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181.
The Urban Heat Island Intensity of Paris: A Case Study Based on a Simple Urban Surface Parametrization 总被引:1,自引:0,他引:1
We explore the ability of a simple urban surface parametrization, embedded in a mesoscale meteorological model, to correctly
reproduce observed values of the urban heat island (UHI) intensity, which is defined as the urban-rural surface air temperature
difference. To do so, a simple urban scheme was incorporated into the Advanced Regional Prediction System (ARPS). Subsequently,
a simulation was performed with the coupled model over the wider area of Paris, for a 12-day period in June 2006 that was
characterised by conditions prone to UHI development. Simulated 2-m air temperature was compared with observed values for
urban and rural stations, yielding mean errors of 1.4 and 1.5 K, respectively. More importantly, it was found that the model
also displayed an overall good capability of reproducing the observed temperature differences. In particular, the magnitude (up to 6 K) and timing of the diurnal cycle of the UHI intensity was simulated well, the model
exhibiting a mean error of 1.15 K. As a result, our conclusion is that the ARPS model, extended with simple urban surface
physics, is able to capture observed urban-rural air temperature differences well, at least for the domain and period studied. 相似文献
182.
In an experiment on methane-emission measurements from rice fields amended with urea, biogas spent slurry (BSS) + urea, and farm yard manure (FYM) + urea, three distinctive peaks in the methane emissions were observed at 15, 46, and 69 days after transplanting (DAT) due to the availability of readily degradable C-sources. In all cases, the highest peak was at 69 DAT. The steepest Eh drop to a minimum of -320 mV was reached within two weeks of submergence. pH ranged between 7.5 and 8.5. The combined fertilization (FYM + urea) plot showed the maximum emission rate of 4.86 mg m–2 h–1 with a total load of 49.44 kg ha–1 and was 2.3 times higher than (BSS + urea)-treated plot (22.08 kg ha–1). Grain yields in urea, (BSS + urea) and (FYM + urea) plots were 3.34, 2.94, and 2.85 t ha–1 respectively, suggesting that biogas slurry is a preferred source over FYM causing lesser environmental pollution without any significant reduction in grain yield. 相似文献
183.
The A-type Mayurbhanj Granite Pluton (3.09 Ga), occurring along the eastern margin of the Singhbhum-Orissa Craton, eastern India, represents the final phase of acid plutonism in this crustal block of Archean age. The granite shows a bimodal association with a voluminous gabbroid body, exposed mainly along its western margin, and is associated with the Singhbhum Shear zone. The granite pluton is composed mainly of a coarse ferrohastingsite–biotite granite phase, with an early fine-grained granophyric microgranitic phase and a late biotite aplogranitic phase. Petrogenetic models of partial melting, fractional crystallisation and magma mixing have been advocated for the evolution of this pluton. New data, combined with earlier information, suggest that two igneous processes were responsible for the evolution of the Mayurbhanj Granite Pluton: partial melting of the Singhbhum Granite; followed by limited amount of mixing of acid and basic magmas in an anorogenic extensional setting. The necessary heat for partial melting was provided by the voluminous basaltic magma, now represented by the gabbroid body, emplaced at a shallow crustal level and showing a bimodal association with the Mayurbhanj Granite Pluton. The Singhbhum Shear Zone provided a possible channel way for the emplacement of the basic magma during crustal extension. It is concluded that all three phases of the Mayurbhanj Granite Pluton were derived from the same parent magma, generated by batch partial melting of the Singhbhum Granite at relatively high temperatures (980 °C) and low pressures (4 to <2 kbar) under anhydrous conditions. The coarse ferrohastingsite biotite granite phase shows evidence of limited and heterogeneous assimilation of country rock metasediments. However, the early microgranite phase and late aplogranite phase have not assimilated any metasediments. Compositional irregularities observed along the western margin of the Mayurbhanj Granite Pluton in contact with the gabbro body including a continuous fractionating sequence from quartz diorite to alkali-feldspar granite in the Notopahar area. Gradational contacts between the gabbro and the Mayurbhanj Granite Pluton in the Gorumahisani area etc., may be attributed to a limited amount of mixing between the gabbroid magma and the newly generated Mayurbhanj Granite magma. The mixing was mainly of liquid–liquid diffusive type, with a subordinate amount of mixing of solid–liquid type. Although A-type granites are commonly described as having high total REE (e.g. 270–400 ppm), studies on the late aplogranite phase of the Mayurbhanj Granite show that total REE values (100 ppm) are low. This low REE abundance may be attributed to the progressive residual nature of the Singhbhum Granite source during continued partial melting, when the magmas of the microgranite and coarse granite phases had already been removed from the source region. 相似文献
184.
