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101.
102.
Christian Tamburini Madeleine Goutx Catherine Guigue Marc Garel Dominique Lefvre Bruno Charrire Richard Sempr Stphane Pepa Michael L. Peterson Stuart Wakeham Cindy Lee 《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(18):1533-1546
We used a new experimental device called PASS (PArticle Sinking Simulator) during MedFlux to simulate changes in in situ hydrostatic pressure that particles experience sinking from mesopelagic to bathypelagic depths. Particles, largely fecal pellets, were collected at 200 m using a settling velocity NetTrap (SV NetTrap) in Ligurian Sea in April 2006 and incubated in high-pressure bottles (HPBs) of the PASS system under both atmospheric and continuously increasing pressure conditions, simulating the pressure change experienced at a sinking rate of 200 m d−1. Chemical changes over time were evaluated by measuring particulate organic carbon (POC), carbohydrates, transparent exopolymer particles (TEP), amino acids, lipids, and chloropigments, as well as dissolved organic carbon (DOC) and dissolved carbohydrates. Microbial changes were evaluated microscopically, using diamidinophenylindole (DAPI) stain for total cell counts and catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH) for phylogenetic distinctions. Concentrations (normalized to POC) of particulate chloropigments, carbohydrates and TEP decreased under both sets of incubation conditions, although less under the increasing pressure regime than under atmospheric conditions. By contrast, dissolved carbohydrates (normalized to DOC) were higher after incubation and significantly higher under atmospheric conditions, suggesting they were produced at the expense of the particulate fraction. POC-normalized particulate wax/steryl esters increased only under pressure, suggesting biochemical responses of prokaryotes to the increasing pressure regime. The prokaryotic community initially consisted of 43% Bacteria, 12% Crenarchaea and 11% Euryarchaea. After incubation, Bacteria dominated (90%) the prokaryote community in all cases, with γ-Proteobacteria comprising the greatest fraction, followed by the Cytophaga–Flavobacter cluster and α-Proteobacteria group. Using the PASS system, we obtained chemical and microbial evidence that degradation by prokaryotes associated with fecal pellets sinking through mesopelagic waters is limited by the increasing pressure they experience. 相似文献
103.
104.
Asma Sakka Hlaili Boutheina Grami Nathalie Niquil Michel Gosselin Dominique Hamel Marc Troussellier Hassine Hadj Mabrouk 《Estuarine, Coastal and Shelf Science》2008
The structure and the trophic interactions of the planktonic food web were investigated during summer 2004 in a coastal lagoon of south-western Mediterranean Sea. Biomasses of planktonic components as well as bacterial and phytoplankton production and grazing by microzooplankton were quantified at four stations (MA, MB, MJ and R) inside the lagoon. Station MA was impacted by urban discharge, station MB was influenced by industrial activity, station MJ was located in a shellfish farming sector, while station R represented the lagoon central area. Biomasses and production rates of bacteria (7–33 mg C m−3; 17.5–35 mg C m−3 d−1) and phytoplankton (80–299 mg C m−3; 34–210 mg C m−3 d−1) showed high values at station MJ, where substantial concentrations of nutrients (NO3− and Si(OH)4) were found. Microphytoplankton, which dominated the total algal biomass and production (>82%), were characterized by the proliferation of several chain-forming diatoms. Microzooplankton was mainly composed of dinoflagellates (Torodinium, Protoperidinium and Dinophysis) and aloricate (Lohmaniellea and Strombidium) and tintinnid (Tintinnopsis, Tintinnus, Favella and Eutintinnus) ciliates. Higher biomass of these protozoa (359 mg C m−3) was observed at station MB, where large tintinnids were encountered. Mesozooplankton mainly represented by Calanoida (Acartia, Temora, Calanus, Eucalanus, Paracalanus and Centropages) and Cyclopoida (Oithona) copepods, exhibited higher and lower biomasses at stations MA/MJ and MB, respectively. Bacterivory represented only 35% of bacterial production at stations MB and R, but higher fractions (65–70%) were observed at stations MA and MJ. Small heterotrophic flagellates and aloricate ciliates seemed to be the main controllers of bacteria. Pico- and nanophytoplankton represented a significant alternative carbon pool for micrograzers, which grazing represented 67–90% of pico- and nano-algal production in all stations. Microzooplankton has, however, a relatively low impact on microphytoplankton, as ≤45% of microalgal production was consumed in all stations. This implies that an important fraction of diatom production would be channelled by herbivorous meso-grazers to higher consumers at stations MA and MJ where copepods were numerous. Most of the microalgal production would, however, sink particularly at station MB where copepods were scare. These different trophic interactions suggest different food web structures between stations. A multivorous food web seemed to prevail in stations MJ and MA, whereas microbial web was dominant in the other stations. 相似文献
105.
106.
Elliot M. Schneiderman Tammo S. Steenhuis Dominique J. Thongs Zachary M. Easton Mark S. Zion Andrew L. Neal Guillermo F. Mendoza M. Todd Walter 《水文研究》2007,21(25):3420-3430
Many water quality models use some form of the curve number (CN) equation developed by the Soil Conservation Service (SCS; U.S. Depart of Agriculture) to predict storm runoff from watersheds based on an infiltration-excess response to rainfall. However, in humid, well-vegetated areas with shallow soils, such as in the northeastern USA, the predominant runoff generating mechanism is saturation-excess on variable source areas (VSAs). We reconceptualized the SCS–CN equation for VSAs, and incorporated it into the General Watershed Loading Function (GWLF) model. The new version of GWLF, named the Variable Source Loading Function (VSLF) model, simulates the watershed runoff response to rainfall using the standard SCS–CN equation, but spatially distributes the runoff response according to a soil wetness index. We spatially validated VSLF runoff predictions and compared VSLF to GWLF for a subwatershed of the New York City Water Supply System. The spatial distribution of runoff from VSLF is more physically realistic than the estimates from GWLF. This has important consequences for water quality modeling, and for the use of models to evaluate and guide watershed management, because correctly predicting the coincidence of runoff generation and pollutant sources is critical to simulating non-point source (NPS) pollution transported by runoff. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
107.
