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101.
The plankton food web structure and trophodynamics in the neritic area of Sagami Bay were investigated from January 2003 to
December 2005, based on abundance, biomass, production rate and nutritional requirements of pico- (0.2–2 μm), nano- (2–20
μm), micro- (20–200 μm) and mesoplankton (>200 μm: mainly copepods CI-CVI) at 0–10 m depth. The average carbon biomass of
the total plankton community was higher in spring and summer (1.452 and 1.466 g C m−2, respectively) than in winter and autumn (0.676 and 0.686 g C m−2, respectively). The average values of primary production and of production rate and food requirement of heterotrophic organisms
were higher in summer than in other seasons. During the study period the biomass, production rate and food requirement of
small heterotrophs (i.e. bacteria: BA; heterotrophic nanoflagellates: HNF; microzooplankton: MZ) were much higher than those
of copepod secondary (CSP) and tertiary producers (CTP), indicating that the microbial food web was the main route of carbon
flow from phytoplankton (PP) to CSP and CTP, rather than the grazing food chain. In particular, during summer and autumn the
biomass of pico- and nano-size PP plus BA was greater than that of micro-size PP, suggesting the high prevalence of the microbial
food web (pico-/nanophytoplankton/BA-HNF/MZ-copepods). During winter and spring, the biomass of micro-size PP was greater
than that of pico- and nano-size PP plus BA, suggesting that the indirect route (microphytoplankton-MZ-copepods) probably
prevailed, while the microbial food web might be important. 相似文献
102.
Koichi Mimura Michioki Okamoto Kenichiro Sugitani Shigemasa Hashimoto 《Meteoritics & planetary science》2007,42(3):347-355
Abstract— We performed shock‐recovery experiments on insoluble organic matter (IOM) purified from the Murchison meteorite, and determined the abundances and isotope ratios of hydrogen and carbon in the shocked IOM sample. We also performed shock experiments on type III kerogen and compared the results of these experiments with the experimental results regarding IOM. The shock selectively released D and 13C from the IOM, while it preferably released H and 12C from the kerogen. The release of these elements from IOM cannot be explained in terms of the isotope effect, whereas their release from kerogen can be explained by this effect. The selective release of heavier isotopes from IOM would be due to its structure, in which D and 13C‐enriched parts are present as an inhomogeneity and are weakly attached to the main network. Shock gave rise to a high release of D even at a lower degree of dehydrogenation compared with the stepwise heating of IOM. This effective release of D is probably an inherent result of shock, in which a dynamic high‐pressure and high‐temperature condition prevails. Thus, shock would effectively control the hydrogen isotope behavior of extraterrestrial organic matter during the evolution of the solar nebula. 相似文献
103.
Evaluation of SEBS for estimation of actual evapotranspiration using ASTER satellite data for irrigation areas of Australia 总被引:2,自引:0,他引:2
Weiqiang Ma Mohsin Hafeez Hirohiko Ishikawa Yaoming Ma 《Theoretical and Applied Climatology》2013,112(3-4):609-616
Spatial knowledge of land surface evapotranspiration (ET) is of prime interest for environmental applications, such as optimizing irrigation water use, irrigation system performance, crop water deficit, drought mitigation strategies, and accurate initialization of climate prediction models especially in arid and semiarid catchments where water shortage is a critical problem. The recent drought in Australia and concerns about climate change have highlighted the need to manage water resources more sustainably especially in the Murrumbidgee catchment which utilizes bulk water for food production. This study deals with the application of a Surface Energy Balance System (SEBS) algorithm based on Advanced Spaceborne Thermal Emission and Reflection radiometer (ASTER) data and field observations has been proposed and tested for deriving ET over Coleambally Irrigation Area, located in the southwest of NSW, Australia. We have used 12 ASTER scenes covering the time period of 2002, 2003, 2004, 2005, 2006, and 2009 for estimating the actual ET over the study area. To validate the proposed methodology, the ground-measured ET was compared to the ASTER-derived actual ET values for the study area. The derived ET value over the study area is much closer to the field measurement. From the remote sensing results and observations, the root mean square error is 0.89 and the mean absolute percentage difference is 2.87 %, which demonstrate the reasonability of SEBS ET estimation for the study area. 相似文献
104.
The effect of background plasma on particle acceleration via Poynting fluxes is studied in 3D PIC simulation of electron-positron
and electron-ion plasmas. When a strongly magnetized ejecta at the center expands to low-temperature electron-positron ambient
plasma background and a low-density clump, electromagnetic wave front accelerates particles in the background and clump, and
captures them in the Ponderomotive potential well. We do not observe any instability, and the momentum distributions of background
and clump form a power law of slope close to −1.5 with a sharp peak in the middle. When an ejecta expands to the ion-electron
interstellar medium (ISM), the acceleration via Poynting flux is severely damped due to the charge separation. 相似文献
105.
1 IntroductionSnowdensificationiscriticalforcalculationsinengineering glaciology,snowavalancheforecasting ,springflooding,andotherpracticalaspects.Itisalsoimportantforinterpretingicecoredataincludingthosetakenfromratherwarmsiteswheresurfacelay ersexperiencemelting ,sinceitwouldaffectthechangeofannuallayerthicknesswithtime.Whileextensivestudies(e.g .AndersonandBenson 1 963 ;Bader1 960 ,1 962 ;Koji ma 1 95 4,1 95 5 ,1 95 6,1 95 7,1 95 8,1 95 9,1 964;Keeler 1 967;Gow 1 975 ;MaenoandE binuma 1… 相似文献
106.
