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461.
Geoff A. Wilson 《Geoforum》2009,40(2):269-280
Based on reconceptualisations of multifunctional agriculture as a normative spectrum of decision-making (strong to weak multifunctionality) bounded by productivist and non-productivist action and thought [Hollander, G.M., 2004. Agricultural trade liberalization, multifunctionality, and sugar in the south Florida landscape. Geoforum 35, 299-312; Holmes, J., 2006. Impulses towards a multifunctional transition in rural Australia: gaps in the research agenda. Journal of Rural Studies 22, 142-160; Wilson, G.A., 2007. Multifunctional Agriculture: A Transition Theory Perspective. CAB International, Wallingford], this paper argues that there is currently insufficient research into the geography of multifunctionality. Building on current human geography debates about issues of scale, the paper suggests that we should conceive of multifunctionality as a spatially complex nested hierarchy comprising different interlinked ’layers’ of multifunctional decision-making ranging from the farm level to the national and global levels. It suggests that the notion of multifunctional agriculture only makes sense if it is applied at the farm level as the most important spatial scale for the implementation of multifunctional action ‘on the ground’. Multifunctionality can be interpreted as having ’direct’ expression only at the ’lower’ geographical scales (i.e. farm, community and regional levels in particular) while the regional, national and global levels show ’indirect’ expressions of multifunctionality that are mediated by local level actors in order to find tangible expression on the ground. The notion of global-level multifunctionality is the most challenging, as this level lacks political and ideological coherence about the required directions necessary for implementation of strong multifunctionality pathways. The paper concludes by arguing that much work still awaits those investigating the spatiality of multifunctionality, in particular with regard to the question whether global-level strong multifunctionality is possible, or whether strong multifunctionality in one territory is predicated on weak multifunctionality in others. 相似文献
462.
There is a widespread belief that poverty leads to the spread of HIV/AIDS. However, intra-country comparisons of the phenomenon have been limited. This study seeks to fill this gap by examining the relationship between poverty and HIV prevalence amongst the 10 administrative regions of Ghana. Based on the available data for poverty and HIV, certain distinct patterns emerge. For example, poverty levels are the highest in the three northern regions (Upper East, Upper West and Northern region) even though their HIV prevalence is one of the lowest. It clearly follows that there are more complex forces at work than just the effects of poverty alone. To unravel some of these puzzles, the paper proposes a key role for culture, globalization and geographical accessibility. In addition, it is suggested that local level studies in a multivariate framework have much to contribute to the identification and quantification of relevant relationships. 相似文献
463.
464.
465.
Computational Fluid Dynamical Modelling of Concentration Fluctuations in an Idealized Urban Area 总被引:2,自引:2,他引:0
Turbulent mixing induces variability in concentration that is important in many applications, such as reactive plumes, risk
assessments or odour impact analyses (when the effects can have time scales on the order of a second). In urban canopies,
the variability may be modified by the presence of buildings. Our purpose is to study concentration fluctuation variance in
built-up areas using an Eulerian approach. We performed numerical simulations with the computational fluid dynamics model
Mercure_Saturne, which is a three-dimensional model adapted to atmospheric flow and pollutant dispersion. We use a k − ϵ turbulence closure and predict the concentration variance with a transport equation model. The model performance is evaluated
with the near-full scale experiment MUST (Mock Urban Setting Test), a field experiment conducted in Utah’s West Desert Test
Center. The modelled root-mean-square of the concentration fluctuations is compared to measurements for 20 of the MUST trials.
The model shows good agreement with the measurements, with the fraction of predictions within a factor of two of observations
of 60.1%, with better results for horizontal lines of detectors than for the detectors on vertical masts (with fractions of
predictions within a factor of two of observations of respectively 66.4% and 52.6%). The influence of different parameters
on the fluctuation variance is also studied and we show the importance of taking into account the stability of the stratification
when modelling the turbulent kinetic energy. 相似文献
466.
