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排序方式: 共有193条查询结果,搜索用时 15 毫秒
151.
Numerical investigation of infragravity wave amplifications during harbor oscillations influenced by variable offshore topography 总被引:1,自引:1,他引:0
The infragravity (IG) period oscillations inside an elongated rectangular harbor near the offshore fringing reef induced by normal-incident bichromatic short wave groups are simulated using a fully nonlinear Boussinesq model, FUNWAVE 2.0. Based on an IG wave separation procedure, this article presents a systematical investigation on how the maximum IG period component amplitude, the bound and free IG waves, and their relative components inside the harbor change with respect to the plane reef-face slope and the incident short wave amplitude under the condition of the 2nd to the 5th modes. For the given harbor and the ranges of the reef-face slope and the incident short wave amplitude studied in this paper, it is shown that both the maximum IG period component amplitude and the free IG wave component amplitude inside the harbor fluctuate widely with the reef-face slope, and their changing trends with the reef-face slope are almost identical with each other, while the bound IG waves inside the harbor seem insensitive to it. Both the maximum IG period component amplitude and those of the bound and free IG standing waves inside the harbor change cubically with the incident short wave amplitude. 相似文献
152.
Podymov Oleg Zatsepin Andrei Kubryakov Arseny Ostrovskii Alexander 《Ocean Dynamics》2020,70(2):199-211
Ocean Dynamics - In this paper, we analyze seasonal and interannual variability of vertical turbulent diffusion coefficient (Kt). Our calculations are based on the time series from 2013 to 2016,... 相似文献
153.
The Binary star DataBase(BDB, http://bdb.inasan.ru) combines data from catalogs of binary and multiple stars of all observational types. There is a number of ways for variable stars to form or to be a part of binary or multiple systems. We describe how such stars are represented in the database. 相似文献
154.
Marjan Marbouti Oleg Antropov Jaan Praks Patrick B.Eriksson Vahid Arabzadeh Eero Rinne Matti Lepp?ranta 《地球空间信息科学学报》2021,24(2):313-332
In this study, we assess the potential of X-band Interferometric Synthetic Aperture Radar imagery for automated classification of sea ice over the Baltic Sea. A bistatic SAR scene acquired by the TanDEM-X mission over the Bothnian Bay in March of 2012 was used in the analysis. Backscatter intensity, interferometric coherence magnitude, and interferometric phase have been used as informative features in several classification experiments. Various combinations of classification features were evaluated using Maximum likelihood (ML), Random Forests (RF) and Support Vector Machine (SVM) classifiers to achieve the best possible discrimination between open water and several sea ice types (undeformed ice, ridged ice, moderately deformed ice, brash ice, thick level ice, and new ice). Adding interferometric phase and coherence-magnitude to backscatter-intensity resulted in improved overall classification per- formance compared to using only backscatter-intensity. The RF algorithm appeared to be slightly superior to SVM and ML due to higher overall accuracies, however, at the expense of somewhat longer processing time. The best overall accuracy (OA) for three methodologies were achieved using combination of all tested features were 71.56, 72.93, and 72.91% for ML, RF and SVM classifiers, respectively. Compared to OAs of 62.28, 66.51, and 63.05% using only backscatter intensity, this indicates strong benefit of SAR interferometry in discriminating different types of sea ice. In contrast to several earlier studies, we were particularly able to successfully discriminate open water and new ice classes. 相似文献
155.
It is often assumed that three-dimensional topographic maps provide more effective route planning, navigation, orientation, and way-finding results than traditional two-dimensional representations. The research reported here investigates whether three-dimensional spatial mappings provide better support for route planning than two-dimensional representations. In a set of experiments performed as part of this research, human subjects were randomly shown either a two- or three-dimensional hologram of San Francisco and were asked to plan a bicycling route between an origin and a destination point. In a second task, participants used these holograms to identify the highest elevation point in the displayed area. The eye-movements of the participants, throughout the process of looking at the geospatial holograms and executing the tasks, were recorded. The eye-tracking metrics analysis indicates with a high statistical level of confidence that three-dimensional holographic maps enable more efficient route planning. In addition, the research group is developing a new algorithm to analyze the differences between participant-selected routes and a set of "good routes." The algorithm employs techniques used to represent the boundary of objects and methods for assessing the difference between objects in modern digital image recognition, image registration, and image alignment applications. The overall goal is to create a theoretical framework for investigating and quantifying route planning effectiveness. 相似文献
156.
This paper is concerned with the hydroelastic responses of a mat-like, rectangular very large floating structure (VLFS) edged with a pair of horizontal/inclined perforated anti-motion plates in the context of the direct coupling method. The updated Lagrangian formulae are applied to establish the equilibrium equations of the VLFS and the total potential formula is employed for fluids in the numerical model including the viscous effect of the perforated plates through the Darcy''s law. The hybrid finite element-boundary element (FE-BE) method is implemented to determine the response reduction of VLFS with attached perforated plates under various oblique incident waves. Also, the numerical solutions are validated against a series of experimental tests. The effectiveness of the attached perforated plates in reducing the deflections of the VLFS can be significantly improved by selecting the proper design parameters such as the porous parameter, submergence depth, plate width and inclination angle for the given sea conditions. 相似文献
157.
