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91.
92.
最近在石油勘探中关于如何测知正确的地温分布一事据认为是非常重要的。已有人提出从电测井所取得的井下温度(BHT)中推定与实际地温的近似值(静态温度,TF)的方法(Dowdle和Cobb,1975;田中、佐藤,1977)。田中等的经验式 TF=K(BHT-15)+15中的校正系数K,根据地区变化,与地温梯度具有密切的相关性。TF与BHT的关系以TF=K·BHT+α…(1)表示,K根据地温梯度的不同,变化在1.04~1.71之间。例如6.42~6.53℃/100m时,TF=1.71BHT—12.6;3.75~4.30℃/100m时,TF=1.29BHT-0.5;2.1℃/100m以下时,TF=1.04BHT+5.5。所有这些一次回 相似文献
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当前国际上关于海底矿床的研究开发,虽集中于金属矿床,然而从世界资源供需关系上看来,磷资源的重要性并不小.磷矿床大体分为四种类型,即有机沉积物矿床、鸟粪矿床、与碱性复合岩体伴生的磷灰石矿以及碳酸盐岩矿床.本文介绍的海成磷灰土(磷块岩)矿床即属于有机沉积物矿床类型.据调查从海成磷灰土矿床采到的磷矿石,约占全世界磷矿石产量的80%(冈野,1975).日本过去也曾对北大东岛的鸟粪矿床及能登半岛的中新统中部地层中的磷灰土进行过开采,但目前磷矿石则全部依赖进口.在全世界面临着沙漠化现象的今天,对于化肥原料上不可缺少的磷资源应如何保证,这确乎是农业政策上一个极为重要的课题.本文拟以海成磷灰土在海底如何形成、怎样分布等问题为中心,简单介绍一下国际上的研究现状. 相似文献
95.
MacDermott AJ Barron LD Brack A Buhse T Drake AF Emery R Gottarelli G Greenberg JM Haberle R Hegstrom RA Hobbs K Kondepudi DK McKay C Moorbath S Raulin F Sandford M Schwartzman DW Thiemann WH Tranter GE Zarnecki JC 《Planetary and Space Science》1996,44(11):1441-1446
A characteristic hallmark of life is its homochirality: all biomolecules are usually of one hand, e.g. on Earth life uses only L-amino acids for protein synthesis and not their D mirror images. It is therefore suggested that a search for extra-terrestrial life can be approached as a Search for Extra-Terrestrial Homochirality (SETH). A novel miniaturized space polarimeter, called the SETH Cigar, is described which could he used to detect optical rotation as the homochiral signature of life on other planets. Moving parts are avoided by replacing the normal rotating polarizer by multiple fixed polarizers at different angles as in the eye of the bee. It is believed that homochirality will be found in the subsurface layers on Mars as a relic of extinct life. 相似文献
96.
Recovery of polluted ecosystems: the case for long-term studies 总被引:6,自引:0,他引:6
Hawkins SJ Gibbs PE Pope ND Burt GR Chesman BS Bray S Proud SV Spence SK Southward AJ Langston WJ 《Marine environmental research》2002,54(3-5):215-222
Recovery of marine ecosystems from pollution has tended to receive less attention than the study of new or continuing impacts, but such studies are important in charting recovery from acute incidents and following legislation to deal with chronic contamination. Recovery is inevitably a long-term process, and where such studies have been made they are often too short-lived. Interest quickly wanes following an acute incident and governmental bodies rapidly switch to new legislative priorities for chronic inputs. We review three case studies: recovery of dogwhelk populations after local extinction by tributyl tin leachates from anti-fouling paints; recovery of rocky shore communities from oil spills; and recovery of estuarine ecosystems from industrial and urban development. We then make some generalisations about recovery processes before making a plea for long-term studies of polluted areas. 相似文献
97.
Li FL Findlay AM Jowett AJ Skeldon R 《International journal of population geography : IJPG》1996,2(1):51-67
"The research reported here evaluates whether students come to the UK mainly for educational reasons, and therefore perceive their stay as temporary, or whether emigration for study is being used as part of a conscious strategy by people intending to become future labour migrants.... The simplest interpretation of the results appears to be that migration, experienced as a result of international moves for study purposes, does not influence planning of further migration moves. But the research also indicates that migration for education is closely tied to other types of population redistribution and should be treated by population geographers as an integral part of international migration systems." Data were collected by questionnaire survey from 349 engineering students at Hong Kong universities and 82 Hong Kong students studying engineering in the UK. 相似文献
98.
Helama S Schöne BR Kirchhefer AJ Nielsen JK Rodland DL Janssen R 《Marine environmental research》2007,63(3):185-199
Annual growth increments were examined from shells of the ocean quahog (Arctica islandica L.) from northwest Norway and from tree-ring samples of the Scots pine (Pinus sylvestris L.) from nearby coastal areas. The reconstructed annual growth increments were used to compare growth variability in marine and terrestrial ecosystems. Spatiotemporal comparison of the growth records showed statistically significant correlation during the 19th century A.D., indicative of ecosystem-independent response to pre-anthropogenic climate variations. Geographical correlation between marine and terrestrial records was only observed at the local scale. Years with particularly low winter or high summer North Atlantic Oscillation (NAO) indices showed the best synchronization of marine and terrestrial growth. Despite strong correlation during historical time, our palaeoecological evidence suggests that marine and terrestrial ecosystems may show dissimilar growth reaction to recently observed positive winter-NAO phases. 相似文献
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100.
The managed realignment of coastal defences and subsequent creation of intertidal habitats is one of several 'soft' engineering options that could reduce the costs of maintaining embankments and at the same time deliver environmental benefits. The managed realignment at Tollesbury was one of the first in the UK, undertaken as an experimental test case to improve understanding of the practical techniques and processes involved. Independent studies were undertaken on the development of soils, benthic invertebrates and vegetation within the site in addition to methods of enhancing the process of natural colonisation of saltmarsh plants. Bathymetric and vegetation monitoring were undertaken on the adjacent estuary to determine any breach effect that may be attributed to the realignment. This paper summarises the results from the vegetation, sedimentation and invertebrate monitoring and discusses the implications for other managed realignment schemes in the UK. 相似文献