全文获取类型
收费全文 | 103篇 |
免费 | 4篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 1篇 |
大气科学 | 16篇 |
地球物理 | 26篇 |
地质学 | 23篇 |
海洋学 | 21篇 |
天文学 | 10篇 |
综合类 | 4篇 |
自然地理 | 7篇 |
出版年
2019年 | 4篇 |
2017年 | 4篇 |
2016年 | 2篇 |
2015年 | 1篇 |
2014年 | 6篇 |
2013年 | 11篇 |
2012年 | 4篇 |
2011年 | 9篇 |
2010年 | 4篇 |
2009年 | 6篇 |
2008年 | 7篇 |
2007年 | 7篇 |
2006年 | 2篇 |
2005年 | 4篇 |
2004年 | 2篇 |
2003年 | 1篇 |
2002年 | 2篇 |
2001年 | 2篇 |
2000年 | 6篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1995年 | 1篇 |
1993年 | 2篇 |
1992年 | 1篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1979年 | 1篇 |
1977年 | 1篇 |
1976年 | 1篇 |
排序方式: 共有108条查询结果,搜索用时 187 毫秒
81.
Andrey V. Pnyushkov Igor V. Polyakov Vladimir V. Ivanov Takashi Kikuchi 《Polar Science》2013,7(2):53-71
Recent mooring-based observations at several locations along the continental slope of the Arctic Ocean's Eurasian Basin showed a transformation of the Boundary Current (BC) from a mostly barotropic flow in Fram Strait to a jet-like baroclinic current northeast of Svalbard, and the reemergence of the barotropic structure of the flow in the eastern Eurasian Basin. This transformation is accompanied by a weakening of the flow from ~24 cm/s in Fram Strait to ~5 cm/s at the Lomonosov Ridge. The maximum of the baroclinic component of the BC at an intermediate depth (~200–370 m) is associated with the Atlantic Water core. The depth range of the baroclinic current maximum is controlled by cross-slope density gradients above and below the baroclinic velocity maximum as follows from the geostrophic balance of forces. According to the model simulations, the BC splits into shallow and deep branches in the proximity of Svalbard due to a divergence of isobaths, confirming topographically-controlled BC behavior. The shallow branch is located at a shelf break with a typical bottom depth of ~200 m and current speed of up to ~24 cm/s. The discussed results, which provide insight on some basic aspects of the dynamics of the BC (the major oceanic heat source for the Arctic Ocean), may be of importance for understanding of the ocean's role in shaping the arctic climate system state. 相似文献
82.
Coral species composition of drilled cores from emergent bank reefs, and coral cover of the surface of old and living reefs located along the coast of the state of Bahia, Eastern Brazil, revealed that there is a marked change in the occurrence of the major building coral species in different time intervals of the reef structure, as well as in the living surface of reefs located in two different geographical sites. Holocene core sections from two reef areas (12 degrees 40'S-38 degrees 00'W and 18 degrees 00'S-39 degrees 00'W) have as major reef builders, on its topmost core interval (3 to 4 ky old), the endemic coral Mussismilia braziliensis Verrill, 1868, which also dominate on the 2.5-3.5 ky old surfaces of truncated reef tops. At the base of the cores (the 2m lower interval, older than 4 ky BP), another endemic coral Mussismilia harttii Verrill, 1868 is the dominant reef component. The relative abundance of M. braziliensis on the living surfaces of shallow reefs from both areas, shows that in the southern area, it is up to 98% on reefs located 60 km off the coast, in depths between 3 and 4m, but do not exceed 1.3% on the surface of the northern reefs located 1-2 km off the coast in depths 4-5m. The Holocene falling sea level that occurred along the coast of Brazil since 5.1 ky BP, causes an increasing runoff into the area of coastal reefs. This phenomenon may have affected the nearshore reef building fauna, replacing a more susceptive coral fauna with one better adapted to low light levels and higher sediment influx. The high turbidity associated with early Holocene shelf flooding, should also be responsible for the absence of M. braziliensis during the initial stages of reef buildup in Brazil. At the present time, the rapidly increasing human pressure, due to changes in land uses of the coastal zone (increasing sedimentation rate, nutrification of coastal waters, industrial pollution) and underwater practices, such as overfishing and an intense tourism, is aggravating the recovery capacity of this already naturally threatened coral community. If this situation coupled with increasing sea surface temperature persists, modern coral reef growth, in Brazil cannot be maintained and the major reef building coral species of the reefs in Bahia, a remnant endemic coral fauna will very soon appear in the list of endangered species. 相似文献
83.
