全文获取类型
收费全文 | 134篇 |
免费 | 3篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 1篇 |
大气科学 | 7篇 |
地球物理 | 24篇 |
地质学 | 31篇 |
海洋学 | 49篇 |
天文学 | 22篇 |
自然地理 | 8篇 |
出版年
2020年 | 3篇 |
2019年 | 2篇 |
2017年 | 3篇 |
2016年 | 6篇 |
2015年 | 3篇 |
2014年 | 1篇 |
2013年 | 2篇 |
2012年 | 5篇 |
2011年 | 4篇 |
2010年 | 10篇 |
2009年 | 7篇 |
2008年 | 13篇 |
2007年 | 17篇 |
2006年 | 10篇 |
2005年 | 3篇 |
2004年 | 7篇 |
2003年 | 3篇 |
2002年 | 4篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 2篇 |
1998年 | 8篇 |
1997年 | 4篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 1篇 |
1989年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1981年 | 1篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有142条查询结果,搜索用时 375 毫秒
1.
Yuhei Yamamoto Yoshio Takahashi Yutaka Kanai Yoshio Watanabe Tomoya Uruga Hajime Tanida Yasuko Terada Hiroshi Shimizu 《Applied Geochemistry》2008,23(8):2452-2461
The uranium LIII-edge XANES spectra for natural rocks at the concentration range of 0.96–124 mg kg−1 were measured using a log spiral bent crystal Laue analyzer (BCLA) combined with a multi-element Ge detector. It was found that the quality of the XANES spectra using the BCLA was greatly improved due to a reduction of interfering fluorescence from major components such as Rb and Sr. The ratio of signal to background intensities in the U LIII-edge XANES spectra increased by a factor of 2.9–17 with the use of the BCLA, which greatly enhanced the detection limit for the speciation of the oxidation states of U or the U(IV)/U(VI) ratio of natural samples. In addition, it was demonstrated that the fluorescence XANES method coupled with the BCLA enable determination of the speciation of U for various natural samples such as acidic igneous rocks, ferromanganese nodules, sediments, and some sedimentary rocks such as shale and limestone. 相似文献
2.
Horizontal and vertical distributions of mercury were determined in seawater in Minamata Bay and Yatsushiro Sea. The concentrations of total and particulate mercury respectively ranged from 56–285 ng l–1 and 2.1–506 ng l–1. They were both highest in the inner most part of Minamata Bay where the sediment was most heavily polluted, and decreased with increasing distance from there. Vertically, an evident increase in concentration was observed near the bottom. A good agreement was found between the mercury content in suspended matter and that in fine sediment particles.These facts show that the particulate mercury is supplied mostly from the bottom sediment, and that it is spreading offshore with dispersing in seawater. This process would eventually result in the pollution of sediment in Yatsushiro Sea. 相似文献
3.
Mjelde Rolf Fjellanger Jan Petter Digranes Per Kodaira Shuichi Shimamura Hideki Shiobara Hajime 《Marine Geophysical Researches》1997,19(1):81-96
A 140 km long wide-angle seismic profile has been acquired by use of 6 Ocean Bottom Seismographs across the Jan Mayen Ridge, North Atlantic. The profile was acquired twice; once with a traditionally tuned standard source and secondly with a somewhat smaller source tuned on the first bubble pulse. Analysis of the frequency content of the data reveals that the single-bubble source within the 10-15 Hz frequency range generates a signal with a level about 5 db above that of the standard source. These differences can partly be related to differences in airgun depth. The higher output level for these frequencies enables the single-bubble source to resolve intra-crustal structures with a higher degree of certainty, when compared to the data acquired by use of the standard source array. The standard source seems to generate slightly more energy for frequencies around 6 Hz, probably due to the use of a large 1200 in/sup3 gun in this array. These low frequencies a re of importance for mapping of lower crustal and upper mantle structures, and it is recommended that this is taken into account when seismic sources for mapping of deep crustal and upper mantle structures are designed. 相似文献
4.
Bacterial degradation of the hydrocarbons of lubricating oils was investigated by mass spectrometric analysis which gives
both total amount and the composition of hydrocarbon types of residual oil. An unused lubricating oil, which mainly consisted
of hydrocarbon types with only a small percentage ofn-alkanes, was degraded by marineBacillus sp. andPseudomonas sp. with 55 % and 25 % decreases in 10 days, respectively. Susceptibility of respective hydrocarbon types to biodegradation
was in the following order: alkanes > non-condensed cycloalkanes, mono-aromatics > condensed cycloalkanes. A used lubricating
oil of different brand showed a larger decrease than the unused oil. Both species of bacteria degraded large portions of alkane
fraction of Arabian light crude oil. 相似文献
5.
We have developed an analytical treatment for the wave-induced response of a seabed with inhomogeneous permeability, by employing the boundary layer approximation. By assuming an exponential function for vertically distributed permeability, the inhomogeneous consolidation equation was formulated as Bessel's differential equation. Subsequently, we proposed some representative quantities for examining the effects of inhomogeneity of permeability. The main effects of inhomogeneity are that the boundary layer becomes thinner and the phase delay in the direction of depth becomes larger as the inhomogeneity becomes significant. In addition, it was shown that the boundary layer is properly evaluated by using the averaged permeability. 相似文献
6.
