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31.
Colin Neal Nils Christophersen Richard Neale Christopher J. Smith Paul G. Whitehead Brian Reynolds 《水文研究》1988,2(2):155-165
Variations in the concentration of Cl in rainfall and stream runoff are presented for two catchments in the Hafren forest of mid-Wales, Great Britain. Despite the large fluctuations in rainfall concentrations, Cl in the streamwater remains relatively constant. Using the two-reservoir Birkenes model, an attempt was made to simulate observed Cl in streamwater. The original model was unable to reproduce the observations and several modifications are suggested to provide better simulations. The resulting model is not the only one capable of reproducing the observations; other hydrochemical models will most probably also achieve this although emphasis will in each case be placed on different aspects. In this paper, it is suggested that the stochastic properties of water movement and chemical processes can account for the streamwater chemistry responses observed. On the catchment scale these processes will lead to an apparently deterministic behaviour that may well be described by simple relationships. 相似文献
32.
Nils Aall Barricelli 《Earth, Moon, and Planets》1988,43(3):307-309
Phobos' proximity to the Roche limit, and some of its consequences deserving attention by the Phobos' mission, are the subject of this note. 相似文献
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The apparent ionization constants for silicic acid, k1 and k2, and the ionic product of water, kw, have been determined in 0.05, 0.1, 0.2, 0.4 and 2.0 M Na(CI) media at 25°C. The medium dependence of these constants was found to fit equations of the form where K1 is the ionization constant in pure water, αi and bi are parameters of which bi has been adjusted to present data. The following results were obtained (αi, bi): pK1 = 9.84, (1.022, ?0.11); pK2 = 13.43, (2.044, ?0.20); and pKw = 14.01 (1.022, ?0.22). ki values are collected in Tables I and II. Attempts have been made to explain the medium dependence of k1 and k2 with weak sodium silicate complexing according to the equilibria giving k11 = 0.37M?1 and k21= 3.0M?1. However, these weak interactions cannot be interpreted unambiguously from potentiometric data at different 1-levels. Probably the medium dependence could equally well be expressed by variations in the activity coefficients.The measurements were performed as potentiometric titrations using a hydrogen electrode. The average number of OH- reacted per Si(OH)4, Z, has been varied within the limits 0 ? Z ? 1.1 and B1, the total concentration of Si(OH)4, between 0.001 M and 0.008 M. k1 was evaluated from experimental data with B ? 0.003 M, and k2 with B ? 0.008 M and Z ? 0.95. 相似文献
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39.
N. Ryde 《Astronomische Nachrichten》2010,331(4):433-448
In 2006 ESO Council authorized a Phase B study of a European AO‐telescope with a 42 m segmented primary with a 5‐mirror design, the E‐ELT. Several reports and working groups have already presented science cases for an E‐ELT, specifically exploiting the new capabilities of such a large telescope. One of the aims of the design has been to find a balance in the performances between an E‐ELT and the James Webb Space Telescope, JWST. Apart from the larger photon‐collecting area, the strengths of the former is the higher attainable spatial and spectral resolutions. The E‐ELT AO system will have an optimal performance in the near‐IR, which makes it specially advantageous. High‐resolution spectroscopy in the near‐infrared has, however, not been discussed much. This paper aims at filling that gap, by specifically discussing spectroscopy of stellar (mainly red giant), photospheric abundances. Based on studies in the literature of stellar abundances, at the needed medium to high spectral resolutions in the near‐infrared (0.8–2.4 μm), I will try to extrapolate published results to the performance of the E‐ELT and explore what could be done at the E‐ELT in this field. A discussion on what instrument characteristics that would be needed for stellar abundance analyses in the near‐IR will be given (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
40.
Predicting riverine dissolved silica fluxes to coastal zones from a hyperactive region and analysis of their first-order controls 总被引:2,自引:1,他引:1
Jens Hartmann Nils Jansen Hans H. Dürr Akira Harashima Kenji Okubo Stephan Kempe 《International Journal of Earth Sciences》2010,99(1):207-230
Silicate weathering and resulting transport of dissolved matter influence the global carbon cycle in two ways. First by the
uptake of atmospheric/soil CO2 and second by providing the oceanic ecosystems via the fluvial systems with the nutrient dissolved silica (DSi). Previous
work suggests that regions dominated by volcanics are hyperactive or even “hot spots” concerning DSi-mobilization. Here, we
present a new approach for predicting DSi-fluxes to coastal zones, emphasizing “first-order” controlling factors (lithology,
runoff, relief, land cover and temperature). This approach is applied to the Japanese Archipelago, a region characterized
by a high percentage of volcanics (29.1% of surface area). The presented DSi-flux model is based on data of 516 catchments,
covering approximately 56.7% of the area of the Japanese Archipelago. The spatial distribution of lithology—one of the most
important first order controls—is taken from a new high resolution map of Japan. Results show that the Japanese Archipelago
is a hyperactive region with a DSi-yield 6.6 times higher than the world average of 3.3 t SiO2 km−2 a−1, but with large regional variations. Approximately 10% of its area exceeds 10 times the world average DSi-yield. Slope constitutes
another important controlling factor on DSi-fluxes besides lithology and runoff, and can exceed the influence of runoff on
DSi-yields. Even though the monitored area on the Japanese Archipelago stretches from about 31° to 46°N, temperature is not
identified as a significant first-order model variable. This may be due to the fact that slope, runoff and lithology are correlated
with temperature due to regional settings of the Archipelago, and temperature information is substituted to a certain extent
by these factors. Land cover data also do not improve the prediction model. This may partly be attributed to misinterpreted
land cover information from satellite images. Implications of results for Earth System and global carbon cycle modeling are
discussed. 相似文献