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141.
142.
Massachusetts Bay is a semi-enclosed embayment in the western Gulf of Maine about 50 km wide and 100 km long. Bottom sediment resuspension is controlled predominately by storm-induced surface waves and transport by the tidal- and wind-driven circulation. Because the Bay is open to the northeast, winds from the northeast (‘Northeasters’) generate the largest surface waves and are thus the most effective in resuspending sediments. The three-dimensional oceanographic circulation model Regional Ocean Modeling System (ROMS) is used to explore the resuspension, transport, and deposition of sediment caused by Northeasters. The model transports multiple sediment classes and tracks the evolution of a multilevel sediment bed. The surficial sediment characteristics of the bed are coupled to one of several bottom-boundary layer modules that calculate enhanced bottom roughness due to wave–current interaction. The wave field is calculated from the model Simulating WAves Nearshore (SWAN). Two idealized simulations were carried out to explore the effects of Northeasters on the transport and fate of sediments. In one simulation, an initially spatially uniform bed of mixed sediments exposed to a series of Northeasters evolved to a pattern similar to the existing surficial sediment distribution. A second set of simulations explored sediment-transport pathways caused by storms with winds from the northeast quadrant by simulating release of sediment at selected locations. Storms with winds from the north cause transport southward along the western shore of Massachusetts Bay, while storms with winds from the east and southeast drive northerly nearshore flow. The simulations show that Northeasters can effectively transport sediments from Boston Harbor and the area offshore of the harbor to the southeast into Cape Cod Bay and offshore into Stellwagen Basin. This transport pattern is consistent with Boston Harbor as the source of silver found in the surficial sediments of Cape Cod Bay and Stellwagen Basin. 相似文献
143.
海洋对人为CO2吸收的三维模式研究 总被引:1,自引:0,他引:1
文中用包含海洋化学过程和一个简单生物过程的三维碳循环模式模拟了海洋对大气CO2的吸收,并分析了碳吸收的纬度分布。模拟工业革命以来海洋对大气CO2的吸收表明:海洋碳吸收再加上大气CO2的增加只占由化石燃料燃烧、森林砍伐和土地利用的变化而释放到大气中的CO2的2/3。1980~1989年期间海洋年平均吸收2.05GtC。海洋人为CO2的吸收有明显的纬度特征。模式计算的海洋CO2的吸收在总量与纬度分布上与观测结果比较相符。 相似文献
144.
145.
A Matrix Approach Coupled with Monte Carlo Techniques for Solving the Net Radiative Balance of the Urban Block 总被引:2,自引:0,他引:2
Marta J. N. Oliveira Panão Helder J. P. Gonçalves Paulo M. C. Ferrão 《Boundary-Layer Meteorology》2007,122(1):217-241
A new method is developed for solving the shortwave and longwave net radiative balance of a three-dimensional urban structure,
represented by parallelepiped blocks uniformly distributed in each direction. The method is based on a novel approach to determine
the shape factors among surfaces, which are estimated by Monte Carlo techniques due to the complex geometry associated with
the three-dimensional urban structure. Then, a set of linear equations is solved to quantify the radiative balance, in order
to obtain their exact solution, considering all the inter-reflections among surfaces. The comparison between the new and the
ray-tracing tracking methods resulted in a Pearson correlation coefficient of 0.996. However, by integrating the linear equations’
exact solution with Monte Carlo techniques, the new method reduces by a factor of 36 the central processing unit (CPU) time
used to perform the calculations of the ray-tracing tracking method. The use of the model for a sensitivity study allows us
to verify the effective absorptance and emittance increases with the canyon aspect ratio of the urban layout. An urban structure
formed by square cross-sectional blocks absorbs more solar radiation than an urban structure formed by rectangular cross-sectional
blocks. The approximation of a specific geometry for an equivalent bi-dimensional infinite street can be applied for rectangular
cross-sectional blocks, where the width is 11 times or more greater than the depth dimension. 相似文献
146.
田青文 《地球科学与环境学报》1988,(3)
空间测角网三维平差,就是根据观测的水平方向值和垂直角计算出各方向间不受坐标系约束的空间角,将由空间角组成的空间测角网纳入参心空间直角坐标系中进行平差,求得待定点的参心空间直角坐标、大地经纬度、高斯坐标和高程。这样,既可克服需将测站坐标系和参心空间直角坐标系相联系而进行天文观测的弊端,又可使平差值免受垂线偏差的影响,从而开拓了三维平差的应用前景。 相似文献
147.
自然界中的地质体,不可能是规则的几何形体,用规则形体的理论方法去逼近,往往造成很大的误差。本文的方法则是对一三度体,用水平截面法对其切割,并用一多边形去逼近,从而得到一精确的数学解析表达式,来确定一三度体的重力异常。本文的方法不仅精度高,而且速度快,是目前一种比较好的正演方法。 相似文献
148.
Masanori Sakamoto Kiyoji Shiono Shinji Masumoto Kiyoshi Wadatsumi 《Natural Resources Research》1993,2(2):140-147
In this article we describe the basic framework of the computerized geologic mapping system cigma. The system, whic is based on a mathematical formulation of geologic concepts, consists of the following six subsystems: (1) input of geologic data set; (2) inference of stratigraphic sequence; (3) construction of logical models of geologic structures; (4) determination of three-dimensional geologic boundary surfaces; (5) construction of three-dimensional solid model of geologic structures; and (6) graphical presentation. Geologic structures are summarized in several tables called logical models of geologic structures. Each model is constructed automatically from input data on structural relations between geologic bodies. The model interprets the data automatically to create data files necessary to determine the shapes of geologic boundaries; it also provides a threedimensional solid model of geologic structures referring to the shapes of boundaries. As a prototype, we introduce two types of contacts corresponding to conformity and unconformity into the logical model and show that it is possible to draw a geologic map automatically. More complex geologic structures can be introduced into the geologic mapping system through further formulation of geologic structures. 相似文献
149.
《海洋学报(英文版)》1997,16(4):537-551
Reseach on three-dimensional tide current mathemtical model of coast and its applicationTXReseachonthree-dimensionaltidecurren... 相似文献
150.
This work provides a general hydrodynamic circulation model that can be used to understand density driven flows, which may arise in the case of suspension of fine-grained materials. The research is expected to provide a better understanding of the characteristics of spatial and temporal variability of current, which is associated with the period of ebb and flood tidal cycles.The model development includes extending the existing three-dimensional (3D) ADCIRC model with (1) baroclinic forcing term and (2) transport module of suspended and soluble materials. The transport module covers the erosion, material suspension and deposition processes for cohesive type sediment. In the case of an idealized tidal inlet in stratified water, the inclusion of baroclinic term can demonstrate the prevailing longshore sediment transport. It is shown that the model has application to the transport of the cohesive sediments from the mouth of the Mississippi River along the north shore of the Gulf of Mexico towards and along the Texas coast. 相似文献