全文获取类型
收费全文 | 212篇 |
免费 | 10篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 6篇 |
大气科学 | 16篇 |
地球物理 | 49篇 |
地质学 | 56篇 |
海洋学 | 28篇 |
天文学 | 50篇 |
综合类 | 3篇 |
自然地理 | 16篇 |
出版年
2021年 | 3篇 |
2020年 | 2篇 |
2019年 | 3篇 |
2018年 | 5篇 |
2017年 | 11篇 |
2016年 | 6篇 |
2015年 | 5篇 |
2014年 | 5篇 |
2013年 | 7篇 |
2012年 | 6篇 |
2011年 | 10篇 |
2010年 | 14篇 |
2009年 | 17篇 |
2008年 | 16篇 |
2007年 | 12篇 |
2006年 | 11篇 |
2005年 | 7篇 |
2004年 | 7篇 |
2003年 | 7篇 |
2002年 | 10篇 |
2001年 | 7篇 |
2000年 | 6篇 |
1999年 | 8篇 |
1998年 | 5篇 |
1997年 | 3篇 |
1995年 | 2篇 |
1994年 | 7篇 |
1992年 | 2篇 |
1990年 | 1篇 |
1988年 | 1篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1979年 | 5篇 |
1977年 | 1篇 |
1971年 | 1篇 |
1955年 | 1篇 |
排序方式: 共有224条查询结果,搜索用时 125 毫秒
121.
André Andrian Padial Priscilla Carvalho Sidinei Magela Thomaz Solana Meneghel Boschilia Roberta Becker Rodrigues Josilaine Taeco Kobayashi 《Aquatic Sciences - Research Across Boundaries》2009,71(4):389-398
Aquatic macrophytes produce large amounts of organic matter and have an essential structuring role in floodplains. This process highlights the importance of this community to aquatic biodiversity maintenance. We investigated the role of a flood disturbance on the response of macrophyte assemblages in regional and local structuring in the Upper Paraná River floodplain. Plant species were recorded before (November 2006) and after (March 2007) an uncommon increase in water level caused by the El Niño South Oscillation, which is considered a disturbance. Samples were taken in lakes and backwaters located in the floodplain and connected to three distinct rivers (that differentiate three sub-systems). Species richness and the assemblage structure of macrophyte patches underwent significant changes after the flood disturbance, depending on the specific sub-system (rivers) to which the lakes were connected. In addition, flood disturbance had a strong impact on community organization at the local scale. However, regionalization with respect to sub-systems remained significant after the flood disturbance. Our results emphasize the importance of connection to the river on macrophyte community composition and richness, and suggest that flood events in the Upper Paraná River floodplain disrupt community organization only at fine (local) scales. 相似文献
122.
Purification of seawater contaminated with undegradable aromatic ring compounds using ozonolysis followed by titanium dioxide treatment 总被引:1,自引:0,他引:1
Treatment of aromatic ring compounds, 2,4-dichlorophenoxy acetic acid (2,4-D), 2,4,5-trichloro-phenoxy acetic acid (2,4,5-T), and bisphenol A, in the artificial seawater, i.e. Allen seawater, was carried out by ozonation and titanium dioxide (TiO2) photocatalyst treatment. Each compound was degraded and varnished within 30 min by only ozonolysis at pH 9.0 and at 20 degrees C, while the TOC value of each compound decreased gradually but reached almost constant value, i.e. about 70-80% of the initial value, at even 30 min of ozonation time. Ozonolysis (30 min of ozonation time) followed by TiO2 photocatalyst treatment (50h of reaction time) was a very effective method for decreasing the TOC values of aromatic ring compounds in the artificial seawater. In consequence, TOC values of 2,4-D, 2,4,5-T, and bisphenol A could be reduced to about 28, 21, and 34% of their initial values, respectively. 相似文献
123.
124.