Summary The electromagnetic radiation of cloud discharge known as atmospheric radio noise field strength (ARNFS) shows a gradual fall from a frequency of 9 kHz to 81 kHz as studied over a period of two years at Calcutta, very close to Bay of Bengal. The main characteristic features of ARNFS at Calcutta are that-(i) ARNFS shows that midday median value is smaller than midnight median value in all months, (ii) level of daily minimum is higher in February and monsoon compared to other seasons, (iii) sunrise effect and sunset effect are well correlated with local sunrise and sunset times, (iv) the magnitude of sunrise fade and sunrise fade rate are maximum in April and lowest during winter period, (v) the magnitude of sunset fade is higher in premonsoon and postmonsoon while it is lowest in monsoon, (vi) number of occurrence of both sunrise effect and sunset effect is remark-ably smaller in monsoon. The positions of the sun and of atmospheric sources are jointly the causes of seasonal and diurnal variations. The missing of sunrise effect and sunset effect are due to local cloud activity and variation of electron density during geomagnetic storms.With 7 Figures 相似文献
185.
The expected proton and neutrino fluxes from decays of massive metastable relic particles are calculated using the HERWIG QCD event generator. The predicted proton spectrum can account for the observed flux of extremely high energy cosmic rays beyond the Greisen-Zatsepin-Kuzmin cutoff, for a decaying particle mass of
(1012) GeV. The lifetime required is of
(1020) yr if such particles constitute all of the dark matter (with a proportionally shorter lifetime for a smaller contribution). Such values are plausible if the metastable particles are hadron-like bound states from the hidden sector of supersymmetry breaking which decay through nonrenormalizable interactions. The expected ratio of the proton to neutrino flux is given as a diagonistic of the decaying particle model for the forthcoming Pierre Auger Project. 相似文献
186.
Origin of phlogopite-orthopyroxene inclusions in chromites from the Merensky Reef of the Bushveld Complex,South Africa 总被引:1,自引:1,他引:0
Chusi?LiEmail author Edward?M.?Ripley Arindam?Sarkar Dongbok?Shin Wolfgang?D.?Maier 《Contributions to Mineralogy and Petrology》2005,150(1):119-130
About 30% of the chromite grains of variable sizes in a chromitite seam at the base of the Merensky Reef of the Bushveld Complex
on the farm Vlakfontein contain abundant composite mineral inclusions. The inclusions are polygonal to circular with radial
cracks that protrude into the enclosing chromite. They vary from a few microns to several millimeters in diameter and are
concentrated in the cores and mantles of chromite crystals. Electron backscattered patterns indicate that the host chromites
are single crystals and not amalgamations of multiple grains. Na-phlogopite and orthopyroxene are most abundant in the inclusions.
Edenitic hornblende, K-phlogopite, oligoclase and quartz are less abundant. Cl-rich apatite, rutile, zircon and chalcopyrite
are present at trace levels. Na-phlogopite is unique to the inclusions; it has not been found elsewhere in the Bushveld Complex.
Other minerals in the inclusions are also present in the matrix of the chromitite seam, but their compositions are different.
