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981.
F. J. Cerino Córdova Ph.D. A. M. García León Ph.D. R. B. Garcia Reyes Ph.D. M. T. Garza González Ph.D. E. Soto Regalado Ph.D. M. N. Sánchez González Ph D. I. Quezada López 《International Journal of Environmental Science and Technology》2011,8(4):695-704
A central composite face-centered design was used to study and to optimize lead biosorption from aqueous solution on Aspergillus terreus biomass. Four factors such as stirring speed, temperature, solution pH and biomass dose at different levels were studied.The hierarchical quadratic model were established by adding replicates at the central point and axial points to the initial full factorial design (24). The percentage removal of lead was affected by biomass dose, pH, and interactions between pH and biomass dose, pH and stirring speed, pH and temperature. The hierarchical quadratic model described adequately the response surface based on the adjusted determination coefficient (R2 Adj= 0.97) and the adequate precision ratio (42.21). According to this model, the optimal conditions to remove lead completely from aqueous solutions (at initial lead concentration of 50 mg/L and solutions of 100 mL) with Aspergillus terreus were at pH 5.2, 50 °C, stirring speed of 102/min and a biomass dose of 139 mg.The response surface methodology can be used to determine the optimal conditions for metal adsorption on several adsorbents. In addition, results reported in this research demonstrated the feasibility of employing A. terreus as biosorbent for lead removal. 相似文献
982.
Shavkat Rakhmatullaev Antoine Marache Frédéric Huneau Philippe Le Coustumer Masharif Bakiev Mikael Motelica-Heino 《Environmental Earth Sciences》2011,63(3):447-460
The paper presents the results of a new geostatistical approach to generate bathymetric surface models from point measurement
converted into continuous contour surfaces of reservoir bottoms in Uzbekistan. Sedimentation of reservoirs raises engineering,
environmental and economical issues for the communities around the world in areas affected by a strong water deficit. Because
of Uzbekistan’s arid climatic conditions, and uneven spatial and temporal water resources distribution, responsive and innovative
water availability assessment surveys of all major water reservoirs are required. Bathymetric surveying is a traditional method
that is carried out for the estimation of reservoir volumes and surface areas of the corresponding reservoir stages in order
to assess the water availability. Volume and surface area differences derived from multiple surveys of a reservoir provide
storage loss estimates over time due to sedimentation. However, two main factors, such as intensive field data measurement
and post data-processing, often limit the frequency of these surveys. Alternatively, innovative depth measurement technologies
coupled with contouring and surface mapping programs provide automated reservoir volume and surface area calculations. This
significantly reduces time, workload and financial burdens for reservoir sedimentation projects. This research proposes the
use of geostatistical approach to assess the reservoir sedimentation in the Akdarya reservoir of Uzbekistan. The geostatistical
approach includes (semi-) variogram analysis and interpolation (kriging and simulations—turning bands) techniques predicting
values at unsampled locations for generating digital bathymetric surface models of reservoir bottom conditions in order to
calculate the volume and surface area at a given water elevation. The simulation enables to have range of reservoir volumes
and surface areas with the same probability, in comparison to the kriging and traditional methods. This gives a real estimation
of the resource availability for water operators to manage natural resources and hydraulic infrastructure in a sustainable
manner. 相似文献
983.
984.
Mathieu?Le?CozEmail author Pierre?Genthon Pierre?M.?Adler 《Mathematical Geosciences》2011,43(7):861-878
Multiple-point statistics are used to model facies heterogeneities in the vadose zone of the Komadugu-Yobe River valley (southeastern
Niger) which is presently submitted to an undergoing intensive agricultural development; therefore, increasing quantitative
and qualitative pressures are exerted on groundwater resources. The sand–clay heterogeneities are analyzed by means of a Landsat
image acquired during a high flow period over a 160 km stretch in the downstream part of the valley and a set of 50 boreholes
drilled near the town of Diffa (4 km×4 km area). The horizontal variograms of heterogeneities are characterized by a noticeably
constant length scale of 380 m and clayey objects are shown to be randomly distributed in space according to a Poisson process.
A set of two-dimensional vertical images is built based on a Boolean procedure and the Snesim algorithm is used to simulate
synthetic three-dimensional media. When the vertical correlation length is fitted, the three-dimensional model satisfactorily
reproduces the second order statistics of heterogeneities and the specific facies patterns. 相似文献
985.
986.
