全文获取类型
收费全文 | 231篇 |
免费 | 14篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 7篇 |
大气科学 | 13篇 |
地球物理 | 60篇 |
地质学 | 93篇 |
海洋学 | 16篇 |
天文学 | 41篇 |
综合类 | 1篇 |
自然地理 | 16篇 |
出版年
2022年 | 3篇 |
2021年 | 8篇 |
2020年 | 11篇 |
2019年 | 8篇 |
2018年 | 13篇 |
2017年 | 11篇 |
2016年 | 13篇 |
2015年 | 10篇 |
2014年 | 11篇 |
2013年 | 21篇 |
2012年 | 12篇 |
2011年 | 14篇 |
2010年 | 15篇 |
2009年 | 14篇 |
2008年 | 14篇 |
2007年 | 7篇 |
2006年 | 14篇 |
2005年 | 7篇 |
2004年 | 8篇 |
2003年 | 8篇 |
2002年 | 6篇 |
2001年 | 2篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1993年 | 1篇 |
1992年 | 1篇 |
1991年 | 2篇 |
1989年 | 2篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 1篇 |
排序方式: 共有247条查询结果,搜索用时 140 毫秒
71.
TheInternationalSymposiumontheGSSPofthePermian TriassicBoundaryandthePaleozoic MesozoicEventswasheldinChangxingCounty ,ZhejiangProvince,ChinaonAugust 1 0 - 1 3,2 0 0 1 .Thesymposiumreceivedand printed 47abstracts.About 60geologistsfrom 1 3countriesattendedthescientifi… 相似文献
72.
Fiona Nunan Dražen Cepić Bwambale Mbilingi Konstantine Odongkara Ernest Yongo Monica Owili 《社会与自然资源》2018,31(3):306-319
Social ties influence access to knowledge and cooperation in natural resource management, with the sharing of certain characteristics thought to be positive for social cohesion and participatory forms of management. In this article, a holistic characterisation of fisherfolk personal networks is developed, disaggregating results by the main occupational groups within the fisheries studied, to provide a more nuanced understanding of the personal networks of types of fisherfolk. Links are then made between the characteristics of personal networks and evidence on how fisherfolk benefit from their networks, interpreted as contributing to social cohesion within the communities. The personal networks of fisherfolk (boat crew, boat owners and traders/processors) of Kenya, Tanzania and Uganda bordering Lake Victoria were investigated using personal network analysis, with fisherfolk asked who they discuss their fisheries activities with. The analysis found that networks based on the same occupation were more characteristic of fish traders/processors networks than those of boat crew and boat owners and that shared ethnicity, gender and location were characteristic of boat owner and boat crew networks, though shared ethnicity may reflect the composition of the communities rather than choice. Social and economic interactions within the networks were based on provision of credit, social support and advice, suggesting that these form the basis of social cohesion and should be taken into consideration in working with fishing communities in both development interventions and designing collaborative management approaches. 相似文献
73.
Monica Cerruti-Sola Piero Cipriani Marco Pettini 《Monthly notices of the Royal Astronomical Society》2001,328(1):339-352
The thermodynamic behaviour of self-gravitating N -body systems has been worked out by borrowing a standard method from molecular dynamics. The link between dynamics and thermodynamics is made in the microcanonical ensemble of statistical mechanics. Through the computation of basic thermodynamic observables and of the equation of state in the plane, the clustering phase transition appears to be of the second-order type. The dynamical–microcanonical averages are compared with their corresponding canonical ensemble averages, obtained through standard Monte Carlo computations. The latter seem to have completely lost any information about the phase transition. Finally, our results – obtained in a 'microscopic' framework – are compared with some existing theoretical predictions – obtained in a 'macroscopic' (thermodynamic) framework: qualitative and quantitative agreement is found, with an interesting exception. 相似文献
74.
