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231.
A three-dimensional(3D) global adiabatic spectral primitive equation model has been designed.The main features are as follows.(1) Adoption of spherical harmonics and Tschebyscheff polynomials as the basis functions in the horizontal and vertical respectively,but the unknowns in the spectral equations are two-dimensional;(2) Inclusion of the tropopause,which may vary with time and space;(3) Suggestion of a spectral method for representing the vertical structure of the atmosphere applicable to the unsmoothed profile case;(4) In consideration of nonlinear vertical aliasing a technique is proposed to avoid it and nonlinear computational instability.Based on real data forecasts up to 48 hours have been performed.The results show that the statistical verifications with the model are superior on the average to those with the T42L9 used operationally before 1995 at NMC of China at the same mean resolution. 相似文献
232.
Coastal sedimentation associated with the December 12th, 1992 tsunami in Flores,Indonesia 总被引:2,自引:0,他引:2
This paper presents the result of a detailed granulometric investigation of sediments deposited by a modern tsunami, the 1992 tsunami in Flores, Indonesia. Eyewitness accounts indicate that sediments were deposited upon coastal lowlands over wide areas as a result of the tsunami inundation. Distinctive vertical and lateral variations in particle size composition are characteristic features of the tsunami deposits and these are intimately related to sedimentary processes associated with flood inundation. The geomorphological and sedimentary evidence is used here to establish a preliminary model of tsunami sedimentation. This information is believed to be of great value in understanding sedimentary processes associated with tsunami flooding and in the interpretation of palaeo-tsunami deposits. 相似文献
233.
Vertical and horizontal variations of the frequency of crustal earthquakes (h ≤ 35 km) that have occurred in and around Turkey
are analyzed, using data from the Global Hypocenter Data Base and the IRIS data for the period 1964–1998. Fits of various
magnitude scales to the observations have been used to construct a homogeneous catalogue. Depth distribution of the parameters
derived from the Gutenberg–Richter relationship reveals that there is a depth dependence in the a- and b-values of the frequency
distribution. It is observed that unknown focal depths (0, 10, 33 km) are dominant in the total seismicity reported, and give
rise to substantial changes to the vertical distribution of these parameters. It is also observed that the parameters of either
a or b alone may not be used as a measure of regional seismicity of the study area in which high and low seismic activity
observed over short distances. In contrast, distribution of modal (a/b) values provides detailed images of the local areas
presented by high and low seismic zones. This study presents evidence that low b-values are associated with major strike-slip
faults, particularly exhibiting high apparent stresses.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
234.
235.
M. Radulian L. Ardeleanu P. Campus J. Šílený G. F. Panza 《Studia Geophysica et Geodaetica》1996,40(4):367-380
Summary The inversion of high-frequency seismograms is performed to retrieve source mechanisms, hypocentral depths and source time functions of two weak Vrancea earthquakes (ML=3.3), one that occurred in the crust, the other in the lithospheric part of the mantle. The digital waveforms recorded by the local Romanian network are used. Synthetic seismograms are computed by the modal summation method, using the point source approximation, for horizontally layered anelastic media. For each source-to-station path a different structural model is adopted which represents the best 1-D approximation of the medium in this azimuth. Thus, lateral inhomogeneities are taken into account in a simplified way. The source is described by the full moment tensor, allowing both deviatoric and volumetric components to be resolved.Although the structural models are simplified for the range of epicentral distances (15<<<170 km) considered, we find that the fit between the synthetic and observed seismograms is satisfactory for frequencies less than a few Hz. The few P-wave polarities available are not sufficient to determine a reliable source mechanism by standard methods, while the waveform inversion allows us to retrieve source mechanisms that are stable with respect to different boundary conditions and in good agreement with the observed polarities. The source time function is the less stable inverted parameter, being the most influenced by the simplification of the structural models. 相似文献
236.
This work introduces a geometric formalism, based on the use of phasors in the Argand-Gauss plane for the design and sizing of inertial dampers to be applied to multimodal structural oscillators. Their damping effect depends on the fact that the response of the secondary oscillator (the damper) delays the response of the primary mass to be controlled by 90°, so that the elastic force transmitted by the damper becomes a viscous force on the controlled oscillator. When such condition occurs we say that the damper is ‘tuned’ to the main oscillator; the damping induced by the damper is modest and serves only to limit the displacement of main oscillator.Our geometrical approach provides a method whose language is close to that of structural mechanics, thus paving the way to the professional for: (i) sizing the damper parameters; and (ii) evaluating the stability to the damped system and its performance limits. The aim of the development is explore the use of dampers to control the initial response modes of buildings under horizontal seismic and aerodynamic loads. Having introduced the concept of a monomass oscillator equivalent to a given mode of vibration, we develop a multimodal multidamper model which we then use to perform numerical evaluations. Several control strategies (involving changes in number and position of the dampers) are considered in relation to variation in bandwidth and intensity of the external forcing action. We discuss the advantages and limitations of this passive approach to structural control. 相似文献
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239.
当前无人机低空航空摄影测量生成的数字正射影像DOM中,房屋边缘大量存在锯齿失真的现象,严重影响了对影像建筑物的判读和提取,降低了无人机航测数字正射影像的使用效益。提出一种利用数字表面模型DSM点云数据,提取其房屋边缘,并进行规则化处理,然后在此基础上进行数字微分纠正,生成正射影像的方法。实验结果表明,利用该方法可有效防止数字正射影像中房屋边缘存在的锯齿失真现象。 相似文献
240.
通过对ISO定义与OSI模型的各个不同层面的讨论,指出具体定义的内容和方法,实现自动数据采系统间或自动采集系统与上位数据机间数据交换,由于采用模块化,结构化设计思路,使这个协议易于实现并具有很妇的可扩充性,实现了数据传输过程由纵向传输到横向模型的转变,便于通讯程序的维护。 相似文献