairs of measures) of a set of 12 configurational measures. Their use is also demonstrated by means of an empirical example.  相似文献   
89.
The correlation between ground motion intensity measures (IM) and single-degree-of-freedom (SDOF) deformation demands is described in this study. Peak ground acceleration (APG), peak ground velocity (VPG), peak ground displacement (DPG), spectral acceleration at the first-mode period of vibration [As(T1)] and ratio of VPG to APG are used as IM parameters, and the correlation is characterized by correlation coefficients p. The numerical results obtained by nonlinear dynamic analyses have shown good correlation between As(T1) or VPG and deformation demands. Furthermore, the effect of As(T1) and VPG as IM on the dispersion of the mean value of deformation demands is also investigated for SDOF systems with three different periods T=0.3 s, 1.0 s, 3.0 s respectively.  相似文献   
90.
Three dispersion measures of a random variable, i.e., the standard deviation, the mean deviation (MD) about the mean and the second L-moment, are analyzed in terms of their properties and mutual relationships. Emphasis is placed on the MD, as it is less recognized than two other dispersion measures. The relationships between the dispersion measures are derived for distributions commonly applied in flood frequency analysis (FFA). For distributions that are unbounded, there is a distribution-dependent constant value of the ratio of dispersion measures, or equivalently of respective coefficients of variation. For two-parameter distributions that are lower-bounded, the relationship between the coefficients of variation is also distribution dependent and is not linear. For lower-bounded three-parameter distributions, the dispersion measure ratios, or equivalently the ratios of coefficients of variation, depend on the coefficient of skewness and show a strong distributional dependence. For selected distributions, the three dispersion measures are compared both in terms of the robustness to the largest samples element and the accuracy of upper quantile estimation. The MD statistics may be highly competitive to the two other dispersion measure statistics if applied in FFA for parameters estimation.  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