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581.
J. B. Witter P. Hernandez A. J. L. Harris N. Pérez 《Pure and Applied Geophysics》2012,169(10):1875-1889
We apply a measurement technique that utilizes thermal video of vapor-dominated volcanic plumes to estimate the H2O gas flux at three degassing volcanoes. Results are compared with H2O flux measurements obtained using other methods to verify the thermal camera-derived values. Our estimation of the H2O emission rate is based on the mass and energy conservation equations. H2O flux is quantified by extracting the temperature and width of the gas plume from the thermal images, calculating the transit velocity of the gas plume from the thermal video, and combining these results with atmospheric parameters measured on-site. These data are then input into the equations for conservation of mass and energy. Selected volcanoes for this study were Villarrica in Chile, Stromboli in Italy, and Santa Ana in El Salvador. H2O fluxes estimated from the thermal imagery were 38–250?kg?s?1 at Villarrica, 4.5–14?kg?s?1 for Stromboli’s Central Crater, and 168–219?kg?s?1 at Santa Ana. These compare with H2O flux values estimated by other methods of 73–220, 3–70 and 266?kg?s?1, at the three volcanoes, respectively. The good agreement between thermal image-derived results and those estimated by other methods seem to validate this method. 相似文献
582.
The thermal signature of volcanic eruptions on Io and Earth 总被引:1,自引:0,他引:1
Ashley Gerard Davies Laszlo P. Keszthelyi Andrew J.L. Harris 《Journal of Volcanology and Geothermal Research》2010
We investigate a spectrum-based technique to identify the style of active volcanic eruptions on Jupiter's moon Io. Thermal remote sensing of Io has had to rely primarily on low-spatial-resolution data, similar to low-spatial-resolution satellite data applied to detecting and charting the temporal evolution of terrestrial hot spots. These terrestrial analyses use data from sensors designed to monitor the weather and sea surface temperature. On Io, such low-spatial-resolution data are used to classify eruption styles (modes of emplacement) by means of several criteria related to the temporal evolution of the infrared spectrum associated with the eruptive activity at each hot spot, which we term “thermal signature.” We find that the ratio of the emission at 2 and 5 µm, and how this ratio changes with time, is often diagnostic of eruption style, even in low-spatial-resolution data. Tests using thermal data for terrestrial “ground truth” cases show that our classification system is valid on Earth. The results of our analysis can be used to aid in the design of future space-based instruments that can be used for volcano monitoring on Io, as well as Earth. 相似文献
583.
Stuart A. Harris 《寒旱区科学》2010,2(5):0371-0383
In the Cordillera of western North America, the influence of the Pacific Interdecadal Oscillation only affects coastal areas west of the Coast Range and the lowlands of western and southern Alaska. The rest of the area is subject to a climate controlled by the relative strengths of three distinct air masses, viz., the cold cA/cP air that is dominant in winter, the mP air bringing cool moist air over the mountains throughout the year, and the dry hot cT air from the deserts of the southwestern United States. The Arctic Front marks the boundary between the cA/cP air mass and the other two. Changes in the relative strengths of these air masses appear to explain the climatic changes documented throughout the region. Thus, in the last 30 years, the average position of the Arctic Front has moved north from about 53°N to 58°N, causing the warming in northern British Columbia and cooling south of Calgary, Alberta. This concept of changing positions of the air masses also appears to explain the mechanism behind the past climatic changes in this region. During the last Neoglacial event (c.1400-1900 A.D.), it appears that the cA/cP air mass had strengthened enough to push the Arctic