全文获取类型
收费全文 | 315篇 |
免费 | 15篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 9篇 |
大气科学 | 34篇 |
地球物理 | 96篇 |
地质学 | 75篇 |
海洋学 | 72篇 |
天文学 | 41篇 |
综合类 | 2篇 |
自然地理 | 6篇 |
出版年
2022年 | 1篇 |
2021年 | 4篇 |
2020年 | 8篇 |
2019年 | 11篇 |
2018年 | 11篇 |
2017年 | 10篇 |
2016年 | 5篇 |
2015年 | 6篇 |
2014年 | 15篇 |
2013年 | 17篇 |
2012年 | 7篇 |
2011年 | 9篇 |
2010年 | 15篇 |
2009年 | 15篇 |
2008年 | 10篇 |
2007年 | 10篇 |
2006年 | 16篇 |
2005年 | 15篇 |
2004年 | 18篇 |
2003年 | 15篇 |
2002年 | 10篇 |
2001年 | 14篇 |
2000年 | 9篇 |
1999年 | 10篇 |
1998年 | 7篇 |
1997年 | 3篇 |
1996年 | 2篇 |
1995年 | 7篇 |
1994年 | 4篇 |
1993年 | 1篇 |
1992年 | 3篇 |
1991年 | 1篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 4篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1975年 | 3篇 |
1974年 | 2篇 |
1973年 | 8篇 |
1972年 | 1篇 |
1971年 | 3篇 |
排序方式: 共有335条查询结果,搜索用时 31 毫秒
11.
Kyle D. Squires Hidekatsu Yamazaki 《Deep Sea Research Part I: Oceanographic Research Papers》1995,42(11-12)
The effect of small-scale turbulence on marine and aquatic particle transport has traditionally been to act as a means for creating homogeneous distributions. However, previous numerical simulations of heavy particle transport in turbulent flows have shown that particles are preferentially concentrated by turbulence and that effects of preferential concentration are most pronounced for particle parameters comparable to the Kolmogorov scales. Therefore, the focus of the present work is examination of the preferential concentration of marine particles. Application of Kolmogorov scaling indicates that effects of preferential concentration may be important for marine particles with diameters of order 1 mm in the upper mixed layer. Numerical simulations of unstratified isotropic turbulence are then used to support the notion that preferential concentration of particles possessing material characteristics representative of those encountered in marine environments can occur. In the simulations, particles of order 1 mm diameter are idealized as rigid spheres with a density ratio of 1.005. Simulation results demonstrate preferential concentration with peak particle number densities ranging from 10 to 60 times the global mean value. Implications of preferential concentration are also discussed, together with the limitations of the approach employed in the present study. 相似文献
12.
Masahiro Ueno 《Journal of Oceanography》1990,46(3):125-134
In each of six areas with various horizontal scale from 0.4 to 15.6 nautical miles, many surveys with vertical net hauls are made for sampling fish eggs and larvae. Though values ofC
A are widely spread in each area, the variances
2 and the meanm of catch numbers calculated from each survey follow approximately the relation from a Poisson mixture model (PMM).
相似文献
13.
Kentaro Terada Hitoshi Negoro Kiyoshi Hayashida Shunji Kitamoto Hiroshi Tsunemi Hiroshi Oya Takayuki Ono Akira Morioka Yuzuru Tawara Toshifumi Mukai Masahiro Hoshino Toshio Terasawa 《Earth, Moon, and Planets》1994,66(1):75-81
An ASCA observation of the Jovian impact of the comet Shoemaker-Levy 9 is reported. Four impacts of H, L, Q1 and R were observed and four impacts of B, C, G, and Q2 were observed within 60 minutes after their impacts. No significant flaring of X-ray emission was observed. Upper limit X-ray fluxes of 90 % confidence level, averaged 5 minutes just after the impacts, were 2.4 × 10–13 erg sec–1 cm–2, 3.5 × 10–13 erg sec–1 cm–2, 1.6 × 10–13 erg sec–1 cm–2 and 2.9 × 10–13 erg sec–1 cm–2 for the impacts of H, L, Q1 and R, respectively, in the 0.5(0.7 for H and Q1)–10 keV energy range. However, a hint of X-ray enhancement around Jupiter from July 17 to July 19 was detected with about 2 6 × 10–14 erg sec–1 cm–2 in the 0.5–10 keV energy range. 相似文献
14.
