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221.
Predicting phosphorus dynamics in complex terrains using a variable source area hydrology model
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Amy S. Collick Daniel R. Fuka Peter J. A. Kleinman Anthony R. Buda Jennifer L. Weld Mike J. White Tamie L. Veith Ray B. Bryant Carl H. Bolster Zachary M. Easton 《水文研究》2015,29(4):588-601
Phosphorus (P) loss from agricultural watersheds has long been a critical water quality problem, the control of which has been the focus of considerable research and investment. Preventing P loss depends on accurately representing the hydrological and chemical processes governing P mobilization and transport. The Soil and Water Assessment Tool (SWAT) is a watershed model commonly used to predict run‐off and non‐point source pollution transport. SWAT simulates run‐off employing either the curve number (CN) or the Green and Ampt methods, both assume infiltration‐excess run‐off, although shallow soils underlain by a restricting layer commonly generate saturation‐excess run‐off from variable source areas (VSA). In this study, we compared traditional SWAT with a re‐conceptualized version, SWAT‐VSA, that represents VSA hydrology, in a complex agricultural watershed in east central Pennsylvania. The objectives of this research were to provide further evidence of SWAT‐VSA's integrated and distributed predictive capabilities against measured surface run‐off and stream P loads and to highlight the model's ability to drive sub‐field management of P. Thus, we relied on a detailed field management database to parameterize the models. SWAT and SWAT‐VSA predicted discharge similarly well (daily Nash–Sutcliffe efficiencies of 0.61 and 0.66, respectively), but SWAT‐VSA outperformed SWAT in predicting P export from the watershed. SWAT estimated lower P loss (0.0–0.25 kg ha?1) from agricultural fields than SWAT‐VSA (0.0–1.0+ kg ha?1), which also identified critical source areas – those areas generating large run‐off and P losses at the sub‐field level. These results support the use of SWAT‐VSA in predicting watershed‐scale P losses and identifying critical source areas of P loss in landscapes with VSA hydrology. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
222.
Raj Kumar Suchandra A. Bhowmick Sulagna Ray Vihang Bhatt Suhe Surendran Sujit Basu Abhijit Sarkar Vijay K. Agarwal 《Natural Hazards》2009,49(2):275-291
Accurate prediction of ocean surface waves is a challenging task with many associated difficulties. Availability of good quality
wind and wave information from satellite platforms inspired the scientific community to assimilate such data in various spectral
wave models for enhancing the accuracy of prediction. Over the Indian Ocean, which is the region of interest for the present
study, wave heights in extreme situation can go up to 12–14 m, thereby increasing the probability of coastal hazards. This
region is further governed by the southern ocean swells that propagate thousands of kilometers. These are, in general, not
well captured by the spectral wave models. Therefore, assimilation of altimeter data in open ocean wave model WAM has been
attempted with the aim of enhancing the quality of prediction of significant wave height. Further, simulated wave spectra
have been assimilated in a coastal wave model SWAN. This assimilation has been found to significantly improve the prediction
of the height of wind waves as well as swell waves.
V. Bhatt and S. Surendran are former students of Meteorology and Oceanography Group, Space Applications Centre, ISRO, Ahmedabad. 相似文献
223.
Slope stability analysis on a regional scale using GIS: a case study from Dhading,Nepal 总被引:1,自引:0,他引:1
A spatially distributed physically based slope stability model combined with a hydrological model is presented and applied
to a 350-km2 area located in Dhading district, Nepal. Land slide safety factor maps are generated for five cases, including three steady
state conditions assuming either completely dry soils, half saturated soils, or fully saturated soils, and two quasi-dynamic
conditions, i.e. soil wetness resulting from storm events with, respectively a 2 or 25-year return period. For the quasi-dynamic
cases, two methods are used, one based on accumulation of groundwater flow from upstream areas, and the other on accumulation
of soil water from direct infiltration. The methodology delineates areas most prone to shallow land sliding in function of
readily available data as topography, land-use and soil types. For the study area only 29% of the soils are unconditionally
stable, while 25% of the soils are found to be unstable under fully saturated conditions. The comparison between the methods
based on contributing area or on infiltration for quasi-dynamic conditions show that the approach based on infiltration is
more reliable for the study area. The proposed methodology for predicting landslide susceptibility on a regional scale, based
on basic data in GIS form, may be useful for other remote regions where detailed information is not available. 相似文献
224.
