全文获取类型
收费全文 | 642篇 |
免费 | 27篇 |
国内免费 | 10篇 |
专业分类
测绘学 | 3篇 |
大气科学 | 17篇 |
地球物理 | 149篇 |
地质学 | 171篇 |
海洋学 | 142篇 |
天文学 | 145篇 |
综合类 | 9篇 |
自然地理 | 43篇 |
出版年
2022年 | 2篇 |
2021年 | 6篇 |
2020年 | 4篇 |
2019年 | 15篇 |
2018年 | 7篇 |
2017年 | 24篇 |
2016年 | 13篇 |
2015年 | 11篇 |
2014年 | 30篇 |
2013年 | 23篇 |
2012年 | 13篇 |
2011年 | 27篇 |
2010年 | 22篇 |
2009年 | 33篇 |
2008年 | 28篇 |
2007年 | 37篇 |
2006年 | 31篇 |
2005年 | 28篇 |
2004年 | 40篇 |
2003年 | 21篇 |
2002年 | 18篇 |
2001年 | 28篇 |
2000年 | 20篇 |
1999年 | 14篇 |
1998年 | 15篇 |
1997年 | 15篇 |
1996年 | 13篇 |
1995年 | 6篇 |
1994年 | 4篇 |
1993年 | 12篇 |
1992年 | 5篇 |
1991年 | 7篇 |
1990年 | 5篇 |
1989年 | 11篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 7篇 |
1983年 | 5篇 |
1982年 | 4篇 |
1981年 | 8篇 |
1980年 | 6篇 |
1979年 | 7篇 |
1977年 | 6篇 |
1976年 | 4篇 |
1975年 | 3篇 |
1974年 | 3篇 |
1972年 | 2篇 |
1971年 | 3篇 |
排序方式: 共有679条查询结果,搜索用时 31 毫秒
441.
Qi Li Zhishen Wu Xing-lin Lei Yutaka Murakami Takashi Satoh 《Environmental Geology》2007,51(7):1157-1164
Geological sequestration of CO2 into depleted hydrocarbon reserviors or saline aquifers presents the enormous potential to reduce greenhouse gas emission
from fossil fuels. However, it may give rise to a complicated coupling physical and chemical process. One of the processes
is the hydro-mechanical impact of CO2 injection. During the injection project, the increase of pore pressures of storing formations can induce the instability,
which finally results in a catastrophic failure of disposal sites. This paper focuses mainly on the role of CO2-saturated water in the fracturing behavior of rocks. To investigate how much the dissolved CO2 can influence the pore pressure change of rocks, acoustic emission (AE) experiments were performed on sandstone and granite
samples under triaxial conditions. The main innovation of this paper is to propose a time dependent porosity method to simulate
the abrupt failure process, which is observed in the laboratory and induced by the pore pressure change due to the volume
dilatancy of rocks, using a finite element scheme associated with two-phase characteristics. The results successfully explained
the phenomena obtained in the physical experiments. 相似文献
442.
Tadashi Maruyama Katsutoshi Iemura Takashi Azuma Toshikazu Yoshioka Masaru Sato Riichiro Miyawaki 《Tectonophysics》2007,429(1-2):45-60
The 2004 Mid-Niigata Prefecture earthquake sequence (mainshock magnitude, MJMA 6.8), which occurred in an active fold-and-thrust belt in northern central Japan, generated a small thrust surface rupture (< 20 cm of vertical displacement) along a previously unmapped northern extension of the active Muikamachi–Bonchi–Seien fault zone, on the eastern margin of the epicentral region. To better understand past seismic behavior of the rupture, we conducted a paleoseismic trenching study across the 10-cm-high west-side-up surface rupture at the foot of a pre-existing 1.8-m-high east-facing scarp, which probably resulted from past earthquake(s). A well-defined west-dipping thrust fault zone accompanied by drag folding and displacing the upper Pliocene to lower Pleistocene strata and the unconformably overlying upper Pleistocene (?) to Holocene strata was exposed. The principal fault zone is connected directly to the 2004 surface rupture. From the deformational characteristics of the strata and radiocarbon dating, we inferred that two large paleoseismic events occurred during the past 9000 years prior to the 2004 event. These two pre-2004 events have a nearly identical fault slip (at minimum, 1.5 m), which is ≥ 15 times that of the 2004 event (∼ 10 cm). These paleoseismic data, coupled with the geological and geomorphological features, suggest that the 2004 event represented non-characteristic behavior of the fault, which can potentially generate a more destructive earthquake accompanied by meter-scale surface displacement. This study provides insight into the interpretation of past faulting events and increases our understanding of rupture behavior. 相似文献
443.
