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141.
Wolf-Rainer Abraham Alexandre José Macedo Luiz Humberto Gomes Flavio C. A. Tavares 《洁净——土壤、空气、水》2007,35(4):339-347
The load of pathogenic bacteria, their fate and their dangerousness in the Tietê River were assessed along 100 km starting from the city of São Paulo, Brazil. The data were compared with those from two German rivers. High loads of pathogens were found in the Tietê River near the city of São Paulo (Escherichia coli O157:H7, Shigella flexneri, and Shigella boydii), which were absent 30 km downstream of São Paulo. The antibiotic resistances observed in the Tietê river were rather low and decreased after the major input in São Paulo to significantly lower levels about 30 km downstream. While the Brazilian isolates were more susceptible for ampicillin than the German ones, the reverse was observed for gentamycin. For optimal control of infections in humans critical areas where these bacteria survived longer and their elimination mechanisms should be identified as well as the extent and the origin of antibiotic resistance should be determined. 相似文献
142.
André F. Lotter H. John B. Birks Wolfgang Hofmann Aldo Marchetto 《Journal of Paleolimnology》1998,19(4):443-463
Surface sediments from 68 small lakes in the Alps and 9 well-dated sediment core samples that cover a gradient of total phosphorus (TP) concentrations of 6 to 520 g TP l-1 were studied for diatom, chrysophyte cyst, cladocera, and chironomid assemblages. Inference models for mean circulation log10 TP were developed for diatoms, chironomids, and benthic cladocera using weighted-averaging partial least squares. After screening for outliers, the final transfer functions have coefficients of determination (r2, as assessed by cross-validation, of 0.79 (diatoms), 0.68 (chironomids), and 0.49 (benthic cladocera). Planktonic cladocera and chrysophytes show very weak relationships to TP and no TP inference models were developed for these biota. Diatoms showed the best relationship with TP, whereas the other biota all have large secondary gradients, suggesting that variables other than TP have a strong influence on their composition and abundance. Comparison with other diatom – TP inference models shows that our model has high predictive power and a low root mean squared error of prediction, as assessed by cross-validation. 相似文献
143.
144.
Dabrio Cristino J. Zazo Cari Lario Javier Goy José Luis Sierro Francisco J. Borja Francisco González José Ángel Flores José Abel 《Geologie en Mijnbouw》1998,77(3-4):263-281
This first sedimentary interpretation of two incised-valley fills in the Gulf of Cádiz (southern Spain), which accumulated during the last fourth-order eustatic cycle in response to fluvial incision, changes of sea level, and correlative deposition, relates the filling of the estuarine basins and their barriers with four regional progradation phases, H1 to H4. The cases studied are the wave-dominated Guadalete, and the mixed, tide and wave-dominated Odiel-Tinto estuaries. The sequence boundary is a type-1 surface produced during the lowstand of the Last Glacial period ca. 18 000 14C yr BP. No fluvial lowstand deposits were found in the area. Due to rapid transgression the valley fills consist of transgressive and highstand sediments. The maximum landward advance of the estuarine barriers occurred ca. 6500–6000 14C yr BP during the maximum of the Flandrian transgression, but there is no evidence of sea level rising appreciably above the present. A large part of the estuaries was filled during H1 (ca. 6500–4400 14C yr BP) but ravinement by shifting tidal inlets destroyed most of the coeval barriers. During the H2 phase (ca. 4200–2550 14C yr BP) sedimentation was favoured by arid conditions and concentrated in the axial estuarine zones and the barriers. Between H2 and H3 prevailing winds changed from W to WSW, increasing spit growth to the east and south-east. Progradation of bay-head deltas and flood-plains during H3 (ca. 2300–800 14C yr BP) and H4 (500 yr ago to the present) further reduced the accommodation space in the largely-filled valleys, and sediment by-passed the estuaries and accumulated in the estuarine barriers as fast-growing spits. Arid conditions and increasing human activity have caused rapid coastal modifications. 相似文献
145.
René V. Cormier 《Boundary-Layer Meteorology》1975,9(3):315-324
This research provides a study of the behavior of vertically integrated boundary-layer winds (IBLWs). This information should be helpful for both theoretical and practical applications, e.g., boundary-layer parameterization in general circulation models, air pollution models, and low-level parachuting operations. The study concerned itself with winds integrated up to a height of 300 m in the United States. The only data suitable for studying the behavior of IBLWs for such heights were measurements taken on tall towers. An extensive search indicated that data were readily available from only four towers instrumented to or above 300 m. These were located in rural locations in Texas, Oklahoma, Nevada, and South Carolina. At each location, means and coefficients of variation of IBLWs were computed, plotted as a function of time since sunrise/sunset, and compared. The research shows that IBLWs may differ appreciably in magnitude at different locations; may have considerable universality in behavior, and may also be ‘regionally’ dependent; and that IBLWs have a pronounced diurnal variation linked to sunrise/sunset time. 相似文献
146.
