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951.
This paper summarized six aspects such as the harm characteristics, type and index, climatic characteristics, causes, responding to globe changes, protecting technology and answering tactics of hot-dry wind and high temperature heat wave. There is distinction and relationship between hot dry wind and high temperature heat wave. This includes that both of hot-dry wind and high temperature heat wave belong to serious shorter time scale weather disasters. Lower humidity and higher temperature are their main characteristics. The two causes of abnormal circulation characteristics and impacts of the disasters from climate change are basically the same. The disasters may occur in the same area during the same period. Arid season is helphul for their development and aggravation damage. There are differences on harm characteristics, type and index, climatic characteristics, protecting technology and answering tactics in this two weather disasters in that the high temperature heat wave is the comprehensiveness meteorological disasters and dry-hot wind is the agrometeorological disasters. 相似文献
952.
金沙江中游上江坝址河床深厚覆盖层建高坝可行性探讨 总被引:2,自引:0,他引:2
摘 要 上江坝址为金沙江中游龙头水库的比选坝址之一,坝址河床覆盖层最厚达206.2 m,在深厚覆盖层上修建最低249 m级的高土石坝,大坝规模达到甚至超过世界前沿水平,筑坝技术难度大。通过测绘、钻探、物探、物理力学测试等工作揭示:(1)河床覆盖层由漂卵石、低液限粘土、砾卵石、碎块石、砂砾石等组成;(2)河床覆盖层中各粗粒土强度相对较高,低液限粘土强度较低,为坝基一条连续完整的相对软弱带;(3)坝址位于龙蟠断陷盆地内,主要受新构造垂直差异运动的影响,河床接受金沙江上游及坡体上物质堆积,逐渐形成了现今的深厚覆盖层。初步研究本坝址在河床覆盖层上建高土石坝是可行的,但需要对坝基采取工程处理措施。探讨了不同建坝方案所引发的工程地质问题,为筑坝技术研究提供了地质依据。 相似文献
953.
954.
We re-examine the maximum brightness temperature that a synchrotron source can sustain by adapting standard synchrotron theory
to an electron distribution that exhibits a deficit at low energy. The absence of low energy electrons reduces the absorption
of synchrotron photons, allowing the source to reach a higher brightness temperature without the onset of catastrophic cooling.
We find that a temperature of ∼1014 K is possible at GHz frequencies. In addition, a high degree of intrinsic circular polarisation is produced. We compute the
stationary, synchrotron and self-Compton spectrum arising from the continuous injection of such a distribution (modelled as
a double power-law) balanced by radiative losses and escape, and compare it with the simultaneously observed multi-wavelength
spectrum of the BL Lac object S5 0716+714. This framework may provide an explanation of other high brightness-temperature
sources without the need for mechanisms such as coherent emission or proton synchrotron radiation. 相似文献
955.
M. Rosenberg 《Planetary and Space Science》2008,56(9):1190-1193
Recently, the sputtering of fast meteoroids by impinging atmospheric particles, and the subsequent interaction of the sputtered material with the atmosphere, has been proposed to explain the meteor luminosity observed at high altitudes. In this brief communication, we consider the possibility of a lower hybrid instability driven by the ionized component of the material sputtered from a fast large meteoroid at high altitudes. 相似文献
956.
Highly-reduced dynamic orbits and their use for global gravity field recovery: A simulation study for GOCE 总被引:1,自引:0,他引:1
The so-called highly reduced-dynamic (HRD) orbit determination strategy and its use for the determination of the Earth’s gravitational
field are analyzed. We discuss the functional model for the generation of HRD orbits, which are a compromise of the two extreme
cases of dynamic and purely geometrically determined kinematic orbits. For gravity field recovery the energy integral approach
is applied, which is based on the law of energy conservation in a closed system. The potential of HRD orbits for gravity field
determination is studied in the frame of a simulated test environment based on a realistic GOCE orbit configuration. The results
are analyzed, assessed, and compared with the respective reference solutions based on a kinematic orbit scenario. The main
advantage of HRD orbits is the fact that they contain orbit velocity information, thus avoiding numerical differentiation
on the orbit positions. The error characteristics are usually much smoother, and the computation of gravity field solutions
is more efficient, because less densely sampled orbit information is sufficient. On the other hand, the main drawback of HRD
orbits is that they contain external gravity field information, and thus yield the danger to obtain gravity field results
which are biased towards this prior information. 相似文献
957.