Goodenough Spring (Texas, USA) is a large spring near the border of the American state of Texas and the Mexican state of Coahuila, discharging into the international Amistad Reservoir on the river Rio Grande (Rio Bravo). Discharge was routinely measured from 1928 until 1968 to partition the flow of the river between the two countries in accordance with water-use treaties. Samples were analyzed for water-quality parameters in 1967–1968 prior to inundation under 45 m of Amistad Reservoir in 1968. Subsequently, discharge has been estimated indirectly by the International Boundary and Water Commission (IBWC). For the first direct measurements of the spring in 37 years, velocity and cross-sectional measurements were made and water samples collected in the summer of 2005 using advanced self-contained underwater breathing apparatus (SCUBA) techniques. Spring discharge was calculated at 2.03 m3 s–1, approximately one-half of the historical mean of 3.94 m3 s–1. In situ and laboratory analyses of samples for temperature, pH, dissolved oxygen, specific conductance, alkalinity, nitrate-nitrogen, dissolved solids, chloride, sulfate, fluoride, phosphorus, calcium, sodium, potassium, magnesium, and iron showed the water quality to be very good for human consumption and crop irrigation. Measurement values are relatively unchanged from those reported 37 years prior. 相似文献
225.
Ung Jin Na Samit Ray Chaudhuri Masanobu Shinozuka 《Soil Dynamics and Earthquake Engineering》2008,28(2):147-158
Past experience has shown that ports are often susceptible to severe damage during earthquakes. From field damage data of 1995 Kobe earthquake, it is observed that the seismic behavior of port structures shows significant variability. In this study, a 2D numerical model, representing PC1 berth located in Port Island, Kobe and damaged in the 1995 Kobe earthquake, has been developed and used to simulate seismic behavior. It has been found that the uncertainties in the friction angle and the shear modulus of reclaimed soil contribute most to the variability of the residual horizontal displacement (RHD) response of the quay wall of port structures. To investigate the propagation of uncertainties of soil–structure system to the quay wall, a tornado diagram and a first-order second-moment analysis are used. Uncertainty of ground motions has also been investigated. Based on the results, design considerations have been provided. 相似文献
226.
227.
Vanessa Haverd Ray Leuning David Griffith Eva van Gorsel Matthias Cuntz 《Boundary-Layer Meteorology》2009,130(2):209-228
One-dimensional Lagrangian dispersion models, frequently used to relate in-canopy source/sink distributions of energy, water
and trace gases to vertical concentration profiles, require estimates of the standard deviation of the vertical wind speed,
which can be measured, and the Lagrangian time scale, T
L
, which cannot. In this work we use non-linear parameter estimation to determine the vertical profile of the Lagrangian time
scale that simultaneously optimises agreement between modelled and measured vertical profiles of temperature, water vapour
and carbon dioxide concentrations within a 40-m tall temperate Eucalyptus forest in south-eastern Australia. Modelled temperature
and concentration profiles are generated using Lagrangian dispersion theory combined with source/sink distributions of sensible
heat, water vapour and CO2. These distributions are derived from a multilayer Soil-Vegetation-Atmospheric-Transfer model subject to multiple constraints:
(1) daytime eddy flux measurements of sensible heat, latent heat, and CO2 above the canopy, (2) in-canopy lidar measurements of leaf area density distribution, and (3) chamber measurements of CO2 ground fluxes. The resulting estimate of Lagrangian time scale within the canopy under near-neutral conditions is about 1.7
times higher than previous estimates and decreases towards zero at the ground. It represents an advance over previous estimates
of T
L
, which are largely unconstrained by measurements. 相似文献
228.