147.
148.
Audouin Dollfus André Cailleux Bernard Cervelle Chon Trung Hua Jean-Claude Mandeville 《Geochimica et cosmochimica acta》1980,44(9):1293-1310
Extension of remote sensing of planetary bodies to the ultraviolet is now feasiable up to 2000 Å from earth-orbiting telescopes and spacecraft. The benefits of this extension is analysed on the basis of laboratory spectra taken on a large variety of terrestrial, lunar and meteoritic samples. Knowledge of the albedo for two wavelengths at 2300 and 6500 Å permits classification of a surface into one of the following types: lunar, carbonaceous chondrites, ordinary chondrites, achondrites or acidic rocks, basaltic rocks, irons. For lunar-type surfaces, a simple albedo measurement at 6500 Å can be converted into quantitative abundance determinations of silicate, aluminium oxide and iron; a large amount of telescopic lunar photometry data is available for mapping these abundances. Extension of the photometry to 2300 Å permits quantitative measurement of TiO2 abundances. For asteroids and non-icy satellites, rock-type classification and constraints in chemical abundances of Si, Al, Fe and Ti can be derived from photometry at 2300 and 6500 Å. The IUE telescope already orbiting the earth, the Space Telescope to come, the lunar polar orbiter and other spacecraft under prospect are potentially available to provide the photometric observations at 6500 and 2300 Å required. 相似文献
149.
Résumé Les auteurs utilisent toutes les données chimiques, volcanologiques, chronologiques et tectonophysiques fournies pour un certain nombre de massif continentaux (Mont-Dore et autres). La synthèse de toutes ces études montre qu'il existe deux magmas continentaux indépendants: le magma basaltique venant du manteau (sima) et le magma rhyolitique fourni par la croûte supérieure (sial). Le mélange de ces deux magmas et l'action secondaire de la' gravité et de la pneumatolyse expliquent logiquement la totalité des phénomènes géochimiques des volcans continentaux.
The authors used all the chemical, volcanological, chronological and tectonophysical data supplied for a certain number of continental mountain massifs (Mont-Dore and others). The synthesis of these studies shows that there are two independent continental magmas: the basaltic magma coming from the mantle (sima) and the rhyolitic magma supplied by the upper crust (sial). The mixing of these two magmas, with the secondary action of gravity and pneumatolysis logically explains the totality of the geochemical phenomena in continental volcanoes.
Zusammenfassung Die Autoren benutzten alle chemischen, vulkanologischen, chronologischen und tektonisch-physikalischen Daten, die von einer bestimmten Anzahl von kontinentalen Massiven (Mont-Dore und andere) entnommen wurden.Das Ergebnis dieser Studien zeigt, daß es zwei voneinander unabhängige kontinentale Magmen gibt.Das basaltische Magma, vom Sima stammend, und das rhyolitische Magma aus der oberen Sial-Kruste. Die Vermischung dieser beiden Magmen und die zusätzliche Wirkung der Gravitation und Pneumatolyse erklären auf natürliche Weise die Gesamtheit der geochemischen Phänomene des kontinentalen Vulkanismus.
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150.
René Charlot 《Precambrian Research》1976,3(3):273-299
Twenty total rock Rb/Sr isochrons () and many individual data, mainly obtained by the K/Ar and Rb/Sr methods, on total rocks and minerals show that the orogenic story of the Precambrian of the Anti-Atlas, which was studied in its western and central parts, began with the Eburnean orogeny (1900-1650 m.y.). Up to now there is no good evidence of an older basement, even if the rather high initial ratio (0.707–0.709) of some Eburnean granites might suggest that such a basement exists at depth. There is also no geochronological evidence of plutonism until in early Panafrican time (680 m.y.) there started a period of intense magmatic and thermal activity which was ended by the emplacement of late post-tectonic granites at 530-520 m.y.The late Panafrican acid volcanism does not generally give suitable material for Rb/Sr dating, because of the great mobility of the radiogenic strontium in such a material even under very weak thermal conditions. 相似文献