Differences in physiological response to increased seawater temperature in nearshore and offshore corals in northern Vietnam 总被引:1,自引:0,他引:1
Faxneld S Jörgensen TL Nguyen ND Nyström M Tedengren M 《Marine environmental research》2011,71(3):225-233
Effects of elevated seawater temperature show high spatial heterogeneity and variation within and among coral species. The objective of this study was to investigate how two coral species, Porites lutea and Galaxea fascicularis, from two high latitude reefs differently exposed to chronic disturbance, respond to elevated seawater temperatures. Corals were collected from reefs nearshore (i.e. subjected to high sediment load, higher chlorophyll α concentrations, turbidity etc.) and offshore (i.e. less exposed). The corals were exposed in the lab to gradually increasing temperatures (25.5-33.5?°C) for 72?h after which they were allowed to recover to ambient temperature (25.5?°C) for 24?h. Production and respiration were measured after 24, 48, 72 and 96?h. The results show that P. lutea from nearshore reefs suffered an initial decrease in gross primary production/respiration (GP/R) ratio after 24?h, after only a moderate temperature increase (+2?°C, from 25.5 to 27.5?°C), while there was no difference in GP/R ratio between heat-exposed and controls the other days, indicating that the chronic disturbance in the nearshore reef had no effect on their thermotolerance. Furthermore, P. lutea from the offshore reef showed a decrease in GP/R ratio both after 24?h and 72?h (33.5?°C) of exposure. In comparison, G. fascicularis showed a decrease in GP/R ratio after 48?h, 72?h and 96?h of exposure for the nearshore corals. Also, after 72?h these corals had withdrawn their polyps. There were no differences between heat-treated and controls for the offshore G. fascicularis. This implies that the chronically disturbed G. fascicularis had lower thermotolerance when exposed to a temperature increase. This study, hence, shows that the response of corals to elevated seawater temperature varies with species and environmental background history. 相似文献
987.
988.
The objective of a field development optimization process, or workflow, is to investigate various options and determine a course of action that will deliver the largest expected value from an asset. The analysis is often complicated by uncertainty in important inputs. Ideally, operators desire workflows and tools that integrate reservoir engineering and optimization principles in a fast-solving model that can be used to explore the full range of the uncertain inputs. This need is acute in the screening and concept selection stage where the primary objective is to determine the sensitivity of competing concepts to the sources of uncertainty. In these early stages, model results can be used to determine whether additional information should be collected, and to narrow down the number of competing options. The objective of this research is the development of a workflow and tool that integrates reservoir response surfaces within a project optimization model that contains facility and operational options, and to use this model to investigate the impacts of uncertainty on decision making. The integration of technical options is critical because a static view of capital investment and facility constraints causes a systematic undervaluation and can introduce error to development decisions. The new workflow and integrated reservoir-economic optimization tool developed in this research leverage methods and engineering work products that are already known to industry, for example, experimental design (ED) and response surface methods (RSMs). A demonstration is provided for a gas flood project using a stylized reservoir. Specifically, we investigate the selection of initial well configurations and injection capacities while simultaneously accounting for the options to update these decisions after production information is acquired in the early periods of production. The workflow is used to optimize the development of a gas flood. As a second step, the workflow is used to solve a value of information problem. 相似文献
989.
P.J. O’Farrell W.J. De LangeD.C. Le Maitre B. ReyersJ.N. Blignaut S.J. MiltonD. Atkinson B. EgohA. Maherry C. ColvinR.M. Cowling 《Journal of Arid Environments》2011,75(6):612-623
Arid regions are home to unique fauna, flora, and vulnerable human populations, and present a challenge for sustainable land-use management. We undertook an assessment and valuation of three key services, grazing, tourism and water supply in the arid Succulent Karoo biome in western South Africa - a globally recognised biodiversity hotspot. We were looking for ways and values that could be used to promote conservation in this region through the adoption of sustainable land-use practices which have human welfare benefits. Our study adopted a variety of methods in valuing these services in developing ranges of values for these services. At the biome level, total annual values ranged from $ 19-114 million for grazing, $ 2-$ 20 million for tourism, and $ 300-3120 million for water. These values are generally low compared with values derived for other biomes and regions and do not adequately reflect known dependence and the importance of ecosystem services to the residents of this biome. The ecosystems here provide small but critical benefits enabling communities to sustain themselves and small changes in service levels can have major welfare effects. Highlighting these sensitivities will require finding more appropriate ways to link ecological and social factors. 相似文献
990.