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181.
Evolution of the Upper Rhone River discharge and suspended sediment load during the last 80 years and some implications for Lake Geneva 总被引:1,自引:0,他引:1
182.
S. Siegesmund K. Ullemeyer T. Weiss E. K. Tschegg 《International Journal of Earth Sciences》2000,89(1):170-182
Marbles as building stones as well as in their natural environments show complex weathering phenomena. The most important
damage scenario is based on the highly anisotropic thermal expansion coefficient α of calcite, i.e. extreme expansion parallel and contraction normal to the crystallographic c-axis. Therefore, the rock fabric
and especially the lattice-preferred orientation (texture) of calcite and/or dolomite as the predominant mineral phases in
marbles have a significant influence on the mechanical weathering. The textures of marbles from five different locations vary
from a more or less perfect prolate to moderate oblate shape of the [006] pole figure tensor. Accordingly, the texture-derived
bulk thermal dilatation anisotropy covers a broad range from –0.048 to 0.680. The modelled thermal dilatations correlate with
those obtained from experimental measurements. The difference in magnitude is basically explained by the microcrack fabrics
which was not considered in the computations. All samples show a deterioration due to thermal treatment regardless of the
strength of texture. The directional dependence of (a) the total magnitude of the thermal dilatation coefficient and (b) of
the residual strain is highest in marbles with a strong texture, whereas the Carrara marble with a weak texture exhibits a
uniform crack formation. The progressive loss of cohesion along grain boundaries due to dilatancy may serve as an example
for the initial stage of physical weathering.
Received: 10 February 1999 / Accepted: 16 October 1999 相似文献
183.
To evaluate the texture-controlled part on the thermally induced degradation of marbles, the anisotropic thermal dilatation was calculated from texture analyses of four exemplary samples from the Carrara area in Italy and compared to experimentally measured dilatation coefficients. The thermal dilatation as determined in the experiment is controlled by an intrinsic part (anisotropic single crystal properties and texture) and an extrinsic part (e.g. thermally induced microcracks). As expected from theoretical calculations, there is a correlation between the strongest dilatation and the c-axis maxima and the weakest dilatation and the a-axis maxima according to the single crystal data of calcite. However, a quantitative correlation could not be established. Obviously, other fabric parameters like the grain size, grain shape anisotropies, grain boundary geometries and microcrack formation during heating modify the texture-controlled part significantly. After thermal treatment up to 130°C, all samples show a residual strain. However, the magnitude and directional dependence is remarkably different and is unequivocally correlated to both the microstructure and the texture. Since the number of parameters controlling the physical weathering is very large, a comprehensive quantification of fabrics is indispensible for the understanding of thermally controlled degradation processes of physical weathering in marbles. 相似文献
184.
Chemical Separation and Isotopic Variations of Cu and Zn From Five Geological Reference Materials 总被引:6,自引:0,他引:6
John B. Chapman Thomas F.D. Mason Dominik J. Weiss Barry J. Coles Jamie J. Wilkinson 《Geostandards and Geoanalytical Research》2006,30(1):5-16
This paper presents an adapted anion exchange column chemistry protocol which allowed separation of high-purity fractions of Cu and Zn from geological materials. Isobaric and non-spectral interferences were virtually eliminated for consequent multiple-collector ICP-MS analysis of the isotopic composition of these metals. The procedure achieved ∼ 100% recoveries, thus ensuring the absence of column-induced isotopic fractionation. By employing these techniques, we report isotopic analyses for Cu and Zn from five geological reference materials: BCR-027 blende ore (BCR), δ65 Cu = 0.52 ± 0.15‰ (n = 10) and δ66 Zn = 0.33 ± 0.07‰ (n = 8); BCR-030 calcined calamine ore (BCR), δ66 Zn = -0.06 ± 0.09‰ (n = 8); BCR-1 basalt (USGS), δ66 Zn = 0.29 ± 0.12‰ (n = 8); NOD-P-1 manganese nodule (USGS), δ65 Cu = 0.46 ± 0.08‰ (n = 10) and δ66 Zn = 0.78 ± 0.09‰ (n = 9); SU-1 Cu-Co ore (CCRMP), δ65 Cu = -0.018 ± 0.08‰ (n = 10) and δ66 Zn = 0.13 ± 0.17‰ (n = 6). All uncertainties are ± 2s; copper isotope ratios are reported relative to NIST SRM-976, and zinc isotope ratios relative to the Lyon-group Johnson Matthey metal (batch 3-0749 L) solution, JMC Zn. These values agree well with the limited data previously published, and with results reported for similar natural sample types. Samples were measured using a GVi IsoProbe MC-ICP-MS, based at the Natural History Museum, London. Long-term measurement reproducibility has been assessed by repeat analyses of both single element and complex matrix samples, and was commonly better than ± 0.07‰ for both δ66 Zn and δ65 Cu. 相似文献
185.
