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   62篇
  免费   5篇
  国内免费   20篇
测绘学   8篇
大气科学   14篇
地球物理   6篇
地质学   22篇
海洋学   17篇
综合类   11篇
自然地理   9篇
  2023年   1篇
  2022年   4篇
  2021年   4篇
  2020年   3篇
  2019年   2篇
  2018年   4篇
  2017年   6篇
  2016年   3篇
  2015年   3篇
  2014年   2篇
  2013年   1篇
  2012年   1篇
  2011年   2篇
  2010年   6篇
  2009年   5篇
  2008年   8篇
  2007年   4篇
  2006年   5篇
  2005年   2篇
  2004年   4篇
  2003年   3篇
  2002年   2篇
  2000年   2篇
  1999年   4篇
  1998年   1篇
  1997年   2篇
  1989年   1篇
  1986年   1篇
  1984年   1篇
排序方式: 共有87条查询结果,搜索用时 390 毫秒
71.
????????????????????EDM??????????????????????3?????????????????????????????????????????????????????????????????????????  相似文献   
72.
蔡锋  陈峰 《台湾海峡》1998,17(2):172-179
本文通过对大嶝码头拟建区沉积环境的详细,对比其几年来表层沉积物的变化状况,建立三维粒度参数图象,并结合柱状沉积物的参数演化,建立了该区域新近年代沉积环境演化模式。通过岸、滩的实地考察,采用海图对比分析,计算出拟建区岸滩宽度、高程的变化,并对其原因、泥沙运移规律进行探讨,计算出其年淤积强度,为该项工程建成后的防护问题提供依据。  相似文献   
73.
针对如何优选出三频BDS最优载波相位线性组合观测量的问题,基于三频GNSS载波相位组合观测量理论,本文提出最优组合观测量选取的模糊聚类分析法。首先构建满足超宽巷组合和窄巷组合条件,且具有不同巷数、电离层数及噪声放大因子的三频BDS组合观测量,并假定各参数均为最优值的理论最优组合观测量;然后对满足条件的超宽巷组合和窄巷组合用模糊聚类分析法进行聚类排序;最后根据各组合观测量与假定的最优组合观测量聚为一类的先后顺序,确定三频BDS最优组合观测量的选取顺序。结果表明:模糊聚类分析法通过组合观测量的聚类排序,实现了最优组合观测量的筛选。无几何TCAR算法也验证了模糊聚类分析结果的正确性。  相似文献   
74.
In this paper, Visual MODFLOW is used to simulate groundwater flow and transport within the study area based on a certain scenario, assessing the leakage impact of a Sewage Plant accidental pool on groundwater using NH3-N as the assessment factor. In the model constructed, soil absorption and degradation was taken into account; the adsorption process of NH3-N adopted the Langmuir equation and the degradation was simplified as a first-order dynamic reaction. The leakage process was defined as a recharge with contaminants in the case that where there are two accidents happening to the Sewage Plant within a one month interval. The result of the model indicated that the NH3-N concentration of groundwater increased sharply when the Sewage Plant was malfunctioning. The peak of NH3-N concentration under the accident pool was about 8.0 × 10−5 mg/L at the first accident. When the second accident happened, the NH3-N concentration increased to a maximum of about 1.1 × 10−4 mg/L. At a location of about 20 m from the accident pool, the concentration declined to about one sixth of the center, which demonstrated that the NH3-N concentration increase caused by leakage of the accident pool was little, and the spatial influence also was small. The paper provides a method of dealing with the transport of physically and chemically reactive substances in groundwater with Visual MODFLOW and assessing the Sewage Plant accident pool leakage impact on groundwater quantitatively.  相似文献   
75.