Nikolai Kiselev Vera Rosenbush Klaus Jockers Sergey Velichko Sen Kikuchi 《Earth, Moon, and Planets》2005,97(3-4):365-378
We present the electronic database (EAR-C-COMPIL-5-DB-COMET-POLARIMETRY-V1.0, NASA Planetary Data System) involving published and some unpublished results of cometary polarimetry. The database contains more than 2600 measurements of linear and circular polarization for 64 comets since 1940s. The narrow-band and wide-band measurements within the spectral region 0.3–2.2 micron are presented. The ranges of phase angles, helio- and geocentric distances of comets are 0.4–122°, 0.6–4.8 AU, 0.03–4.9 AU, respectively. We have comprised more than 60 references to the published papers and unpublished sources. The data we included are presented in a tabular format in the ASCII codes. The database can be used as the observational basis for detailed theoretical modeling, interpretation of the phase-angle and spectral dependence of polarization, classification of comets, laboratory simulating, and for selecting future space-mission targets. Analysis of the available data allowed us to summarize some observed characteristics of linearly and circularly polarized light and their phase-angle, heliocentric, spectral, and spatial dependencies. 相似文献
84.
K.?ShimodaEmail author M.?Okuno Y.?Syono M.?Kikuchi K.?Fukuoka M.?Koyano S.?Katayama 《Physics and Chemistry of Minerals》2004,31(8):532-542
Shock-recovery experiments for obsidian and its fused glass have been carried out with pressure up to 35 GPa. Structural evolution accompanying the shock compression was investigated using X-ray diffraction technique, Raman and infrared spectroscopy. The densities of obsidian and its fused glass increased with applied shock pressure up to 25 GPa. Densification reached a maximum of 4.7 and 3.6% for obsidian and its fused glass, respectively. The densification mechanism is attributed to reduction of the T–O–T angle, and changes in ring statistics in the structure. Density reduction observed at greater than 25 GPa of applied shock pressure is due to partial annealing of the high-density glass structures brought by high post-shock residual temperature. The density of fused glass is almost equal to its original value at 35 GPa while the shocked obsidian has a slightly lower value than its original value. Amorphization of crystallites present in the obsidian due to shock compression is probably the cause of the density decrease. The structural evolution observed in shock-compressed obsidian and its fused glass can be explained by densification resulting from average T–O–T angle reduction and increase of small rings, and subsequent structural relaxation by high post-shock temperature at applied shock compression above 25 GPa. 相似文献
85.
Y. Shimada M. Okuno Y. Syono M. Kikuchi K. Fukuoka N. Ishizawa 《Physics and Chemistry of Minerals》2002,29(4):233-239
The densification and structural changes in SiO2 glass compressed up to 43.4 GPa by shock experiments are investigated quantitatively by the X-ray diffraction technique.
Direct structural data (average Si–O and Si–Si distances and Si–O–Si angles, coordination number of the Si atom) of these
shock-densified SiO2 glasses have been obtained by analyzing the radial distribution function curves, RDF(r), calculated with X-ray diffraction data. The coordination number of all densified glasses is about 4 and shows almost no
pressure variation. The SiO2 glass has shown density increase of 11% at a shock compression of 26.3 GPa. This density evolution could not be explained
by the coordination change. The reduction of the average Si–O–Si angle (144° at 0 GPa to 136° at 26.3 GPa) obtained from RDF(r) data may account for this density increase. This Si–O–Si angle change may be caused by shrinkage of the network structure
and the increase of small rings of SiO4 tetrahedra. For higher shock pressure, a decrease in the Si–O–Si angle to 140° was observed. This is consistent with the
decrease in density at 32.0 and 43.2 GPa. This decrease in the Si–O–Si angle and density could be attributed to an annealing
effect due to high after-shock residual temperature. This pressure dependence of average Si–O–Si angles in shock-densified
SiO2 glass agrees with the results of our previous Raman spectroscopic study. On the other hand, the pressure variation for the
first sharp diffraction peak (FSDP) was analyzed to estimate the evolution of intermediate range structures. It is suggested
that the mean d value (d
m
) obtained from the position of FSDP strongly depends on the shock and residual temperature, as well as shock pressure.
Received: 29 June 2001 / Accepted: 14 November 2001 相似文献
86.
