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181.
Katy A. Boon Peter Rostron Michael H. Ramsey 《Geostandards and Geoanalytical Research》2011,35(3):353-367
In the assessment of potentially contaminated land, the number of samples and the uncertainty of the measurements (including that from sampling) are both important factors in the planning and implementation of an investigation. Both parameters also effect the interpretation of the measurements produced, and the process of making decisions based upon those measurements. However, despite their importance, previously there has been no method for assessing if an investigation is fit‐for‐purpose with respect to both of these parameters. The Whole Site Optimised Contaminated Land Investigation (WSOCLI) method has been developed to address this issue, and to allow the optimisation of an investigation with respect to both the number of samples and the measurement uncertainty, using an economic loss function. This function was developed to calculate an ‘expectation of (financial) loss’, incorporating costs of the investigation itself, subsequent land remediation, and potential consequential costs. To allow the evaluation of the WSOCLI method a computer program ‘OCLISIM’ has been developed to produce sample data from simulated contaminated land investigations. One advantage of such an approach is that as the ‘true’ contaminant concentrations are created by the program, these values are known, which is not the case in a real contaminated land investigation. This enables direct comparisons between functions of the ‘true’ concentrations and functions of the simulated measurements. A second advantage of simulation for this purpose is that the WSOCLI method can be tested on many different patterns and intensities of contamination. The WSOCLI method performed particularly well at high sampling densities producing expectations of financial loss that approximated to the true costs, which were also calculated by the program. WSOCLI was shown to produce notable trends in the relationship between the overall cost (i.e., expectation of loss) and both the number of samples and the measurement uncertainty, which are: (a) low measurement uncertainty was optimal when the decision threshold was between the mean background and the mean hot spot concentrations. (b) When the hot spot mean concentration is equal to or near the decision threshold, then mid‐range measurement uncertainties were optimal. (c) When the decision threshold exceeds the mean of the hot spot, mid‐range measurement uncertainties were optimal. The trends indicate that the uncertainty may continue to rise if the difference between hot spot mean and the decision threshold increases further. (d) In any of the above scenarios, the optimal measurement uncertainty was lower if there is a large geochemical variance (i.e., heterogeneity) within the hot spot. (e) The optimal number of samples for each scenario was indicated by the WSOCLI method, and was between 50 and 100 for the scenarios considered generally; although there was significant noise in the predictions, which needs to be addressed in future work to allow such conclusions to be clearer. 相似文献
182.
This study investigates the mechanism of formation of convection plumes of mushroom shape in sub-solidus mantle and their prediction.The seismic-tomographic images of columnar structures of several hundreds kilometers in diameter have been reported by several researchers,while the much cherished mushroom-shaped plume heads could only be found in computational geodynamics(CGD) models and simple small-scale laboratory analogue simulations.Our theory of transient instability shows that the formation of conv... 相似文献
183.
采用物理模型实验方法对不同潮差驱动下咸水入侵距离进行实验研究,结果表明存在潮差临界值使得咸水入侵距离最短,当潮差小于该临界值,咸水入侵距离随潮差增大呈快速减小趋势,而大于该临界值则呈缓慢增大趋势。基于实验数据对盐淡水混合进行理论分析,揭示了实验现象的产生机制:①潮差增大过程中盐淡水混合由高度分层变为均匀混合,导致驱动咸潮入侵的动力发生了改变;②当盐淡水为弱混合类型,盐淡水高度分层,重力环流输运是盐进入河口的主要方式,潮汐强度增大减小了盐淡水分层,减弱了重力环流的输运作用,因此入侵距离变小;③当盐淡水为强混合类型,盐淡水混合均匀,重力环流输运作用大大减弱,潮汐扩散成为主要的输运方式,潮汐增强使得扩散能力增大,因此潮汐强度越大,咸潮入侵距离越大。 相似文献
184.
The modified Soil Conservation Service curve number (CN) method is widely used in long‐term continuous models to predict daily surface runoff. However, it has been shown that this method gives poor results in reproducing peak flows in high rainfall periods. This is because there is an inaccuracy stemming from the model algorithm as it adjusts the daily runoff curve number as a function of soil moisture content at the end of the previous day. This paper proposes an alternative daily based curve number technique that can provide better prediction of daily runoff during the high flow season. The proposed method uses the temporally weighted average curve number (TWA‐CN) to estimate daily surface runoff, while considering the effect of rainfall during a given day as well as the antecedent soil moisture condition. To test the applicability of the TWA‐CN method, it was incorporated with the long‐term, continuous simulation watershed models SWAT and SWAT‐G. Simulations were conducted for the Miho River watershed located in the middle of South Korea. The graphical displays and statistics of the determination coefficient (R2) and the Nash–Sutcliffe model efficiency (NSE) of the observed and simulated daily runoff indicated that the modified SWAT with the TWA‐CN method may provide better runoff prediction (R2 = 0·837, NSE = 0·833) than the original SWAT (R2 = 0·815, NSE = 0·824). Likewise, the determination coefficient (R2 = 0·816) and the Nash–Sutcliffe efficiency (NSE = 0·834) for the modified SWAT‐G are also higher than the original version (R2 = 0·782, NSE = 0·825). It is expected that the improved capability in predicting surface runoff using the suggested CN estimate method will provide a sound contribution to the accurate simulations of water yield. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
185.
