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991.
O. G. Epshtein A. G. Dlugach A. V. Starovoytov B. F. Romanyuk 《Lithology and Mineral Resources》2011,46(2):115-134
The areal geological-geophysical study of Quaternary sediments was carried out in two areas of the eastern Barents Sea (Central
Deep and Murmansk Bank). This communication is mainly dedicated to the results of seismoacoustic investigations. It has been
established that the Quaternary sequence unconformably overlying the pre-Cenozoic strata in the studied areas is as follows
(from bottom to top): marine-glaciomarine Late Glacial-Holocene sediments, massive diamictons (the main part of the section),
and glaciotectonites formed after the underlying Mesozoic unconsolidated sediments. The Pleistocene diamictons, origin of
which is still debatable, are the main studied object. They constitute two seismostratigraphic complexes (SSC). According
to the accepted stratigraphic subdivision, they are represented by the Upper Weichselian SSC III (Maximum Last Glaciation)
and Lower Weichselian SSC V (Middle Weichselian SSC IV is eroded here). Complexes SSC V and SSC III composed of till overlie
the older sediments with the exaration unconformity. Complex SSC V is preserved locally, while SSC III is characterized by
the regional distribution. Complex SSC III is universally enveloped unconformably without erosional surface by an acoustically
uniform thin-bedded member of Late Glacial-Holocene glaciomarine and marine sediments (SSC II+I). Unlike SSC V, SSC III demonstrates
lateral heterogeneity in both studied areas consisting of two seismofacies, one of which forms very specific acoustically
transparent bodies (ATBs). Sediments of SSC III avoided subsequent erosion. Therefore, their glacial nature is distinctly
reflected in the complex distribution of thickness and peculiar morphology of corresponding bodies. 相似文献
992.
R. Kerrich B. J. Fryer R. W. King L. M. Willmore E. van Hees 《Contributions to Mineralogy and Petrology》1987,97(2):156-168
Major structural discontinuities in the Abitibi greenstone belt acted as conduits for outgassing of the Archean crust, as reflected in fixation of a select group of lithophile elements including Si, C, K, Rb, Ba, Li, Cs, B and Pb, in metasomatized faults. For two of the largest structures, the Destor-Porcupine (DP) and Kirkland Lake — Cadillac (KC) fault zones 6×1015 g Si, 3×1015 g CO2 and 1015 g K were introduced into the faults during expulsion of an estimated 6×1018 g aqueous fluids. Strontium isotope ratios of tourmaline, piemontite, actinolite and scheelite mineral separates, characterized by Rb/Sr0.02, are concordant with respect to 87Sr/86Sr initial ratios over local sectors of the faults. The Sr isotope data record geographic variations which, from east to west on the KC fault is 0.7031–0.7041 (Val d'Or), 0.7008–0.7022 (Bourlemaque), 0.7017–0.7019 (Bousquet), 0.7029–0.7031 (Noranda), and 0.7013 to 0.7015 (Kirkland Lake). At Timmins, on the PD fault, 87Sr/86Sr initial ratios cluster at 0.7010 to 0.7020. Metasomatised fault zones are systematically more radiogenic than contiguous host lithologies, and imply a source reservoir (0.7010 to 0.7041) generally more radiogenic than the upper mantle at 2690 Ma (0.700±0.001), or contemporaneous volcanic rocks of mafic to ultramafic composition (0.700 to 0.7012). Whereas certain minerals are concordant and retentive, Rb-Sr isochrons based on suites of rocks at progressive intensities of metasomatism, have been systematically reset over an elpased time of 200 Ma after termination of outgassing, due to disturbance accompanying incremental displacements on structures.Carbon isotope compositions of ferroan dolomites in faults are tightly clustered along local fault sectors, but also display a marked provinciality: from east to west
13C=–6.0 to –8.5 (Malartic), –8.0 to –9.0 (Cadillac), –2.0 to –4.5 (Kirkland Lake), and –0.5 to –3.5 (Timmins). The observed provinciality of both
13C values and 87Sr/86Sr initial ratios is interpreted to reflect compositional heterogeneities in a radiogenic sialic crust and the green-stone belt supracrustal sequence, both of which supplied volatiles, magmas and lithophile elements to the fault structures during late stage transpressive tectonics. 相似文献
993.