Summary Failure deformation of a borehole boundary in response to hydraulic loading via a plastic cylinder is directly related to both the initial stress state and the material properties of the ground. These relationships are utilized for determination ofin situ stress states and material properties of complex geological formations, including fractured hard rock and soft ductile media, by directly measuring diametral deformation of the borehole in relation to the applied pressure. This new method was first developed by means of finite element simulation models, and later confirmed by laboratory model studies. This method was then field tested in an outcropping of homogeneous sandstone and later applied to three underground geological formations: highly stratified shale, rock salt, and fractured green schist. Some of the results of these field applications are presented here to illustrate the validity and usefulness of this method, especially for complex ground where the conventional methods of overcoring and hydrofracturing may be ineffective. The instrumentation of this method involves a borehole probe which utilizes electrically powered hydraulic pumping and computerized data acquisition for rapid measurement and on-site analysis. The significance of the new method is its ability to obtain input data ofin situ stress states and material properties for finite element analysis of earth structures in complex ground. 相似文献
87.
Possibilities of backswing of fault displacement are investigated on the basis of a simple crack model. Although it has been suggested that the backswing would not occur in real earthquakes because of friction, there is evidence that some earthquakes might have caused return motion “locally” on the fault surface. This paper attempts to derive conditions for such local return motion. Spatial extension of the crack beyond the stress-filled region into the stress-deficient region gives a favorable site for the return motion, the site being just outside the stress-filled region. In our model the return motion occurs at this site when the frictional stress is less than about 30% of the regional stress in the stress-filled region. The overall return motion, on the other hand, would not occur unless the frictional stress is less than 10% of the regional stress. 相似文献
88.
Masayuki Kikuchi 《Physics of the Earth and Planetary Interiors》1981,27(2):100-105
Multiple scattering from cracks is considered in the two-dimensional plane-strain condition. It is assumed that identical cracks are distributed uniformly in space and that the effective waves propagate normal to the crack surfaces. Then, the apparent dispersion and attenuation are calculated as functions of frequency for three independent modes of wave propagation: SV, P and SH.The calculated results show that, in each case, the attenuation coefficient Q?1 takes a peak value when the wavelength is nearly twice the crack width, while phase velocity has a maximum deviation from the intrinsic value at a frequency lower than the peak frequency for Q?1. 相似文献
89.
Raman microprobe spectra were made on three post shock, diaplectic plagioclase feldspars. Optical and X-ray diffraction studies indicated that feldspars maintained a partially or totally crystalline state after having passed through the mixed phase zone of Hugoniot response to shock waves (15–38 GPa). The appearance of uniquely glass-type spectra occurs at different shock pressures for each specimen according to its atomic structural arrangement, below 38 GPa for mosaic structured labradorite, near 40 GPa for anorthite and above 50 GPa for the highly ordered low albite. The diaplectic anorthite and labradorite glasses give spectra which indicate the presence of two glass types. Shifts in the band envelope frequencies compared to spectra of fused glass and statically pressure densified glass suggest that these glasses have specific structural arrangements. These differences suggest that the shock and fusion glass-forming processes are not exactly identical. The results from material shocked in the mixed phase region of Hugoniot response show that the phase transitions are effected at different pressures depending upon the feldspar structural type. 相似文献
90.
Variability in the Relative Penetration of Ultraviolet Radiation to Photosynthetically Available Radiation in Temperate Coastal Waters, Japan 总被引:1,自引:0,他引:1
Victor S. Kuwahara Tatsuki Toda Koji Hamasaki Tomohiko Kikuchi Satoru Taguchi 《Journal of Oceanography》2000,56(4):399-408
UVR and PAR wavelengths are attenuated to different extents within the water column, causing variations in spectral composition with depth. The present investigation (a) describes the variability of UVR and PAR penetration at a station in the temperate coastal waters of Sagami Bay and determines (b) the characteristics of relative UVR penetration to the euphotic zone. Examination of the seasonal irradiance profile measurements indicated eight measurements displaying two distinct attenuation coefficients (K
d) for specific UVR wavelengths and PAR. The two attenuation coefficients observed from specific wavelengths in the water column may be caused not only by chlorophyll pigments, but also by dissolved organic material in the upper layer. The 1% depth of surface UVR at 305, 320, 340, and 380 nm averaged 10.8 ± 5.7, 14.9 ± 9.5, 19.8 ± 12.1, and 30.4 ± 17.6 m, respectively. The depth of euphotic layer displayed less variability averaging 62 ± 15 m throughout the entire study. Relative UVR penetration within the euphotic zone averaged 17.8 ± 8.1, 22.9 ± 10, 30.5 ± 13.8, and 46 ± 46.9% for 305, 320, 340, and 380 nm, respectively. A large variation of the relative transmission of UVR within the euphotic zone was found although the spectral composition was relatively stable in the air throughout the study. 相似文献