Ronald B. Smith 《Boundary-Layer Meteorology》2008,129(3):371-393
Dispersion estimates with a Gaussian plume model are often incorrect because of particle settling (β), deposition (γ) or the vertical gradient in diffusivity (K
v
(z) = K
0 + μz). These “non-Gaussian” effects, and the interaction between them, can be evaluated with a new Hankel/Fourier method. Due
to the deepening of the plume downwind and reduced vertical concentration gradients, these effects become more important at
greater distance from the source. They dominate when distance from the source exceeds L
β
= K
0
U/β
2, L
γ
= K
0
U/γ
2 and L
μ
= K
0
U/μ
2 respectively. In this case, the ratio β/μ plays a central role and when β/μ = 1/2 the effects of settling and K gradient exactly cancel. A general computational method and several specific closed form
solutions are given, including a new dispersion relation for the case when all three non-Gaussian effects are strong. A more
general result is that surface concentration scales as C(x) ~ γ
−2 whenever deposition is strong. Categorization of dispersion problems using β/μ, L
γ
and L
μ
is proposed. 相似文献
467.
中国行为地理学研究近期进展 总被引:8,自引:1,他引:7
在中国人文地理学人本主义转向的背景下,中国的行为地理学研究进入新一轮学习与借鉴西方行为地理学理论与方法的高潮,并力求构建具有中国特色的行为地理学研究框架,实施全方位的实证研究与规划应用.本文简要评述了西方行为地理学的最新进展,指出中国行为地理学发展需要借鉴多学科视角和先进技术手段,提升研究的学术价值与应用价值.2003... 相似文献
468.
Mike Taylor 《New Zealand geographer》2011,67(3):190-198
When events such as the Darfield earthquake take place, it is assumed that the response from the geography teaching community provides the opportunity to reinforce the relevance of geography. This article reports the findings of a questionnaire which seeks to explore the question, ‘What were the characteristics of the learning and teaching of Year 11 Geography teachers in the weeks following the Darfield earthquake, September 4, 2010?’ The data offer empirical support for the agency of geography teachers' impressing the relevance of the subject to school students in response to an extreme natural event under New Zealand's collective backyard. 相似文献
469.
470.
Antonio Coppola Alessandro ComegnaGiovanna Dragonetti Miles DyckAngelo Basile Nicola LamaddalenaMohamed Kassab Vincenzo Comegna 《Advances in water resources》2011,34(6):747-759
Solute transport parameters are known to be scale-dependent due mainly to the increasing scale of heterogeneities with transport distance and with the lateral extent of the transport field examined. Based on a transect solute transport experiment, in this paper we studied this scale dependence by distinguishing three different scales with different homogeneity degrees of the porous medium: the observation scale, transport scale and transect scale. The main objective was to extend the approach proposed by van Wesenbeeck and Kachanoski to evaluating the role of textural heterogeneities on the transition from the observation scale to the transport scale. The approach is based on the scale dependence of transport moments estimated from solute concentrations distributions. In our study, these moments were calculated starting from time normalized resident concentrations measured by time domain reflectometry (TDR) probes at three depths in 37 soil sites 1 m apart along a transect during a steady state transport experiment. The Generalized Transfer Function (GTF) was used to describe the evolution of apparent solute spreading along the soil profile at each observation site by analyzing the propagation of the moments of the concentration distributions. Spectral analysis was used to quantify the relationship between the solid phase heterogeneities (namely, texture and stones) and the scale dependence of the solute transport parameters. Coupling the two approaches allowed us to identify two different transport scales (around 4-5 m and 20 m, respectively) mainly induced by the spatial pattern of soil textural properties. The analysis showed that the larger transport scale is mainly determined by the skeleton pattern of variability. Our analysis showed that the organization in hierarchical levels of soil variability may have major effects on the differences between solute transport behavior at transport scale and transect scale, as the transect scale parameters will include information from different scales of heterogeneities. 相似文献