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51.
Soils can be best compacted by repeated shearing. The strain amplitude plays an important role for the maximum compaction that can be reached. Experimental evidence emphasizes a vital impact of simultaneous multidirectional shear loading on the rate and magnitude of soil compaction. Two different vibrocompaction methods were analysed by the numerical simulations in the light of these findings. In an elastic finite element (FE) analysis, strain paths were determined. A strain amplitude‐dependent stiffness at small strains was introduced by multiple runs of the FE calculation to reach an appropriate stiffness for particular distances from the vibrator. Subsequently, the obtained strain paths were used to control single element simulations using hypoplasticity with intergranular strains. The calculated compaction profiles show three zones known from practical evidence: a limited compaction close to the vibrator, a zone of maximum compaction and a non‐densified zone remote from the vibrator. The deep vibrator produces a faster compaction than the top vibrator, especially in the more distant zone. The more efficient work of the deep vibrator can be attributed to a more general multidirectional shearing. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
52.
The paper analyses complex hydrological behaviour of Skradinski Buk, the tufa waterfall, formed on the downstream part of the Krka River located in the coastal part of the Croatian Dinaric karst. This waterfall is the central point of the Krka National Park (KNP) proclaimed in 1985. Skradinski Buk is the seventh, final and the largest tufa barrier on the Krka River. Morphology of Skradinski Buk is composed of 17 unevenly distributed steps and dozens of small depressions. Natural waterfall morphology strongly influenced the complex waterfall hydrological regime. Additionally, hydrological regime is disturbed by the operation of the hydroelectric power plant (HEPP) Jaruga. This paper analyses characteristic (minimum, mean, maximum) annual water levels and discharges monitored at two hydrological stations (Skradinski Buk Gornji-SBG and Nacionalni Park-NP). SBG controls the inflow of water into the waterfall, while the NP is established in order to control the use of water from the HEPP Jaruga operation. It is concluded that the HEPP Jaruga does not comply with the agreement signed between the KNP and the HEPP Jaruga. The goal of the paper is to give detailed hydrological analysis of the Skradinski Buk, which should play the crucial role in the protection of this wonderful and very vulnerable phenomenon. 相似文献
53.
Rossano Piazza Ana Carolina Ruiz-Fernández Mauro Frignani Roberta Zangrando Luca Giorgio Bellucci Ivo Moret Federico Páez-Osuna 《Environmental Geology》2008,54(7):1537-1545
Concentrations of polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) were measured in 13 surficial
sediment samples collected at three lacustrine locations in the surroundings of Mexico City and four coastal areas of the
States of Sinaloa, Sonora, Oaxaca and Veracruz. Total PCB concentrations span the interval 3.18–621 ng g−1. The highest values (63.7–621 ng g−1) were found in Mexico City, which is a highly anthropogenically impacted area, whereas low concentrations (3.18–12.9 ng g−1) were characteristic of seven places, some of them subject to intense hydrodynamics. In these latter cases, values increase
by 18–73 times if normalised against the fine fraction (silt plus clay) content in sediment. Two samples from Mexico City
exceed the ERM (Effect Range Median) guidelines and are likely to cause adverse effects. Samples contain only lower chlorinated
PCBs (mainly 2-, 3- and 4-CB), thus suggesting that the most used PCB commercial mixture was Aroclor 1242. The homologue composition
of the sample taken close to the nuclear power plant of Laguna Verde is identical to this commercial mixture. PAHs in the
same samples have relatively low concentrations (14.9–287 ng g−1), well below ERL (Effect Range Low) guidelines. The composition of PAH mixtures accounts for the influence of both petrogenic
and pyrolitic sources, with these latter prevailing at some places in Mexico City. 相似文献
54.
55.