444.
Kazuhisa GOTO Ryuji TADA Eiichi TAJIKA Timothy J. BRALOWER Takashi HASEGAWA Takafumi MATSUI 《Meteoritics & planetary science》2004,39(7):1233-1247
Abstract The possibility of ocean water invasion into the Chicxulub crater following the impact at the Cretaceous/Tertiary boundary was investigated based on examination of an impactite between approximately 794.63 and 894.94 m in the Yaxcopoil‐1 (Yax‐1) core. The presence of cross lamination in the uppermost part of the impactite suggests the influence of an ocean current at least during the sedimentation of this interval. Abundant occurrence of nannofossils of late Campanian to early Maastrichtian age in the matrices of samples from the upper part of the impactite suggests that the carbonate sediments deposited on the inner rim margin and outside the crater were eroded and transported into the crater most likely by ocean water that invaded the crater after its formation. The maximum grain size of limestone lithics and vesicular melt fragments, and grain and bulk chemical compositions show a cyclic variation in the upper part of the impactite. The upward fining grain size and the absence of erosional contact at the base of each cycle suggest that the sediments were derived from resuspension of units elsewhere in the crater, most likely by high energy currents association with ocean water invasion. 相似文献
445.
Takeshi Ohta Tetsuya Hiyama Hiroki Tanaka Takashi Kuwada Trofim C. Maximov Tetsuo Ohata Yoshihiro Fukushima 《水文研究》2001,15(8):1459-1476
The water and energy exchanges in forests form one of the most important hydro‐meteorological systems. There have been far fewer investigations of the water and heat exchange in high latitude forests than of those in warm, humid regions. There have been few observations of this system in Siberia for an entire growing season, including the snowmelt and leaf‐fall seasons. In this study, the characteristics of the energy and water budgets in an eastern Siberian larch forest were investigated from the snowmelt season to the leaf‐fall season. The latent heat flux was strongly affected by the transpiration activity of the larch trees and increased quickly as the larch stand began to foliate. The sensible heat dropped at that time, although the net all‐wave radiation increased. Consequently, the seasonal variation in the Bowen ratio was clearly ‘U’‐shaped, and the minimum value (1·0) occurred in June and July. The Bowen ratio was very high (10–25) in early spring, just before leaf opening. The canopy resistance for a big leaf model far exceeded the aerodynamic resistance and fluctuated over a much wider range. The canopy resistance was strongly restricted by the saturation deficit, and its minimum value was 100 s m?1 (10 mm s?1 in conductance). This minimum canopy resistance is higher than values obtained for forests in warm, humid regions, but is similar to those measured in other boreal conifer forests. It has been suggested that the senescence of leaves also affects the canopy resistance, which was higher in the leaf‐fall season than in the foliated season. The mean evapotranspiration rate from 21 April 1998 to 7 September 1998 was 1·16 mm day?1, and the maximum rate, 2·9 mm day?1, occurred at the beginning of July. For the growing season from 1 June to 31 August, this rate was 1·5 mm day?1. The total evapotranspiration from the forest (151 mm) exceeded the amount of precipitation (106 mm) and was equal to 73% of the total water input (211 mm), including the snow water equivalent. The understory evapotranspiration reached 35% of the total evapotranspiration, and the interception evaporation was 15% of the gross precipitation. The understory evapotranspiration was high and the interception evaporation was low because the canopy was sparse and the leaf area index was low. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
446.
Drainage density, slope angle, and relative basin position in Japanese bare lands from high-resolution DEMs 总被引:2,自引:0,他引:2
Relationships between drainage density and slope angle for three bare lands in Japan were analyzed with special attention to channels at early erosion stages and channels in a badland-type terrain. Two of the bare lands were caused by volcanic eruptions 1 or 30–40 years ago, and the other one is a landslide scar formed more than 100 years ago. Raster digital elevation models (DEMs) with a 1-m resolution and ortho aerial photos were generated using digital photogrammetry to enable detailed stream-net extraction and topographic analyses. Data for drainage density, slope angle, and relative height for 88 subwatersheds were obtained from the DEMs and derived stream-nets. The relationship between drainage density and slope angle for each subwatershed can be divided into two types: downward sloping and convex upward. Although previous studies suggested that drainage density positively correlates with slope angle if overland flow is dominant, this correlation seldom occurs in the study areas. The two types of drainage density–slope angle relationships correspond to differing channelization stages that reflect the extension and integration of existing channels, as well as the formation of new low-order streams in response to base-level lowering. The location of subwatersheds within each study area seems to play a major role in determining the stages of channel development and, in turn, the types of drainage density–slope angle relationships. 相似文献
447.
