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21.
The Kolmogorov constants for CO2, wind velocity, air temperature, and humidity fluctuations were evaluated from measurements made over soybean and grain sorghum fields and found to be 0.78 ± 0.11, 0.49 ± 0.08, 0.70 ± 0.15, and 0.99 ± 0.16, respectively. These results are consistent with recent observations reported in the literature.Published as Paper No. 7255, Journal Series, Nebraska Agricultural Experiment Station. The work reported here was conducted under Regional Research Project 11-33 and Nebraska Agricultural Experiment Station Project 27-003.Associate Professor and Post Doctoral Research Associate, respectively, Center for Agricultural Meteorology and Climatology, Institute of Agriculture and Natural Resources, University of Nebraska, Lincoln, NE, U.S.A., 68583-0728. 相似文献
22.
Dean W. Matson David W. Muenow Michael O. Garcia 《Contributions to Mineralogy and Petrology》1986,93(3):399-408
Phlogopite micas from nodules in South African kimberlites were analyzed for major elements with the electron microprobe and for volatile contents by high temperature mass spectrometry. The micas are from primary- (deformed) and secondary- (undeformed) textured grains in perodotite xenoliths, glimmerites, MARID (mica-amphibole-rutile-ilmenite-diopside) suite nodules and a mica megacryst. The major element and volatile contents of micas exhibiting these modes of occurrence overlap to a greater extent than indicated in previous studies. Concentrations of volatile species occupying structurally defined crystallographic sites (H2O, F, Cl) are greater for many of the micas than predicted on the basis of the mica formula, particularly for the glimmerite and MARID suite samples. A correlation exists between micas with tetrahedral and octahedral cation deficiencies and those with excess H2O, F and Cl. Substitution of H+ for tetrahedral and possibly octahedral cations may be responsible for the excess H2O in these micas. Except for one sample, the major element and volatile data for the peridotite, glimmerite and MARID suite micas indicate that they crystallized at oxygen fugacities below the quartz-fayalite-magnetite buffer. F and K2O are in the correct proportion in the micas to provide the source for these elements in alkali basalts, but not in mid-ocean ridge basalts. Kaersutite amphibole is a more likely source of potassium and fluorine in mid-ocean ridge basalts. 相似文献
23.
An examination of the Alaskan earthquake catalogs revealed that from 1928 through 1965, twelve earthquakes of magnitudes (M) in the range 5.6 to 7.3 were located in and around Seward Peninsula region of western Alaska. Moreover, a number of earthquakes of M < 5.0 were found to distribute over the same area. Further investigation of the seismicity employing a local seismographic network in the above area showed a higher level of onshore and offshore seismic activity than had been previously recognized. A number of clusters of earthquakes have been identified. Some of them are located in the epicentral areas of past strong earthquakes (M > 5.5) and some are located in areas traversed by mapped faults. The nature of the seismicity as identified with the local network data is primarily crustal over the entire study area. Investigation of focal mechanisms of isolated strong earthquakes or clusters of small earthquakes show normal faulting as the dominant mode of strain energy release in the western part of Alaska. Moreover, in areas lying, approximately, south and north of Kotzebue Sound, the principal components of horizontal stresses tend to orient in the NW-SE and WNW-ESE directions, respectively. 相似文献
24.
25.
The fish assemblages of two South Carolina estuarine tide pools located in the North Edisto River were sampled from June to October 1977, and during June and July 1978, by haul seine, lift net and channel net. The nekton was dominated numerically byFundulus heteroclitus, Leiostomus xanthurus, Menidia menidia andAnchoa mitchilli. Oyster reef areas were dominated numerically byGobiosoma bosci andF. heteroclitus. The relative abundance of tide pool fishes differs from deep water areas of the North Edisto River as described from otter trawls, but is similar to that described by others for South Carolina tidal creeks. 相似文献
26.
Mustafa Aktar Hayrullah Karabulut Serdar Özalaybey Dean Childs 《Geophysical Journal International》2007,171(3):1363-1375
Three main shocks M-1, M-2 and M-3 (17 October 2005 at 05:45 UTC, M w 5.4; 17 October at 09:46 UTC, M w 5.8 and 20 October at 21:40 UTC, M w 5.9) and their associated aftershocks within the Gulf of S i ğac i k, 50 km southwest of Izmir, Turkey were studied in detail. A temporary seismic network deployed during the activity allowed the hypocentre of M-3 and subsequent aftershocks to be determined with high accuracy. A relative relocation technique was used to improve the epicentres of M-1 and M-2. All three main shocks have strike-slip mechanisms which agree with the linear trends of the aftershock locations. Two distinct zones were illuminated by the aftershock locations. The zones contain clear echelon patterns with slightly different orientations from the trend of the aftershock distribution. M-2 and M-3 ruptured along of the eastern rupture zone which aligns N45°E. However the strike direction of M-1 is not clearly identified. The alignment of the two rupture zones intersect at their southern terminus at an angle of 90°. The fault zones form conjugate pair system and static triggering is considered as a probable mechanism for the sequential west to east occurrence of M-1, M-2 and M-3. This earthquake sequence provides seismological evidence for conjugate strike-slip faulting co-existing within a region dominated by north–south extension and well-developed east–west trending normal faults. 相似文献
27.
