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71.
The knowledge rules of debris flow event: A case study for investigation Chen Yu Lan River, Taiwan 总被引:1,自引:0,他引:1
Debris flow, one of the most active hydrological processes, brings about a great loss of life and properties in the Chen Yu Lan River area, Nan-Tou County, Taiwan. The goal of this study is to manage and monitor the debris flows in a vast area. Thus, the strategy is to collect hydraulical and in-situ data easily and quickly through our spatial information system. Then, a novel Data Mining technique will be developed to find a rule-based knowledge system of debris flow. The entire study can be divided into two parts. In the first part, using spatial information the debris flow image is extracted from the outbreak area. The system provides precise positional information pertaining to the debris flow events. Attributes such as effective watershed area, Normalized Difference Vegetation Index (NDVI), and slope are automatically obtained from the system. In the second part of this study, K-mean theory is used to classify the observed hydraulical and in-situ data into different categories. Then, the ‘Effective Rough Set’ method is successfully used to analyze the factors influencing the debris flow phenomenon and delivers rational knowledge rules. The contribution of this study is presented that NDVI, slope and effective watershed area are the major factors influencing debris flow in the study area. The knowledge rules can provide better understanding on the elevation of high potential debris catchments. 相似文献
72.
Most submarine gas hydrates are located within the two-phase equilibrium region of hydrate and interstitial water with pressures (P) ranging from 8 to 60 MPa and temperatures (T) from 275 to 293 K. However, current measurements of solubilities of methane in equilibrium with hydrate in the absence of a vapor phase are limited below 20 MPa and 283.15 K, and the differences among these data are up to 30%. When these data were extrapolated to other P-T conditions, it leads to large and poorly known uncertainties. In this study, in situ Raman spectroscopy was used to measure methane concentrations in pure water in equilibrium with sI (structure one) methane hydrate, in the absence of a vapor phase, at temperatures from 276.6 to 294.6 (±0.3) K and pressures at 10, 20, 30 and 40 (±0.4%) MPa. The relationship among concentration of methane in water in equilibrium with hydrate, in mole fraction [X(CH4)], the temperature in K, and pressure in MPa was derived as: X(CH4) = exp [11.0464 + 0.023267 P − (4886.0 + 8.0158 P)/T]. Both the standard enthalpy and entropy of hydrate dissolution at the studied T-P conditions increase slightly with increasing pressure, ranging from 41.29 to 43.29 kJ/mol and from 0.1272 to 0.1330 kJ/K · mol, respectively. When compared with traditional sampling and analytical methods, the advantages of our method include: (1) the use of in situ Raman signals for methane concentration measurements eliminates possible uncertainty caused by sampling and ex situ analysis, (2) it is simple and efficient, and (3) high-pressure data can be obtained safely. 相似文献
73.
The equivalent operator equation is derived from the full primitive nonlinear equations of the atmospheric motion and the properties and physical senses of the operators are studied.In the infinite dimensional Hilbert space,the global asymptotic behavior of the atmosphere system with the non-stationary external forcing is studied under the assumption of the bounded external forcing.The existence theorems of the global absorbing set and the global attractor are obtained.Thus,the conclusions deduced from the large-scale atmosphere(Li and Chou 1996a;1996b) are extended to the general atmosphere. 相似文献
74.
经验正交函数展开精度的稳定性研究 总被引:7,自引:3,他引:7
在文献[1]中,我们已从理论和数值模拟两个方面研究了用经验正交函数作基函数缩减气候数值模式自由度的可行性与有效性。用理论模型作数值试验的结果是令人满意的,应用于实际气候数值模拟,一个还需考虑的关键问题是大气外强迫等各种因子变化允许的范围内,对实际资料作EOF展开的稳定性问题。本文分别用1951—1984年500 hPa月平均高度距平场资料,1966—1975年500 hPa候平均高度距平场资料,1965—1978年夏季500 hPa逐日高度距平场资料作EOF展开,并提出了经验正交函数展开精度稳定性的判断方法,旨在证明实际资料EOF展开在大气外强迫等各种因子变化的允许范围内是稳定的,以便为我们用实际资料的经验正交函数作基函数建立一个合理的简化动力模型提供坚实的资料基础。 相似文献
75.