Magma ascent and eruptive processes from textural and compositional features of Monte Nuovo pyroclastic products, Campi Flegrei, Italy 总被引:1,自引:0,他引:1
Geochemical and textural studies were carried out on alkaline products of the AD 1538 Monte Nuovo eruption. Due to the integration of the volcanological study with eyewitness reports, the dynamics and timing of each phase of the eruption and the volume of emitted magmas are known in detail. On this basis, unique in Campi Flegrei, the relations between magma chamber mechanisms, eruptive styles, magma ascent dynamics and volatile exsolution processes have been explored. Glass and phenocryst compositions indicate that the erupted magma has a homogeneous phono-trachytic composition. Textures and compositions of phenocrysts indicate that they crystallised at equilibrium with the melt in the magma chamber, likely as a mushy boundary layer along the chamber wall, where the temperature was below the liquidus temperature of the crystal free-chamber core. The estimated crystallisation temperature is 850±40°C. The magma phase relations in Petrogenys Residua System suggest that phenocryst crystallisation occurred at
between 100 and 200 MPa, corresponding to depths ranging from 3 to 8 km. The microlite composition and their close genetic relations with vesicles indicate that groundmass crystallisation occurred during the eruption as a consequence of magma degassing and vesiculation induced by decompression during its ascent toward the surface. Crystal size distributions reveal that microlites grew in two stages of undercooling that we define as: (1) magma migration onset upward from the chamber and (2) magma rising through the conduit to the surface, possibly lasting tens of days and few days, respectively. These results provide information on the physical conditions that characterise pre- and syn-eruptive processes, which may be useful in order to define eruptive scenarios and to evaluate short-term precursors. Furthermore, the collected data provide for the first time information on degassing-induced crystallisation during the eruption of a highly evolved alkaline magma.Editorial responsibility: M. Carroll 相似文献
75.
Lara F. Prez Tove Nielsen Tine L. Rasmussen Monica Winsborrow 《Boreas: An International Journal of Quaternary Research》2019,48(1):72-91
The east Greenland margin has been influenced by oceanographic and cryospheric processes since the late Miocene, when the southwards flow of the East Greenland Current (EGC) initiated and ice sheets first advanced across the margin. However, the relative importance of these processes, and their influence on the sedimentation of the margin through time remains poorly understood. High‐resolution single‐channel seismic, chirp sub‐bottom profiles and swath bathymetry data were acquired along the middle/lower slope and proximal basinal area off Liverpool Land, central‐east Greenland margin. In this study, seismic‐stratigraphical and morphological analyses allowed us to distinguish between the major sedimentary processes that influenced this margin during the Quaternary. The stratigraphical architecture reveals mass transport deposits (MTDs) related to glacially influenced down‐slope sedimentation. These are intercalated with buried contourite systems associated with bottom‐current controlled along‐slope sedimentation. The distribution of the MTDs suggests the influence of two distinct ice‐stream systems. Initial phases of down‐slope deposition during the early‐middle Quaternary appears to be related to distal deposition fed by an ice stream from the Scoresby Sund area in the south. Shallow sedimentary processes, together with morphological analysis of the sea floor, show that the most recent activity of down‐slope processes during the latest Quaternary has occurred in the north, linked to an ice stream from the Kong Oscar Fjord area. These observations document a temporal shift in the relative dominance of the Scoresby Sund and Kong Oscar Fjord ice‐stream systems. The glacial influence on the margin has been interrupted by periods of stronger activity of along‐slope bottom‐current flow, demonstrating that the EGC periodically controlled sedimentation on the continental margin. 相似文献
76.
Net autotrophy in a fluvial lake: the relative role of phytoplankton and floating-leaved macrophytes
Monica Pinardi Marco Bartoli Daniele Longhi Pierluigi Viaroli 《Aquatic Sciences - Research Across Boundaries》2011,73(3):389-403
This study combined water- and sediment flux measurements with mass balances of dissolved gas and inorganic matter to determine
the importance of pelagic and benthic processes for whole-system metabolism in a eutrophic fluvial lake. Mass balances of
dissolved O2, inorganic carbon (DIC), nitrogen (DIN), phosphorous (SRP), particulate N (PN) and P (PP) and Chl a were calculated at a nearly monthly frequency by means of repeated sampling at the lake inlet and outlet. Simultaneously,
benthic fluxes of gas and nutrients, including denitrification rates, and the biomass of the dominant pleustophyte (Trapa natans) were measured, and fluxes of O2 and CO2 across the water–atmosphere interface were estimated from diel changes in outlet concentrations. On an annual scale, Middle
Lake exhibited CO2 supersaturation, averaging 313% (range 86–562%), but was autotrophic with a net O2 production (6.35 ± 2.05 mol m−2 y−1), DIC consumption (−31.18 ± 18.77 mol m−2 y−1) and net export of Chl a downstream (8.38 ± 0.95 mol C m−2 y−1). Phytoplankton was the main driver of Middle Lake metabolism, with a net primary production estimated at 33.24 mol O2 m−2 y−1, corresponding to a sequestration of 4.18 and 0.26 mol m−2 y−1 of N and P, respectively. At peak biomass, T. natans covered about 18% of Middle Lake’s surface and fixed 2.46, 0.17 and 0.02 mol m−2 of C, N and P, respectively. Surficial sediments were a sink for O2 (−14.47 ± 0.65 mol O2 m−2 y−1) and a source of DIC and NH4
+ (18.84 ± 2.80 mol DIC m−2 y−1 and 0.83 ± 0.16 mol NH4
+ m−2 y−1), and dissipated nitrate via denitrification (1.44 ± 0.11 mol NO3
− m−2 y−1). Overall, nutrient uptake by primary producers and regeneration from sediments were a minor fraction of external loads.