Morphology and tectonics of the Yap Trench 总被引:5,自引:0,他引:5
Fujiwara Toshiya Tamura Chiori Nishizawa Azusa Fujioka Kantaro Kobayashi Kazuo Iwabuchi Yo 《Marine Geophysical Researches》2000,21(1-2):69-86
We conducted swath bathymetry and gravity surveys the whole-length of the Yap Trench, lying on the southeastern boundary of the Philippine Sea Plate. These surveys provided a detailed morphology and substantial insight into the tectonics of this area subsequent the Caroline Ridge colliding with this trench. Horst and graben structures and other indications of normal faulting were observed in the sea-ward trench seafloor, suggesting bending of the subducting oceanic plate. Major two slope breaks were commonly observed in the arc-ward trench slope. The origin of these slope breaks is thought to be thrust faults and lithological boundaries. No flat lying layered sediments were found in the trench axis. These morphological characteristics suggest that the trench is tectonically active and that subduction is presently occurring. Negative peaks of Bouguer anomalies were observed over the arc-ward trench slope. This indicates that the crust is thickest beneath the arc-ward trench slope because the crustal layers on the convergent two plates overlap. Bouguer gravity anomalies over the northern portion of the Yap Arc are positive. These gravity signals show that the Yap Arc is uplifted by dynamic force, even though dense crustal layers underlie the arc. This overlying high density arc possibly forces the trench to have great water depths of nearly 9000 m. We propose a tectonic evolution of the trench. Subduction along the Yap Trench has continued with very slow rates of convergence, although the cessation of volcanism at the Yap Arc was contemporaneous with collision of the Caroline Ridge. The Yap Trench migrated westward with respect to the Philippine Sea Plate after collision, then consumption of the volcanic arc crust occurred, caused by tectonic erosion, and the distance between the arc and the trench consequently narrowed. Lower crustal sections of the Philippine Sea Plate were exposed on the arc-ward trench slope by overthrusting. Intense shearing caused deformation of the accumulated rocks, resulting in their metamorphism in the Yap Arc. 相似文献
125.
Noriyuki Narukage Masahito Kubo Ryohko Ishikawa Shin-nosuke Ishikawa Yukio Katsukawa Toshihiko Kobiki Gabriel Giono Ryouhei Kano Takamasa Bando Saku Tsuneta Frédéric Auchère Ken Kobayashi Amy Winebarger Jim McCandless Jianrong Chen Joanne Choi 《Solar physics》2017,292(3):40
Precise polarization measurements in the vacuum ultraviolet (VUV) region are expected to be a new tool for inferring the magnetic fields in the upper atmosphere of the Sun. High-reflectivity coatings are key elements to achieving high-throughput optics for precise polarization measurements. We fabricated three types of high-reflectivity coatings for a solar spectropolarimeter in the hydrogen Lyman-\(\upalpha \) (Ly\(\upalpha \); 121.567 nm) region and evaluated their performance. The first high-reflectivity mirror coating offers a reflectivity of more than 80 % in Ly\(\upalpha \) optics. The second is a reflective narrow-band filter coating that has a peak reflectivity of 57 % in Ly\(\upalpha \), whereas its reflectivity in the visible light range is lower than 1/10 of the peak reflectivity (\(\sim 5~\%\) on average). This coating can be used to easily realize a visible light rejection system, which is indispensable for a solar telescope, while maintaining high throughput in the Ly\(\upalpha \) line. The third is a high-efficiency reflective polarizing coating that almost exclusively reflects an s-polarized beam at its Brewster angle of 68° with a reflectivity of 55 %. This coating achieves both high polarizing power and high throughput. These coatings contributed to the high-throughput solar VUV spectropolarimeter called the Chromospheric Lyman-Alpha SpectroPolarimeter (CLASP), which was launched on 3 September, 2015. 相似文献
126.
Tsutomu Ota Katsura Kobayashi Tomoo Katsura Eizo Nakamura 《Contributions to Mineralogy and Petrology》2008,155(1):19-32
Pressure–temperature conditions of tourmaline breakdown in a metapelite were determined by high-pressure experiments at 700–900°C
and 4–6 GPa. These experiments produced an eclogite–facies assemblage of garnet, clinopyroxene, phengite, coesite, kyanite
and rare rutile. The modal proportions of tourmaline clearly decreased between 4.5 and 5 GPa at 700°C, between 4 and 4.5 GPa
at 800°C, and between 800 and 850°C at 4 GPa, with tourmaline that survived the higher temperature conditions appearing corroded
and thus metastable. Decreases in the modal abundance of tourmaline are accompanied by decreasing modal abundance of coesite,
and increasing that of clinopyroxene, garnet and kyanite; the boron content of phengite increases significantly. These changes
suggest that, with increasing pressure and temperature, tourmaline reacts with coesite to produce clinopyroxene, garnet, kyanite,
and boron-bearing phengite and fluid. Our results suggest that: (1) tourmaline breakdown occurs at lower pressures and temperatures
in SiO2-saturated systems than in SiO2-undersaturated systems. (2) In even cold subduction zones, subducting sediments should release boron-rich fluids by tourmaline
breakdown before reaching depths of 150 km, and (3) even after tourmaline breakdown, a significant amount of boron partitioned
into phengite could be stored in deeply subducted sediments. 相似文献
127.