Viacheslav G. Makarov Oleg V. Zaytsev Valentina D. Budaeva Felipe Salinas-Gonzalez 《Journal of Oceanography》2008,64(5):675-690
A unified method of approximation, extrapolation, and objective layering is offered for processing vertical oceanographic
profiles. The method is demonstrated using seawater density and consists of adjustable splitting of each individual profile
into N vertical layers based on tentative, piecewise linear homogeneous approximation with specified accuracy and a final fitting
of an N-layered analytical model to data. A set of 3N coefficients of the model includes one density value at the sea surface; N−1 depths of layer interfaces; and N pairs of coefficients that describe a profile shape within the n-th layer—an asymptotic density value (a key parameter for extrapolation) and a vertical scale of maximum density variability
(related to vertical gradient). Several distinctive characteristics of the technique are: (1) It can be used for the analysis
of the vertical structure of individual profiles when N is an unknown parameter, and spatial interpolation when N should be equal for all profiles. (2) A justified downward extrapolation of incomplete data is possible with the model, especially
if historical deepwater profiles are available. (3) Layer interfaces, as well as other coefficients, are derived with only
one fitting to the entire profile. (4) The technique, using its general formulation, can serve as a parent for developing
various types of models. The simpler step-like (with hyperbolic or exponential approximation) and more complicated smooth
(continuous in gradient space) models were designed and tested against a large number of density profiles from the Sea of
Okhotsk and the Gulf of California. Comparison of parametric, z-levels and isopycnal averaging was done for the region off the northeastern coast of Sakhalin. 相似文献
158.
Yuliy A. Dashevsky Semen Petrov Alexandr N. Vasilevskiy Oleg B. Bocharov Gleb V. Dyatlov 《Studia Geophysica et Geodaetica》2017,61(1):69-92
Reliable estimates of the fluid pressure in the pore space of rocks are critical for different aspects of petroleum exploration and production including injection operations and scenarios of water flooding. Numerous approaches are available for formation pore pressure evaluation, however, these measurements become a challenge inside a cased borehole, and a list of possible options is short: either the casing is to be perforated, or the production tubing needs to be disconnected to perform the pressure tests. We present a method for through-casing evaluation of formation pore pressure without shutting down production. We suggest equipping an observation well with a borehole gravimeter and acquiring time variations of the vertical component of the gravity field. Changes in gravity occur during gas production and are related to time variations of formation pore pressure. Gravity changes obtained in the observation well are supposed to be inverted for time-dependent formation pore pressure variations beyond the casing. Our results and recommendations are based on numerical modeling of pore pressure spatial distribution during gas field exploitation and relevant changes in borehole gravity. Benchmark models were elaborated in order to consider a dynamic process of pressure changes in time and space under conditions similar to those in the Medvezhye gas field (Russia). Different modeling scenarios are considered for early and late stages of gas field exploitation. The sensitivity analysis was performed to estimate quantitatively a sensitivity of borehole temporal gravity changes to variations in formation pore pressure behind the casing. Based on resolution analysis we justify the possibility to extract the gravity measurements directly related to changes in pore pressure from the total changes in the gravity field due to reservoir exploitation. The impact of pore pressure on the gravity field measured in boreholes during the water flooding is also evaluated, and obtained results are discussed. 相似文献
159.
Mathematical Geosciences - Machine-learning-based proxy models are often used to replace many of the flow simulations required in optimizations of subsurface flow processes. Because the optimizer... 相似文献
160.
Relationships between reference mafic dikes and deformations in the Gridino zone, Belomorian province, Fennoscandian Shield, make it possible to subdivide the deformations into three groups: pre-dike, synmagmatic, and post-dike. The Neoarchaean eclogite-bearing mélange was formed by disintegration of large eclogite slices in the course of ductile flow, which was associated with synkinematic granitoid magmatism and metamorphism varying from the granulite to amphibolite facies. Exotic blocks, including those of eclogites, are distributed in the TTG gneisses as layers and lenses, whose thicknesses range from a few to a few hundred metres and which are conformable with the foliation. Ductile flow brought the rock complexes to the depth level where brittle–ductile deformations were possible. As a result, certain parts of the mélange were deformed in a more rigid setting. A number of mafic dike swarms were emplaced into relatively cold rocks in an extensional environment in the earliest Palaeoproterozoic. The dikes cut across all earlier structures and are thus an important benchmark for distinguishing Neoarchaean and Palaeoproterozoic processes. Post-dike (~1.9 Ga) tectonic activity was associated with local deformations and discrete metamorphic retrogression to amphibolite facies. None of them significantly affected the pre-existing regional structure. 相似文献