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531.
532.
Results of the estimation of azimuth-dependent phase center variations (PCVs) of GPS satellite antennas using global GPS data
are presented. Significant variations of up to ±3–4 mm that are demonstrated show excellent repeatability over eight years.
The application of the azimuthal PCVs besides the nadir-dependent ones will lead to a further reduction in systematic antenna
effects. In addition, the paper focuses on the benefit of a possible transition from relative to absolute PCVs. Apart from
systematic changes in the global station coordinates, one can expect the GPS results to be less dependent on the elevation
cut-off angle. This, together with the significant reduction of tropospheric zenith delay biases between GPS and VLBI, stands
for an important step toward more consistency between different space geodetic techniques. 相似文献
533.
Five heavy rainfall events were investigated with radar and raingauge data. Special attention was paid to quality check and adjustment of radar data. Attenuation effects could be observed on both, C-Band and on X-Band radar. Adjustment of radar data to raingauge values turned out to be difficult in the vicinity of heavy local rain cells. Four adjustment methods were analysed and radar data from different radar stations were compared. As a further result of this project, the spatial extent of the precipitation fields was identified by adjusted radar data and compared to raingauge data. For each rainfall event, radar derived accumulated rainfall images and catchment time series were produced. 相似文献
534.
535.
Bruno Merz Jana Friedrich Markus Disse Jochen Schwarz Johann G. Goldammer Jochen Wächter 《Natural Hazards》2006,38(1-2):3-20
The German Research Network for Natural Disasters (DFNK) linked 15 partners with scientific expertise in the field of natural
hazards. Main objectives were the development and provision of the scientific fundamentals for an advanced risk management
of important natural disasters in Germany, i.e., floods, earthquakes, storms and wildland fires. This included risk analyses,
the development of information systems for supporting disaster management, and recommendations for risk reduction measures.
This paper gives an overview of DFNK and summarises its experiences concerning multidisciplinarity and user-orientation. It
illustrates the concept of risk chains, causally linking the different processes from hazard to risk. The step from hazard
to risk requires interdisciplinary research teams. The experiences show that integrative concepts allow results not achievable
with mono-disciplinary approaches. Integrative approaches pave the way to harmonised safety considerations taking into account
the different hazards in a region within a common framework. User-orientation, policy advice and development of operational
tools are key issues of disaster research. The experiences of DFNK illustrate the limitations of a research network in bridging
the gap between research and application within rather short-term projects. Successful cooperation with users could be established
by those activities where, at the beginning of the project, a user was identified who had a strong interest in solving an
urgent problem. 相似文献
536.
Assessment of Discharge through a Dike Breach and Simulation of Flood Wave Propagation 总被引:2,自引:0,他引:2
This paper presents a simple and fast method to calculate flow through a dike breach. The approach was based on two-dimensional
numerical simulations of idealized dike breakages at straight river-sections. As a result, computation of discharge through
a breach can be achieved by use of the new developed formula (denoted as dike break formula). Furthermore, a methodology that combines one-dimensional hydrodynamic modelling, the dike break formula and a simple GIS-based
method to estimate inundation areas is described. This fast and easy-to-handle tool can be utilized for near real-time forecasting
or evacuation decisions. Detailed predictions were made for a number of flood and dike break scenarios at the River Rhine
to prove the accuracy of the new method compared with two-dimensional numerical models. 相似文献
537.
Peter Steigenberger Volker Tesmer Manuela Krügel Daniela Thaller Ralf Schmid Sibylle Vey Markus Rothacher 《Journal of Geodesy》2007,81(6-8):503-514
Troposphere parameters estimated from space-geodetic techniques, like the Global Positioning System (GPS) or Very Long Baseline
Interferometry (VLBI), can be used to monitor the atmospheric water vapor content. Although the troposphere can only be monitored
at discrete locations, the distribution of the instruments, at least the GPS antennas, can be assumed to be quasi-global.
Critical in the data analysis are systematic effects within each single technique that significantly degrade the accuracy
and especially the long-term stability of the zenith delay determination. In this paper, consistent time-series of troposphere
zenith delays and gradients from homogeneously reprocessed GPS and VLBI solutions are compared for a time period of 11 years.