This work suggests that the creation of fluvial lakes can produce net autotrophic systems, with elevated rates of phytoplanktonic
primary production, largely sustained by allochtonous nutrient inputs. These hypereutrophic aquatic bodies are net C sinks,
although they simultaneously release CO2 to the atmosphere. 相似文献
77.
Chiara Elmi Maria Franca Brigatti Luca Pasquali Monica Montecchi Angela Laurora Daniele Malferrari Stefano Nannarone 《Physics and Chemistry of Minerals》2011,38(6):459-468
A multi-methodical approach has been applied for characterizing the bulk and surface crystal chemical features of a high-temperature
vesuvianite crystal from skarns of Mount Somma-Vesuvius Volcano (Naples, Italy). Vesuvianite belongs to the space group P4/nnc with unit cell parameters a = 15.633(1) Å, c = 11.834(1) Å and chemical formula (Ca18.858 Na0.028 Ba0.004 K0.006 Sr0.005 □0.098)19.000 (Al8.813 Ti0.037 Mg2.954 Mn0.008 Fe0.1142+ Fe1.3753+ Cr0.008 B0.202)13.511 Si18.000(O0.261 F0.940 OH7.799)9.000. Structure refinement, which converges at R = 0.0328, demonstrates a strong positional disorder down the fourfold axes, indicating that the Y1 site is split into two
positions (Y1A and Y1B) alternatively occupied. However, because of X4 proximity to Y1B and Y1A, X4 cannot be occupied if
Y1B or Y1A are. Overall Y1 occupancy (Y1A + Y1B) reaches approximately 0.5, as common in vesuvianite and occupancy of Y1B
site is extremely limited. Moreover, T1 position, limitedly occupied, accommodates the excess of cations generally related
to Y position. A small quantity (0.202 apfu) of boron is sited at the T2 site that, like T1, is poorly occupied. The determination
of the amount of each element on the (100) vesuvianite surface, obtained through X-ray photoelectron spectroscopy high-resolution
spectra in the region of the Si2p, Al2p, Mg1s, and Ca2p core levels, evidences that a greater amount of aluminum and a smaller amount of calcium characterize the surface with respect
to the bulk. Although both of these features require further investigation, we may consider the Al increase can be related
to preferential orientation of Al-rich sites on the (100) plane. Furthermore, the surface structure of vesuvianite suggests
that Al, Ca, and Mg cations maintain coordination features at the surface similar to the bulk. Silica, however, while presenting
fourfold coordination, shows also a [1]-fold small coordinated component at binding energy 99.85 eV, due to broken Si–O bonds
at the surface. The presence of eight- and nine-coordinated Ca cations is suggested by a large XPS feature resulting from
the merging of Ca2p3/2 and Ca2p1/2 peaks at 348.45 and 352.05 eV, respectively. 相似文献
78.
79.
It is found that perturbations presumedly associated with swarms, the B patterns and the BG pattern precursors of strong earthquakes in New Zealand, California and Apennines, propagate in the crust of the Earth with a velocity of the order of cm1 . The hypothesis that a single travelling elastic perturbation causes a set of precursors of the same strong earthquake is discussed and it is concluded that each precursor is associated with a different perturbation. 相似文献
80.
Simone Recchi Francesca Matteucci Annibale D'Ercole Monica Tosi 《Astrophysics and Space Science》2003,284(2):623-626
We study the effect of different star formation regimes on the dynamical and chemical evolution of Blue Compact Dwarf galaxies.
To do that, we adopt a 2-D hydrocode coupled with detailed chemical yields originating from SNeII, SNeIa and from intermediate-mass
stars. We apply this kind of simulation to a model of galaxy resembling IZw18.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献