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341.
342.
Wilson Yetoh Fantong Hiroshi Satake Festus T. Aka Samuel N. Ayonghe Kazuyoshi Asai Ajit K. Mandal Andrew A. Ako 《Environmental Earth Sciences》2010,60(1):107-120
Unplanned exploitation of groundwater constitutes emerging water-related threats to MayoTsanaga River Basin. Shallow groundwater
from crystalline and detrital sediment aquifers, together with rain, dams, springs, and rivers were chemically and isotopically
investigated to appraise its evolution, recharge source and mechanisms, flow direction, and age which were used to evaluate
the groundwater susceptibility to contamination and the basin’s stage of salinization. The groundwater which is Ca–Na–HCO3 type is a chemically evolved equivalent of surface waters and rain water with Ca–Mg–Cl–SO4 chemistry. The monsoon rain recharged the groundwater preferentially at an average rate of 74 mm/year, while surface waters
recharge upon evaporation. Altitude effect of rain and springs show a similar variation of −0.4‰ for δ18O/100 m, but the springs which were recharged at 452, 679, and 773 m asl show enrichment of δ18O through evaporation by 0.8‰ corresponding to 3% of water loss during recharge. The groundwater which shows both local and
regional flow regimes gets older towards the basins` margin with coeval enrichment in F− and depletion in NO3
−. Incidentally, younger groundwaters are susceptible to anthropogenic contamination and older groundwaters are sinks of lithologenic
fluoride. The basins salinization is still at an early stage. 相似文献
343.
Karst aquifers: can they be protected? 总被引:1,自引:1,他引:0
Panno SV 《Ground water》2006,44(4):494-494
344.
Indigenous knowledge related to climate variability and change: insights from droughts in semi-arid areas of former Makueni District,Kenya 总被引:1,自引:1,他引:0
Chinwe Ifejika Speranza Boniface Kiteme Peter Ambenje Urs Wiesmann Samuel Makali 《Climatic change》2010,100(2):295-315
This article describes the indigenous knowledge (IK) that agro-pastoralists in larger Makueni District, Kenya hold and how
they use it to monitor, mitigate and adapt to drought. It examines ways of integrating IK into formal monitoring, how to enhance
its value and acceptability. Data was collected through target interviews, group discussions and questionnaires covering 127
households in eight villages. Daily rainfall data from 1961–2003 were analysed. Results show that agro-pastoralists hold IK
on indicators of rainfall variability; they believe in IK efficacy and they rely on them. Because agro-pastoralists consult
additional sources, the authors interpret that IK forms a basic knowledge frame within which agro-pastoralists position and
interpret meteorological forecasts. Only a few agro-pastoralists adapt their practices in anticipation of IK-based forecasts
partly due to the conditioning of the actors to the high rainfall variability characteristic of the area and partly due to
lack of resources. Non-drought factors such as poverty, inadequate resources and lack of preparedness expose agro-pastoralists
to drought impacts and limit their adaptive capacity. These factors need to be understood and effectively addressed to increase
agro-pastoralists’ decision options and the influence of IK-based forecasts on their decision-making patterns. The limited
intergenerational transfer of IK currently threatens its existence in the longer term. One way to ensure its continued existence
and use is to integrate IK into the education curriculum and to link IK with formal climate change research through the participation
of the local people. However, further studies are necessary to address the reliability and validity of the identified IK indicators
of climate variability and change. 相似文献
345.
346.
Peter R. Gent Stephen G. Yeager Richard B. Neale Samuel Levis David A. Bailey 《Climate Dynamics》2010,34(6):819-833
A decadal climate projection between 1980 and 2030 using a nominal 0.5° resolution in the atmosphere and land components has
been performed using the Community Climate System Model, version 3.5. The mean climate is compared to a companion simulation
using a nominal 2° resolution in the atmosphere and land components. The increased atmosphere resolution has several benefits,
and produces a significantly better mean climate. The maximum sea surface temperature biases in the major upwelling regions,
including the West Coast of the USA, are reduced by more than 60%. Precipitation patterns are improved in the summer Asian
monsoon, mostly due to the better resolved orography, and in the eastern tropical Pacific Ocean south of the equator. The
improved precipitation patterns lead to better river flows in many rivers worldwide. The atmospheric circulation in the Arctic
also improves, which leads to a better regional sea ice thickness distribution in the Arctic Ocean. 相似文献
347.
