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111.
Nur Shafwaty Sa’at 《社会与自然资源》2018,31(7):773-789
In community-based natural resource management, there is an emerging body of research on the work of external actors and their influence in community–resource interrelationships and community management decisions. Contributing to this research, this study examined the work of external actors using findings from semistructured interviews and participant observations conducted in Klong Prasong subdistrict, Krabi Province, Thailand, in mid-2014. The external actors, through Janus-faced linkages, are able to influence community–resource interrelationships and management approaches both positively and negatively. This case study also revealed university researchers, ecotourists, and private investors as non-conventional external actors. By influencing decision-making structures and environmental stewardship, external actors impact on the governance of a community natural resource. 相似文献
112.
First insights into the demography of the rare gorgonian Spinimuricea klavereni in the Mediterranean Sea 下载免费PDF全文
We present the results of the first study to highlight the demography, morphometry and growth rates of Spinimuricea klavereni, a rare Mediterranean endemic gorgonian exceptionally common in shallow depths of the Northeast Marmara Sea. In the study area, this species forms vast populations on rocks, boulders and attached to pebbles/stones/shells on soft substrates between 20 and 45 m depth, with a total average density of 0.3 colonies·m?2 but comprising patches up to 3 colonies·m?2. Colonies, which are on average 42.9 (±20.1) cm in height, can reach up to 110 cm. Unlike other Mediterranean gorgonians, the colonies studied here showed fast growth rates that decreased with increasing colony height, between 1.5–11.1 and 4.96 ± 3.01 cm·year?1 on average. The low necrosis and high growth rates displayed by this species in the Northeast Marmara Sea confirm the previously hypothesized opportunistic behaviour of the species. The unique community consisting of S. klavereni and other rare gorgonian/soft corals has limited distribution in this area and should be considered to be a vulnerable marine ecosystem. Therefore we recommend that some conservation measures are taken, including the prohibition of all fisheries and anchoring over these assemblages. 相似文献
113.
Farhan Ali Khalid Farooq Hasan Mujtaba Ahmad Riaz Ehsan Ulhaq 《Journal of the Geological Society of India》2016,88(6):718-724
On August 10, 2010 a series of landslides of more than 90,000 m3 occurred along the Muree-Kohala road in the northern area of Pakistan. A study was undertaken to evaluate the likely impacts of percent saturation and bulk density on mobilized shear strength along the basal rupture surface of the landslide. A series of unconfined compression test and unconsolidated undrained triaxial tests were performed on remolded samples of different densities with varied percentages of saturation. The results of these tests suggest that soil cohesion and friction decreases with increasing saturation. The tests also showed that the shear strength parameters tend to increase with increasing dry density; however, all the samples exhibited a noticeable loss of shear strength with increasing degree of saturation, independent of soil density.Limit equilibrium slope stability analyses were performed along the most probable failure planes, based on shear strength parameters corresponding to degrees of saturation, which varied between 30% to about 100%. This resulted in drop of factor of safety from FS = 1.64 down to 0.51 as the degree of saturation approaches unity.These results suggest that the causative factor in triggering the landslide along Murree-Kohala was the partial saturation of the zone that developed the basal rupture plane. As rain infiltrated the slope, the bulk unit weight of the soil increased, while the shear strength along the developing plane of rupture decreased sufficiently to concentrate shear strain when the material became more than 60% saturation (FS < 1.0). 相似文献
114.
Spatio‐temporal distribution of actual evapotranspiration in the Indus Basin Irrigation System 下载免费PDF全文
Strategic planning of optimal water use requires an accurate assessment of actual evapotranspiration (ETa) to understand the environmental and hydrological processes of the world's largest contiguous irrigation networks, including the Indus Basin Irrigation System (IBIS) in Pakistan. The Surface Energy Balance System (SEBS) has been used successfully for accurate estimations of ETa in different river basins throughout the world. In this study, we examined the application of SEBS using publically available remote sensing data to assess spatial variations in water consumption and to map water stress from daily to annual scales in the IBIS. Ground‐based ETa was calculated by the advection‐aridity method, from nine meteorological sites, and used to evaluate the intra‐annual seasonality in the hydrological year 2009–2010. In comparison with the advection‐aridity, SEBS computed daily ETa was slightly underestimated with a bias of ?0.15 mm day?1 during the kharif (wet; April–September) season, and it was overestimated with a bias of 0.23 mm day?1 in the rabi (dry; October–March) season. Monthly values of the ETa estimated by SEBS were significantly (P < 0.05) controlled by mean air temperature and rainfall, among other climatological variables (relative humidity, sunshine hours and wind speed). Because of the seasonal (kharif and rabi) differences in the water and energy budget in the huge canal command areas of the IBIS, ETa and rainfall were positively correlated in the kharif season and were negatively correlated during the rabi season. In addition, analysis of the evaporation process showed that mixed‐cropping and rice–wheat dominated areas had lower and higher water consumption rates, respectively, in comparison with other cropping systems in the basin. Basin areas under water stress were identified by means of spatial variations in the relative evapotranspiration, which had an average value of 0.59 and 0.42 during the kharif and the rabi seasons, respectively. The hydrological parameters used in this study provide useful information for understanding hydrological processes at different spatial and temporal scales. Results of this study further suggest that the SEBS is useful for evaluation of water resources in semi‐arid to arid regions over longer periods, if the data inputs are carefully handled. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
115.
