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排序方式: 共有283条查询结果,搜索用时 31 毫秒
191.
A rheological model has been developed for simulating the secondary consolidation of soils. Numerical procedures have been incorporated into a coupled consolidation program using results from a representative oedometer test. A solution of a two-dimensional problem has also been performed. The technique is numerically stable and has provided satisfactory predictions for the consolidation settlements and the dissipation of pore water pressure within soils. 相似文献
192.
193.
Vietnam is highly prone to climatic hazards, including extreme weather events and marked seasonal changes. Climatic hazards have wide-ranging implications for human health, but in most hazard-prone countries there has been little household level research on health risks. Drawing on the results of exploratory research in low-income communities in the Central Provinces and the Mekong Delta, this paper uses a qualitative approach to examine how the social dimensions of vulnerability can come into play in the generation of health outcomes associated with hazards. It explores particularly how aspects of economic livelihood, physical location, education and protective behaviour combined to influence the exposure and susceptibility of households, as well as to shape their capability to avoid adverse health impacts. These aspects were closely linked with, but not solely determined by, income-poverty: underlining the argument that understanding of risks to health in low-income settings requires careful analysis of this complex shaping of vulnerability. It also requires recognition that health protection for the poor may be articulated more in terms of protection of wider livelihood assets than preventive health actions per se. 相似文献
194.
The aim of this paper is to obtain, from a numerical study using the discrete element method, quantitative information on the behaviour of a rockfill dam, particularly the effect of rock ageing on the movements of the dam. A numerical model is defined at three different scales: the block scale, the elementary representative volume scale and the dam scale. The model uses the discrete element code PCF2D, considering breakable clusters of 2D balls. Three rock-ageing laws, taking into account the time-evolving resistance for blocks, are proposed. The different parameters are determined from experimental data of laboratory tests performed on rock blocks. The relevance of the model seems acceptable, considering that the displacements obtained in the simulations are in the same order of magnitude as the displacements measured on the actual dam. 相似文献
195.
Tam Giang–Cau Hai lagoon wetland directly or indirectly provides the likelihoods for about 300,000 persons living around as well as on the lagoon. Due to expansion of aquacultures, intensive fishing, and lack of an appropriate management scheme, the biological resources in the lagoon are degraded. This study provides information on the direct use values of the lagoon wetland, using market price approach. This information on economic values can be used for designing new policies and making trade-offs among alternative management options for the lagoon wetland. 相似文献
196.
Thanh Son Nguyen Lennart Börgesson Masakazu Chijimatsu Jan Hernelind Lanru Jing Akira Kobayashi Jonny Rutqvist 《Environmental Geology》2009,57(6):1239-1254
In order to demonstrate the feasibility of geological disposal of spent CANDU fuel in Canada, a safety assessment was performed
for a hypothetical repository in the Canadian Shield. The assessment shows that the maximum long term radionuclide release
from such repository would meet international criteria for dose rate; however, uncertainties in the assumed evolution of the
repository were identified. Such uncertainties could be resolved by the consideration of coupled Thermal-Hydro-Mechanical-Chemical
(THMC) processes. In Task A of the DECOVALEX-THMC project, THM models were developed within the framework of the theory of
poroelasticity. Such model development was performed in an iterative manner, using experimental data from laboratory and field
tests. The models were used to perform near-field simulations of the evolution of the repository in order to address the above-mentioned
uncertainties. This paper presents the definition and rationale of task A and the results of the simulations. From a repository
safety point of view, the simulations predict that the maximum temperature would be well below the design target of 100°C;
however, the stress on the container can marginally exceed the design value of 15 MPa. However, the most important finding
from the simulations is that a rock damage zone could form around the emplacement borehole. Such damage zone can extend a
few metres from the walls of the emplacement holes, with permeability values that are orders of magnitude higher than the
initial values. The damage zone has the potential to increase the radionuclide transport flux from the geosphere; the effect
of such an increase should be taken into account in the safety assessment and mitigated if necessary by the provision of sealing
systems.
Prepared for publication in Environmental Geology.
DECOVALEX-THMC Special Issue. 相似文献
197.
Thi Thao Dinh To Quyen Nguyen Gia Co Quan Vo Dong Nghi Nguyen Hon Quoc Tran Tien Khoa Le 《International Journal of Environmental Science and Technology》2017,14(12):2613-2622
Magnetic photo-Fenton catalysts based on spinel CuFe2O4 were successfully prepared by the starch-assisted sol–gel method. Various synthetic conditions such as annealing temperatures (700, 800 and 900 °C) and molar ratios of Cu2+/Fe3+/C6H10O5 in the precursor solution (from 1:2:2 to 1:2:4) were, respectively, used in order to study the influences of annealing temperatures and precursor starch contents on the magnetic and catalytic properties of CuFe2O4 powders. The photo-Fenton catalytic activity was evaluated via the degradation of methylene blue under ultraviolet and visible irradiation with H2C2O4 as a new oxidizing agent. According to the results, when the annealing temperature increased to 800 °C, the spinel CuFe2O4 phase amount was increased, which strongly enhances the photo-Fenton catalytic performance. However, above 800 °C, the catalytic activity was reduced, due to the increase in particle size. The starch content also affected the surface Cu2+ content and the particle size of catalysts. The catalyst prepared at 800 °C with the molar Cu2+/Fe3+/C6H10O5 ratio of 1:2:3 presented the best photo-Fenton performance, owing to its highest surface Cu2+ content. This catalyst also exhibits ferromagnetic properties (saturation magnetization of 25.836 emu/g and coercivity of 1010.23 Oe), which allows them to be easily separated from the solution by a magnet. 相似文献
198.
Thanh Son Nguyen Suched Likitlersuang Hiroyasu Ohtsu Takafumi Kitaoka 《Arabian Journal of Geosciences》2017,10(16):369
Rainfall-induced landslides frequently occur in humid temperate regions worldwide. Research activity in understanding the mechanism of rainfall-induced landslides has recently focused on the probability of slope failure involving non-homogeneous soil profiles. This paper presents probabilistic analyses to assess the stability of unsaturated soil slope under rainfall. The influence of the spatial variability of shear strength parameters on the probability of rainfall-induced slope failure is conducted by means of a series of seepage and stability analyses of an infinite slope based on random fields. A case study of shallow failure located on sandstone slopes in Japan is used to verify the analysis framework. The results confirm that a probabilistic analysis can be efficiently used to qualify various locations of failure surface caused by spatial variability of soil shear strength for a shallow infinite slope failure due to rainfall. 相似文献
199.
Geoelectrical profiling with multi-electrode systems has become an important tool for monitoring dike embankments bordering rivers. Profiles running perpendicular to the dike axis are affected by the dike topography, with the amplitude of this effect dependent on the surface geometry and the choice of the electrode configuration. Investigations using seven different electrode configurations have shown that some configurations are less sensitive to the topography than others.The topography correction method (TCM) is an important tool for processing data from measurements at river dikes. This method is generally recommended for flank angles steeper than 10°. The topography effect is calculated by two-dimensional finite element modelling. The resulting synthetic data of a homogeneous dike body are used to apply a topographic correction for each measurement.The topographic effect and correction procedure is demonstrated for synthetic dike data and for a data set from a river dike in Thai Binh province (Vietnam). The topography can be ignored for flank angles less than 25° if an averaged Half-Wenner electrode configuration is used. This configuration has proved to be less affected by undulated topography and the focusing effect of averaging the two data sets provides reliable structural information without the need for time-consuming data inversion. 相似文献
200.