全文获取类型
收费全文 | 1845篇 |
免费 | 281篇 |
国内免费 | 266篇 |
专业分类
测绘学 | 94篇 |
地球物理 | 661篇 |
地质学 | 882篇 |
海洋学 | 77篇 |
天文学 | 5篇 |
综合类 | 295篇 |
自然地理 | 378篇 |
出版年
2024年 | 5篇 |
2023年 | 16篇 |
2022年 | 40篇 |
2021年 | 51篇 |
2020年 | 54篇 |
2019年 | 58篇 |
2018年 | 49篇 |
2017年 | 43篇 |
2016年 | 43篇 |
2015年 | 44篇 |
2014年 | 72篇 |
2013年 | 79篇 |
2012年 | 69篇 |
2011年 | 63篇 |
2010年 | 59篇 |
2009年 | 74篇 |
2008年 | 85篇 |
2007年 | 124篇 |
2006年 | 123篇 |
2005年 | 112篇 |
2004年 | 105篇 |
2003年 | 127篇 |
2002年 | 80篇 |
2001年 | 93篇 |
2000年 | 92篇 |
1999年 | 65篇 |
1998年 | 73篇 |
1997年 | 79篇 |
1996年 | 70篇 |
1995年 | 71篇 |
1994年 | 61篇 |
1993年 | 50篇 |
1992年 | 38篇 |
1991年 | 26篇 |
1990年 | 16篇 |
1989年 | 12篇 |
1988年 | 21篇 |
1987年 | 15篇 |
1986年 | 16篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1979年 | 4篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1954年 | 4篇 |
排序方式: 共有2392条查询结果,搜索用时 15 毫秒
151.
Conductivity models were compiled in two geological provinces with thinsediments. The first province is the margin of the Precambrian East EuropeanPlatform. The second one is the Phanerozoic Rhenish Massif as a part of CentralGermany Hercinicum. In both provinces, a conducting layer was revealed at thebase of the upper crust by the magnetotelluric soundings. Its depth is around10 km in the East European Platform and around 15 km in the Rhenish Massif.The conductance of the layer reaches a few tens of Siemens in the first provinceand is almost an order of magnitude greater in the second one.A good correlation between the conductor and a seismic wave-guide (low-velocityzone) exists at the base of the upper crust. Simultaneous decrease of both electricalresistivity and seismic velocity, suggests an increase of porosity and permeability inpresence of saline water. The depth of rheological weak layer in the PhanerozoicRhenish Massif corresponds to the commonly accepted depth of the thermallyinduced brittle/ductile transition. Contrary similar layer in the Precambrian EasternEuropean Platform is much shallower than the thermally induced transition. Somenew mechanism should be considered. 相似文献
152.
Takeshi Ohmura Takeo Moriya Chengshi Piao Takaya Iwasaki Toshikastu Yoshi Shin'ichi Sakai Tetsuya Takeda Kaoru Miyashita Humihito Yamazaki Kiyoshi Ito Akira Yamazaki Yoji Shimada Katsuya Tashiro Hiroki Miyamachi 《Island Arc》2001,10(3-4):215-227
Abstract The 1995 Kobe (Hyogo-ken Nanbu) earthquake (MJMA 7.2, Mw 6.9) occurred on Jan. 17, 1995, at a depth of 17 km, beneath the areas of southern part of Hyogo prefecture and Awaji Island. To investigate P-wave velocity distribution and seismological characteristics in the aftershock area of this great earthquake, a wide-angle and refraction seismic exploration was carried out by the Research Group for Explosion Seismology (RGES) . The profile including 6 shot points and 205 observations was 135 km in length, extending from Keihoku, Northern Kyoto prefecture, through Kobe, to Seidan on Awaji Island. The charge of each shot was 350–700 kg. The P-wave velocity structure model showed a complicated sedimentary layer which is shallower than 2.5 km, a 2.5 km-thick basement layer whose velocity is 5.5 km/s, overlying the crystalline upper crust, and the boundary between the upper and lower crust.
Almost all aftershock hypocenters were located in the upper crust. However, the structure model suggests that the hypocenters of the main shock and some aftershock clusters were situated deeper than the boundary between the upper and lower crust. We found that the P-velocity in the upper crust beneath the northern part of Awaji Island is 5.64 km/s which is 3% lower than that of the surrounding area. The low-velocity zone coincides with the region where the high stress moment release was observed. 相似文献
Almost all aftershock hypocenters were located in the upper crust. However, the structure model suggests that the hypocenters of the main shock and some aftershock clusters were situated deeper than the boundary between the upper and lower crust. We found that the P-velocity in the upper crust beneath the northern part of Awaji Island is 5.64 km/s which is 3% lower than that of the surrounding area. The low-velocity zone coincides with the region where the high stress moment release was observed. 相似文献
153.