Andrei A. Andreev Lyudmila S. Shumilovskikh Larisa A. Savelieva Raphael Gromig Grigory B. Fedorov Anna Ludikova Bernd Wagner Volker Wennrich Dominik Brill Martin Melles 《Boreas: An International Journal of Quaternary Research》2019,48(2):377-386
Lake Ladoga hosts preglacial sediments, although the Eurasian ice sheet overrode the area during the LGM. These sediments were first discovered by a seismic survey and are investigated using a 22.75‐m‐long core. Its upper 13.30 m comprise Holocene and Lateglacial sediments separated from the lower 11.45 m of preglacial sediments by a hiatus. They consist of highly terrigenous lacustrine sediments, which according to OSL dating, were deposited during an early stage of the last ice age (MIS 5). The palynological data allow a first reconstruction of the Early Weichselian environmental history for northwestern Russia. Birch and alder forests with broad‐leaved taxa dominated during MIS 5d (c. 118–113 ka), suggesting a climate more favourable than in the Holocene. A high content of well‐sorted sands and poorly preserved palynomorphs indicates a shallow‐water environment at least temporarily. More fine‐grained sediments and better preserved organic remains suggest deeper water environments at the core location during MIS 5c (c. 113–88 ka). Pine and spruce became dominant, while broad‐leaved taxa started to disappear, especially after c. 90 ka, pointing to a gradual climate cooling. An increase in open herb‐dominated habitats at the beginning of MIS 5b (c. 88–86 ka) reflects a colder and dryer climate. However, later (c. 86–82 ka) pine and spruce again became more common. Birch and alder forests dominated in the area c. 82–80 ka (beginning of MIS 5a). Although open treeless habitats also became more common at this time, a slight increase in hazel may point to somewhat warmer climate conditions coinciding with the beginning of MIS 5a. The studied sediments also contain numerous remains of freshwater algae and cysts of marine and brackish‐water dinoflagellates and acritarchs documenting that the present lake basin was part of a brackish‐water basin during the Early Weichselian, probably as a gulf of the Pre‐Baltic Sea. 相似文献
186.
As of August 2007, over 5000 near-earth-objects (NEO) have been discovered. Some already represent a potential danger to the Earth while others might become hazards in the future. The Planetary Society organised in 2007 the “Apophis Mission Design Competition” in response to this potential threat with the objective to identify promising concepts to track NEOs; the asteroid 99942 Apophis was taken as the study case. This paper describes the “Houyi” proposal which was evaluated by the competition jury as an innovative approach to this problem. Instead of launching a large satellite for NEO tracking, this novel concept proposes a miniaturized satellite that is piggybacked onto a larger (scientific) mission. Such mission design would drastically reduce the costs for NEO surveillance. The presented scenario uses the ESA’s SOLO mission as a design baseline for the piggyback option. This paper summarizes the architecture of this CubeSat towards Apophis and extends the previous study by focusing on the feasibility of a piggybacked mission in terms of propulsion requirements. 相似文献
187.
Approximation problems on the rotation group SO(3) naturally arise in various fields, like crystallography, chemistry, and biology. For example, in crystallographic texture
analysis one is confronted with the problem of evaluating so-called orientation density functions (ODFs). In many situations
one only has a finite number of measurements at scattered sampling nodes. In order to reconstruct ODFs over all rotations,
so-called Marcinkiewicz–Zygmund inequalities on the rotation group are an important tool. These inequalities provide norm
equivalences between polynomials on SO(3) and their sample values. Recently shown equivalences depend on a density parameter of the sampling set and the proven
inequalities hold true for polynomials on SO(3) whose degree does not exceed an upper bound which is determined by this density parameter. In this paper, we show that
we can enlarge this upper bound for the polynomial degree significantly if we are satisfied by such norm equivalences that
hold with a given probability only. Moreover, we show that there are fixed sampling sets for which we get probabilistic Marcinkiewicz–Zygmund
inequalities that hold for polynomials on SO(3) of all degrees. 相似文献
188.