Tatsuya Oki Mikio Kobayashi Shuji Owada Daiki Matsuura 《International Journal of Mineral Processing》2007
An equal settling ratio is an important factor in estimating particle separation accuracy. However, this factor is often calculated using the settling velocity in stationary water, there are no examples of calculation of the equal settling ratio in an actual separator. This is difficult because particle movement in a separator is very complicated, and even simple periodic motions, such as the oscillation field used with many separators, are ignored in many cases. The authors have previously reported on the relation between the equal settling ratio and the oscillation frequency by analysis of particle movement in vertically oscillating water, using spherical particles of glass (average size 435 μm) and zirconia (202 μm) which have the same settling velocity in stationary water. In this study, the influence of particle diameter on the change in the settling velocity in oscillating water was experimentally investigated for three pairs of glass and zirconia particles having different sizes under 0.5 mm, which have the same settling velocity in stationary water. The settling velocities of different-sized particles decreased at different rates in oscillating water, indicating that the equal settling ratio is reduced by water oscillation. We conclude that water oscillation improves the accuracy of size separation for glass particles over 300 μm and zirconia particles over 150 μm when glass and zirconia particles are separated from each other with the difference of these settling velocities. 相似文献
128.
Li XuYoshitsugu Kobayashi Junchang LüYuong-Nam Lee Yongqing LiuKohei Tanaka Xingliao ZhangSonghai Jia Jiming Zhang 《Cretaceous Research》2011,32(2):213-222
A partial skeleton of the ornithomimid dinosaur, discovered from the Late Cretaceous Qiupa Formation of Luanchuan County, Tantou Basin, Henan Province, China, is described here and assigned to a new genus and species, Qiupalong henanensis, with unique features (a notch on the lateral surface of the lateral posterior process of the proximal end of tibia and a small pit at the contact between astragalus and calcaneum). A phylogenetic analysis in this study suggests that it is a derived ornithomimid and form a monophyly with North American ornithomimids (Struthiomimus altus and Ornithomimus edmontonicus), sharing two characters (straight pubic shaft and large acute angle between pubic shaft and boot). Some characters (small anterior process of the pubic boot and curved pedal unguals) are seen in basal ornithomimosaurs as well, but these features in Q. henanensis are reversal. Qiupalong is the first definitive ornithomimid from outside of the Gobi Desert and is the southern-most occurrence of Late Cretaceous ornithomimid from eastern Asia, demonstrating southern extension of ornithomimid distribution in Asia. 相似文献
129.
Hiroshi Takimoto Ayumu Sato Janet F. Barlow Ryo Moriwaki Atsushi Inagaki Shiho Onomura Manabu Kanda 《Boundary-Layer Meteorology》2011,140(2):295-314
We investigate the spatial characteristics of urban-like canopy flow by applying particle image velocimetry (PIV) to atmospheric
turbulence. The study site was a Comprehensive Outdoor Scale MOdel (COSMO) experiment for urban climate in Japan. The PIV
system captured the two-dimensional flow field within the canopy layer continuously for an hour with a sampling frequency
of 30 Hz, thereby providing reliable outdoor turbulence statistics. PIV measurements in a wind-tunnel facility using similar
roughness geometry, but with a lower sampling frequency of 4 Hz, were also done for comparison. The turbulent momentum flux
from COSMO, and the wind tunnel showed similar values and distributions when scaled using friction velocity. Some different
characteristics between outdoor and indoor flow fields were mainly caused by the larger fluctuations in wind direction for
the atmospheric turbulence. The focus of the analysis is on a variety of instantaneous turbulent flow structures. One remarkable
flow structure is termed ‘flushing’, that is, a large-scale upward motion prevailing across the whole vertical cross-section
of a building gap. This is observed intermittently, whereby tracer particles are flushed vertically out from the canopy layer.
Flushing phenomena are also observed in the wind tunnel where there is neither thermal stratification nor outer-layer turbulence.
It is suggested that flushing phenomena are correlated with the passing of large-scale low-momentum regions above the canopy. 相似文献
130.
The mechanical behavior of expansive soils varies according to the chemical composition of the pore fluid. It is well known that electrochemical phenomena on the surface of clay mineral crystals considerably affect their macrostructural behavior. In particular, a change in the pore fluid composition causes osmotic consolidation or swelling. In this study, a model is constructed to describe the characteristic behavior of expansive soils by coupling the interlaminar behavior of clay mineral crystals and the soil skeleton behavior. The interlaminar behavior is derived from the electro-chemo-mechanical coupling equilibrium of mineral crystals, and the soil skeleton behavior is given by a general elastoplastic constitutive model for soils. This modeling approach extends a general model to consider the electro-chemo-mechanical phenomena of mineral crystals. Oedometer tests with the replacement of the cell fluid and the swelling pressure and deformation tests on expansive clays are simulated with the proposed model. The simulation results indicate that the proposed method can reasonably represent the typical behavior of expansive soils. 相似文献