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51.
Chemical weathering in the plain and peninsular sub-basins of the Ganga: Impact on major ion chemistry and elemental fluxes 总被引:3,自引:0,他引:3
Concentrations of major ions, Sr and 87Sr/86Sr have been measured in the Gomti, the Son and the Yamuna, tributaries of the Ganga draining its peninsular and plain sub-basins to determine their contribution to the water chemistry of the Ganga and silicate and carbonate erosion of the Ganga basin. The results show high concentrations of Na and Sr in the Gomti, the Yamuna and the Ganga (at Varanasi) with much of the Na in excess of Cl. The use of this ‘excess Na’ (Na∗ = Nariv − Clriv) a common index of silicate weathering yield values of ∼18 tons km−2 yr−1 for silicate erosion rate (SER) in the Gomti and the Yamuna basins. There are however, indications that part of this Na∗ can be from saline/alkaline soils abundant in their basins, raising questions about its use as a proxy to determine SER of the Ganga plain. Independent estimation of SER based on dissolved Si as a proxy give an average value of ∼5 tons km−2 yr−1 for the peninsular and the plain drainages, several times lower than that derived using Na∗. The major source of uncertainty in this estimate is the potential removal of Si from rivers by biological and chemical processes. The Si based SER and CER (carbonate erosion rate) are also much lower than that in the Himalayan sub-basin of the Ganga. The lower relief, runoff and physical erosion in the peninsular and the plain basins relative to the Himalayan sub-basin and calcite precipitation in them all could be contributing to their lower erosion rates.Budget calculations show that the Yamuna, the Son and Gomti together account for ∼75% Na, 41% Mg and ∼53% Sr and 87Sr of their supply to the Ganga from its major tributaries, with the Yamuna dominating the contribution. The results highlight the important role of the plain and peninsular sub-basins in determining the solute and Sr isotope budgets of the Ganga. The study also shows that the anthropogenic contribution accounts for ?10% of the major ion fluxes of the Ganga at Rajmahal during high river stages (October). The impact of both saline/alkaline soils and anthropogenic sources on the major ion abundances of the Ganga is minimum during its peak flow and therefore the SER and CO2 consumption rates of the river is best determined during this period. 相似文献
52.
We will describe a new laboratory system which was designed to be highly automated and portable while maintaining quality. Driving this design was the recognition of the temporal dependence of physical properties. It becomes apparent that some sedimentary rocks, particularly shales, degrade and disaggregare so completely that mechanical or elastic properties cannot be measured. This temporal dependence displays a time scale much shorter than normal weathering but greater than the time for stress relief. A system was designed to permit field characterization of freshly recovered core material. A benefit of automation and portability is a marked increase in measurement efficiency. The attributes of this system permit rapid characterization of a large number of fresh cores in remote, frontier exploration areas. This feature can significantly reduce prospect evaluation time. Statistically significant rock property databases can be created in a short period of time. 相似文献
53.
Water pollution exerts a pressure of selection on algal populations. In spite of a possible adaptation, often a changed diversity and sociological structure result, from which other effects on higher levels of the nutrient chain may emanate. There are represented some biological indices for characterizing algal communities which may serve as a biological measure of pollution and selfpurification, the problem of diversity being especially taken into account. Moreover, algal tests are used for representing the trophic situation and for determining the limiting nutrient, but also for determining the toxic influencing of biocenosis by hydrocarbons, too. Special attention is paid to heavy metals with regard to their synergistic action and bioaccumulation. On the other hand, the mass culture of algae is a valuable method of wastewater treatment and the recovery of valuable materials, and algae ponds provide an important technique for advanced wastewater purification. 相似文献
54.
The effect of different concentrations, viz. 0.01, 0.001 and 0.0001 ppm of methyl mercuric chloride on survival, growth behaviour and chlorophyll content of Chlorella vulgaris has been studied under various environmental conditions. Methyl mercury at 0.01 ppm is 100% toxic to the test alga. At a sublethal (0.001 ppm) dose of CH3HgCl, Chlorophyll a was more inhibited than Chlorophyll b. Toxicity was found to be very much under the influence of pH as at acid pH growth is highly reduced by a sublethal concentration, whereas the same concentration does not have an inhibitory influence in the alkaline range of pH. Eutrophic waters seem to reduce the heavy metal toxicity in general. 相似文献
55.
L. C. Rai 《洁净——土壤、空气、水》1980,8(6):561-567
A general survey of the various polluted environs e.g., (i) The cement factory, (ii) The aluminium factory; (iii) The fertilizer factory; (iv) Dairy waste, and (v) Township sewage, has been made with a view to studying the distribution, dominance and diversity of algal communities growing therein. This study has revealed that the algal community structure along with physico-chemical factors can be best used for the assessment of water pollution. Oscillatoria has been found dominant in all those polluted environs containing a high amount of nitrogen and phosphorus, thereby indicating that this alga is tolerant to organic pollution. However, a sparse vegetation of algae as recorded in other situations is indicative of either a poor nutrient status of the habitat or the presence of some growth inhibitory substances. 相似文献
56.