We present and apply a simple bottom–up model for estimating non-energy use of fossil fuels and resulting CO2 (carbon dioxide) emissions. We apply this model for the year 2000: (1) to the world as a whole, (2) to the aggregate of Annex I countries and non-Annex I countries, and (3) to the ten non-Annex I countries with the highest consumption of fossil fuels for non-energy purposes. We find that worldwide non-energy use is equivalent to 1,670 ± 120 Mt (megatonnes) CO2 and leads to 700 ± 90 Mt CO2 emissions. Around 75% of non-energy use emissions is related to industrial processes. The remainder is attributed to the emission source categories of solvent and other product use, agriculture, and waste. Annex I countries account for 51% (360 ± 50 Mt CO2) and non-Annex I countries for 49% (340 ± 70 Mt CO2) of worldwide non-energy use emissions. Among non-Annex I countries, China is by far the largest emitter of non-energy use emissions (122 ± 18 Mt CO2). Our research deepens the understanding of non-energy use and related CO2 emissions in countries for which detailed emission inventories do not yet exist. Despite existing model uncertainties, we recommend NEAT-SIMP to inventory experts for preparing correct and complete non-energy use emission estimates for any country in the world. 相似文献
189.
Y. Tsapras R. Street K. Horne C. Snodgrass M. Dominik A. Allan I. Steele D.M. Bramich E.S. Saunders N. Rattenbury C. Mottram S. Fraser N. Clay M. Burgdorf M. Bode T.A. Lister E. Hawkins J.P. Beaulieu P. Fouqu M. Albrow J. Menzies A. Cassan D. Dominis‐Prester 《Astronomische Nachrichten》2009,330(1):4-11
RoboNet‐II uses a global network of robotic telescopes to perform follow‐up observations of microlensing events in the Galactic Bulge. The current network consists of three 2 m telescopes located in Hawaii and Australia (owned by Las Cumbres Observatory) and the Canary Islands (owned by Liverpool John Moores University). In future years the network will be expanded by deploying clusters of 1 m telescopes in other suitable locations. A principal scientific aim of the RoboNet‐II project is the detection of cool extra‐solar planets by the method of gravitational microlensing. These detections will provide crucial constraints to models of planetary formation and orbital migration. RoboNet‐II acts in coordination with the PLANET microlensing follow‐up network and uses an optimization algorithm (“web‐PLOP”) to select the targets and a distributed scheduling paradigm (eSTAR) to execute the observations. Continuous automated assessment of the observations and anomaly detection is provided by the ARTEMiS system (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
190.
M. Dominik † 《Monthly notices of the Royal Astronomical Society》2009,393(3):816-821
Some of the difficulties in determining the underlying physical properties that are relevant for observed anomalies in microlensing light curves, such as the mass and separation of extrasolar planets orbiting the lens star, or the relative source–lens parallax, are already anchored in factors that limit the amount of information available from ordinary microlensing events and in the way these are being parametrized. Moreover, a real-time detection of deviations from an ordinary light curve while these are still in progress can only be done against a known model of the latter, and such is also required for properly prioritizing ongoing events for monitoring in order to maximize scientific returns. Despite the fact that ordinary microlensing light curves are described by an analytic function that only involves a handful of parameters, modelling these is far less trivial than one might be tempted to think. A well-known degeneracy for small impacts, and another one for the initial rise of an event, makes an interprediction of different phases impossible, while in order to determine a complete set of model parameters, the fundamental characteristics of all these phases need to be properly assessed. While it is found that the wing of the light curve provides valuable information about the time-scale that absorbs the physical properties, the peak flux of the event can be meaningfully predicted only after about a third of the total magnification has been reached. Parametrizations based on observable features not only ease modelling by bringing the covariance matrix close to diagonal form, but also allow good predictions of the measured flux without the need to determine all parameters accurately. Campaigns intending to infer planet populations from observed microlensing events need to invest some fraction of the available time into acquiring data that allow to properly determine the magnification function. 相似文献