全文获取类型
收费全文 | 455篇 |
免费 | 15篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 6篇 |
大气科学 | 39篇 |
地球物理 | 80篇 |
地质学 | 106篇 |
海洋学 | 146篇 |
天文学 | 75篇 |
综合类 | 5篇 |
自然地理 | 18篇 |
出版年
2021年 | 2篇 |
2020年 | 6篇 |
2019年 | 8篇 |
2018年 | 7篇 |
2017年 | 17篇 |
2016年 | 21篇 |
2015年 | 13篇 |
2014年 | 17篇 |
2013年 | 24篇 |
2012年 | 10篇 |
2011年 | 15篇 |
2010年 | 13篇 |
2009年 | 23篇 |
2008年 | 22篇 |
2007年 | 26篇 |
2006年 | 20篇 |
2005年 | 24篇 |
2004年 | 25篇 |
2003年 | 19篇 |
2002年 | 13篇 |
2001年 | 12篇 |
2000年 | 14篇 |
1999年 | 14篇 |
1998年 | 15篇 |
1997年 | 8篇 |
1996年 | 10篇 |
1995年 | 8篇 |
1994年 | 6篇 |
1993年 | 3篇 |
1992年 | 3篇 |
1991年 | 8篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1988年 | 3篇 |
1987年 | 4篇 |
1986年 | 6篇 |
1985年 | 3篇 |
1984年 | 3篇 |
1983年 | 10篇 |
1982年 | 3篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1976年 | 2篇 |
1972年 | 1篇 |
1970年 | 1篇 |
排序方式: 共有475条查询结果,搜索用时 15 毫秒
1.
Under strong surface wind forcing during winter, direct current observations in the northern Sea of Japan show the existence of strong near-inertial currents in the deep water that is characterized by the extremely homogeneous vertical structures of temperature and salinity. However, the mechanism generating internal waves in the deep water of the northern Sea of Japan has not been well understood. In this study, to clarify the dynamical link between the surface wind forcing and near-inertial currents in the deep water of the northern Sea of Japan, we drive a general circulation model taking into account realistic wind stress, ocean bottom and land topography. In the northern Sea of Japan, the numerical results show that vertically coherent horizontal currents with a speed of ~ 0.05 m s?1 are excited throughout the homogeneous deep water. A two-layer model successfully reproduces the pattern of the horizontal current velocities shown by the general circulation model, indicating that internal waves emanate westward from the northwestern coast of Japan through coastal adjustment to the strong wind forcing event and, while propagating into the ocean interior, they excite evanescent near-inertial response throughout the lower layer below the interface. 相似文献
2.
Warda Saad Djamal Eddine Aissa Koichiro Watanabe Sachihiro Taguchi 《Arabian Journal of Geosciences》2018,11(2):26
The Tirek gold deposit hosted in the Archean shield is one of the richest sources of mined gold for Algeria. The deposit is controlled by the East Ouzzal shear zone (EOSZ), a transcurrent N–S lithospheric fault. The EOSZ is a late Pan-African dextral-ductile shear zone separating two contrasting Precambrian domains: the Archean In Ouzzal block to the west (Orthogenesis with subordinate metasediments reworked and granulitized during the ca. 2 Ga Eburnean event) and a middle Proterozoic block to the east involved in the ca. 600 Ma Pan-African event. The auriferous quartz veins are mainly oriented in two directions, N–S veins hosted in mylonitic rocks and NE–SW veins hosted in gabbroic or gneissic bands. The NE–SW veins contain the richest ore. Gold ore is found in a system of veins and lenticular quartz veinlets arranged in anastomosing networks. The hydrothermal alteration associated with these veins is characteristically a carbonate-sericite-albite-pyrite assemblage. Gold is the main metal of economic importance; it is disseminated in the quartz as grains or fibers along microcracks and as microscopic grains in the host rocks. Microthermometric results and Raman laser data from fluid inclusions demonstrate that the ore-forming fluids contained H2O-CO2±CH4 and were low salinity. Homogenization temperatures are commonly 250–310 °C. In the Tirek deposit, the role of the shear zone that hosts the mineralization was to drain the hydrothermal fluid. Interactions between the fluid and the mafic host rocks and CO2 also contributed to the formation of the hydrothermal gold deposit at Tirek. 相似文献
3.
Study on the selection of unsaturated flow model for the different types of soil and soft rock 总被引:1,自引:1,他引:0
Sajeewani Rajika Amarasinghe Kunio Watanabe Koji Ishiyama 《Environmental Earth Sciences》2011,64(7):1795-1805
Precise estimation of unsaturated hydraulic properties of porous media is indispensable in various study areas, such as analyzing
the moisture flow, the drying process occurring from the surface, and the pollutant migration beneath the ground surface.
Although many empirical/theoretical models describing the unsaturated hydraulic properties have been proposed by several previous
researchers, the best model for the different types of soil/rock may not be identical. Thus, the model selection process and
the estimation technique of the parameters included in the models should be developed. In the present study, the inverse technique
based on the transient evaporation change was investigated to select the model and estimate the model parameters. The experimental
work was based on a relatively low permeable soft rock and a relatively high permeable sandy soil (Toyoura standard sand).
