全文获取类型
收费全文 | 111篇 |
免费 | 21篇 |
国内免费 | 35篇 |
专业分类
测绘学 | 31篇 |
大气科学 | 36篇 |
地球物理 | 7篇 |
地质学 | 41篇 |
海洋学 | 21篇 |
综合类 | 21篇 |
自然地理 | 10篇 |
出版年
2024年 | 1篇 |
2023年 | 7篇 |
2022年 | 8篇 |
2021年 | 13篇 |
2020年 | 3篇 |
2019年 | 4篇 |
2018年 | 11篇 |
2017年 | 6篇 |
2016年 | 5篇 |
2015年 | 8篇 |
2014年 | 8篇 |
2013年 | 11篇 |
2012年 | 7篇 |
2011年 | 10篇 |
2010年 | 10篇 |
2009年 | 8篇 |
2008年 | 10篇 |
2007年 | 11篇 |
2006年 | 7篇 |
2005年 | 4篇 |
2004年 | 2篇 |
2002年 | 3篇 |
2000年 | 2篇 |
1999年 | 2篇 |
1996年 | 1篇 |
1989年 | 3篇 |
1988年 | 2篇 |
排序方式: 共有167条查询结果,搜索用时 31 毫秒
101.
102.
利用1979-2009年逐月NCEP/NCAR再分析资料和福建省66站降水资料,分析了3-4月南极涛动(AAO)的变化对后期福建前汛期(5-6月)降水的影响。结果表明:3-4月平均的AAO指数与福建前汛期降水有很好的正相关性,前期AAO偏强时,后期前汛期降水偏多,反之亦然;且AAO异常时降水的同号率为100%。对AAO异常年的分析发现,当前期AAO异常强时,后期北方冷空气活动频繁,南方暖湿气流输送强盛,在华南北部产生强烈锋生,导致福建前汛期降水偏多;反之,降水偏少。上述结论为福建前汛期降水预测提供了一条可行的新途径。 相似文献
103.
通过多种仪器分析,测定了胶州湾李村河河口区4个沉积物柱状样品的有机碳(TOC)、酸可挥发硫化物(AVS)及重金属元素活性部分(活性金属)的含量,并系统讨论了其环境响应特征。研究发现,胶州湾李村河河口区三角洲沉积物中的有机碳、AVS和活性金属元素的分布受与河口的距离及沉积相带分布的影响。近河口细粒物质沉积区域的有机质受陆源控制,有机碳含量较高,AVS和活性金属元素含量高,活性铁的含量是AVS形成的主控因素,同时AVS也是多数活性金属元素在沉积物中的主要赋存形态。而离河口较远区域,有机碳含量受海、陆双向物源控制,AVS含量主要受控于有机质含量,两者含量均相对较低,活性金属元素含量也较低,多数金属元素(Cd、Cr、Cu、Mn、Pb、Zn等)主要以依附于铁的形态存在。根据上述沉积特点,将胶州湾李村河河口区沉积环境划分为3类区域5种类型,分别是一类区域中的水下分流河道和分流间湾,二类区域中的水下分流河道和分流间湾及三类区域中的前缘席状砂。 相似文献
104.
Numerical simulation of Qiaotou Landslide deformation caused by drawdown of the Three Gorges Reservoir,China 总被引:6,自引:2,他引:4
Jiwei Jiang Dominik Ehret Wei Xiang Joachim Rohn Ling Huang Shaojun Yan Renneng Bi 《Environmental Earth Sciences》2011,62(2):411-419
Landslides located beside reservoirs tend to be unstable or are characterized by large deformation during the drawdown process.
This has been accepted by many experts. In this paper, we use Qiaotou Landslide, which is located beside the Three Gorges
Reservoir (TGR), as a typical case study to investigate and predict the deformation mechanism during the drawdown process
of TGR in detail. According to field investigation, the landslide mass is mainly composed of thick, loose silt and clay mixed
with fragments of rock. Bedrock is mainly composed of silty sandstone. Field and laboratory tests indicate that the landslide
mass has a high permeability coefficient. If the water level declines fast, intense seepage force may result. Based on these
data, we establish a three-dimensional geological model of Qiaotou Landslide by FLAC3D and perform a numerical simulation using the saturated–unsaturated fluid–solid coupling theory. For the simulation, we assume
that the drawdown from 175 to 145 m takes place with a speed of 25 cm/day, which is based on the extreme water level regulation
program of TGR. The simulation shows that this causes a significant deformation in the landslide mass and that the maximum
displacement within the landslide is 24.2 cm. During the drawdown process, the maximum displacement zone is shifting from
the upper part of the landslide where bedrock surface is steeper and thickness of loose deposits is less to the middle part
of the landslide where bedrock surface is less steep and thickness of loose deposits is higher. The deformation mechanism
indicates that in the early stage of the drawdown the deformation of the landslide mass is mainly caused by seepage and in
the later stage mainly by consolidation. 相似文献
105.
