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441.
Spatial interpolation methods for nonstationary plume data 总被引:1,自引:0,他引:1
Plume interpolation consists of estimating contaminant concentrations at unsampled locations using the available contaminant data surrounding those locations. The goal of ground water plume interpolation is to maximize the accuracy in estimating the spatial distribution of the contaminant plume given the data limitations associated with sparse monitoring networks with irregular geometries. Beyond data limitations, contaminant plume interpolation is a difficult task because contaminant concentration fields are highly heterogeneous, anisotropic, and nonstationary phenomena. This study provides a comprehensive performance analysis of six interpolation methods for scatter-point concentration data, ranging in complexity from intrinsic kriging based on intrinsic random function theory to a traditional implementation of inverse-distance weighting. High resolution simulation data of perchloroethylene (PCE) contamination in a highly heterogeneous alluvial aquifer were used to generate three test cases, which vary in the size and complexity of their contaminant plumes as well as the number of data available to support interpolation. Overall, the variability of PCE samples and preferential sampling controlled how well each of the interpolation schemes performed. Quantile kriging was the most robust of the interpolation methods, showing the least bias from both of these factors. This study provides guidance to practitioners balancing opposing theoretical perspectives, ease-of-implementation, and effectiveness when choosing a plume interpolation method. 相似文献
442.
443.
Torsti Jarmo Kocharov Leon Laivola Jarno Chertok Ilya Thompson Barbara J. 《Solar physics》2003,214(1):177-193
Energetic particle observations of the ERNE instrument on board SOHO enable measurements of 3He and 4He fluxes beyond 15 MeV nucleon–1 with good statistical resolution. We report results of a survey of the ERNE observations covering the period from 8 February 1999 to 6 December 2000. We find 10 and 5 days during which the 3He-to-4He ratio exceeds the levels of 20% and 50%, respectively. Those periods include, in particular, four 3He-rich events that are sufficiently strong for a reasonably accurate estimate of the time-intensity profiles. We analyze the history of solar and interplanetary phenomena associated with these high-energy 3He-rich events. Basic properties of such events and significant solar and interplanetary factors are formulated. The significant factors comprise, in particular, a strong, impulsive flare, typically observed about
day before the 3He onset, and an interplanetary shock wave or magnetic field enhancement arriving at 1 AU about frac43 day after the 3He onset. The high-energy 3He-rich events make up a new kind of hybrid events, possessing the impulsive-type composition and the gradual-type time-profiles. We emphasize a dependence of the resultant particle event on the history of the particular solar eruption comprising coronal mass ejection (CME) and the flare associated with the CME. 相似文献
444.
445.
K. David Newell John H. Doveton Daniel F. Merriam Barbara Sherwood Lollar William M. Waggoner L. Michael Magnuson 《Natural Resources Research》2007,16(3):277-292
In late 2005 and early 2006, the WTW Operating, LLC (W.T.W. Oil Co., Inc.) #1 Wilson well (T.D. = 5772 ft; 1759.3 m) was drilled
for 1826 ft (556.6 m) into Precambrian basement underlying the Forest City Basin in northeastern Kansas. Approximately 4500
of the 380,000 wells drilled in Kansas penetrate Precambrian basement. Except for two previous wells drilled into the arkoses
and basalts of the 1.1-Ga Midcontinent Rift and another well drilled in 1929 in basement on the Nemaha Uplift east of the
Midcontinent Rift, this well represents the deepest penetration into basement rocks in the state to date. Granite is the typical
lithology observed in wells that penetrate the Precambrian in the northern Midcontinent. Although no cores were taken to definitively
identify lithologies, well cuttings and petrophysical logs indicate that this well encountered basement metamorphic rocks
consisting of schist, gneiss, and amphibolitic gneiss, all cut by aplite dikes.
The well was cased and perforated in the Precambrian, and then acidized. After several days of swabbing operations, the well
produced shows of low-Btu gas, dominated by the non-flammable component gases of nitrogen (20%), carbon dioxide (43%), and
helium (1%). Combustible components include methane (26%), hydrogen (10%), and higher molecular-weight hydrocarbons (1%).
Although Coveney and others [Am. Assoc. Petroleum Geologists Bull., v. 71, no, 1, p. 39–48, 1987] identified H2-rich gas in two wells located close to the Midcontinent Rift in eastern Kansas, this study indicates that high levels of
H2 may be a more widespread phenomenon than previously thought. Unlike previous results, the gases in this study have a significant
component of hydrocarbon gas, as well as H2, N2, and CO2. Although redox reactions between iron-bearing minerals and groundwater are a possible source of H2 in the Precambrian basement rocks, the hydrocarbon gas does not exhibit the characteristics typically associated with proposed
abiogenic hydrocarbon gases from Precambrian Shield sites in Canada, Finland, and South Africa. Compositional and isotopic
signatures for gas from the #1 Wilson well are consistent with a predominantly thermogenic origin, with possible mixing with
a component of microbial gas. Given the geologic history of uplift and rifting this region, and the major fracture systems
present in the basement, this hydrocarbon gas likely migrated from source rocks and reservoirs in the overlying Paleozoic
sediments and is not evidence for abiogenic hydrocarbons generated in situ in the Precambrian basement. 相似文献
446.
