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991.
992.
The quenching rate kN2 of by N2 and the specific recombination rate α1D of O2+ leading to are re-examined in light of available laboratory and satellite data. Use of recent experimental values for the transition probabilities in a re-analysis of AE-C satellite 6300 Å airglow data results in a value for kN2 of 2.3 × 10?11 cm3s?1 at thermospheric temperatures, in excellent agreement with the laboratory measurements. This implies a value of JO2 = 1.5 × 10?6s?1 for the O2 photodissociation rate in the Schumann-Runge continuum. The specific recombination coefficient α1D = 2.1 × 10?7cm3s?1 is also in agreement with the laboratory value. Implications for the suggested reaction are discussed. 相似文献
993.
Brian H. Baker 《Journal of Volcanology and Geothermal Research》1976,1(4):387-388
994.
995.
The internal temperatures, heat fluxes, and rates of evolution of volcanic liquids for lunar models with initial radioactivities and temperatures that decrease going downward in the Moon are calculated. These conditions lead to a volcanism concentrated very early in lunar history even when other heat sources, e.g. melting due to accretion, are excluded. 相似文献
996.
997.
Jose Villanueva-Diaz David W. Stahle Brian H. Luckman Julian Cerano-Paredes Mathew D. Therrell Malcom K. Cleaveland Eladio Cornejo-Oviedo 《Climatic change》2007,83(1-2):117-131
The understanding of historic hydroclimatic variability is basic for planning proper management of limited water resources
in northeastern Mexico. The objective of this study was to develop a network of tree-ring chronologies to reconstruct hydroclimate
variability in northeastern Mexico and to analyze the influence of large-scale circulation patterns, such as ENSO. Precipitation
sensitive tree-ring chronologies of Douglas-fir were developed in mountain ranges of the Sierra Madre Oriental and used to
produce winter-spring precipitation reconstructions for central and southern Nuevo Leon, and southeastern Coahuila. The seasonal
winter-spring precipitation reconstructions are 342 years long (1659–2001) for Saltillo, Coahuila and 602 years long (1400–2002)
for central and southern Nuevo Leon. Both reconstructions show droughts in the 1810s, 1870s, 1890s, 1910s, and 1970s, and
wet periods in the 1770s, 1930s, 1960s, and 1980s. Prior to 1800s the reconstructions are less similar. The impact of ENSO
in northeastern Mexico (as measured by the Tropical Rainfall Index) indicated long-term instability of the Pacific equatorial
teleconnection. Atmospheric circulation systems coming from higher latitudes (cold fronts or `nortes’) and others developed
in the Gulf of Mexico (tropical storms, hurricanes) also influence the climatic conditions characterizing this region. The
recent development of new and longer tree-ring chronologies for the region will contribute to a better understanding of the
interannual and multidecadal climatic variability of northeastern Mexico. 相似文献
998.
Sahel Mahdavi Bahram Salehi Cecilia Moloney Weimin Huang Brian Brisco 《International Journal of Digital Earth》2018,11(7):703-729
Speckle degrades the radiometric quality of a Synthetic Aperture Radar (SAR) image. Previous methods for speckle reduction have used a fixed-size window for filtering the entire image. This, however, may not be effective for the entire image, as land covers of different sizes require different filtering windows. In this paper, a novel method is proposed by which each pixel in the image is filtered with a window appropriate for the size of object within it. The real in-phase and the imaginary quadrature components of the SAR images determine the best window size and the pixels in the intensity image are filtered using their own optimal windows. The proposed method is presented for both single- and multi-polarized SAR images, and the results of several common filters that were modified are presented. This approach is applied to two RADARSAT-2 images: one over San Francisco, California, USA and the other over St. John’s, Newfoundland and Labrador, Canada, producing results that were similar to, or outperformed, comparable filters while retaining details and suppressing speckle effectively. While the method was successful for single-look intensity data, it offers great potential for multi-look and amplitude data as well. 相似文献
999.
David B. Reeves Edward J. Chesney Ryan T. Munnelly Donald M. Baltz Brian D. Marx 《Estuaries and Coasts》2018,41(7):1835-1847
Oil and gas platforms (platforms) provide high-relief habitat in the northern Gulf of Mexico’s hypoxic zone that are important to associated fishes. Hypoxia develops near the bottom and reef-associated fishes utilize vertical structure in the well-oxygenated waters overlaying hypoxia. A video array was used to profile the water column and to estimate abundances and depth distributions of fishes before, during, and after summer hypoxia at platforms experiencing intense (seaward) and mild hypoxia (shoal). Gray snapper abundance increased at shoal platforms (10× greater after vs. before the hypoxia season), while abundance remained stable at seaward platforms. However, there was no significant relationship between gray snapper abundance and oxygen concentrations. Sheepshead, Atlantic spadefish, blue runner, and Atlantic bumper abundances varied throughout the summer, but there was no significant effect of hypoxia. Occupation of bottom waters by fishes was consistent throughout the study period at shoal platforms, but fishes were rarely observed in the bottom 3 m and congregated in the water immediately above the hypoxic layer when hypoxia was present at seaward platforms. Nevertheless, patterns of fish abundances were not driven by the presence or absence of hypoxia. The vertical dimension of platforms is a unique and key aspect of their ecological value, especially in the hypoxic zone, and should be considered for artificial reef management. 相似文献
1000.
Characterisation of a Natural Quartz Crystal as a Reference Material for Microanalytical Determination of Ti,Al, Li,Fe, Mn,Ga and Ge 总被引:2,自引:0,他引:2
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Andreas Audétat Dieter Garbe‐Schönberg Andreas Kronz Thomas Pettke Brian Rusk John J. Donovan Heather A. Lowers 《Geostandards and Geoanalytical Research》2015,39(2):171-184
A natural smoky quartz crystal from Shandong province, China, was characterised by laser ablation ICP‐MS, electron probe microanalysis (EPMA) and solution ICP‐MS to determine the concentration of twenty‐four trace and ultra trace elements. Our main focus was on Ti quantification because of the increased use of this element for titanium‐in‐quartz (TitaniQ) thermobarometry. Pieces of a uniform growth zone of 9 mm thickness within the quartz crystal were analysed in four different LA‐ICP‐MS laboratories, three EPMA laboratories and one solution‐ICP‐MS laboratory. The results reveal reproducible concentrations of Ti (57 ± 4 μg g?1), Al (154 ± 15 μg g?1), Li (30 ± 2 μg g?1), Fe (2.2 ± 0.3 μg g?1), Mn (0.34 ± 0.04 μg g?1), Ge (1.7 ± 0.2 μg g?1) and Ga (0.020 ± 0.002 μg g?1) and detectable, but less reproducible, concentrations of Be, B, Na, Cu, Zr, Sn and Pb. Concentrations of K, Ca, Sr, Mo, Ag, Sb, Ba and Au were below the limits of detection of all three techniques. The uncertainties on the average concentration determinations by multiple techniques and laboratories for Ti, Al, Li, Fe, Mn, Ga and Ge are low; hence, this quartz can serve as a reference material or a secondary reference material for microanalytical applications involving the quantification of trace elements in quartz. 相似文献