Experimental equipment was developed to precisely measure the evaporation rate for the high permeable sandy soil. The Genetic
Algorithm (GA) was adopted in the inverse technique as an optimization tool. In order to simplify the problem, only the drying
process from the saturated condition was considered. It was established that the information concerning the transient evaporation
change could be used for the model selection and parameter estimation. Further, the saturation distribution could be used
for the selection of the models. The present study provides important information for the development of the model selection
process. 相似文献
4.
Evaluation of image processing methods for geological interpretation in the different environments in Libya 总被引:1,自引:0,他引:1
Nureddin M. Saadi Koichiro Watanabe Hideki Mizunaga 《Arabian Journal of Geosciences》2011,4(3-4):635-643
This study evaluates the use of image processing techniques and methodologies of digital integration of multi-disciplinary geoscientific data to reduce the ambiguity in geological interpretations in different geological environments in Libya. To realize this objective, three areas were selected for this study; Eljufra, an arid environment; the mountainous environment Tarhunah; and the Jifara Plain, a coastal plain environment. Two types of remote sensing data were used in this study: Landsat Enhanced Thematic Mapper Plus (ETM+) and European Remote Sensing Satellite. The digital elevation model extracted from Shuttle Radar Topography Mission and digital topographic maps scale 1:50,000 were used for remote sensing interpretation. GIS and remote sensing-based methods were used to process and integrate all raster and vector layers data. This study offered dramatic benefits for geological interpretations and provided new insights into the efficiency of image processing methods in different geological environments. 相似文献
5.
Tetsuichi Fujiki Kazuhiko Matsumoto Shuichi Watanabe Takuji Hosaka Toshiro Saino 《Journal of Oceanography》2011,67(3):295-303
We deployed a profiling buoy system incorporating a fast repetition rate fluorometer in the western subarctic Pacific and
carried out time-series observations of phytoplankton productivity from 9 June to 15 July 2006. The chlorophyll a (Chl a) biomass integrated over the euphotic layer was as high as 45–50 mg Chl a m−2 in the middle of June and remained in the 30–40 mg Chl a m−2 range during the rest of observation period; day-to-day variation in Chl a biomass was relatively small. The daily net primary productivity integrated over the euphotic layer ranged from 144 to 919 mg C m−2 day−1 and varied greatly, depending more on insolation rather than Chl a biomass. In addition, we found that part of primary production was exported to a 150-m depth within 2 days, indicating that
the variations in primary productivity quickly influenced the organic carbon flux from the upper ocean. Our results suggest
that the short-term variability in primary productivity is one of the key factors controlling the carbon cycle in the surface
ocean in the western subarctic Pacific. 相似文献
6.
Satoshi?KitajimaEmail author Naoki?Iguchi Naoto?Honda Tatsuro?Watanabe Osamu?Katoh 《Journal of Oceanography》2015,71(3):287-296
We investigated the horizontal distribution of Nemopilema nomurai medusae using a midwater trawl in the southwestern Sea of Japan from September to October of each year from 2006 to 2012. Numerous medusae of this species found in 2006, 2007, and 2009 were mainly distributed far (>40 km) from the mainland of Japan in the western part of the survey area, but were distributed in the stations closest (<25 km) to the mainland in the eastern part, particularly in 2006 and 2009. These distribution patterns were associated with the path of the second branch of the Tsushima Warm Current (TWC) that flows offshore to the west of Oki Islands and usually approaches the mainland of Japan to the east of Oki Islands. Differences in jellyfish distribution across the survey periods were related to the distribution of the second branch being associated with types, position and intensity of eddies in the eastern part of the survey area. Hence, the formations of eddies and consequent variation in the path of the TWC would be responsible for transporting medusae from offshore to near the mainland to the east of Oki Islands. Individuals with large bells accumulated in the northwestern part of the survey area, where a cyclonic eddy was present downstream of the third branch of the TWC. This variation in bell size distribution may be ascribed to differences in the physical and/or biological factors among the three branches of the TWC. 相似文献
7.
Measurements of size-separated aerosol number concentrations at Midagahara (altitude, 1,930 m), on the western slope of Mt. Tateyama near the coast of the Japan Sea, were performed each autumn from 2006 to 2011. High number concentrations of particles larger than 2 μm were frequently seen in 2006 and 2009 when the influence of Asian dust might have been significant. The pH and the ratio of Ca2+ to total ions were high in the rainwater bulk sampled when high number concentrations of coarse particles were observed. The mean pH of rainwater during the autumn in 2006 was significantly higher than that in 2007 and 2008. Acidic species might have been neutralized by the Asian dust particles. Dust particles may highly affect the natural environment, such as forest ecosystems, at high elevations during seasons without snow cover. 相似文献
8.