Samuel Nicolay Georges Mabille Xavier Fettweis Michel Erpicum 《Climate Dynamics》2009,33(7-8):1117-1129
A wavelet-based methodology is applied to relevant climatic indices and air temperature records and allow to detect the existence of unexpected cycles. The scale spectrum shows the presence of two cycles of about 30 and 43 months, respectively, in the air–temperature time series, in addition to the well-known cycles of 1 day and 1 year. The two cycles do not affect the globe uniformly: some regions seem to be more influenced by the period of 30 months (e.g. Europe), while other areas are affected by the period of 43 months (e.g. North-West of the USA). Similar cycles are found in the indices and the regions influenced by these indices: the NAO index and the Western Europe display a cycle of 30 months, while the cycle of 43 months can be found in the ENSO index and in regions where it is known to have an impact. 相似文献
348.
Marcelo Samuel Berman 《Astrophysics and Space Science》2009,321(3-4):157-160
We “explain”, using a Classical approach, how the Universe was created out of “nothing”, i.e., with no input of initial energy nor mass. The inflationary phase, with exponential expansion, is accounted for, automatically, by our equation of state for the very early Universe. This is a Universe with no-initial infinite singularity of energy density. 相似文献
349.
OluKayode J. Samuel Chris Cornford Martin Jones Olabisi A. Adekeye Samuel O. Akande 《Organic Geochemistry》2009,40(4):461-483
Biomarker and n-alkane compound specific stable carbon isotope analyses (CSIA) were carried out on 58 crude oil samples from shallow water and deepwater fields of the Niger Delta in order to predict the depositional environment and organic matter characteristics of their potential source rocks. Using a source organofacies prediction approach from oil geochemistry, the presence in the western deepwater oils relatively abundant C27 steranes, C30 24-n-propyl cholestane, low oleanane index, relatively low pr/ph ratios, gammacerane, and positive to nearly flat C12–C30 n-alkane compound specific stable carbon isotope profiles, suggests that the source facies that expelled these oils contain significant marine derived organic matter deposited under sub-oxic and stratified water column conditions. This contrasts with the terrigenous organic matter dominated source rocks accepted for shallow water Niger Delta oils. Oils in the shallow water accumulations can be separated into terrigenous and mixed marine-terrigenous families. The terrigenous family indicates expulsion from source rock(s) containing overwhelmingly higher plant source organic matter (average oleanane index = 0.48, high C29 steranes) as well as having negative sloping n-alkane isotope profiles. Oxic source depositional conditions (pr/ph > 2.5) and non-stratified conditions (absence to low gammacerane content) are inferred for the terrigenous family. The mixed marine-terrigenous family has biomarker properties that are a combination of the deepwater and terrigenous shallow water oils. Bitumen extracts of the sub-delta Late Cretaceous Araromi Formation shale in the Dahomey Basin are comparable both molecularly and isotopically to the studied western deepwater oil set, but with an over all poor geochemical correlation. This poor geochemical match between Araromi shale and the western deepwater oils does not downgrade the potential of sub-delta Cretaceous source rock contribution to the regional oil charge in the deepwater Niger Delta. 相似文献
350.
Geochemical fingerprinting is a rapidly expanding discipline in the earth and environmental sciences. It is anchored in the recognition that geological processes leave behind chemical and isotopic patterns in the rock record. Many of these patterns, informally referred to as geochemical fingerprints, differ only in fine detail from each other. For this reason, the approach of fingerprinting requires analytical data of very high precision and accuracy. 相似文献