The Mg/(Mg+Fe2+) ratios of orthopyroxene in the inclusions are slightly higher than those of orthopyroxene in the matrix. K-phlogopite in
the inclusions contains more Na than in the matrix. The average compositions of the inclusions are characterized by high MgO
(26 wt%), Na2O (2.4 wt%) and H2O (2.6 wt%), and low CaO (1.1 wt%) and FeO (4.4 wt%). The δ18O value of the trapped melt, estimated by analysis of inclusion-rich and inclusion-poor chromites, is ∼7‰. This value is consistent
with the previous estimates for the Bushveld magma and with the δ18O values of silicate minerals throughout the reef. The textural features and peculiar chemical compositions are consistent
with entrapment of orthopyroxene with variable amounts of volatile-rich melts during chromite crystallization. The volatile-rich
melts are thought to have resulted from variable degrees of mixing between the magma on the floor of the chamber and Na-K-rich
fluids expelled from the underlying crystal pile. The addition of fluid to the magma is thought to have caused dissolution
of orthpyroxene, leaving the system saturated only in chromite. Both oxygen and hydrogen isotopic values are consistent with
the involvement of a magmatic fluid in the process of fluid addition and orthopyroxene dissolution. Most of the Cr and Al
in the inclusions was contributed through wall dissolution of the host chromite. Dissolution of minor rutile trapped along
with orthopyroxene provided most of the Ti in the inclusions. The Na- and K-rich hydrous silicate minerals in the inclusions
were formed during cooling by reaction between pyroxene and the trapped volatile-rich melts. 相似文献
187.
Some of the major metropolitan centers in the world are highly susceptible to flash floods and major disruptions, owing to sudden and excessive rainfall events. The city of Mumbai, India’s financial capital, suffered one such event on 19 June, 2015. This was a second event of such nature, following the landmark event of 26 July, 2005. Such extreme rainfall events are often brought about by certain rapidly developing, local disturbances, which if actively monitored, may be provide important information that can be of great use for early warning to civic authorities and emergency planners. In this paper, we have analyzed a number of different meteorological and remotely sensed parameters, a few days before the actual event, to track the development and eventual culmination of a “perfect storm” that affected Mumbai and left the city tattered. We show how regional upper layer disturbance patterns are developed, induced by warming of sea-surface temperature (SST) and sustained by instability in the atmospheric boundary layers to quickly develop into massive cyclonic storms. 相似文献
188.
Gopinath Sarkar 《Pure and Applied Geophysics》1966,65(1):43-47
Summary Wave motion due to two kinds of impulsive twist on the surface has been discussed. The discontinuous nature of solution has been obtained. A function-theoretic approach has been made for solving the problem. 相似文献
189.
Landslide risk assessment using concepts of danger pixels and fuzzy set theory in Darjeeling Himalayas 总被引:4,自引:1,他引:3
Landslide risk assessment (LRA) is a key component of landslide studies. The landslide risk can be defined as the potential
for adverse consequences or loss to human population and property due to the occurrence of landslides. The LRA can be regional
or site-specific in nature and is an important information for planning various developmental activities in the area. LRA
is considered as a function of landslide potential (LP) and resource damage potential (RDP). The LP and RDP are typically
characterized by the landslide susceptibility zonation map and the resource map (i.e., land use land cover map) of the area,
respectively. Development of approaches for LRA has always been a challenge. In the present study, two approaches for LRA,
one based on the concept of danger pixels and the other based on fuzzy set theory, have been developed and implemented to
generate LRA maps of Darjeeling Himalayas, India. The LRA map based on the first approach indicates that 1,015 pixels of habitation
and 921 pixels of road section are under risk due to landslides. The LRA map derived from fuzzy set theory based approach
shows that a part of habitat area (2,496 pixels) is under very high risk due to landslides. Also, another part of habitat
area and a portion of road network (7,204 pixels) are under high risk due to landslides. Thus, LRA map based on the concept
of danger pixels gives the pixels under different resource categories at risk due to landslides whereas the LRA map based
on the concept of fuzzy set theory further refines this result by defining the degree of severity of risk to these categories
by putting these into high and low risk zones. Hence, the landslide risk assessment study carried out using two approaches
in this paper can be considered in cohesion for assessing the risks due to landslides in a region. 相似文献
190.