Genki I. Matsumoto Yukinori Tani Koji Seto Tomoko Tazawa Masumi Yamamuro Takahiro Watanabe Toshio Nakamura Tetsuo Takemura Satoshi Imura Hiroshi Kanda 《Journal of Paleolimnology》2010,44(2):677-693
Antarctic climate changes influence environmental changes at both regional and local scales. Here we report Holocene paleolimnological
changes in lake sediment core Sk4C-02 (length 378.0 cm) from Lake Skallen Oike in the Soya Kaigan region of East Antarctica
inferred from analyses of sedimentary facies, a range of organic components, isotope ratios of organic carbon and nitrogen,
and carbon-14 dating by Tandetron accelerator mass spectrometry. The sediment core was composed of clayish mud (378.0–152.5 cm)
overlain by organic sediments (152.5 cm-surface). The age of the surface and the core bottom were 150 (AD1950-1640) and ca.
7,030 ± 73 calibrated years before present (cal BP), respectively, and the mean sedimentation rate was estimated to be 0.55 mm/year.
Multi-proxy analyses revealed that the principal environmental change in the core is a transition from marine to lacustrine
environments which occurred at a depth of 152.5 cm (ca. 3,590 cal BP). This was caused by relative sea level change brought
about by ongoing retreat of glaciers during the mid-Holocene warming of Antarctica, and ongoing isostatic uplift which outpaced
changes in global (eustatic) sea level. The mean isostatic uplift rate was calculated to be 2.8 mm/year. The coastal marine
period (378.0–152.5 cm, ca. 7,030–3,590 cal BP) was characterized by low biological production with the predominance of diatoms.
During the transition period from marine to freshwater conditions (152.5-approximately 135 cm, ca. 3,590–3,290 cal BP) the
lake was stratified with marine water overlain by freshwater, with a chemocline and an anoxic (sulfidic) layer in the bottom
of the photic zone. Green sulfur bacteria and Cryptophyta were the major photosynthetic organisms. The Cryptophyta appeared
to be tolerant of the moderate salinity and stratified water conditions. The lacustrine period (approximately 135 cm-surface,
ca. 3,290 cal BP-present) was characterized by high biological production by green algae (e.g. Comarium clepsydra and Oedegonium spp.) with some contributions from cyanobacteria and diatoms. Biological production during this period was 8.7 times higher
than during the coastal marine period. 相似文献
9.
Hideo Shiogama Masahiro Watanabe Masakazu Yoshimori Tokuta Yokohata Tomoo Ogura James D. Annan Julia C. Hargreaves Manabu Abe Youichi Kamae Ryouta O’ishi Rei Nobui Seita Emori Toru Nozawa Ayako Abe-Ouchi Masahide Kimoto 《Climate Dynamics》2012,39(12):3041-3056
In this study, we constructed a perturbed physics ensemble (PPE) for the MIROC5 coupled atmosphere–ocean general circulation model (CGCM) to investigate the parametric uncertainty of climate sensitivity (CS). Previous studies of PPEs have mainly used the atmosphere-slab ocean models. A few PPE studies using a CGCM applied flux corrections, because perturbations in parameters can lead to large radiation imbalances at the top of the atmosphere and climate drifts. We developed a method to prevent climate drifts in PPE experiments using the MIROC5 CGCM without flux corrections. We simultaneously swept 10 parameters in atmosphere and surface schemes. The range of CS (estimated from our 35 ensemble members) was not wide (2.2–3.2?°C). The shortwave cloud feedback related to changes in middle-level cloud albedo dominated the variations in the total feedback. We found three performance metrics for the present climate simulations of middle-level cloud albedo, precipitation, and ENSO amplitude that systematically relate to the variations in shortwave cloud feedback in this PPE. 相似文献
10.
Y. Muraki Y. Matsubara S. Masuda S. Sakakibara T. Sako K. Watanabe R. Bütikofer E.O. Flückiger A. Chilingarian G. Hovsepyan F. Kakimoto T. Terasawa Y. Tsunesada H. Tokuno A. Velarde P. Evenson J. Poirier T. Sakai 《Astroparticle Physics》2008,29(4):229-242
In association with the large solar flare of April 15, 2001, the Chacaltaya neutron monitor observed a 3.6σ enhancement of the counting rate between 13:51 and 14:15 UT. Since the enhancement was observed beginning 11 min before the GLE, solar neutrons must be involved in this enhancement. The integral energy spectrum of solar neutrons can be expressed by a simple power law in energy with the index γ=-3.0±1.0. On the other hand, an integral energy spectrum of solar protons has been obtained in the energy range between 650 MeV and 12 GeV. The spectrum can also be expressed by a power law with the power index γ=-2.75±0.15. The flux of solar protons observed at Chacaltaya (at 12 GeV) was already one order less than the flux of the galactic cosmic rays. It may be the first simultaneous observation of the energy spectra of both high-energy protons and neutrons. Comparing the Yohkoh soft X-ray telescope images with the observed particle time profiles, an interesting picture of the particle acceleration mechanism has been deduced. 相似文献