伊犁北部博罗霍努岩体年代学和地球化学研究及其大地构造意义 总被引:3,自引:8,他引:3
博罗霍努岩体是发育在新疆伊犁北部的一个大型海西期花岗岩体,总体沿近 SE—NW 向分布,出露面积逾2000km~2。该岩体主要包括三类花岗岩:灰黑色辉石闪长岩、浅色黑云母花岗岩和紫红色黑云母钾长花岗岩。锆石 U—Pb La-ICP-MS 定年表明,辉石闪长岩的年龄为301±7Ma,黑云母花岗岩的年龄范围为294±7~285±7Ma,而黑云母钾长花岗岩则形成于280±5~266±6Ma。岩石地球化学分析显示,黑云母花岗岩和钾长花岗岩以准铝或弱过铝Ⅰ型花岗岩为主,个别属于弱过铝 S 型花岗岩。在微量元素方面,这些花岗岩均富集轻稀土而亏损重稀土,但来自两个剖面的花岗岩具有不同的稀土元素配分模式,可能代表它们的岩浆源区有所不同,因此需要进一步对这些花岗岩进行同位素地质学研究。相对于洋脊花岗岩而言,博罗霍努岩体的花岗岩明显富集 K,Rb,Ba 和 Th,同时,显著亏损 Nb,Ta,Y 和 Yh。以上地球化学特征及微量元素判别图表明,这些花岗岩类形成于俯冲有关的火山岛弧环境。结合伊犁及邻区岩浆岩的特征及其时代,可以认为博罗霍努岩体的形成与天山北部洋壳向南的俯冲造山作用有关。西天山北部俯冲造山作用最终在中二叠世结束,并在中一晚二叠世进入陆内造山和伸展拉张阶段。 相似文献
108.
In New Caledonia, the occurrence of one of the World’s largest and best-exposed subduction/obduction complex is a key point
for the understanding of the geodynamic evolution of the whole Southwest Pacific region. Within the ophiolite, pre-and post-obduction
granitoids intrude the ultramafic allochthon and provide new time constraints for the understanding of obduction processes.
At 27.4 Ma, a new East-dipping subduction generated the active margin magmatism along the western coast of the island (Saint-Louis
massif). At 24.3 Ma, the eastward shift of the magma activity and slightly different geochemical features (Koum-Borindi massif)
was either related to the older slab break-off; or alternatively, due to the eastward migration of the mantle wedge following
the collision of the eastern margin of the Low Howe rise. Finally, the occurrence of a granulite-facies xenolith in the Koum-Borindi
massif with comparable 24.5 Ma U–Pb zircon age and isotopic features (initial εNd = 5.1) suggests that these evolved magmas were generated within the lithospheric mantle beneath a continental crust of normal
thickness. Geochronological evidence for continuous convergence during the Oligocene infers an East-dipping Eocene-Oligocene
subduction/obduction system to have existed in the Southwest Pacific from the d’Entrecasteaux zone to the North Island of
New Zealand. 相似文献
109.
Dominique Courault Philippe Drobinski Yves Brunet Pierre Lacarrere Charles Talbot 《Boundary-Layer Meteorology》2007,124(3):383-403
Land-use practices such as deforestation or agricultural management may affect regional climate, ecosystems and water resources.
The present study investigates the impact of surface heterogeneity on the behaviour of the atmospheric boundary layer (ABL),
at a typical spatial scale of 1 km. Large-eddy simulations, using an interactive soil–vegetation–atmosphere surface scheme,
are performed to document the structure of the three-dimensional flow, as driven by buoyancy forces, over patchy terrain with
different surface characteristics (roughness, soil moisture, temperature) on each individual patch. The patchy terrain consists
of striped and chessboard patterns. The results show that the ABL strongly responds to the spatial configuration of surface
heterogeneities. The stripe configuration made of two patches with different soil moisture contents generates the development
of a quasi- two-dimensional inland breeze, whereas a three-dimensional divergent flow is induced by chessboard patterns. The
feedback of such small-scale atmospheric circulations on the surface fluxes appears to be highly non-linear. The surface sensible
and latent heat fluxes averaged over the 25-km2 domain may vary by 5% with respect to the patch arrangement. 相似文献
110.
Emile A. Okal Jacques Talandier Dominique Reymond 《Pure and Applied Geophysics》2007,164(2-3):309-323
The 2004 Sumatra-Andaman tsunami was recorded by hydrophones of the International Monitoring System at Site H08 near Diego
Garcia, notably in frequency bands extending outside the range of the Shallow Water Approximation. Despite the severe high-pass
filtering involved in this instrumentation, we show that the spectral amplitudes recovered around T = 87 s can be successfully explained by generation from the seismic source, in the framework of the normal mode theory of
tsunami excitation. At the lower frequencies characteristic of more conventional tsunami waves (800 to 3200 s), the signal
is probably present in the hydrophone records, but reliable deconvolution of its spectral amplitude is precluded by the fact
that the instrumental filters lowered the tsunami signal to the level of resolution of the instrument digitizer. In the context
of distant tsunami warning, hydrophone records could provide useful insight into high-frequency tsunami components, and even
at lower, more conventional, frequencies, provided that an unfiltered channel could be recorded routinely. 相似文献