Front south of the 49th parallel. Incursions of mP air increased with localized areas of short-term heavy snowfalls resulting in small-scale advances of glaciers in these regions. This accounts for the variability in timing and extent of these glacial advances, while the resulting increased Chinook activity produced the development of a sand sea between Medicine Hat and Regina on the southern Prairies. The cT air mass was relatively weak, permitting these changes. During the maximum of the Altithermal/Hysithermal warm event (6,000 years B.P.), the Arctic Front had retreated into the southern Yukon Territory as the cT air mass became stronger. The mP air could not move inland as easily, resulting in drier climates across the region. Prairie plants mi- grated into the southern Yukon Territory, and land snails from the eastern United States were able to migrate up the Saskatchewan River system as far as Lake Louise, Alberta. On the southern Prairies, the many small sloughs and lakes dried up. During the maximum of the Late Wisconsin Glacial event (15,000 years B.P.), the Arctic Front had moved south to the vicinity of 30°N, while there had been a southward movement of the Zone of Intertropical Convergence from the equator to about 10°S. The mP air was also very strong and dumped enormous quantities of snow in the glaciated Canadian Cordillera, but it does not appear to have moved south any distance into the northern United States, witness the limited glaciation and widespread permafrost that developed there. Instead, there is evidence for buffering of the climatic changes in the closed basins in the northern Cordillera of the contiguous United States. The source of the cT air mass had moved south into the northern part of South America, permitting an exchange of savannah biota between the two continents. An extensive area of white dune sands inundated both savannah and forest along the inland hills in Guyana. This parallels the massive changes in African climatology during the last Ice Age (Fairbridge, 1964). If these changes occurred each time there was a major glaciation in the Northern Hemisphere, this would explain the movement of biota from all terrestrial environments between the two American continents in the last 2 million years. A similar northward movement of climatic belts occurred in South America, with the cA air from Antarctica expanding northwards into southern Argentina and Chili. However paucity of data and the potential effects of El Ni o and the Southern Oscillation make it difficult toprovide details of the changes there in the present state of knowledge. This technique of studying the mechanisms of present-day climatic changes and applying the results to past climatic events has considerable potential for elucidating past climatic changes elsewhere in continental regions. This may prove particularly valuable in studying the Siberian anticyclone that is the main cause of the distribution of permafrost, but this will need international cooperation to be successful. 相似文献
584.
了解气候变化对冬小麦生育期的影响,可为农业应对气候变化、调整农作物种植结构提供科学依据。本文利用1996—2022年近26 a拉萨冬小麦生育期以及逐日平均气温(Tm)、最高气温(Tmax)、最低气温(Tmin)、气温日较差(DTR)、相对湿度(RH)、降水量(Pr)、日照时数(S)和≥0 ℃积温(∑T0)等资料,采用线性倾向估计、Pearson相关系数和优势分析方法等,分析了拉萨河谷冬小麦生育期变化特征以及影响的主导气象因子。结果表明:(1)近26 a拉萨河谷冬小麦营养生长期(Vegetative Growth Period,VGP)、生殖生长期(Reproductive Growth Period,RGP)和全生育期(Whole Growth Period,WGP)的Tm均呈上升趋势,Tmin升温率大于Tmax的升温率,DTR、RH呈减小趋势,∑T0、Pr和S趋于增加。(2)冬小麦拔节前各生育期提早,提早率为0.47~6.75 d/10 a;拔节后各生育期推迟,推迟率为3.17~7.03 d/10 a;VGP、WGP延长,RGP缩短。(3)拉萨河谷10月、1月Tmin和2月Tm的升高,是冬小麦出苗、分蘖和返青期提前的主要因素,导致冬小麦拔节后生育期推迟的重要因素则是4—5月S增加及6月RH减少。 相似文献
585.
记述了广东省南雄盆地上白垩统主田组3组恐龙行迹,由杨梅坑足迹点的足迹命名了南雄鸭嘴龙足迹(Hadrosauropodus nanxiongensis ichnosp. nov.)一新种;古市足迹点的足迹归入鸭嘴龙足迹一未定种(Hadrosauropodus isp.)。这是中国鸭嘴龙足迹属的首次描述,将该足迹的分布从北美拓展至中国,并为南雄盆地存在大型的鸭嘴龙提供了新的化石证据。还整理了中国已描述的大型鸟脚类足迹:中国足迹(Sinoichnites)被定为非正式的塑模标本;扬子足印(Yangtzepus)被归入兽脚类足迹;禽龙足迹(Iguanodonopus)被认为是裸名,归入禽龙足迹(Iguanodontipus);嘉荫足迹(Jiayinosauropus)增加了新材料并得以具体描述;内乡足迹(Neixiang footprint)得以重新描述。 相似文献
586.