Strain and tilt changes measured during a water injection experiment at the Nojima Fault zone, Japan 总被引:2,自引:0,他引:2
Kunio Fujimori Hiroshi Ishii Atsushi Mukai Shigeru Nakao Shigeo Matsumoto Yasuhiro Hirata 《Island Arc》2001,10(3-4):228-234
Abstract In order to make geophysical and geological investigations of the Nojima Fault on Awaji Island, Japan, three boreholes measuring 1800 m, 800 m and 500 m deep were drilled into the fault zone. The fault is one of the seismic source faults of the 1995 Hyogo-ken Nanbu earthquake of M 7.2. A new multicomponent borehole instrument was installed at the bottom of the 800 m borehole and continuous observations of crustal strain and tilt have been made using this instrument since May 1996. A high-pressure water injection experiment within the 1800 m borehole was done in February and March 1997 to study the geophysical response, behavior, permeability, and other aspects of the fault zone. The injection site was located approximately 140 m horizontally and 800 m vertically from the instrument. Associated with the water injection, contraction of approximately 0.7 × 10−7 str (almost parallel to the fault) and tilt of approximately 1 × 10-7 rad in the sense of upheaval toward the injection site were observed. In addition to these controlled experiments, the strainmeter and tiltmeter also recorded daily variations. We interpret strain and tilt changes to be related to groundwater discharge and increased ultra-micro seismicity induced by the injected water. 相似文献
154.
155.
General characteristics of the recent horizontal crustal movement in Chinese mainland 总被引:5,自引:0,他引:5
1 Introduction of GPS observation dataThe Crustal Movement Observation Network of China (CMONOC) is a major scientific project in China organized by China Seismological Bureau and paticipated by the Bureau of Surveying and Mapping of the General Staff, the Chinese Academy of Sciences and the National Bureau of Surveying and Mapping. Based on the observation data of 25 fiducial stations and 56 basic stations in CMONOC (Figure 1 and Table 1), collected from August 26 to September… 相似文献
156.
SOURCE RADIATION AND RESPONSES OF WAVE PROPAGATION 总被引:2,自引:0,他引:2
Recordings of seismic waves propagating from earthquake source to a station at the earth's surface are a system response function.The convolution operator in time domain can be simplified as a multiplication operator in frequency domain.We discuss in frequency domain the separation of source,path and site effects for global scaling of earthquake source radiation.Also discussed are source scaling model,faulting mechanism,and the H/V inversion problems with crustal and near surface structures.Gross features of apparent source spectra appear to be not much region-dependent although there may be difference between tectonic styles within a region of tectonic mixture for which we need further study as data accumulate.Vertical spectra may be a better approach to approximate source radiation,as it has less crustal amplification effects than horizontal spectra.The H/V ratio is evidently a comprehensive indicator of amplification effects from near surface to deep structure.This gives it potential as an inversion tool to deduce site crustal structure. 相似文献
157.
Based on the long period surface wave data recorded by the China Digital Seismograph Network (CDSN), theQ
R
of fundamental mode Rayleigh wave with periods from 10 s to 146 s is determined for the eastern Sino-Korean paraplatform
in this paper. TheQ
β
models of the crust and upper mantle are respectively obtained for the 4 paths, with the aid of stochastic inverse method.
It shows that in the eastern Sino-Korean paraplatform, the average crustalQ
β
is about 200, and that there exists a weak attenuation layer in the middle crust (about 10–20 km deep) which is possibly
related to earthquake-prone layer. A strong attenuation layer (lowQ) of 70 km thick extensively exists in the uppermost mantle, with the buried depth about 80 km. The averageQ
R
of fundamental mode Rayleigh wave is between the value of stable tectonic region and that of active tectonic region, and
much close to the latter.
Contribution No. 96A0001, Institute of Geophysics, SSB, China.
Funded by the Chinese Joint Seismological Science Foundation. 相似文献
158.
青藏块体北缘跨断层测量资料宏观分析 总被引:1,自引:1,他引:1
本文在系统整理青藏块体北缘跨断层测量资料的基础上,进行了形变类型的划分,探讨了不同类型形变所反映的断层运动性能。 相似文献
159.
160.