江苏一次夏季强雷暴天气过程的综合分析   总被引:2,自引:0,他引:2  
姜麟  王卫芳  韩桂荣  赵凯 《气象科学》2006,26(3):316-322
本文对2002年8月24日江苏的一次强雷暴天气进行了热力参数和动力学诊断分析,并结合多普勒雷达回波和红外卫星云图进行综合分析,结果表明,这次强雷暴处于地面高能量场中,而在垂直方向上与锋生函数、假相当位温、涡度散度的某些分布特征有较好的对应关系;在多普勒雷达回波图上表现强回波带的相互合并加强并形成较为典型的弓形回波;在卫星云图上MCS云团相互合并成典型的圆形,尺度较大,亮温较低,导致了强雷暴天气的发生。  相似文献   
76.
通过深层次构造岩中不同粒度矿物多晶条带塑性流动的比较和形成机理的探讨,得出矿物多晶条带的流度规律:在深层次构造岩中加工状态下生成的数种矿物多晶条带共生时,其晶粒较小着塑性流动的流度较大。结合单矿物多晶条带的粒度规律得出:在深层次构造岩中由动态重结晶所生成的数种单矿物多晶条带共生时,其中脆-韧性转化点温度较高的矿物,其多晶条带的塑性流动的流度较大。根据温压条件由低至高矿物的脆-韧性转化序列和岩石圈大陆部分各圈层的主要组成矿物,可知岩石圈大陆部分各圈层的塑性流动具有协调性。  相似文献   
77.
多年冻土区采暖房屋架空不通风式桩基础应用   总被引:1,自引:0,他引:1  
李英武  马伟芳 《冰川冻土》1989,11(2):167-171
  相似文献   
78.
在参阅国内外海上丝绸之路文化研究成果基础上,从时间、空间、线路和内容四个层次阐明"海上丝绸之路"的内涵,借鉴瑞典"哥德堡号"仿古商船的成功经验,以"南海一号"古商船为例,提出了构建海上丝路文化旅游开发模式,打造文化旅游精品;完善海上丝路文化研究,申报世界文化遗产;萃取海上丝路文化主题,形成城市特色文化品牌;整合海上丝路文化与阳江文化,策划"蔚蓝阳江,千年船说"主题形象工程等开发思路.  相似文献   
79.
Evaluation of the sound-structure interaction is important for effective control of noise and vibration in structural acoustic systems. Cracked elastic structure-sound interaction problems are studied by employing the hybrid fractal FEM and BEM. The degrees of freedom of the system can be reduced greatly through adopting fractal FEM in discretizing the cracked elastic structure; while the exterior acoustic field is calculated by BEM, which automatically satisfies Sommerfeld‘s radiation condition. Numerical examples are given and show that the resonant frequencies of the structure-acoustic coupled system decrease as the depth of the crack increases, and that the crack has a significant effect on the acoustical field in the vicinity of the crack tip.  相似文献   
80.
We observed a phytoplankton bloom downstream of a large estuarine plume induced by heavy precipitation during a cruise conducted in the Pearl River estuary and the northern South China Sea in May–June 2001. The plume delivered a significant amount of nutrients into the estuary and the adjacent coastal region, and enhanced stratification stimulating a phytoplankton bloom in the region near and offshore of Hong Kong. A several fold increase (0.2–1.8 μg Chl L−1) in biomass (Chl a) was observed during the bloom. During the bloom event, the surface water phytoplankton community structure significantly shifted from a pico-phytoplankton dominated community to one dominated by micro-phytoplankton (>20 μm). In addition to increased Chl a, we observed a significant drawdown of pCO2, biological uptake of dissolved inorganic carbon (DIC) and an associated enhancement of dissolved oxygen and pH, demonstrating enhanced photosynthesis during the bloom. During the bloom, we estimated a net DIC drawdown of 100–150 μmol kg−1 and a TAlk increase of 0–50 μmol kg−1. The mean sea–air CO2 flux at the peak of the bloom was estimated to be as high as ∼−18 mmol m−2 d−1. For an average surface water depth of 5 m, a very high apparent biological CO2 consumption rate of 70–110 mmol m−2 d−1 was estimated. This value is 2–6 times higher than the estimated air–sea exchange rate.  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