Studies on the chemically stabilized soils have shown that the effectiveness of treatment is largely dependent on soil’s natural
environment. In tropical kaolin soils, phosphoric acid may be used as an alternative to traditional alkaline stabilizers for
improving soil properties. This research was carried out in an effort to identify the time-dependent soil-stabilizer reactions.
Data for the study of characterization of treated samples were obtained from X-ray diffractometry, energy dispersive X-ray
spectrometry, field emission scanning electron microscopy, Fourier transform infrared spectroscopy, and leaching analysis.
Based on the collected data, the kaolinite mineral with pH-dependent structural properties showed slightly different behavior
both in basic and in acidic mediums. Also, it was found that the chemical stabilizers preferentially attacked the alumina
surface of the clay particles. Therefore, it was rational to suggest that with respect to lime and phosphoric acid treatment,
aluminate hydrate compounds are more likely to be formed. 相似文献
116.
Amin Eisazadeh Khairul Anuar Kassim Hadi Nur 《Geotechnical and Geological Engineering》2012,30(6):1435-1440
Studies on the chemically stabilized soils have shown that the effectiveness of treatment is largely dependent on soil??s natural environment. In this research, the time-dependent changes induced in permanent cation exchange capacity of lime and phosphoric acid treated soils, comprised mainly of montmorillonite and kaolinite minerals, were investigated. Also, in order to study the relationship between the exchange capacity and acidity/alkalinity of pore water, pH measurements were performed on cured samples. Based on the collected data, it was found that the pH of stabilized soils showed a tendency for reaching soil??s natural pH with increasing curing time. In addition, the increase in number of broken bonds around the edges of soil particles and also the formation of cementitious compounds that acquired negative charges contributed to achieving higher CECp values at longer curing periods. Nevertheless, the kaolinite mineral with pH-dependent structural properties, showed a rather limited behavior in the acidic medium. From engineering point of view, the lime treated samples revealed the highest degree of improvement with an approximately ten-fold strength increase in comparison to the natural soil over an 8?months curing period. 相似文献
117.
This is an examination of the gravitational instability of the major large-scale perturbation modes for a fixed value of the
azimuthal wave number m = 1 in nonlinearly nonstationary disk models with isotropic and anisotropic velocity diagrams for
the purpose of explaining the displacement of the nucleus away from the geometric center (lopsidedness) in spiral galaxies.
Nonstationary analogs of the dispersion relations for these perturbation modes are obtained. Critical diagrams of the initial
virial ratio are constructed from the rotation parameters for the models in each case. A comparative analysis is made of the
instability growth rates for the major horizontal perturbation modes in terms of two models, and it is found that, on the
average, the instability growth rate for the m = 1 mode with a radial wave number N = 3 almost always has a clear advantage
relative to the other modes. An analysis of these results shows that if the initial total kinetic energy in an isotropic model
is no more than 12.4% of the initial potential energy, then, regardless of the value of the rotation parameter Ω, an instability
of the radial motions always occurs and causes the nucleus to shift away from the geometrical center. This instability is
aperiodic when Ω = 0 and is oscillatory when Ω ≠ 0 . For the anisotropic model, this kind of structure involving the nucleus
develops when the initial total kinetic energy in the model is no more than 30.6% of the initial potential energy. 相似文献
118.
