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南海西缘新生代沉积盆地形成动力学探讨 总被引:8,自引:3,他引:5
通过对南海西缘新生代沉积盆地伸展作用、沉降、构造变形等特征分析,检查印支地块多条近北西向走滑断裂时间、幅度等特征以及与盆地之间联系,结果表明印度-欧亚碰撞引起的逃逸作用与南海西缘新生代盆地没有直接的成因联系;两个与俯冲有关的不同扩张机制与南海西缘新生代盆地有成因联系,即(1)太平洋板块在古新世到始新世的滚动后退,太平洋-欧亚板块汇聚速率的降低驱使这些盆地产生初始伸展作用;(2)渐新世到中中新世古南海南倾俯冲板块的拖曳力,进一步驱使这些盆地的伸展及接着的南海扩张. 相似文献
53.
SUN Jinlong XU Huilong QIU Xuelin ZHAN Wenhuan LI Yamin CAS Key Laboratory of Marginal Sea Geology South China Sea Institute of Oceanology the Chinese Academy of Sciences Guangzhou Guangdong China Graduate University of the Chinese Academy of Sciences Beijing China 《《地质学报》英文版》2009,83(1)
The coastal hard rock with a thickness of over 5 m and a distribution area of nearly 200 ha in the Haishan Island,south China,has long drawn researchers' attention.However,there were controversies over its formation and classification,and these controversies in turn lead to the dispute of sea level changes and coastal uplift-subsidence of this area.To investigate its diagenesis and evolution,petrographic analysis,elemental geochemistry,isotopic analysis,and radiocarbon dating were used in the present stu... 相似文献
54.
Wei Luo Minghui Zhao Jiazheng Zhang Chunhui Tao Xuelin Qiu Yu Ren 《Marine Geophysical Researches》2017,38(1-2):27-37
Two earthquakes were recorded by 20 ocean bottom seismometers (OBS) deployed in the Southwest Indian Ridge (SWIR) area during a three-dimensional seismic survey in 2010. Their magnitudes (both M b = 4.4) and hypocenters have been determined by National Earthquake Information Center (NEIC) only using land seismic stations onset times. After the frequency analysis and the band-pass filtering of the OBSs’ data, 7 and 13 P-phase onset times from OBSs were successfully picked for these two events, respectively. Then these two events were relocated by HYPOSAT program with onset times together from OBSs and land seismic stations using different velocity models. These relocation experiments confirm both the importance of adding OBSs’ onset data and the need to apply a local oceanic velocity model for the location of these two events happened on the SWIR. This research has accumulated a wealth of experience for earthquakes observation and research using OBSs in the ocean. 相似文献
55.
The continental margins of the southwest subbasin in the South China Sea mark a unique transition from multi-stages magma-poor continental rifting to seafloor spreading. We used reflection and refraction profiles across the margins to investigate the rifting process of the crust. Combining with the other seismic profiles acquired earlier, we focused on the comparative geological interpretation from the result of multichannel seismic analysis and wide-angle seismic tomography. Our result provides the evidence of upper crustal layer with abundant fractures below the acoustic basement with a P-wave velocity from 4.0 to 5.5 km s?1. It indicates extensive deformation of the brittle crust during the continental rifting and can make a good explanation for the observed extension discrepancy in the rift margins of the South China Sea. The seismic chronostratigraphic result shows the possibility of the intra-continental extension center stayed focused for quite a long time in Eocene. Additionally, our evidence suggested that continental margin of the southwest subbasin had experienced at least three rifting stages and the existence of the rigid blocks is an appropriate explanation to the asymmetric rifting of the South China Sea. 相似文献
56.
丹江口水库二期蓄水后,根据2013~2015年地震台网监测成果分析,库区地震主要以微震、极微震为主,震中位置每年均呈团状或带状聚集在5个密集区,没有随库水位变化发生明显迁移现象。丹库区地震强度和频度高于汉库区,丹库区以水库地震居多,汉库区以水库地震及其他类型非构造地震居多。 相似文献
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58.
Xia Wang Shuying Bai Xianguo Lu Qiufen Li Xuelin Zhang Li Yu 《Stochastic Environmental Research and Risk Assessment (SERRA)》2008,22(4):477-486
The Songhua Lake in the Northeast China is chosen as a study case in this paper. Monitoring of samples and analysis 18 indexes
related to the eutrophication in the Songhua Lake had been conducted in 2002–2004. Ecological risk assessment methods are
employed here. The study results showed that total phosphorus and total nitrogen were main risk factors to impact on the eutrophication
of the Songhua Lake, and influence of the phosphorus on the lake eutrophication was larger than that of nitrogen. Algal growth
potential test was also conducted to validate the results. High phosphorus and high nitrogen concentrations were mostly distributed
in Huifahekou and Jiaohe sites of the Songhua Lake. Threshold values of total phosphorus, total nitrogen and Chl-a concentrations
from dose-effective examination were 0.065 mg/L, 0.843 mg/L, and 11.90 μg/L, respectively. The probability of the eutrophication
appeared in the Songhua Lake was 0.69, of them, risk-free type area was 19.21% of total lake area, slight risk type area was
30.10%, middle risk type area was 16.50%, heavy risk type area was 25.8%, hyper risk type area was 8.39%. In order to control
the eutrophication in the Songhua Lake, maximum permission discharges of total phosphorus and total nitrogen to the lake would
be 2,123.78, 7,018.82 t/a, respectively. 相似文献
59.
Using an airgun array in a land reservoir as the seismic source for seismotectonic studies in northern China: experiments and preliminary results 总被引:15,自引:0,他引:15
This paper reports the field setup and preliminary results of experiments utilizing an airgun array in a reservoir in north China for a seismotectonic study. Commonly used in offshore petroleum resource exploration, the airgun source was found to be more useful than a traditional explosive source for large‐scale and long offset land seismic surveys. The airgun array, formed by four 1,500 in3 airguns (a total of 6,000 in3 in volume) was placed at a depth of 6–9 m into the reservoir to generate the pressure impulse. No direct evidence was found that the airgun source adversely affected the fish in the reservoir. The peak ground acceleration recorded on the top of the reservoir dam 100 m away was 17.8 gal in the horizontal direction; this is much less than the designed earthquake‐resistance threshold of 125 gal for this dam. The energy for one shot of this airgun array is about 6.68 MJ, equivalent to firing a 1.7 kg explosive. The seismic waves generated by the airgun source were recorded by receivers of the regional seismic networks and a temporary wide‐angle reflection and refraction profile formed by 100 short‐period seismometers with the maximum source‐receiver offset of 206 km. The seismic wave signature at these long‐offset stations is equivalent to that generated by a traditional blast source in a borehole with a 1,000–2,000 kg explosive. Preliminary results showed clear seismic phases from refractions from the multi‐layer crustal structures in the north China region. Forward modelling using numerical simulation confirms that the seismic arrivals are indeed from lower crustal interfaces. The airgun source is efficient, economical, environmentally friendly and suitable for being used in urbanized areas. It has many advantages over an explosive source for seismotectonic studies such as the high repeatability that is supreme for stacking to improve signal qualities. The disadvantage is that the source is limited to existing lakes or reservoirs, which may restrict experimental geometry. 相似文献
60.