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931.
D. J. Christian N. P. Gibson E. K. Simpson R. A. Street I. Skillen D. Pollacco A. Collier Cameron Y. C. Joshi F. P. Keenan H. C. Stempels C. A. Haswell K. Horne D. R. Anderson S. Bentley F. Bouchy W. I. Clarkson B. Enoch L. Hebb G. Hébrard C. Hellier J. Irwin S. R. Kane T. A. Lister B. Loeillet P. Maxted M. Mayor I. McDonald C. Moutou A. J. Norton N. Parley F. Pont D. Queloz R. Ryans B. Smalley A. M. S. Smith I. Todd S. Udry R. G. West P. J. Wheatley D. M. Wilson 《Monthly notices of the Royal Astronomical Society》2009,392(4):1585-1590
We report the discovery of WASP-10b, a new transiting extrasolar planet (ESP) discovered by the Wide Angle Search for Planets (WASP) Consortium and confirmed using Nordic Optical Telescope FIbre-fed Echelle Spectrograph and SOPHIE radial velocity data. A 3.09-d period, 29 mmag transit depth and 2.36 h duration are derived for WASP-10b using WASP and high-precision photometric observations. Simultaneous fitting to the photometric and radial velocity data using a Markov Chain Monte Carlo procedure leads to a planet radius of 1.28 R J , a mass of 2.96 M J and eccentricity of ≈0.06. WASP-10b is one of the more massive transiting ESPs, and we compare its characteristics to the current sample of transiting ESP, where there is currently little information for masses greater than ≈ 2 M J and non-zero eccentricities. WASP-10's host star, GSC 2752−00114 (USNO-B1.0 1214−0586164) is among the fainter stars in the WASP sample, with V = 12.7 and a spectral type of K5. This result shows promise for future late-type dwarf star surveys. 相似文献
932.
Sediment-water exchanges of ammonium (NH4 +), nitrate + nitrite (NOx ?), filterable reactive phosphorus (FRP, primarily ortho-phosphate), and oxygen (O2) under aphotic (heterotrophic) conditions were determined at 2–5 stations in the Neuse River Estuary, from 1987 to 1989. Shallow (1 m), sandy stations were sampled along the salinity gradient. Fluxes from deep (>2 m) sites were compared to the shallow sites in two salinity zones. Grain size became finer and organic content increased with depth in the oligohaline zone but not in the mesohaline zone. Net release of NH4 + and FRP occurred at all sites. Fluxes varied from slight uptake to releases of 200–500 μmol m?2 h?1 (NH4 +) and 150–900 μmol m?2 h?1 (FRP). Net NOx ? exchange was near zero, but were ±100 μmol m?2 h?1 over the year. Release of NH4 + and FRP from the shallow sandy stations decreased with distance down the estuary, but O2 uptake did not change. The deeper oligohaline site had twofold higher rates of NH4 + and FRP release and O2 uptake than the shallow site, but no differences occurred between depths in the mesohaline zone. Temperature and organic content were important controls for all fluxes, but water column NOx ? concentration was also important in regulating NOx ? exchanges. Ratios of oxygen consumption to NH4 + release were near the predicted ratio (Redfield model) at oligohaline sites but increased down estuary at mesohaline sites. This may be due to greater nitrification rates promoted by autotrophy in the sediments. 相似文献
933.
Roohollah Shirani Faradonbeh Alireza Salimi Masoud Monjezi Arash Ebrahimabadi Christian Moormann 《Environmental Earth Sciences》2017,76(16):584
Roadheading machines play a vital role in excavation operation in tunneling and mining industries notably when selective mining is required. Roadheaders are more effective in soft to medium rock formations due to a higher cutting rate in such strata. A precise prediction of machine’s performance is a crucial issue, as it has considerable effects on excavation planning, project’s cost estimation, machine specification selection as well as safety of the project. In this research, a database of machine performance and some geomechanical parameters of rock formations from Tabas coal mine project, the largest and fully mechanized coal mine in Iran, has been established, including instantaneous cutting rate (ICR), uniaxial compressive strength, Brazilian tensile strength, rock quality designation, influence of discontinuity orientation (Alpha angle) and specific energy. Afterward, the parameters were analyzed through genetic programming (GP) and gene expression programming (GEP) approaches to yield more accurate models to predict the performance of roadheaders. As statistical indices, coefficient of determination, root mean square error and variance account were used to evaluate the efficiency of the developed models. According to the obtained results, it was observed that developed models can effectively be implemented for prediction of roadheader performance. Moreover, it was concluded that performance of the GEP model is better than the GP model. A high conformity was observed between predicted and measured roadheader ICR for GEP model. 相似文献
934.