The effect of iron on montmorillonite stability. (I) Background and thermodynamic considerations 总被引:1,自引:0,他引:1
It is envisaged that high-level nuclear waste (HLW) will be disposed of in underground repositories. Many proposed repository designs include steel waste canisters and bentonite backfill. Natural analogues and experimental data indicate that the montmorillonite component of the backfill could react with steel corrosion products to produce non-swelling Fe-rich phyllosilicates such as chamosite, berthierine, or Fe-rich smectite. In K-bearing systems, the alteration of montmorillonite to illite/glauconite could also be envisaged. If montmorillonite were altered to non-swelling minerals, the swelling capacity and self-healing properties of the bentonite backfill could be reduced, thereby diminishing backfill performance. The main aim of this paper was to investigate Fe-rich phyllosilicate mineral stability at the canister-backfill interface using thermodynamic modelling. Estimates of thermodynamic properties were made for Fe-rich clay minerals in order to construct approximate phase-relations for end-member/simplified mineral compositions in logarithmic activity space. Logarithmic activity diagrams (for the system Al2O3-FeO-Fe2O3-MgO-Na2O-SiO2-H2O) suggest that if pore waters are supersaturated with respect to magnetite in HLW repositories, Fe(II)-rich saponite is the most likely montmorillonite alteration product (if fO2(g) values are significantly lower than magnetite-hematite equilibrium). Therefore, the alteration of montmorillonite may not be detrimental to nuclear waste repositories that include Fe, as long as the swelling behaviour of the Fe-rich smectite produced is maintained. If fO2(g) exceeds magnetite-hematite equilibrium, and solutions are saturated with respect to magnetite in HLW repositories, berthierine is likely to be more stable than smectite minerals. The alteration of montmorillonite to berthierine could be detrimental to the performance of HLW repositories. 相似文献
15.
Polar and neutral isopranyl glycerol ether lipids as biomarkers of archaea in near-surface sediments from the Nankai Trough 总被引:1,自引:0,他引:1
The molecular and carbon isotopic compositions of polar isopranyl glycerol ether lipids, which are direct indicators of viable archaea, and neutral isopranyl glycerol ether lipids, which are derived from polar lipids via hydrolysis, in near-surface sediments from a methane seep in the Nankai Trough (off central Japan) were investigated. Procedures for extracting, separating and derivatizing polar and neutral ether lipids for detection using gas chromatography were first examined with one sediment sample and a cultivated methanogen. For all sediment samples, archaeol and hydroxyarchaeol were detected in both the polar and neutral ether lipid fractions. Acyclic and cyclic biphytanes were also detected in both types of lipid fractions after treatment with HI/LiAlH4 for ether cleavage and alkylation. The δ13C values of archaeol, sn-2-hydroxyarchaeol, and sn-3-hydroxyarchaeol in the sample from 0.82 m below the seafloor were lower than −100‰ relative to PDB, indicating that diverse living methanotrophic archaea are present in the seep sediments. Biphytanes released from polar ether lipids in the same sample were less depleted in δ13C (−71‰ to −36‰). The wide range of δ13C values suggests that the biphytanes were derived not only from methanotrophic but also from non-methanotrophic archaea, and that the relative contributions of the methanotrophic and non-methanotrophic archaea differed, depending on the biphytane compound. The vertical profiles and δ13C values of the neutral ether lipids were similar to those of the intact polar ether lipids, suggesting that neutral ether lipids derived from fossil archaea in the samples had mainly been lost by the time of sampling. 相似文献
16.
Geological and geomorphological characteristics of landslides triggered by the 2004 Mid Niigta prefecture earthquake in Japan 总被引:8,自引:0,他引:8
The 2004 Mid Niigta prefecture earthquake (MJMA 6.8) triggered more than one thousand landslides in the Miocene to Quaternary sedimentary rocks in Japan. The most common landslides were shallow disrupted landslides on steep slopes, which has been common in many previous disastrous earthquakes in the world. The Mid Niigta prefecture earthquake also triggered more than one hundred deep landslides, providing valuable information on the conditions for their occurrence. A field investigation and the interpretation of aerial photographs taken before and after the earthquake suggest that reactivation of existing landslides and undercutting of slopes are the most important factors for deep landslides to be triggered by earthquakes. In addition, planar sliding surfaces seem to be essential for the generation of catastrophic landslides triggered by this earthquake. Planar bedding–parallel sliding surfaces were formed at the boundary between the overlying permeable sandstone and underlying siltstone or along the bedding planes of alternating beds of sandstone and siltstone. Sliding surfaces along the slope-parallel oxidation front were formed in the area of black mudstone. New landslides (rockslide-avalanches) occurred with the sliding surfaces in a several-cm thick tuff interbedded in siltstone. One rockslide-avalanche occurred on a slope where buckling deformation preceded the earthquake. Gentle valley bottom sediments were mobilized in many locations, probably because they were saturated and partial liquefaction had occurred due to the earthquake shaking. 相似文献
17.