Electrical conductivity, σ, of six ultramafic rocks (garnet-bearing peridotites and an eclogite) has been investigated in the temperature range 670–1820 K under known environment. Between 670 and ~1320 K σ increases with 1/T monotonically, first slowly, by 1–1.5 orders of magnitude. Above 1320 K σ increases sharply; an increase of 3–4 orders of magnitude is observed between 1320 and 1670 K. In the same temperature range the σ values for all the six rocks fall within 1.5 orders of magnitude, the lowest conductivity being for a spinel lherzolite. The range of σ values is narrowed at higher temperatures. The differences in σ values above 1470 K may be explained on the basis of varying degrees of partial melting in the rocks. Over the entire range of temperature, the σ values for the ultramafic rocks are lower than those reported for basalts but higher (by 1–2 orders of magnitude) than those for single-crystal olivines. 相似文献
57.
P. Rai F. L. Imperial President 《Fragblast: International Journal for Blasting and Fragmentation》2005,9(4):219-232
The present research paper is a case study in a limestone quarry in the Philippines where major problems in terms of improper fragmentation (large boulder count and poor pay-loader performance), poor wall control, and poor heave characteristics of the muck pile were witnessed. The paper highlights the role of modifying the firing pattern and, also, the application of stemming plug without incorporating any change in the stemming column length due to which incremental expansion in the mesh area could be implemented to determine the optimum mesh area. The optimum mesh area, due to the said changes in the blast design, was considerably larger in comparison to the pre-existing mesh area. The study has also highlighted the importance of indirect methods for characterizing and precisely adjudging the blast performance. 相似文献
58.
The Dhanbad district in Jharkhand faces acute water scarcity and is chronically drought-prone. The groundwater resources in
the area have not been fully exploited. The present study was undertaken to evaluate the groundwater prospective zones. Landsat-5
Multi Spectral Scanner (MSS) data of band 2 and band 4 and false colour composite (FCC) of band 2, 3, 4 were interpreted visually
to differentiate different hydromorphogeological units and to delineate the major trends of lineaments. The different geomorphic
features identified are linear ridges, residual hills, and pediplain, buried pediment and dissected pediplain, besides lineaments.
The study shows that the pediplain and buried pediments are promising zones for groundwater prospecting. The occurrence and
movement of groundwater is restricted to the unconsolidated material, weathered and fractured rocks. For the selection of
tube well sites, geoelectrical resistivity investigations have been carried out at the sites, which were found suitable based
on hydrogeomorphological and hydrogeological studies. Twenty-six Vertical Electrical Soundings (VES) have been carried out
by using Schlumberger electrode configuration, which have brought out 3 to 7 layered sub-surface layers. The resistivity of
water-bearing weathered/fractured rocks varies from 120–150 ohm m. The integrated studies have revealed that the blue colour
zones are most promising for groundwater exploration and dug wells may be dug up to depths of 30±5m. 相似文献
59.
We analysed local earthquake waveforms recorded on a broad-band seismic network in northwestern Himalayas to compute the intrinsic and scattered attenuation parameters from coda waves. Similar to other tectonically active and heterogeneous regions, attenuation-frequency relation for western Himalaya is Q −1 c = (113 ± 7) f (1.01±0.05) where Qc is the coda Q parameter. Intrinsic ( Q −1 i ) and scattering ( Q −1 s ) attenuations was separated using Qc and direct S -wave Q data ( Qd ) . It is observed that estimated Q −1 c is close to Q −1 i and both of them are much larger than Q −1 s suggesting that coda decay is predominantly caused by intrinsic attenuation. At higher frequencies, both the attenuation parameters Qc and, Qd are similar indicating that coda is predominantly composed of back-scattered S waves at these frequencies. 相似文献
60.
S. S. Rai D. Srinagesh P. V. S. S. Rajagopala Sarma 《Journal of Earth System Science》1996,105(4):441-450
Earthquake hypocenters and travel time residuals have been analysed to constrain the geometry and physical state of the subducted
Indian plate in the Indo-Burmese convergence zone. A critical analysis of earthquake hypocenters reveals the existence of
a non-uniform Benioff zone, progressively shortening from north to south. The deepest level of seismicity is observed beneath
the Naga hills (160 km) followed by that under the Chin hills (120 km) and Arakan-Yoma ranges (80 km). The region seems to
be devoid of moderate sized shallow (< 40 km) earthquakes. Differential travel time residuals from pairs of shallow and intermediate
depth earthquakes recorded at teleseismic distances show significantly faster travel time (up to l.2s) in the north-northeast
and south-southwest azimuths, whilst slower arrivals (1.2 to 1.5 s) are recorded in the transverse direction. This observation
points to the presence of a high velocity slab possibly linked to the subduction of the Indian oceanic lithosphere. 相似文献