基于波作用量守恒方程建立了波流共存场中多向随机波浪传播变形数学模型,模型中考虑了波浪绕射的影响和水流引起的波浪弥散多普勒效应,应用包含水流和地形影响的激破波模式计算波浪破碎的能量耗散,采用一阶上迎风有限差分格式离散控制方程。分别计算了有无近岸流情况下单向和多向随机波浪的波高分布,考虑水流影响的数值计算结果与物理模型实验数据吻合良好,比较分析表明,所建立的数学模型能够复演由于离岸流引起的波高增大,可用于波流共存场多向随机波浪传播变形的模拟和预报。 相似文献
7.
A numerical study of tropospheric ozone in the springtime in East Asia 总被引:11,自引:0,他引:11
The Models-3 Community Multi-scale Air Quality modeling system (CMAQ)coupled with the Regional Atmospheric Modeling System (RAMS)is applied to East Asia to study the transport and photochemical transformation of tropospheric ozone in March 1998.The calculated mixing ratios of ozone and carbon monoxide are compared with ground 1evel observations at three remote sites in Japan and it is found that the model reproduces the observed features very well.Examination of several high episodes of ozone and carbon monoxide indicates that these elevated levels are found in association with continental outflow,demonstrating the critical role of the rapid transport of carbon monoxide and other ozone precursors from the continental boundary layer.In comparison with available ozonesonde data,it is found that the model-calculated ozone concentrations are generally in good agreement with the measurements,and the stratospheric contribution to surface ozone mixing ratios is quite limited. 相似文献
8.
Yoshihisa?MinoEmail author Chiho?Sukigara Makio?C.?Honda Hajime?Kawakami Kazuhiko?Matsumoto Masahide?Wakita Minoru?Kitamura Tetsuichi?Fujiki Kosei?Sasaoka Osamu?Abe Jan?Kaiser Toshiro?Saino 《Journal of Oceanography》2016,72(6):819-836
Intensive observations using hydrographical cruises and moored sediment trap deployments during 2010 and 2012 at station K2 in the North Pacific Western Subarctic Gyre (WSG) revealed seasonal changes in δ 15N of both suspended and settling particles. Suspended particles (SUS) were collected from depths between the surface and 200 m; settling particles by drifting sediment traps (DST; 100–200 m) and moored sediment traps (MST; 200 and 500 m). All particles showed higher δ 15N values in winter and lower in summer, contrary to the expected by isotopic fractionation during phytoplankton nitrate consumption. We suggest that these observed isotopic patterns are due to ammonium consumption via light-controlled nitrification, which could induce variations in δ 15N(SUS) of 0.4–3.1 ‰ in the euphotic zone (EZ). The δ 15N(SUS) signature was reflected by δ 15N(DST) despite modifications during biogenic transformation from suspended particles in the EZ. δ 15N enrichment (average: 3.6 ‰) and the increase in C:N ratio (by 1.6) in settling particles suggests year-round contributions of metabolites from herbivorous zooplankton as well as TEPs produced by diatoms. Accordingly, seasonal δ 15N(DST) variations of 2.4–7.0 ‰ showed a significant correlation with primary productivity (PP) at K2. By applying the observed δ 15N(DST) vs. PP regression to δ 15N(MST) of 1.9–8.0 ‰, we constructed the first annual time-series of PP changes in the WSG. This new approach to estimate productivity can be a powerful tool for further understanding of the biological pump in the WSG, even though its validity needs to be examined carefully. 相似文献
9.
Hedonic approaches based on spatial econometrics and spatial statistics: application to evaluation of project benefits 总被引:1,自引:0,他引:1
This study discusses the theoretical foundation of the application of spatial hedonic approaches—the hedonic approach employing
spatial econometrics or/and spatial statistics—to benefits evaluation. The study highlights the limitations of the spatial
econometrics approach since it uses a spatial weight matrix that is not employed by the spatial statistics approach. Further,
the study presents empirical analyses by applying the Spatial Autoregressive Error Model (SAEM), which is based on the spatial
econometrics approach, and the Spatial Process Model (SPM), which is based on the spatial statistics approach. SPMs are conducted
based on both isotropy and anisotropy and applied to different mesh sizes. The empirical analysis reveals that the estimated
benefits are quite different, especially between isotropic and anisotropic SPM and between isotropic SPM and SAEM; the estimated
benefits are similar for SAEM and anisotropic SPM. The study demonstrates that the mesh size does not affect the estimated
amount of benefits. Finally, the study provides a confidence interval for the estimated benefits and raises an issue with
regard to benefit evaluation. 相似文献
10.
Dissolved and particulate concentrations of silver in Tokyo Bay estuarine waters and Japanese rivers were determined in this
study. The dissolved silver concentrations in the surface water of Tokyo Bay range from 5.9 to 15.1 pmol kg−1, which is comparable to those in the surface water of the Japan Sea, but two or three times higher than those in the surface
water of the open ocean. However, elevated concentrations of dissolved silver are not found in Tokyo Bay compared with those
in other highly urbanized estuaries, such as San Francisco Bay (20∼243 pmol kg−1). In the Tokyo Bay estuary, silver typically exhibits non-conservative mixing behavior, which is a common feature in the
other estuaries reported previously. Dissolved silver concentrations decrease with salinity from the rivers to the mouth of
Tokyo Bay. Silver is efficiently scavenged by suspended particulates, as evidenced by the high conditional distribution coefficients
for silver throughout the estuary (log Kd > 5.0 ± 0.6). The silver fluxes into Tokyo Bay via inflowing rivers and atmospheric deposition were estimated as 83 kg y−1 and 15 kg y−1, respectively. A simple budget calculation shows that the silver supplied from rivers and atmosphere must be rapidly scavenged
within the Tokyo Bay estuary. 相似文献