Norikazu Matsuoka Cline E. Thomachot Chiaki T. Oguchi Tamao Hatta Masahiro Abe Hiroyuki Matsuzaki 《Geomorphology》2006,81(3-4):408-420
Rates and processes of rock weathering, soil formation, and mountain erosion during the Quaternary were evaluated in an inland Antarctic cold desert. The fieldwork involved investigations of weathering features and soil profiles for different stages after deglaciation. Laboratory analyses addressed chemistry of rock coatings and soils, as well as 10Be and 26Al exposure ages of the bedrock. Less resistant gneiss bedrock exposed over 1 Ma shows stone pavements underlain by in situ produced silty soils thinner than 40 cm and rich in sulfates, which reflect the active layer thickness, the absence of cryoturbation, and the predominance of salt weathering. During the same exposure period, more resistant granite bedrock has undergone long-lasting cavernous weathering that produces rootless mushroom-like boulders with a strongly Fe-oxidized coating. The red coating protects the upper surface from weathering while very slow microcracking progresses by the growth of sulfates. Geomorphological evidence and cosmogenic exposure ages combine to provide contrasting average erosion rates. No erosion during the Quaternary is suggested by a striated roche moutonnée exposed more than 2 Ma ago. Differential erosion between granite and gneiss suggests a significant lowering rate of desert pavements in excess of 10 m Ma− 1. The landscape has been (on the whole) stable, but the erosion rate varies spatially according to microclimate, geology, and surface composition. 相似文献
18.
In east Asia, acidic gases derived from fossil fuel combustion have increased in the past decades. On the other hand, the Asian dust, also called Kosa (yellow sand) is transported following windstorms from arid lands in the Asian continent. Many researchers have been interested in the reaction between acidic aerosols and Kosa aerosols as well as the long-range transport of these emissions. To investigate the characteristics of chemical components in precipitation on a long-term basis over Japan, precipitation was sequentially collected from April 1984 to March 1997 at Kanazawa located near the coast of the Sea of Japan. Precipitation samples were collected at 1 mm intervals for the first 5 mm rainfall and all volume of rainwater after 6 mm for all precipitation events with an automatic wet only precipitation collector. According to the analyses of precipitation including Kosa aerosols during Kosa periods, the reaction in the air between Kosa and acidic components during the long-range transport was discussed. 相似文献
19.
Abstract. Near-infrared (NIR) and visible light microthermometry was applied to the fluid inclusions in sphalerite from a possible southeast extension of the Toyoha polymetallic deposit. Sphalerite occurs as euhedral-subhedral crystals or collo-form aggregates with a variety of color, which contain a well-developed growth banding. Combined with morphological observations, fluid inclusions in dark-colored sphalerite were examined using a near-infrared light microscopic technique, whereas those in light-colored sphalerite and quartz were examined by a conventional visible light microscopy.
Salinities of fluid inclusions in dark-colored sphalerite have a wide variation (1.0–10.3 wt % NaCl equiv.) compared to that in light-colored sphalerite and quartz (0.0–3.4 wt % NaCl equiv.). These variations suggest that the conventional microthermometric data from light-colored sphalerite and quartz were inadequate to interpret the ore formation process. Dark-colored colloform sphalerite and a dark core of subhedral sphalerite formed from high-salinity fluids (6.5–10.3 wt % NaCl equiv.) under highly supersaturated conditions with respect to sphalerite. The NIR and visible light microthermometry of fluid inclusions in sphalerite combined with its morphological observations is an invaluable method to infer the formation conditions of sphalerite. The NIR and visible light microthermometry is useful to reveal how the nature of ore fluids changed with time. 相似文献 20.
Todor Ganev Fumio Yamazaki Tsuneo Katayama Teruyuki Ueshima 《Soil Dynamics and Earthquake Engineering》1997,16(7-8):459-470
This paper presents results from forced vibration tests, microtremor observations and earthquake response analysis of a nuclear reactor containment model constructed on stiff soil in Hualien, Taiwan. The dynamic behavior of the soil-structure system is simulated successfully with two numerical models: a sway-rocking model, whose soil parameters are evaluated on the basis of the continuum formulation method, and a finite element model, using the program SASSI with the flexible volume substructuring approach. The dependences of the soil parameters of both models on the amplitudes of the different dynamic excitations are investigated in detail. An original numerical simulation of microtremor is performed. Comparison with results of a previous study involving a rigid tower on a soft soil site in Chiba, Japan is offered. 相似文献
|