Adnan R. Al-Azri Sergey A. Piontkovski Khalid A. Al-Hashmi Joaquim I. Goes Helga do R. Gomes Patricia M. Glibert 《Estuaries and Coasts》2014,37(2):325-338
Cochlodinium polykrikoides formed large blooms in the coastal waters of Oman from October 2008 through mid-January 2009, and satellite images from Aqua-MODIS and region-wide reports suggest that this bloom was found throughout the Arabian Gulf and Sea of Oman for more than 10 months. The unusual occurrence of this species appears to have supplanted the more regularly occurring bloom species, Noctiluca scintillans, in 2008–2009. For the first 2 weeks of the coastal Omani bloom, C. polykrikoides abundance was near monospecific proportions, with cell densities ranging from 4.6?×?103 to 9?×?106 cells L?1 and very high levels of chlorophyll a (78.0 μg L?1) were also recorded. The regional progression of the bloom likely began with stronger than normal upwelling along the Iranian and northern Omani coasts during the southwest monsoon in late summer, followed by discharge of unusually warm coastal plume water along the coast of Oman with the reversal of monsoonal winds in late October. The occurrence and persistence of high densities of C. polykrikoides in Oman coastal water were also significantly influenced by an elevated nutrient load and warmer than normal temperatures. Concentrations of nutrients, especially NH4 +, urea, PO4 3?, and organic nitrogen and phosphorus, were manyfold higher than observed in the year prior or since. These findings suggest that mesoscale features were important in bloom dynamics more regionally, but locally the bloom was sustained by nutrient enrichment supplemented by its mixotrophic capabilities. 相似文献
119.
Ahmed I. Rushdi Khalid F. Al-Mutlaq Bernd R. T. Simoneit Adnan Al-Azri Ali A. Z. DouAbul Sheikha Al-Zarban Faiza Al-Yamani 《Arabian Journal of Geosciences》2010,3(2):113-131
River runoff and atmospheric fallout (dust and air particulate matter) are major input sources of natural and anthropogenic
terrestrial organic and inorganic components to the Arabian seas. In this study, we report on the various lipid tracer compounds
that might be transported to the Arabian Gulf by rivers, dust, and air particulate matter. These are based on geochemical
analysis of sediment, dust, and particulate samples collected from Iraq, Kuwait, and Saudi Arabia. The samples were extracted
with a dichloromethane/methanol mixture and analyzed by gas chromatography-mass spectrometry. The extractable organic compounds
(lipids) in the samples include n-alkanes, n-alkanoic acids, n-alkanols, methyl n-alkanoates, steroids, triterpenoids, carbohydrates, and petroleum hydrocarbons. The steroids and triterpenoids were major
components in river and wetland samples. The major sources of these lipids were from natural vegetation, microbial (plankton
and bacteria) residues in the sediments, sand, and soils, with some contribution from anthropogenic sources. Accordingly,
these sources could be major inputs to the Arabian seas besides the autochthonous marine products. Future studies of the organic
and inorganic biogeochemistry on river, dust, and coastal areas are needed to characterize the various regional sources, transformation,
and diagenetic processes of the organic matter en route to the marine environment. 相似文献
120.
Submarine and coastal karstic groundwater discharges along the southwestern Mediterranean coast of Turkey 总被引:1,自引:1,他引:0
C. Serdar Bayari N. Nur Ozyurt Mehmet Oztan Yalin Bastanlar Guzden Varinlioglu Hayati Koyuncu Haldun Ulkenli Serdar Hamarat 《Hydrogeology Journal》2011,19(2):399-414
A 120 km-long part of the southwestern coast of Turkey, with well-developed karst terrain in contact with the sea, has been investigated by systematic diving surveys to determine the submarine groundwater discharges (SGDs). The physical, chemical and isotopic data have been used to determine the rate of the fresh groundwater end member (FEM) and its temporal dynamics. About 150 SGDs have been detected by diving surveys employed mostly up to a depth of 30 m below sea level (bsl). Among those, 15 SGDs are in the form of coastal or submarine caves with entrances ranging between sea surface and 40 m bsl. The FEM contribution in SGDs ranges from a few percent to more than 80%. Stable isotope data suggest a range of mean recharge area elevations extending from the coast to more than 1,000 m inland. In many of the SGDs, the FEMs are characterized by tritium-based residence times ranging from recent to several decades. Hypothetical geochemical calculations of mixing between freshwater and seawater end members reveal that more than 45% of freshwater contribution is required for karst development in the SGDs. Models suggest a threshold pH of 7.6 or lower for the carbonate rock dissolution. 相似文献