The homogeneity of these completely reprocessed time-series is essential to avoid misinterpretations due to individual model
changes. Co-located sites are used to investigate systematic effects and the long-term behavior of the two space-geodetic
techniques. Both techniques show common signals in the troposphere parameters at a very high level of precision. The biases
between the troposphere zenith delays are at the level of a few millimeters. On the other hand, long-term trends significantly
differ for the two techniques, preventing climatological interpretations at present. Tests assume these differences to be
due to mathematical artifacts such as different sampling rates and unmodeled semi-annual signals with varying amplitudes. 相似文献
538.
The contribution of the International VLBI Service for Geodesy and Astrometry (IVS) to the ITRF2005 (International Terrestrial
Reference Frame 2005) has been computed by the IVS Analysis Coordinator’s office at the Geodetic Institute of the University
of Bonn, Germany. For this purpose the IVS Analysis Centres (ACs) provided datum-free normal equation matrices in Solution
INdependent EXchange (SINEX) format for each 24 h observing session to be combined on a session-by-session basis by a stacking
procedure. In this process, common sets of parameters, transformed to identical reference epochs and a prioris, and especially representative relative weights have been taken into account for each session. In order to assess the quality
of the combined IVS files, Earth orientation parameters (EOPs) and scaling factors have been derived from the combined normal
equation matrices. The agreement of the EOPs of the combined normal equation matrices with those of the individual ACs in
terms of weighted root mean square (WRMS) is in the range of 50–60 μas for the two polar motion components and about 3 μs
for UT1−UTC. External comparisons with International GNSS Serive (IGS) polar motion components is at the level of 130–170 μas
and 21 μs/day for length of day (LOD). The scale of the terrestrial reference frame realized through the IVS SINEX files agrees
with ITRF2000 at the level of 0.2 ppb. 相似文献
539.
Christian Tueckmantel Silke Schmidt Markus Neisen Neven Georgiev Thorsten J. Nagel Nikolaus Froitzheim 《Swiss Journal of Geoscience》2008,101(1):295-310
The Rhodope Metamorphic Province represents the core of an Alpine orogen affected by strong syn- and postorogenic extension. We report evidence for multiple phases of extensional unroofing from the western border of the Rila Mountains in the lower Rila valley, SW Bulgaria. The most prominent structure is the Rila-Pastra Normal Fault (RPNF), a major extensional fault and shear zone of Eocene to Early Oligocene age. The fault zone includes, from base to top, mylonites, ultramylonites and cataclasites, indicating deformation under progressively decreasing temperature, from amphibolite-facies to low-temperature brittle deformation. It strikes E–W with a top-to-the-N-to NW-directed sense of shear. Basement rocks in the hanging wall and footwall both display amphibolite-facies conditions. The foliation of the hanging-wall gneisses, however, is discordantly cut by the fault, while the foliation of the footwall gneisses is seen to curve into parallelism with the fault when approaching it. Two ductile splays of the RPNF occur in the footwall, which are subparallel to the foliation of the surrounding gneisses and merge laterally into the mylonites of the main fault zone. The concordance between the foliation in the footwall and the RPNF suggests that deformation and cooling in the footwall occurred simultaneously with extensional shearing, while the hanging-wall gneisses had already been exhumed previously. The RPNF is associated with thick deposits of an Early Oligocene, syntectonic breccia on top of its hanging wall. Integrating our results with previous studies, we distinguish the following stages of extensional faulting: (1) Late Cretaceous NW–SE extension (Gabrov Dol Detachment), exhumation of the present day hanging wall of the RPNF; (2) Eocene to Early Oligocene NW–SE to N–S extension (RPNF); (3) Miocene to Pliocene E–W extension (Western Border Fault), formation of the Djerman Graben; (4) Holocene to recent N–S to NW–SE extension (Stob Fault), reactivating the SW part of the Western Border Fault. 相似文献
540.
Markus Bth 《Tectonophysics》1983,95(3-4)
On the basis of a newly published, revised earthquake catalogue for the Greek area, a study is made of its seismicity in terms of earthquake frequency and energy as functions of space, time and magnitude. In addition, attempts are made to estimate the maximum possible magnitudes as functions of space. The study is essentially a methodological experiment, with tectonophysical and engineering results. 相似文献