As a unique low-temperature water mass in Antarctic coastal region, the Ice Shelf Water (ISW) is an important component for the formation of the Antarctic Bottom Water (AABW). In this paper, we present a criterion for ISW identification based on freezing point at the sea surface, and we study spatial distribution of ISW in front of the Amery Ice Shelf (AIS) and its flow path in Prydz Bay by analyzing hydrographic data from Australian cruises in 2001 and 2002, as well as Chinese cruises in 2003, 2005, 2006, and 2008, all being made in the austral summer. The relatively cold and fresh ISW occurred as several discrete water blocks with cold cores in front of the AIS, within the depth range of 100?600 m, under the seasonal thermocline. ISW had obvious temporal and spatial variations and the spatial distribution pattern changed greatly after 2005. Most of ISW was concentrated west of 73°E during 2001 to 2003 and 2006, but it was widespread to east in 2005 and 2008. In all observation years, a small amount of cold ISW always occurs at the west end of the AIS front section, where the coldest ISW in the whole section also occurred in 2001, 2003 and 2006. Considering general cyclonic circulation pattern under the AIS, the ISW flowing out from west end of the AIS front might have experienced the longest cooling period under ice shelf, so it would have the lowest temperature. Analysis of data from meridian sections in Prydz Bay in 2003 implied that ISW in the west could spread north to the continental break along the east flank of the Fram Bank near 70.5°E, mix with the upwelling Circumpolar Deep Water and possibly contribute to the formation of AABW. 相似文献
106.
107.
本文提出,利用遮蔽区域中二个测点的同步遮蔽角和方位角资料,就可计算出所测区域中任意一点的遮蔽角和方位角序列,并清除了经纬仪高度对遮蔽角的影响。配合太阳视运动轨迹,用图解法或数值计算法即可求出相应点的实际日出、日落时间和可照时数。 相似文献
108.
Four species in the genus Navicula were isolated using the serial dilution method. Based on scanning electron microscopy(SEM) and sequence comparisons of two segments of genes(small ribosomal subunit and large subunit of Rubisco), the species were identified as Navicula perminuta, N. pseudacceptata, N. vara, and N. rhynchocephala. Based on phylogenetic analysis and culture trials, there was a close relationship between N. perminuta and N. vara. Growth of these species was evaluated using measurements of optical density at 680 nm(OD680) under various environmental factors. Results showed that the optimum culture conditions were 25℃, 50–100 μmol photons m-2 s-1, pH 8.0, and salinities from 25 to 30. However, the favorable salinity for N. perminuta was surprisingly high at 35. Nutrient requirement analysis demonstrated that growth of Navicula depended on the availability of SiO32-. Their relative growth rates(RGR) peaked at the highest tested level(0.25 mmol/L). The optimal concentrations of NO3- and PO43- were 3.6 mmol/L and 0.18 mmol/L, respectively. Culture of these Navicula species for abalone or sea cucumber aquaculture should take these factors into consideration. 相似文献
109.
三维模型重建中影像纹理重组织方法研究 总被引:2,自引:0,他引:2
针对物体三维重建中影像文件多、纹理数据量大这一问题,提出了影像纹理数据重组织的数学模型和一个纹理重组织解决方案,根据这一方案对两组飞机模型的纹理进行了处理。试验结果表明.该方法能够有效地减少纹理数据量。 相似文献
110.
大多数旅游需求预测研究是基于目的地游客总数或消费总量开展的,尚未按不同的旅游目的或客源地细分进行预测.以天津欢乐谷主题公园为案例地,选择2014年第40周到2015年第26周为研究时段,利用通信大数据,提出了一种面向客源地的聚类-ARIMA组合预测模型.通过对不同客源地的时序数据进行聚类,选取各类别中的代表性客源地分别构建ARIMA预测模型.结果表明:对欢乐谷主题公园各客源地分别建模与聚类后通过6个代表客源地建模得到的结果一致;后者可以降低80%的预测成本.该方法具有较高的预测精度和较低的计算成本,适合面向客源地的短期旅游需求预测,可为旅游目的地提供更具针对性的旅游需求管理、分析与决策支撑. 相似文献