L. Gurioli D. Andronico P. Bachelery H. Balcone-Boissard J. Battaglia G. Boudon A. Burgisser M. R. Burton K. Cashman S. Cichy R. Cioni A. Di Muro L. Dominguez C. D’Oriano T. Druitt A. J. L. Harris M. Hort K. Kelfoun J. C. Komorowski U. Kueppers J. L. Le Pennec T. Menand R. Paris L. Pioli M. Pistolesi M. Polacci M. Pompilio M. Ripepe O. Roche E. Rose-Koga A. Rust F. Schiavi L. Scharff R. Sulpizio J. Taddeucci T. Thordarson 《Bulletin of Volcanology》2015,77(6):1-33
587.
O. Bruguier D. Bosch R. T. Pidgeon D. I. Byrne L. B. Harris 《Contributions to Mineralogy and Petrology》1999,136(3):258-272
Conventional and SHRIMP U-Pb analyses of zircon, monazite, titanite and apatite from the high grade rocks of the Northampton
Complex in Western Australia provide constraints on the timing of metamorphic processes and deformation events in the northern
Darling Mobile Belt (western margin of the Archean Yilgarn Craton). Paragneisses and mafic volcanics and/or intrusions have
undergone granulite facies metamorphism in a probable extensional tectonic setting prior to formation of W- to NW-verging
folds and thrusts cut by normal shears (interpreted as late collapse structures) during the main deformation event (D1). These structures are folded by open to tight folds with NW-striking axial surfaces developed in a second, NE-SW contractional
event (D2). Zircons from a mafic granulite provide an age of 1079 ± 3 Ma attributed to new zircon growth prior to, or at the peak of
regional granulite facies metamorphism. Metamorphic monazites extracted from a paragneiss yield an identical age of 1083 ± 3 Ma.
The similarity of ages between zircons from the mafic granulite (1079 ± 3 Ma) and monazites from the paragneiss (1083 ± 3 Ma)
is interpreted to reflect fast cooling and/or rapid uplift, which is consistent with thrusting of the gneissic units during
the first deformation event (D1) associated with the onset of retrograde metamorphism. Granitic activity at 1068 ± 13 Ma was followed by intrusion of post-D2 pegmatite (989 ± 2 Ma), which constrains the end of metamorphism and associated deformation. Cooling of the complex to about
500 °C is timed by the apatite age of 921 ± 23 Ma. SHRIMP U-Pb ages of detrital zircons from a paragneiss sample yield a maximum
age of 2043 Ma, with no evidence of an Archean Yilgarn signature. A majority of ages between 1.6 and 1.9 Ga are consistent
with derivation from the Capricorn Orogen on the northern margin of the Yilgarn Craton. Younger detrital zircons with 1150–1450 Ma
ages, however, indicate an additional source that had undergone early Grenvillian igneous or metamorphic event(s) and also
places a maximum age constraint upon deposition. The source of this clastic material may have been from within the southern
Darling Mobile Belt or from Greater India (adjacent to the Northampton Complex in Rodinia reconstructions). This study documents
an extended Grenvillian history, with basin formation, sedimentation, granulite facies metamorphism, contractional tectonics
(two periods with orthogonal directions of shortening) and late pegmatite emplacement taking place between 1150–989 Ma on
the western margin of the Yilgarn Craton. Ages recorded in this study indicate that the proposed global distribution of Grenvillian
belts during assembly of the Rodinia supercontinent should be reassessed to include the Darling Mobile Belt.
Received: 7 January 1998 / Accepted: 10 March 1999 相似文献
588.
