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81.
V. B. Titov 《Physical Oceanography》1992,3(2):131-139
Statistical characteristics and the parameters of the temporal variability of currents are analysed using data on current measurements conducted by five moored autonomous buoy stations over Bulgaria's shelf. Estimates of the specific contribution to the variability of synoptic (60%) and mesoscale (40%) oscillations are derived. The qualitative spectrum of the currents is defined, constituted by synoptic oscillations, short-period synoptic oscillations, inertial oscillations, and internal waves. Estimates of periods and oscillation amplitudes are also derived. The kinetic energy of the currents is calculated and the specific contribution of the energy of different-scale oscillations and their interrelations are determined.Translated by V. Puchkin. 相似文献
82.
V. B. Titov 《Physical Oceanography》1990,1(6):461-468
An anticyclonic mesoscale eddy is found using the current and temperature data obtained at six moorings near the eastern foot of the Mascarene Ridge (Southern Hemisphere). Its spatial parameters radius, depth of penetration, and direction of the vertical axis tilt are given. The volume of water transported by the eddy across its radial section is calculated. Numerical characteristics of the spatial-temporal variability of the current and temperature field in the eddy are obtained. The relative contributions of the variability of mesoscale, tidal and inertial, and high-frequency oscillations are estimated.Translated by Mikhail M. Trufanov. 相似文献
83.
Ultramicroscopic particles of biogenic appearance found in recent phosphorite nodules in diatomaceous oozes from the Namibian shelf are described. The particles are mostly represented by three varieties, namely, colloform, rounded, and elongated bacillary particles, which are disseminated over the rock or, more often, form aggregations of various shapes. The aggregations consist of particles of similar types though different in sizes (from fractions of a micrometer to a few micrometers). Mutual intergrowths are also encountered, as well as twins, rosettes, and ball-shaped aggregations of elongated particles resembling vugs of other crystals. These morphological features together with the results of microbiological studies of diatomaceous oozes, in which phosphorite nodules are formed, suggest a nonmicrobial origin of most of the biomorphic particles. 相似文献
84.
85.
Speleogenesis of Selected Caves beneath the Lunan Shilin and Caves of Fenglin Karst in Qiubei, Yunnan 总被引:1,自引:1,他引:1
Yunnan is famous for its attractive karst landscapes especially shilins, fengcong and fenglin. The development of caves beneath the shilins in the vicinity of Lunan is closely connected with the formation of shilins. Most of the waters percolating through shilins run through the caves beneath them and are responsible for their formation. The study of cave speleogenesis deepens knowledge about both the development of shilins and karst structure. In the vicinity of the Lunan Shilin, speleological, morphological and structural geological studies of four karst caves have been accomplished. At Puzhehei, Qiubei, which is characterised by numerous fenglin, fengcong and caves, speleological and morphological studies have been performed. Cave sediments for paleomagnetic analyses have been taken from all studied areas (samples CH 1-9). Karst caves in SE Yunnan are probably much older than the age of the cave sediments (<780,000 years B.P.). The studied areas are located in the vicinity of the Xiaojiang fault (N-S 相似文献
86.
The paper presents systematized and synthesized data on the parameters and evolutionary sequence of metasomatic processes that accompanied interaction between Permian–Triassic trap complex and rocks of the sedimentary cover of the Siberian Platform at the large skarn iron deposits. Relations of the textural–compositional, morphological, and genetic diversity of the skarns and ores with the phases and stages of the origin of ore-bearing volcano-tectonic edifices are demonstrated with reference to the Korshunovskoe and Rudnogorskoe deposits. The genetic reconstructions are based on survey materials and data on the mineralogy of the rocks and ores (obtained by optical and scanning electron microscopy, microprobe analysis, EPR, Raman and IR spectroscopy, and by studying inclusions in minerals). A principally important feature of the volcano-tectonic edifices of the large mineral deposits is their multistage evolution and combinations of fluid-conducting zones, which are related to (1) volcanic apparatuses, (2) shallow-depth magmatic chambers (laccoliths) hosted in carbonate–salt rocks, and (3) multistage fracture structures produced by the collapse of the leached space. The major ore-bearing structures were formed simultaneously with the development of an intermediate magmatic chamber hosted in Cambrian carbonate–salt rocks beneath a seal of terrigenous sedimentary rocks. Magmatic-stage magnesian skarns with disseminated ores in them and in the calciphyres were produced during the prograde stage in the apical parts of the laccoliths, at contacts between the dolerites and dolomites. During the early prograde stage, skarn–ore bodies developed around injection bodies of globulated dolerites, laccoliths, and sills; stockworks and steep bodies of fragmentary magnesian and calcic skarns and ores were formed within the diatremes; and conformable bodies and veins were produced in the splay fracture zones. The later reactivation of faults and fractures and the involvement of connate brines and solutions from the evaporite complex triggered the redeposition of the ore masses, crystallization of the mineral assemblages of hydrated skarns, development of large domains of serpentine–chlorite–epidote–amphibole rocks, calcic skarns, and ores. Data on multiphase fluid inclusions in the forsterite, apatite, and halite indicate that the mineral-forming fluid initially was a highly concentrated solution–melt (total salinity of 60%) with high-density reduced gases. The magnesian skarns were formed during the following stages: (1) forsterite + fassaite + spinel + first-population magnetite (820–740°C); (2) phlogopite + titanite + pargasite + second-population magnetite (600–500°C), and (3) clinochlore + serpentine + tremolite + pyrrhotite + chalcopyrite (≥450°C). 相似文献
87.