Elizabeth M. Green Biqing For Elaina A. Hyde Ivo R. Seitenzahl Keith Callerame Brooke A. White Corryn N. Young Christopher S. Huff Jay Mills Justin D.R. Steinfadt 《Astrophysics and Space Science》2004,291(3-4):267-274
Preliminary results are presented from two ongoing complementary surveys intended to investigate the nature and characteristics of the optically invisible secondaries in post-common envelope subdwarf B (sdB) binary stars. We obtain precise radial velocities to derive periods and minimum companion masses for bright field sdB stars. These data are combined with light curves to search for eclipses, reflection effects, or ellipsoidal variations. We emphasize the importance of using complete unbiased samples, without which it will not be possible to understand the details of the multiple processes that produce these stars. It remains true that all known secondary companions in short-period sdB binaries are nearly invisible, thus they must be either low mass main sequence (MS) stars or compact objects, e.g., white dwarfs. In our small, nearly-complete sample, white dwarf secondaries outnumber MS secondaries by about a factor of five. Known MS masses in short-period sdB binaries are all surprisingly low, indicating a possible bimodal mass distribution for all MS secondaries in sdB binaries. 相似文献
56.
Cattari Serena Calderoni Bruno Cali Ivo Camata Guido de Miranda Stefano Magenes Guido Milani Gabriele Saetta Anna 《Bulletin of Earthquake Engineering》2022,20(4):1939-1997
Bulletin of Earthquake Engineering - This paper provides a comphrensive review of the critical aspects of nonlinear modeling for evaluating the seismic response of masonry structures, emphasizing... 相似文献
57.
58.
Johannes?Horak Ivo?Schmerold Kurt?Wimmer Günther?SchaubergerEmail authorView authors OrcID profile 《Theoretical and Applied Climatology》2017,130(1-2):107-118
In vehicles that are parked, no ventilation and/or air conditioning takes place. If a vehicle is exposed to direct solar radiation, an immediate temperature rise occurs. The high cabin air temperature can threaten children and animals that are left unattended in vehicles. In the USA, lethal heat strokes cause a mean death rate of 37 children per year. In addition, temperature-sensitive goods (e.g. drugs in ambulances and veterinary vehicles) can be adversely affected by high temperatures. To calculate the rise of the cabin air temperature, a dynamic model was developed that is driven by only three parameters, available at standard meteorological stations: air temperature, global radiation and wind velocity. The transition from the initial temperature to the constant equilibrium temperature depends strongly on the configuration of the vehicle, more specifically on insulation, window area and transmission of the glass, as well as on the meteorological conditions. The comparison of the model with empirical data showed good agreement. The model output can be applied to assess the heat load of children and animals as well as temperature-sensitive goods, which are transported and/or stored in a vehicle. 相似文献
59.
Ramos Claudete Gindri dos Santos de Medeiros Diego Gomez Leandro Oliveira Luis Felipe Silva Schneider Ivo André Homrich Kautzmann Rubens Muller 《Natural Resources Research》2020,29(3):1583-1600
Natural Resources Research - This study was focused on physical, petrographical, mineralogical, and chemical characterization of a volcanic-rock mining by-product (dacite rock), as well as on... 相似文献
60.
The aim of this paper is to analyse hydrological measurements obtained from Blue Lake located near the town of Imotski (Croatia), during the period from 6 November 2009 at 10:26 h to 4 September 2010 at 03:26 h (7230 h or 302 days). The water depth, water temperature and electrical conductivity of the water were continuously measured during this period. The measurements were obtained with a CTD DIVER (Schlumberger Water Services). The instrument was fixed at the bottom of Blue Lake, which means that all the measured data refer to a single point of measurement. The data represent the first systematic and continuous monitoring of the hydrological parameters of this fascinating karst phenomenon. The hydrological analysis also involved daily rainfall data and daily mean air temperatures recorded at the nearby Imotski meteorological station. The rate of water level rise and fall and the hourly and daily average inflow and outflow into and from the lake were calculated using the available data. The analysis led to the conclusion that Blue Lake is mainly recharged by water coming from the karst aquifer, the dimensions and the characteristics of which have not yet been adequately studied. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献