Flood basalts, such as the Deccan Traps of India, represent huge, typically fissure-fed volcanic provinces. We discuss the
structural attributes and emplacement mechanics of a large, linear, tholeiitic dyke swarm exposed in the Nandurbar–Dhule area
of the Deccan province. The swarm contains 210 dykes of dolerite and basalt >1 km in length, exposed over an area of 14,500 km2. The dykes intrude an exclusively basaltic lava pile, largely composed of highly weathered and zeolitized compound pahoehoe
flows. The dykes range in length from <1 km to 79 km, and in thickness from 3 to 62 m. Almost all dykes are vertical, with
the others nearly so. They show a strong preferred orientation, with a mean strike of N88°. Because they are not emplaced
along faults or fractures, they indicate the regional minimum horizontal compressive stress (σ
3) to have been aligned ~N–S during swarm emplacement. The dykes have a negative power law length distribution but an irregular
thickness distribution; the latter is uncommon among the other dyke swarms described worldwide. Dyke length is not correlated
with dyke width. Using the aspect ratios (length/thickness) of several dykes, we calculate magmatic overpressures required
for dyke emplacement, and depths to source magma chambers that are consistent with results of previous petrological and gravity
modelling. The anomalously high source depths calculated for a few dykes may be an artifact of underestimated aspect ratios
due to incomplete along-strike exposure. However, thermal erosion is a mechanism that can also explain this. Whereas several
of the Nandurbar–Dhule dykes may be vertically injected dykes from shallow magma chambers, others, particularly the long ones,
must have been formed by lateral injection from such chambers. The larger dykes could well have fed substantial (≥1,000 km3) and quickly emplaced (a few years) flood basalt lava flows. This work highlights some interesting and significant similarities,
and contrasts, between the Nandurbar–Dhule dyke swarm and regional tholeiitic dyke swarms in Iceland, Sudan, and elsewhere.
Editorial responsibility: J. White 相似文献
229.
Mukul Sharma Asish R. Basu Sagar L. Ray 《Contributions to Mineralogy and Petrology》1994,117(1):45-55
We report the results of a Sm-Nd isotopic, major element and rare earth element (REE) study of the Older Metamorphic Group (OMG) tonalite-amphibolite association of the eastern Indian Craton. The Older Metamorphic Tonalite Gneisses (OMTG) have been previously dated to be 3.8 Ga using Sm-Nd isotope systematies, and 3.2–3.4 Ga by Rb-Sr and Pb-Pb dating. The results of this study indicate that the protoliths of the OMG amphibolites are 3.3 Ga isochron age=3.30±0.06 Ga, Nd= +0.9 ± 0.7), and therefore, the OMTG, which intrude into the associated amphibolites, cannot be any older than 3.3 Ga. The amphibolites display light REE enrichment ((Ce/Yb)N=2.2–6.7; La=30–100 x chondrite) and nearly flat heavy REE patterns ((Tb/Lu)N=1.2–1.9); the basaltic parents of the amphibolites were probably generated by the partial melting of a spinel lherzolite mantle. Strong linear relationships between the amphibolites and tonalites in 147Sm/144Nd-143Nd/144Nd space (isochron age =3.29±0.04 Ga, Nd= +0.8 ± 0.8) imply that they are genetically related. The tonalites display fractionated REE patterns (La=100–300 x chondrite) with moderate heavy REE depletions ((Tb/Lu)N=1.9–3.4). The isotopic, major element and REE data are consistent with the derivation of the OMTG from partial melting of OMG amphibolites or equivalent rocks at amphibolegarnet stabilization depths. An initial Nd(t) value of +0.9±0.7 for the amphibolites indicates the presence of a slightly depleted mantle source at 3.3 Ga with 147Sm/144Nd. between 0.20 and 0.22. It is suggested that the growth of continental crust in the eastern Indian craton occurred in response to magmatic underplating in a plume setting. 相似文献
230.
Mylonitic gabbro and altered gabbro were recovered from off-axis high and corner high locations at ridge-transform intersection,
adjacent to Vityaz transform fault of the slow spreading (32–35 mm/yr, full spreading) Northern Central Indian Ridge. Both
the varieties show signatures of extensive alteration caused due to interaction with sea water. Mylonitic gabbro represents
high temperature metamorphism (∼700–800°C) and comprised of hornblende mineral which exhibits well defined foliation/gneissic
appearance along with dynamically recrystallised plagioclase grains frequently intercalated with magnetite-ilmenite. Altered
gabbro from corner high generally includes low temperature greenschist grade (∼300°C) mineralogical assemblages: chlorite,
albite, quartz and locally magnesio hornblende. Crystal plastic deformation resulted in mylonite formation and often porphyroclasts
of plagioclase and clinopyroxene grains, while altered gabbro locally exhibits cataclastic texture. Presence of Vityaz transform
fault and adjacent megamullion at the weakly magmatic ridge-transform intersection and off-axis high locations prompted the
present scenario very much conducive for hydrothermal circulation and further facilitate the exhumation of present suite of
gabbro. 相似文献