Astronomy Reports - In order to solve the problem of deflecting a dangerous asteroid from a collision orbit with the Earth, using a low-thrust engine directed tangentially to the trajectory is... 相似文献
88.
Numerical Simulations of Tsunami Waves and Currents for Southern Vancouver Island from a Cascadia Megathrust Earthquake 总被引:1,自引:0,他引:1
Josef Y. Cherniawsky Vasily V. Titov Kelin Wang Jing-Yang Li 《Pure and Applied Geophysics》2007,164(2-3):465-492
The 1700 great Cascadia earthquake (M = 9) generated widespread tsunami waves that affected the entire Pacific Ocean and caused
damage as distant as Japan. Similar catastrophic waves may be generated by a future Cascadia megathrust earthquake. We use
three rupture scenarios for this earthquake in numerical experiments to study propagation of tsunami waves off the west coast
of North America and to predict tsunami heights and currents in several bays and harbours on southern Vancouver Island, British
Columbia, including Ucluelet, located on the west coast of the island, and Victoria and Esquimalt harbours inside Juan de
Fuca Strait. The earthquake scenarios are: an 1100-km long rupture over the entire length of the subduction zone and separate
ruptures of its northern or southern segments. As expected, the southern earthquake scenario has a limited effect over most
of the Vancouver Island coast, with waves in the harbours not exceeding 1 m. The other two scenarios produce large tsunami
waves, higher than 16 m at one location near Ucluelet and over 4 m inside Esquimalt and Victoria harbours, and very strong
currents that reach 17 m/s in narrow channels and near headlands. Because the assumed rupture scenarios are based on a previous
earthquake, direct use of the model results to estimate the effect of a future earthquake requires appropriate qualification. 相似文献
89.
On 15 July 2009, a Mw 7.8 earthquake occurred off the New Zealand coast, which by serendipitous coincidence occurred while
the International Tsunami Symposium was in session in Novosibirsk, Russia. The earthquake generated a tsunami that propagated
across the Tasman Sea and was detected in New Zealand, Australia and as far away as the US West coast. Small boats close to
the epicenter were placed in jeopardy, but no significant damage was observed despite a measured run-up height of 2.3 m in
one of the Sounds in close proximity to the source (Wilson in GNS Science Report 46:62 2009). Peak-to-trough tsunami heights of 55 cm were measured at Southport, Tasmania and a height of 1 m was measured in Jackson
Bay, New Zealand. The International Tsunami Symposium provided an ideal venue for illustration of the value of immediate real-time
assessment and provided an opportunity to further validate the real time forecasting capabilities with the scientific community
in attendance. A number of agencies with responsibility for tsunami forecast and/or warning, such as the NOAA Center for Tsunami
Research, the Pacific Tsunami Warning Center, GNS Science in New Zealand, the Australian Bureau of Meteorology and the European
Commission Joint Research Centre were all represented at the meeting and were able to demonstrate the use of state of the
art numerical models to assess the tsunami potential and provide warning as appropriate. 相似文献
90.
Earth orientation parameters (EOPs) provide a link between the International Celestial Reference Frame (ICRF) and the International Terrestrial Reference Frame (ITRF). Natural geodynamic processes, such as earthquakes, can cause the motion of stations to become discontinuous and/or non-linear, thereby corrupting the EOP estimates if the sites are assumed to move linearly. The VLBI antenna at the Gilcreek Geophysical Observatory has undergone non-linear, post-seismic motion as a result of the Mw=7.9 Denali earthquake in November 2002, yet some VLBI analysts have adopted co-seismic offsets and a linear velocity model to represent the motion of the site after the earthquake. Ignoring the effects of the Denali earthquake leads to error on the order of 300–600 μas for the EOP, while modelling the post-seismic motion of Gilcreek with a linear velocity generates errors of 20–50 μas. Only by modelling the site motion with a non-linear function is the same level of accuracy of EOP estimates maintained. The effect of post-seismic motion on EOP estimates derived from the International VLBI Service IVS-R1 and IVS-R4 networks are not the same, although changes in network geometries and equipment improvements have probably affected the estimates more significantly than the earthquake-induced deformation at Gilcreek. 相似文献