A. M. S. Smith A. Collier Cameron D. J. Christian W. I. Clarkson B. Enoch A. Evans C. A. Haswell C. Hellier K. Horne J. Irwin S. R. Kane T. A. Lister A. J. Norton N. Parley D. L. Pollacco R. Ryans I. Skillen R. A. Street A. H. M. J. Triaud R. G. West P. J. Wheatley D. M. Wilson 《Monthly notices of the Royal Astronomical Society》2006,373(3):1151-1158
The evolution of the Alfvén turbulence due to three-wave interactions is discussed using kinetic theory for a collisionless, thermal plasma. There are three low-frequency modes, analogous to the three modes of compressible magnetohydrodynamics (MHD). When only Alfvén waves are considered, the known anisotropy of turbulence in incompressible MHD theory is reproduced. Inclusion of a fast mode wave leads to the separation of turbulence into two regimes: small wave numbers where three-wave processes involving a fast mode are dominant, and large wave numbers where the three Alfvén wave process is dominant. Possible application of the anisotropic Alfvén turbulence to the interstellar medium and dissipation of magnetic energy in magnetars are discussed. 相似文献
935.
936.
Diamond drill core traverses across the Platreef were carried out at Tweefontein, Sandsloot, and Overysel in order to establish
the relationship between crustal contamination and platinum group element (PGE) mineralization. The footwall rocks are significantly
different at each of these sites and consist of banded iron formation and sulfidic shales at Tweefontein, of carbonates at
Sandsloot, and of granites and granite gneisses at Overysel. As demonstrated in this study, Platreef rocks are characterized
by two stages of crustal contamination. The first contamination event occurred prior to emplacement of the magma and is present in Platreef rocks at all three sites, as well as in the Merensky
Reef. This event is readily identified on trace element spidergrams and trace element ratio scattergrams. The second contamination event was induced by interaction of the Platreef magma with the local footwall rocks. It is most easily identified at Tweefontein,
where there is a large increase in the FeO content of the Platreef rocks, and at Sandsloot, where there is a large increase
in their CaO and MgO contents, relative to Bushveld rocks that are uncontaminated by the local footwall rocks. At Overysel,
the second contamination event did not result in pronounced changes in the major element composition of the Platreef rocks,
but can be detected in their trace element chemistry. A strong inverse relationship between PGE tenors and S/Se ratios is
interpreted to suggest that the PGE-rich sulfides were formed prior to emplacement of the Platreef magmas through assimilation
of crustal S and became progressively enriched in the PGE during transport. Rather than promoting S-saturation, interaction
of the Platreef magma with the footwall rocks diluted the metal tenors of the sulfides. Although both the Platreef and the
Merensky Reef magmas were contaminated by the same crustal contaminant and were probably PGE-rich, they have radically different
Pd/Pt ratios. Their Pd/Pt ratios suggest that whereas the Merensky Reef magma became PGE-rich due to dissolution of PGE-rich
sulfides segregated from a pre-Merensky magma that had undergone relatively little fractionation prior to reaching S-saturation,
the pre-Platreef magma had undergone greater fractionation prior to the sulfide saturation event, thereby increasing its Pd/Pt
ratio. We suggest that the magmas that formed the Platreef and Merensky Reef may have simply been carrier magmas for sulfides
that had formed elsewhere in the plumbing system of the Bushveld Complex by the interaction of earlier generations of magmas
with the crustal rocks that underlie the Complex. 相似文献
937.