陈培善 《地震学报(英文版)》2008,21(2):217-218
Illustration All the data in this catalog are chosen from the ″Preliminary Seismological Report of Chi-nese Seismic Stations″ (Its abbreviation is ″Monthly Report″). The catalog includes the events of M≥4.7 in and near China and M≥6 all over the world. The ″Monthly Report″ is monthly compiled 相似文献
186.
陈培善 《地震学报(英文版)》2008,21(3):330-331
Illustration All the data in this catalog are chosen from the ″Preliminary Seismological Report of Chi-nese Seismic Stations″ (Its abbreviation is ″Monthly Report″). The catalog includes the events of M≥4.7 in and near China and M≥6 all over the world. The ″Monthly Report″ is monthly compiled 相似文献
187.
Interplay between capillary, gravity and viscous forces in unsaturated porous media gives rise to a range of complex flow phenomena affecting morphology, stability and dynamics of wetting and drainage fronts. Similar average phase contents may result in significantly different fluid distribution and patterns affecting macroscopic transport properties of the unsaturated medium. The formulation of general force balance within simplified pore spaces yields scaling relationships for motion of liquid elements in which gravitational force in excess of capillary pinning force scales linearly with viscous force. Displacement fluid front morphology is described using dimensionless force ratios expressed as Bond and Capillary numbers. The concise representations of a wide range of flow regimes with scaling relations, and predictive capabilities of front morphology based on dimensionless numbers lend support to certain generalizations. Considering available experimental data, we are able to define conditions for onset of unstable and intermittent flows leading to enhanced liquid and gas entrapment. These results provide a basis for delineation of a tentative value of Bo ∼ 0.05 as an upper limit of applicability of the Richards equation (at pore to sample scales) and related continuum-based flow models. 相似文献
188.
Rehan Sadiq Solomon Tesfamariam 《Stochastic Environmental Research and Risk Assessment (SERRA)》2008,22(4):495-505
Environmental indices (EI) constitute a common communication tool that is often used to describe the overall status of environmental
systems (air, water and soil). EI development entails the use of mathematical operators to aggregate various non-commensurate
input parameters in a logical manner. The ordered weighted averaging (OWA) operator is a general mean type operator that provides
flexibility in the aggregation process such that the aggregated value is bounded between minimum and maximum values of the
input parameters. This flexibility of the OWA operator is realized through the concept of orness, which is a surrogate for
decision maker’s attitude. The type of input parameters also affects the choice of aggregation operators. If the input parameters
are linguistic or fuzzy, the aggregation through OWA operators is not possible, and the use of fuzzy arithmetic is warranted.
The concept of fuzzy number OWA (FN-OWA) operators is explored to handle situations in which one or more input parameter has
fuzzy (or linguistic) values. The proposed approach is demonstrated using data provided in an earlier study by Swamee and
Tyagi (ASCE J Environ Eng 126(5):451–455, 2000) for establishing water quality indices. Multiple hypothetical scenarios are also generated to highlight the utility and
sensitivity of the proposed approach. 相似文献
189.
An analogy between turbulent fluid systems and landscape drainage systems [Parker, G., Haff, P.K., Murray, A.B., 2001, EOS, Transactions of the American Geophysical Union, 82, pp. F564.] is suggested by the observation that transport in both systems can be approximated by diffusion with size-proportional effective diffusivities, with a cross-over at small scales to Fickian diffusion. The “landscape” Reynolds number of a typical fluvial landscape is estimated to be of order ReL 106 to 109, these large values reflecting the relative efficiency of fluvial transport compared to creep. ReL is the ratio of the large-scale effective diffusivity of rivers to the small-scale diffusivity of creep processes on hillslopes. The spatial dependence of the effective diffusivity produces rivers with logarithmic long-profiles, similar to the profiles of many rivers in nature, and analogous to the logarithmic dependence of mean fluid velocity on distance from a wall in turbulent flow. The landscape example suggests how other generalized “Reynolds numbers” can be constructed as ratios of large-scale to small-scale diffusivities to measure the efficiencies of complex processes that affect the surface. As an example, the global airline transportation network is estimated to have an efficacy relative to that of direct human mechanisms for transport of similar goods and materials of about 108 as measured by a corresponding “technology” Reynolds number. The appearance of such large dimensionless numbers, pertaining to the consequences of human invention and design, reflects the emergence of the technosphere as an increasingly efficient overlay on the historical domain of biology and surficial geology. 相似文献
190.