This study of fossils (pollen, plant macrofossils, stomata and fish) and sediments (lithostratigraphy and geochemistry) from
the Wendel site in North Dakota, USA, emphasizes the importance of considering ground-water hydrology when deciphering paleoclimate
signals from lakes in postglacial landscapes. The Wendel site was a paleolake from about 11,500 14C yr BP to 11,100 14C yr BP. Afterwards, the lake-level lowered until it became a prairie marsh by 9,300 14C yr BP and finally, at 8,500 14C yr BP, an ephemeral wetland as it is today. Meanwhile, the vegetation changed from a white spruce parkland (11,500 to 10,500
14C yr BP) to deciduous parkland, followed by grassland at 9,300 14C yr BP. The pattern and timing of these aquatic and terrestrial changes are similar to coeval kettle lake records from adjacent
uplands, providing a regional aridity signal. However, two local sources of ground water were identified from the fossil and
geochemical data, which mediated atmospheric inputs to the Wendel basin. First, the paleolake received water from the melting
of stagnant ice buried under local till for about 900 years after glacier recession. Later, Holocene droughts probably caused
the lower-elevation Wendel site to capture the ground water of up-gradient lakes. 相似文献
28.
We investigated the incidence of endozoochory in the semi-arid South African Karoo shrubland and Kalahari savanna by dissecting and germinating seed from dung samples from a wide range of wild mammals and domestic livestock. Intact seeds occurred at a mean density of 1575 seeds kg−1in livestock air-dried dung and 3613 seeds kg−1in air-dried dung of indigenous animals. Seedlings emerged from dung at an average density of 153 kg−1air-dry dung. Seeds of Aizoaceae, Mesembryanthemaceae, Chenopodiaceae and Poaceae were abundant in the dung of wild and domestic herbivores as well as such ant- and termite-eating insectivores as aardvark (Orycteropus afer) and bat-eared fox (Otocyon megalotis). Seeds of fleshy-fruited shrubs occurred in dung of browsing herbivores and the bat-eared fox. Five non-indigenous weeds were found in the dung samples. Although the floras of the Kalahari and Karoo are considered to be largely wind and water-dispersed, endozoochory is a primary or secondary dispersal mechanism in many plant families and for many plant life-forms. Animals dispersed seeds of many species characteristic of fertile and disturbed habitats. In Mesembryanthemaceae, a family in which seeds are primarily dispersed very short distances by raindrops, endozoochory enables occasional long-distance dispersal. 相似文献
29.
30.
Harald Geiger Ian Barnes Karl H. Becker Birger Bohn Theo Brauers Birgit Donner Hans-Peter Dorn Manfred Elend Carlos M. Freitas Dinis Dirk Grossmann Heinz Hass Holger Hein Axel Hoffmann Lars Hoppe Frank Hülsemann Dieter Kley Björn Klotz Hans G. Libuda Tobias Maurer Djuro Mihelcic Geert K. Moortgat Romeo Olariu Peter Neeb Dirk Poppe Lars Ruppert Claudia G. Sauer Oleg Shestakov Holger Somnitz William R. Stockwell Lars P. Thüner Andreas Wahner Peter Wiesen Friedhelm Zabel Reinhard Zellner Cornelius Zetzsch 《Journal of Atmospheric Chemistry》2002,42(1):323-357
Within the German Tropospheric Research Programme (TFS) numerous kinetic and mechanistic studies on the tropospheric reaction/degradation of the following reactants were carried out: oxygenated VOC, aromatic VOC, biogenic VOC, short-lived intermediates, such as alkoxy and alkylperoxy radicals.At the conception of the projects these selected groups were classes of VOC or intermediates for which the atmospheric oxidation mechanisms were either poorly characterised or totally unknown. The motivation for these studies was the attainment of significant improvements in our understanding of the atmospheric chemical oxidation processes of these compounds, particularly with respect to their involvement in photooxidant formation in the troposphere. In the present paper the types of experimental investigations performed and the results obtained within the various projects are briefly summarised. The major achievements are highlighted and discussed in terms of their contribution to improving our understanding of the chemical processes controlling photosmog formation in the troposphere. 相似文献