938.
Lothar Ratschbacher Christian Dingeldey Christine Miller Bradley R. Hacker Michael O. McWilliams 《Tectonophysics》2004,394(3-4):155-170
New 40Ar/39Ar geochronology places time constraints on several stages of the evolution of the Penninic realm in the Eastern Alps. A 186±2 Ma age for seafloor hydrothermal metamorphic biotite from the Reckner Ophiolite Complex of the Pennine–Austroalpine transition suggests that Penninic ocean spreading occurred in the Eastern Alps as early as the Toarcian (late Early Jurassic). A 57±3 Ma amphibole from the Penninic subduction–accretion Rechnitz Complex dates high-pressure metamorphism and records a snapshot in the evolution of the Penninic accretionary wedge. High-pressure amphibole, phengite, and phengite+paragonite mixtures from the Penninic Eclogite Zone of the Tauern Window document exhumation through ≤15 kbar and >500 °C at 42 Ma to 10 kbar and 400 °C at 39 Ma. The Tauern Eclogite Zone pressure–temperature path shows isothermal decompression at mantle depths and rapid cooling in the crust, suggesting rapid exhumation. Assuming exhumation rates slower or equal to high-pressure–ultrahigh-pressure terrains in the Western Alps, Tauern Eclogite Zone peak pressures were reached not long before our high-pressure amphibole age, probably at ≤45 Ma, in accordance with dates from the Western Alps. A late-stage thermal overprint, common to the entire Penninic thrust system, occurred within the Tauern Eclogite Zone rocks at 35 Ma. The high-pressure peak and switch from burial to exhumation of the Tauern Eclogite Zone is likely to date slab breakoff in the Alpine orogen. This is in contrast to the long-lasting and foreland-propagating Franciscan-style subduction–accretion processes that are recorded in the Rechnitz Complex. 相似文献
939.
Particle dynamics are investigated experimentally in supercritical high‐speed open channel flow over a fixed planar bed of low relative roughness height simulating flows in high‐gradient non‐alluvial mountain streams and hydraulic structures. Non‐dimensional equations were developed for transport mode, particle velocity, hop length and hop height accounting for a wide range of literature data encompassing sub‐ and supercritical flow conditions as well as planar and alluvial bed configurations. Particles were dominantly transported in saltation and particle trajectories on planar beds were rather flat and long compared with alluvial bed data due to (1) increased lift forces by spinning motion, (2) strongly downward directed secondary currents, and (3) a planar flume bed where variation in particle reflection and damping effects were minor. The analysis of particle saltation trajectories revealed that the rising and falling limbs were almost symmetrical contradicting alluvial bed data. Furthermore, no or negligible effect of particle size and shape on particle dynamics were found. Implications of experimental findings for mechanistic saltation‐abrasion models are briefly discussed. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
940.
Christian?MoeckEmail author Annette?Affolter Dirk?Radny Horst?Dressmann Adrian?Auckenthaler Peter?Huggenberger Mario?Schirmer 《Hydrogeology Journal》2018,26(1):133-146
A three-dimensional groundwater model was used to improve water resource management for a study area in north-west Switzerland, where drinking-water production is close to former landfills and industrial areas. To avoid drinking-water contamination, artificial groundwater recharge with surface water is used to create a hydraulic barrier between the contaminated sites and drinking-water extraction wells. The model was used for simulating existing and proposed water management strategies as a tool to ensure the utmost security for drinking water. A systematic evaluation of the flow direction between existing observation points using a developed three-point estimation method for a large number of scenarios was carried out. It is demonstrated that systematically applying the developed methodology helps to identify vulnerable locations which are sensitive to changing boundary conditions such as those arising from changes to artificial groundwater recharge rates. At these locations, additional investigations and protection are required. The presented integrated approach, using the groundwater flow direction between observation points, can be easily transferred to a variety of hydrological settings to systematically evaluate groundwater modelling scenarios. 相似文献