Keiichi Tadokoro Kin'Ya Nishigami Masataka Ando Naoshi Hirata Takashi Iidaka Yukihiro Hashida Kunihiko Shimazaki Shiro Ohmi Yasuyuki Kano Makoto Koizumi Shigemitsu Matsuo Hiroo Wada 《Island Arc》2001,10(3-4):235-243
Abstract A water injection experiment was carried out by the scientific drilling program named the 'Nojima Fault Zone Probe' during the two periods 9–13 February and 16–25 March 1997. The pumping pressure at the surface was approximately 4 MPa. The total amount of injected water was 258 m3 . The injection was made between depths of 1480 m and 1670 m in the Disaster Prevention Research Institute, Kyoto University (DPRI) 1800 m borehole drilled into the Nojima Fault zone. A seismic observation network was deployed to monitor seismic activity related to the water injections. Seismicity suddenly increased in the region not far from the injection hole 4 or 5 days after the beginning of each water injection. These earthquakes were likely to be induced by the water injections. Most of the earthquakes had magnitudes ranging from −2 to +1. Numerous earthquakes occurred during the first injection, but only one could be reliably located and it was approximately 2 km north of the injection site. Between the two injection periods, earthquakes concentrated in the region approximately 1 km northwest of the injection site. During and after the second injection experiment, earthquakes were located approximately 1.5 km west of the injection site. Those earthquakes were located approximately 3 km or 4 km from the injection point and between 2 km and 4 km in depth. Values of intrinsic permeability of 10−14 –10−15 m2 were estimated from the time lapse of the induced seismic activity. The coefficient of friction in the area where the induced earthquakes occurred was estimated to be less than 0.3. 相似文献
448.
449.
Tokujiro Takayama Masatoshi Nishi Hiroaki Yamamoto Yoshinori Sanada Shigemi Matsuda Takashi Uchida 《Resource Geology》2004,54(1):89-98
Abstract. The MITI Nankai Trough wells were drilled for exploration of methane-hydrate-bearing sediments in association with seismic inferred bottom simulating reflectors (BSRs). In this project, log data showed low velocity compressional-wave (P-wave) layers below methane-hydrate-bearing formations. Dipole shear sonic acoustic tools (DSI) could not acquire accurate compres-sional velocity in this zone, thus it was not possible to accurately correlate between logging, VSP and surface seismic profiles.
Small amount of gas was presumed to cause the problem in obtaining the low velocity P-wave data. VSP interval velocity data was used to assess the DSI inferred low-velocity layer, which showed lower values than the velocity of the drilling muds. Synthetic seismogram was created by VSP-compensated velocity to compare against corridor stack of VSP. As a result, the depths above and below the methane-hydrate-bearing interval were correlated with synthetic seismograms and reflectivity events on the VSP profiles. By using this correlation technique, distribution of methane-hydrate-bearing formations and free-gas-bearing formations can be determined. 相似文献
Small amount of gas was presumed to cause the problem in obtaining the low velocity P-wave data. VSP interval velocity data was used to assess the DSI inferred low-velocity layer, which showed lower values than the velocity of the drilling muds. Synthetic seismogram was created by VSP-compensated velocity to compare against corridor stack of VSP. As a result, the depths above and below the methane-hydrate-bearing interval were correlated with synthetic seismograms and reflectivity events on the VSP profiles. By using this correlation technique, distribution of methane-hydrate-bearing formations and free-gas-bearing formations can be determined. 相似文献
450.
The Horoman Peridotite Complex is an Alpine-type orogenic peridotite massif in the Hidaka metamorphic belt, Hokkaido, Northern Japan. Because of wide exposure and extremely limited serpentinization, the complex provides important information on uplift and emplacement processes of an Alpine-type peridotite massif into the crust. Based on microstructures, the massif can be divided into five structural units parallel to the lithological layering as follows; (1) Equigranular Zone, (2) Internal Shear Zone (ISZ), (3) Transition Zone, (4) Porphyroclastic Zone and (5) Basal Shear Zone (BSZ). A top-to-the-north sense of shear deformation in the Porphyroclastic Zone and the Basal Shear Zone implies that the Horoman Peridotite Complex had uplifted from the upper mantle to the lower crust along a northward dipping extensional shear-zone systems. After incorporation of the mantle peridotite with lower crustal rocks, the upper part of the massif (i.e. the Equigranular Zone and the Internal Shear Zone) was overprinted by a top-to-the-south sense of shear deformation that was comparable with the sub-horizontal displacement of the crustal granulite sequences in the Hidaka metamorphic belt under transpressive tectonic environment. 相似文献