Shiki Machida Kentaro Nakamura Tetsu Kogiso Ryo Shimomura Koichi Horinouchi Kyoko Okino Yasuhiro Kato 《Island Arc》2021,30(1):e12395
A broad area densely covered by ferromanganese nodules was recently discovered around Minamitorishima (Marcus) Island, representing a high-potential metal resource, particularly for Co, Ni, Mo, and W. We studied 16 nodule samples from nodule fields around Minamitorishima Island. To define the fine-scale chemostratigraphy of the nodules, polished cross-sections of the samples were analyzed by microfocus X-ray fluorescence. Our results show that a general pattern of compositional variation was common throughout the growth history of the nodules in all the regions we studied. Chemical mapping clarified changes in the chemical signature and proportion of five lithological components throughout the growth history: Mn represented columnar δ-MnO2; Fe represented layered amorphous FeOOH*xH2O; Ti represented TiO2*2H2O intergrown with an amorphous FeOOH phase; P, Ca and Y represented particles of biogenic calcium phosphate; and Si, Al, K, Cu, and Ni represented pelagic sediment infills. We proposed a method for a creating a multi-dimensional compositional map of the fine-scale chemostratigraphy observed in the ferromanganese oxide layers on the basis of merging the mapped Mn, Fe, Ti, P, Si and Cu intensities. Multi-dimensional compositional mapping of the sampled nodules from the western North Pacific revealed two fundamental findings: (1) previously recognized first-order Fe–Mn layers, L0, L1, and L2, were further divided into two, three, and four sublayers, respectively, and (2) a delayed supply of material to be nuclei of nodule or a growth hiatus of Fe–Mn layer(s), leading to missing sublayers in the layers L0 and L2, regulated the nodule size. In contrast, layer L1, which does not have any missing sublayers, was commonly observed in the samples for this study and has been reported in studies of other regions in the western Pacific. We propose, therefore, that the layer L1 is a key facies for examining chemostratigraphic correlations with other areas of seafloor. 相似文献
107.
Large-scale turbulent motions enhancing horizontal gas spread in an atmospheric boundary layer are simulated in a wind-tunnel
experiment. The large-scale turbulent motions can be generated using an active grid installed at the front of the test section
in the wind tunnel, when appropriate parameters for the angular deflection and the rotation speed are chosen. The power spectra
of vertical velocity fluctuations are unchanged with and without the active grid because they are strongly affected by the
surface. The power spectra of both streamwise and lateral velocity fluctuations with the active grid increase in the low frequency
region, and are closer to the empirical relations inferred from field observations. The large-scale turbulent motions do not
affect the Reynolds shear stress, but change the balance of the processes involved. The relative contributions of ejections
to sweeps are suppressed by large-scale turbulent motions, indicating that the motions behave as sweep events. The lateral
gas spread is enhanced by the lateral large-scale turbulent motions generated by the active grid. The large-scale motions,
however, do not affect the vertical velocity fluctuations near the surface, resulting in their having a minimal effect on
the vertical gas spread. The peak concentration normalized using the root-mean-squared value of concentration fluctuation
is remarkably constant over most regions of the plume irrespective of the operation of the active grid. 相似文献
108.
Tetsuya Tokiwa Kimikazu Tsusaka Makoto Matsubara Taiki Ishikawa Daisuke Ogawa 《地学前缘(英文版)》2013,4(1):105-111
This paper focuses on the formation mechanism of fractures induced by excavation of a gallery in soft sedimentary rocks in the Horonobe area of Japan.Detailed fracture mapping of the gallery indicates that the fractures consist of both pre-existing shear fractures and excavation damaged zone(EDZ) fractures. EDZ fractures correspond to weak planes associated with bedding planes or transgranular cracks.The EDZ fractures terminate against pre-existing shear fractures.Therefore,even for excavations in soft sedimentary rocks,formation of the EDZ fractures are controlled by pre-existing fractures and earlier weak planes. 相似文献
109.
Sarata K. Sahoo Masahiro Hosoda Ganesh Prasad Hiroyuki Takahashi Atsuyuki Sorimachi Tetsuo Ishikawa Shinji Tokonami Shigeo Uchida 《Acta Geophysica》2013,61(4):876-885
The activity concentrations of 226Ra and 228Ac in weathered Japanese soils from two selected prefectures have been measured using a γ-ray spectroscopy system with high purity germanium detector. The uranium, thorium, and rare earth elements (REEs) concentrations were determined from the same soil samples using inductively coupled plasma mass spectrometry (ICP-MS). For example, granitic rocks contain higher amounts of U, Th, and light REEs compared to other igneous rocks such as basalt and andesites. Therefore, it is necessary to understand the interaction between REEs and nature of soils since soils are complex heterogeneous mixture of organic and inorganic solids, water, and gases. In this paper, we will discuss about distribution pattern of 238U and 232Th along with REEs in soil samples of weathered acid rock (granite) collected from two prefectures of Japan: Hiroshima and Miyagi. 相似文献
110.
Y. Ezoe R. Fujimoto N.Y. Yamasaki K. Mitsuda T. Ohashi K. Ishikawa S. Oishi Y. Miyoshi N. Terada Y. Futaana F.S. Porter G.V. Brown 《Astronomische Nachrichten》2012,333(4):319-323
Recent results of charge exchange emission from solar system objects observed with the Japanese Suzaku satellite are reviewed. Suzaku is of great importance to investigate diffuse X‐ray emission like the charge exchange from planetary exospheres and comets. The Suzaku studies of Earth's exosphere, Martian exosphere, Jupiter's aurorae, and comets are overviewed (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献