Jacek A. Majorowicz Jan Safanda Robert N. Harris Walter R. Skinner 《Global and Planetary Change》1999,20(4):715
New temperature logs in wells located in the grassland ecozone in the Southern Canadian Prairies in Saskatchewan, where surface disturbance is considered minor, show a large curvature in the upper 100 m. The character of this curvature is consistent with ground surface temperature (GST) warming in the 20th century. Repetition of precise temperature logs in southern Saskatchewan (years 1986 and 1997) shows the conductive nature of warming of the subsurface sediments. The magnitude of surface temperature change during that time (11 years) is high (0.3–0.4°C). To assess the conductive nature of temperature variations at the grassland surface interface, several precise air and soil temperature time series in the southern Canadian Prairies (1965–1995) were analyzed. The combined anomalies correlated at 0.85. Application of the functional space inversion (FSI) technique with the borehole temperature logs and site-specific lithology indicates a warming to date of approximately 2.5°C since a minimum in the late 18th century to mid 19th century. This warming represents an approximate increase from 4°C around 1850 to 6.5°C today. The significance of this record is that it suggests almost half of the warming occurred prior to 1900, before dramatic build up of atmospheric green house gases. This result correlates well with the proxy record of climatic change further to the north, beyond the Arctic Circle [Overpeck, J., Hughen, K., Hardy, D., Bradley, R., Case, R., Douglas, M., Finney, B., Gajewski, K., Jacoby, G., Jennings, A., Lamourex, S., Lasca, A., MacDonald, G., Moore, J., Retelle, M., Smith, S., Wolfe, A., Zielinski, G., 1997. Arctic environmental change of the last four centuries, Science 278, 1251–1256.]. 相似文献
589.
Shallow embayments in Connecticut were sampled with a 1-m beam trawl for young-of-year winter flounder from 1990–1993 to determine if there are habitat types within nursery areas which consistently yield higher abundances. Initial examination of catch frequencies and all physical measurements indicated that only sediment type correlated with abundance. There was no consistent pattern in winter flounder catch in relation to salinity, water temperature, water column turbidity, depth interval, channel/non-channel, or the presence of sea lettuce (Ulva lactuca). Catch data were then classified into five habitat types defined by a combination of sediment and overlying litter. Analysis of variance in catch among habitat types showed that mean catch was significantly different among four of the five habitat types. Highest densities within a site most often occurred in mud/shell-litter habitat, followed by mud/wood-litter and mud/no litter habitat; sandy sites with or without litter yielded the lowest densities. Independent sampling of new sites corroborated the distributional pattern seen at the original sites, and importance of mud/shell-litter habitat. The distributional pattern seen here can provide a means of assessing which sites would be expected to support a higher abundance of young-of-year winter flounder, and which sites might provide less, if no other factors intervene. 相似文献
590.
GOES provides thermal data for all of the Hawaiian volcanoes once every 15 min. We show how volcanic radiance time series
produced from this data stream can be used as a simple measure of effusive activity. Two types of radiance trends in these
time series can be used to monitor effusive activity: (a) Gradual variations in radiance reveal steady flow-field extension
and tube development. (b) Discrete spikes correlate with short bursts of activity, such as lava fountaining or lava-lake overflows.
We are confident that any effusive event covering more than 10,000 m2 of ground in less than 60 min will be unambiguously detectable using this approach. We demonstrate this capability using
GOES, video camera and ground-based observational data for the current eruption of Kīlauea volcano (Hawai'i). A GOES radiance
time series was constructed from 3987 images between 19 June and 12 August 1997. This time series displayed 24 radiance spikes
elevated more than two standard deviations above the mean; 19 of these are correlated with video-recorded short-burst effusive
events. Less ambiguous events are interpreted, assessed and related to specific volcanic events by simultaneous use of permanently
recording video camera data and ground-observer reports. The GOES radiance time series are automatically processed on data
reception and made available in near-real-time, so such time series can contribute to three main monitoring functions: (a)
automatically alerting major effusive events; (b) event confirmation and assessment; and (c) establishing effusive event chronology.
Received: 12 January 1999 / Accepted: 13 July 1999 相似文献