This paper examines historical evidence on the occurrence and status of an important landscape element in the Central Tablelands of New South Wales: the swampy meadow/chain of ponds landform. Our findings reject the notion that it is possible to reconstruct this landform as it was at the time of early European settlement, based solely on early colonial documents. Furthermore the analysis of such documents should be used with appropriate caution when benchmarking this landform. These conclusions have been reached by analysing 826 nineteenth-century portion plans, 18 early explorers and settlers’ journals, letters and maps, and nine Surveyor General's maps and plans. We suggest that our findings have significant implications for developing management and restoration strategies, better informing conservation initiatives and the development of policies aimed at protecting, conserving and restoring the swampy meadow/chain of ponds landform. Our experience suggests that researchers involved in historical analyses of documents for similar purposes should be wary about factors such as the limitations and reliability of source data, unwarranted interpretations and the imprecise and/or contradictory use of terms. We also suggest that the possible subjective views of some observers, particularly those with limitations in interpreting such a landform, are further reasons to be cautious. If these factors are not taken into account it is very likely to result in a flawed interpretation. We conclude that both landform awareness and other perceptions of an observer at the time of early European settlement may present a hitherto unrecognised subjective element in this and other analyses which could limit the precision of historical reconstruction, without resort to other complementary methods. 相似文献
447.
The literature on local government management of the environment in Australia has been limited in that it has typically focused on the urban sphere. In contrast, this paper places rurality at the centre of its inquiry. It uses data from 15 case studies of rural local governments in Australia to identify the main factors that inhibit natural resource management by rural councils. These barriers mobilise around four key themes: capacity, commitment, co-ordination and community. While many of the issues raised in this study of non-urban shires have been described in previous research, the paper argues that the geographic location of the areas under investigation aggravates barriers to engaging sustainability initiatives. It is contended that rural local governments need to be resourced accordingly to ensure that natural resource management at the local government level in Australia is not compromised. 相似文献
448.
Genetic algorithms have been shown to be powerful tools for solving a wide variety of water resources optimization problems. Applying these approaches to complex, large-scale water resources applications can be difficult due to computational limitations, especially when a numerical model is needed to evaluate different solutions. This problem is particularly acute for solving field-scale groundwater remediation design problems, where fine spatial grids are often needed for accuracy. Finer grids usually improve the accuracy of the solutions, but they are also computationally expensive. In this paper we present multiscale island injection genetic algorithms (IIGAs), in which the optimization algorithms have different multiscale populations working on different islands (groups of processors) and periodically exchanging information. This new approach is tested using a field-scale pump-and-treat design problem at the Umatilla Army Depot in Oregon, USA. The performance of several variations of this approach is compared with the results of a simple genetic algorithm. The new approach found the same solution as much as 81% faster than the simple genetic algorithm and 9–53% faster than other previously formulated multiscale strategies. These findings indicate substantial promise for multiscale IIGA approaches to improve solution of complex water resources applications at the field scale. 相似文献
449.
A spatial analysis of structural controls on Karst groundwater geochemistry at a regional scale 总被引:7,自引:0,他引:7
Danile Valdes Jean-Paul Dupont Benoît Laignel Sylvie Ogier Thierry Leboulanger Barbara J. Mahler 《Journal of Hydrology》2007,340(3-4):244-255
The coupled spatial investigation of the geometrical and geochemical properties of a chalk karstic aquifer provides information on the degree to which geologic structure controls aquifer functioning and groundwater quality. Major ion concentrations in the chalk aquifer of the Haute-Normandie region (France) were measured at a high spatial resolution (more than 100 sampling sites over a 6000 km2 area) and mapped. The first observation is a continuity of the geochemical properties, in spite of the karstic properties of the aquifer principal components analysis of geochemical maps revealed two types of spatial distributions: ions with an autochthonous origin (Ca2+, HCO3), and ions with a principally allochthonous origin (Cl−, Na+, , ). Mg2+ was categorised as both autochthonous (chalk dissolution) and allochthonous (brought in by infiltration of Tertiary deposits). To better understand the spatial distribution of the geochemistry, the aquifer geochemistry was compared to the physical properties of the aquifer, in particular aquifer thickness (representing aquifer geometry) and piezometric level (representing aquifer flow). Use of spatial correlation between the geochemical and the geometrical properties provided insight regarding the directional structure of the data and give evidence of directional relations between geochemical and geometrical properties. The degree of mineralisation (principally composed of Ca2+ and ions) increased along the direction of flow, corresponding to an increase in chalk dissolution rate along the flowpath. The steepest mineralisation gradients were related to an increase in the Mg/Ca ratio, evidence of longer residence times and corresponding to zones where aquifer flow capacity is limited because of a decrease of the thickness of the flow section (anticlines or faults). These results highlight the dominant role played by the geometry and the structural context in controlling aquifer geochemistry. 相似文献
450.
The territorial dimension of the digital divide is usually considered as a phenomenon that penalizes the peripheral regions,
especially in terms of regional economic development. Taking into account the territorial networking of ICT (Information &
Communication Technologies) infrastructures—particularly high-speed networks—provides what is probably the principal reason
for such a perception. This is particularly true considering that the most-peripheral regions and those with the smallest
population densities are also the poorest in terms of ICT infrastructures. In Western countries, however, the digital divide
is no longer the result of network-related problems. Nowadays, the issue of the skills required to adequately exploit the
potential of ICT is at the forefront. Yet this evolution is likely to lead to an inversion of the inequalities between the
centre and the periphery, as populations without such skills—recent immigrants, the unemployed, the illiterate, people with
little education or on low incomes and other socially marginalized people—are generally concentrated in urban centres. Consequently,
the priority for reducing inequalities of access to ICT resources is no longer the provision of high-performance ICT infrastructures
for peripheral regions, but rather the implementation of continuing education and social action policies within the urban
centres. 相似文献