An approximation approach of seismic analysis of two‐way asymmetric building systems under bi‐directional seismic ground motions is proposed. The procedures of uncoupled modal response history analysis (UMRHA) are extended to two‐way asymmetric buildings simultaneously excited by two horizontal components of ground motion. Constructing the relationships of two‐way base shears versus two‐way roof translations and base torque versus roof rotation in ADRS format for a two‐way asymmetric building, each modal pushover curve bifurcates into three curves in an inelastic state. A three‐degree‐of‐freedom (3DOF) modal stick is developed to simulate the modal pushover curve with the stated bifurcating characteristic. It requires the calculation of the synthetic earthquake and angle β. It is confirmed that the 3DOF modal stick is consistent with single‐degree‐of‐freedom modal stick in an elastic state. A two‐way asymmetric three‐story building was analyzed by UMRHA procedure incorporating the proposed 3DOF modal sticks. The analytical results are compared with those obtained from nonlinear response history analysis. It is shown that the 3DOF modal sticks are more rational and effective in dealing with the assessment of two‐way asymmetric building systems under two‐directional seismic ground motions. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
958.
The Cenozoic basalts from eastern China show commonly high Fe/Mn ratios (average = 68.6 ± 11.5) coupled with OIB-type trace element signature. The Cenozoic basalts form the northern margin and the southern margin of the North China Craton are studied in detail. Model calculations point out that the coupling feature of high Fe/Mn ratio with OIB-type trace element signature of these basalts cannot be produced by neither pyroxene/olivine crystallization nor remelting of previously melted mantle, but require partial melting of a garnet pyroxenite-rich mantle source. Combining these features of the Cenozoic basalts with the Phanerozoic lithospheric evolution of the eastern China, we suggest that the Cenozoic basalts were derived from a garnet pyroxenite-rich mantle source associated with continental crust delamination or oceanic crust subduction. 相似文献
959.
Analysis of the Upper Cretaceous stratigraphy of the Peel Block reveals the basin development of the block to have been influenced by both the inversion of the Roer Valley Graben and Central Netherlands Basin, and the overall Late Cretaceous transgression. Sediments of Santonian to Danian age were deposited on the block. These sediments are compared with the detailed lithostratigraphy of southern Limburg, where Late Cretaceous strata are exposed. Four successions can be recognised in southern Limburg. The two oldest successions, the Santonian Oploo Formation (new name, proposed in the present contribution) and the mainly Early Campanian Vaals Formation, are restricted to the central and northern parts of the block. These siliciclastic formations were deposited under the influence of inversion of the Roer Valley Graben and the Central Netherlands Basin, as well as under the influence of a rising sea level. Towards the north, sands of the Oploo Formation grade into marls and chalks of the Ommelanden Formation. The two youngest successions comprise the largely Late Campanian to Maastrichtian Gulpen and Maastricht Formations and the Danian Houthem Formation. These chalk formations were deposited under the influence of regional subsidence during a sea-level highstand. Subsequent to deposition of the Houthem Formation, a regional regression triggered a change from shallow-marine carbonate to paralic siliciclastic deposition. 相似文献
960.
The continental shelf on the west coast of India is widest off Bombay and leads into a strongly converging channel, the Gulf
of Khambhat. Tides in the Gulf are among the largest on the coast. We use data on amplitude and phase of major semi-diurnal
and diurnal constituents at forty-two ports in the Gulf and surrounding areas to define characteristics of the tides. We then
use a barotropic numerical model based on shallow water wave equations to simulate the sea level and circulation in the region.
The model is forced by prescribing the tide along the open boundaries of the model domain. Observed sea level at Bombay and
currents from the Bombay High region at the centre of the model domain and from a shallow station off the port of Dahanu compare
favourably with the fields simulated by the model. The simulated amplitudes and phases of the four most prominent tidal constituents
also compare favourably with those observed along the coast, except at a few locations where the model spatial resolution
(6.37 km × 6.37 km) appears to be inadequate to resolve the local geometry. Though this encourages us to conclude that the
circulation in the region is dominated by barotropic tides, a concern is that the observational database on hydrography and
directly measured currents in the region is weak. 相似文献