76.
One of the key issues in international climate negotiations is the formulation of targets for emissions reduction for all countries based on the principle of "common but differentiated responsibilities". This formulation depends primarily on the quantitative attribution of the responsibilities of developed and developing countries for historical climate change. Using the Commuity Earth System Model(CESM), we estimate the responsibilities of developed countries and developing countries for climatic change from 1850 to 2005 using their carbon dioxide, methane and nitrous oxide emissions. The results indicate that developed countries contribute approximately 53%–61%, and developing countries approximately 39%–47%, to the increase in global air temperature, upper oceanic warming, sea-ice reduction in the NH, and permafrost degradation. In addition, the spatial heterogeneity of these changes from 1850 to 2005 is primarily attributed to the emissions of greenhouse gases(GHGs)in developed countries. Although uncertainties remain in the climate model and the external forcings used, GHG emissions in developed countries are the major contributor to the observed climate system changes in the 20 th century. 相似文献
77.
差分干涉测量黄河三角洲天然湿地水位变化研究 总被引:1,自引:0,他引:1
利用合成孔径雷达差分干涉测量技术监测湿地水位变化,对湿地保护、恢复和重建具有非常重要的意义.利用C波段VV极化和L波段HH极化合成孔径雷达影像,结合同步野外测量和调查工作,在各季节不同时间间隔下,研究不同湿地类型的后向散射特性差异和干涉相干性差异;在对影响干涉相干性的因素进行评价的基础上,建立差分干涉测量湿地水位变化监测的函数模型,利用获取的合成孔径雷达影像,分析黄河三角洲的天然湿地水位变化.研究结果表明,利用差分干涉测量技术不仅可以获取湿地水位变化,而且还能提供水位变化的空间细节,这是本技术最突出的特色. 相似文献
78.
In north of Taiwan the East China Sea Shelf extends from the coastline of mainland China to the southern Okinawa Trough, showing a shelf-slope-basin bathymetric profile. Sea floor of the East China Sea Shelf is generally smooth and flat. It is wide (230 km) and relatively shallow with an average shelf-break depth of 120 m, reflecting the effect of Quaternary glaciation about 15000 years ago. The Pliocene-Quaternary East China Sea Shelf is underlain by thin sequences of about 1000 m thick shallow marine sediments mainly derived from China, forming an eastward dipping sedimentary wedge due to regional tilting and subsidence and representing the youngest part of the Cenozoic rift margin in southeastern China. The Taiwan Strait Shelf has two phases in development: one is the early phase of the Paleocene-Miocene rift margin and the other is the late stage of the Pliocene-Quaternary foreland sedimentation. It is a foreland shelf and its present morphology results from the combined effects of tectonic subsidence and sedimentation overprinting that of the Late Pleistocene glaciation about 15000 years ago. 相似文献
79.
THE SENSITIVITY INFLUENCE OF NUMERICAL MODEL INITIAL VALUES ON FOUR-DIMENSIONAL ASSIMILATION-STUDY BASED ON LORENZ SYSTEM* 下载免费PDF全文
Numerical experiments of adjoint variational assimilation have been performed using the known Lorenz system.With the increase of sensitivity of model's initial values,it is more and more difficult to use the adjoint method to get the initial values which are consistent with the dynamics of the forecast model.Under some circumstances the algorithm completely fails.This shows that four-dimensional assimilation is related to the limit of predictability.On the other hand.with the increase of model equation's error,the result of variational assimilation may become worse and worse so that the prediction has no meaning.But if the model parameters are corrected when variational assimilation is made,the forecast results can be greatly improved based on Lorenz model. 相似文献
80.
在直流电剖面法的实际工作中,因受各种干扰因素的影响,使之ρ_5曲线复杂化,采用信息理论来处理直流电剖面资料,可以消除一些干扰因素,突出地电异常,为直流电剖面的资料解释提供了新的尝试。 相似文献