994.
The brightness temperatures of the Microwave sensor MSMR (Multichannel Scanning Microwave Radiometer) launched in May 1999
onboard Indian Oceansat-1 IRS-P4 are used to develop a direct retrieval method for latent heat flux by multivariate regression
technique. The MSMR measures the microwave radiances at 8 channels at frequencies of 6.6, 10.7, 18 and 21 GHz at both vertical
and horizontal polarizations. It is found that the surface LHF (Latent Heat Flux) is sensitive to all the channels. The coefficients
were derived using the National Centre for Environmental Prediction (NCEP) reanalysis data of three months: July, September,
November of 1999. The NCEP daily analyzed latent heat fluxes and brightness temperatures observed by MSMR were used to derive
the coefficients. Validity of the derived coefficients was checked within situ observations over the Indian Ocean and with NCEP analyzed LHF for global points. The LHF derived directly from the MSMR brightness
temperature (Tb) yielded an accuracy of 35 watt/m2. LHF was also computed by applying bulk formula using the geophysical parameters extracted from MSMR. In this case the errors
were higher apparently due to the errors involved in derivation of the geophysical parameters. 相似文献
995.
V. Yu. Chevychelov A. A. Korneeva A. A. Virus Yu. B. Shapovalov 《Doklady Earth Sciences》2017,473(2):454-456
The solubility of H2O–CO2–Cl-containing fluids of various concentrations (0, 3, 10, and 23 wt % of HCl and from 0 to ~8–15 wt % of CO2) in dacite, phonolite, and rhyolite melts at 1000°C and 200 MPa was studied in experiments. It was shown that the Cl concentration in the melt increased substantially from rhyolite to phonolite and dacite (up to 0.25, 0.85, and 1.2 wt %, respectively). The introduction of CO2 into the system resulted in an increase in the Cl content in the melt composition by 20–25%. One may suppose that Cl reactivity in a fluid increases in the presence of CO2 to cause growth of the Cl content in the melt. The introduction of CO2 into the system considerably affects the content of H2O in aluminosilicate melts as well. Thus, the addition of CO2 decreases the H2O content in the melt by ~0.5–1.0 wt %. The decrease in the H2O content in an aluminosilicate melt is probably caused by fluid dilution with CO2 resulting in a decrease in the H2O mole fraction and fugacity in the fluid. 相似文献
996.
A. K. Pathak M. Sridhar Y. Harsha A. Markandeyulu B. V. S. N. Raju A. K. Chaturvedi 《Journal of the Geological Society of India》2017,89(6):675-678
Aravalli fold belt has witnessed major tectonism resulting in intense deformation and associated mafic magmatism. Recently acquired high resolution aeromagnetic data over central Aravalli fold belt brought out a conspicuous E-W trending magnetic anomaly extending for more than 35 km in length cutting across the whole succession of Aravalli Supergroup. This anomaly on ground is manifested as undeformed basic dyke intruding into metasediments of Aravalli Supergroup. The E-W trend and undeformed nature of these dykes suggest that they represent post Aravalli mafic magmatism which are emplaced sympathetic to the axial plane of F3 folding. 相似文献
997.
998.
B. URSIN 《Geophysical Prospecting》1982,30(5):569-579
The principles for ray-tracing and wavefront curvature calculations in a three-dimensional medium are reviewed. A new derivation of the transformation of the wavefront curvature matrix at an interface between two inhomogeneous media is given. The derivation is based on a Taylor series expansion of the ray refraction equation at the interface between two inhomogeneous media, and only elementary geometric arguments are used. The wave-front curvature transformation at the interface is obtained by neglecting all terms in the direction of the surface normal. With proper definition of the variables, the derivation is also valid for a reflected wave-front. A simplified transformation rule is derived for a reflected wave of the same type as the incident wave. 相似文献
999.
1000.