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1.
The paper provides a simple analytical tool which can be used to give estimates of the mean value and the standard deviation of the Stokes drift for sea states. This is achieved by providing bivariate distributions of significant wave height with surface Stokes drift as well as with volume Stokes transport. These Stokes drift parameters are defined in terms of significant wave height and characteristic wave periods. Also bivariate distributions of spectral peak period and these two Stokes drift parameters are provided. The paper presents statistical aspects of the Stokes drift parameters, such as the conditional expected values and the conditional variances for given significant wave height, as well as examples of results corresponding to typical field conditions. The present analytical results can be used to make assessment of Stokes drift based on e.g. global wave statistics.  相似文献   
2.
We present a porous medium approach to representing topography, and a new algorithm for the objective interpolation of topography, for use in ocean circulation models of fixed resolution. The representation and algorithm makes use of two concepts; impermeable thin walls and porous barriers. Impermeable thin walls allow the representation of knife-edge sub-grid-scale barriers that block lateral flow between model grid cells. Porous barriers permit the sub-grid scale geometry to modulate lateral transport as a function of elevation. We find that the porous representation and the resulting interpolated topography retains key features, such as overflow sill depths, without compromising other dynamically relevant aspects, such as mean ocean depth for a cell. The accurate representation of the ocean depth is illustrated in a simple model of a tsunami that has a cross-basin travel time very much less dependent on horizontal resolution than when using conventional topographic interpolation and representation.  相似文献   
3.
Bleaching related to seepage of petroleum fluids and subsurface migration of crude oil and natural gas can alter the chemical and mineralogical properties of rocks, while concurrently depleting hydrocarbon reservoirs. Mud volcanoes constitute one type of petroleum seepage present in several areas on the southern margin of the Junggar Basin in the Xinjiang Uygur Autonomous Region, NW China. The results of XRD, XRF, XANES, and Mössbauer spectroscopy on rock samples collected from areas affected by these mud volcanoes revealed an enrichment of certain minerals and elements, as well changes in mineralogical, molecular, or ionic carrier (“species”). After bleaching, reddish sedimentary rocks showed depletion in silica and enrichment of calcium, magnesium, manganese, and iron. Other elements, including aluminum, potassium, sodium, and titanium, were largely unchanged. Reduced iron and sulfur compounds predominated in the bleached rocks, producing changes in color from the original reddish into green, deep gray, and black. Iron and calcium were associated with carbonates, indicating carbonation of these elements during the bleaching processes. Manganese also appeared to be associated with carbonate, though not with sulfate even though sulfate was present in the bleached rocks. Alkaline conditions were apparently the dominant because reduced manganese would have been absent under acidic condition. The alteration of certain minerals, clay minerals in particular, was also observed in bleached rocks, the alteration of smectite-group minerals to chlorite and muscovite, for example. Mineralogical and geochemical changes in rocks bleached by hydrocarbon fluids could provide a better overall understanding of bleaching processes, and may have applications in surface geochemical exploitation and remote imaging.  相似文献   
4.
《Marine pollution bulletin》2009,58(6-12):245-249
The exposure time is a variable which is usually not incorporated into models for toxicity. However, with persistent organic pollutants (POPs) exhibiting a nonspecific mode of action and lipophilic properties this variable can be modeled by the usage of the internal concentrations as a measure of the toxicity with fish. The bioconcentration process with fish is a relatively well understood and predictable process which allows the calculation of the internal lethal concentration. When the exposure time is relatively short the critical internal lethal concentrations are relatively constant for the group of POPs whereaas the LC50 measured in the ambient water is quite variable. When the exposure time is relatively long, results on the measurement of the critical internal concentration with fish over different exposure times has demonstrated that the internal lethal concentration falls with increasing exposure times in a consistent and predictable manner. This reduction in life expectancy can be described in a model which can be used to estimate the critical internal concentration for any exposure time. It also provides information useful in assessing the risk to fish and potentially other species due to the occurrence of residues of POPs in natural aquatic systems. It is suggested that these relationships can be extended to other groups of organisms and chemicals.  相似文献   
5.
《Earth》2009,93(3-4):99-116
The author, who investigated the Wolfe Creek, Australia, in 1962 and edited two Benchmark Sets of Readings on Meteorite Craters and possible Astroblemes in 1977 and 1979, reviews the state of knowledge at the present time. The text is concerned with terrestrial impact structures, geological features, without any consideration of extraterrestrial analogues. A handful of definitive publications are drawn on to present the story of terrestrial impact in a single article. The text covers historical aspects (briefly); the effect of target variations; the paucity of human observation of such large-scale events; distinction from volcanic (endogenous) structures; modification by geological processes; the transience of the crater initially formed on the target, and its subsequent modifications; the global geographic distribution of the 174 structures now listed (of which a number are dubious attributions); their distribution in geological time (many ages being known only known to wide limits, maximum or minimum values); their size distribution; calculations of impact frequencies; shock effects; processes on impact; the stages of formation; impact into shallow marine and deep sea targets; impacts on ice (about which little is known); and finally the input of impact into biotic extinctions. In this last lengthy section, the summaries of the conclusions of scientists researching impact on Earth and palaeontologists researching biotic impact are set side by side. It is concluded that, if the recent foraminiferal evidence obtained by Gerta Keller and associates is taken at its face value, the case of impact as a sole agent in extinction is non-existent: biotic extinction is clearly a complex process involving a number of causes, in some cases it was staggered in time, and different sets of organisms responded quite differently and surprisingly, even in the same extinction event. Extraterrestrial impact may have been one of the causes in some cases, but it may have been regional rather than global in its effects. We may never know how much input it had into the record of biotic extinction on Earth? An enormous amount of new knowledge has arisen from detailed studies of this new family of remarkable geological structures.  相似文献   
6.
《Earth》2009,95(1-4):79-94
In this paper, we examine the nature of the Pliocene Antarctic Peninsula Ice Sheet by comparing the terrestrial and marine geological records of the Antarctic Peninsula and surrounding sea floor with estimated net snow accumulation in the region derived from numerical palaeoclimate model experiments. Pliocene geological data and our new modelling results are consistent and mutually supportive in suggesting that an ice sheet was present even during the warmest episodes of the Pliocene. The combined results suggest that the ice sheet in the Antarctic Peninsula is more robust to globally warmer conditions than is generally assumed, at least up to the climatic limits examined in our study.  相似文献   
7.
8.
《Gondwana Research》2009,15(4):609-616
The 40Ar/39Ar method using a laser probe opened the door to microscale measurements and diffusion profiles frozen in samples. In the first decade since the initial application of a laser for 40Ar/39Ar dating in 1973, practical applications have been few. This is due not only to the fact that the laser and vacuum technologies were immature but that mass spectrometry was also in its infancy. In those days, the sensitivity of a mass spectrometer was generally insufficient to measure the small amount of argon degassed from a geological sample by a laser. These problems have subsequently been solved by new technologies. To understand their current status, a brief history of their development is outlined. This outline focuses on the required detection limit in micro scale measurement, practical approaches for accurate measurement are explained through examples in our laboratory specifically relating to the technical aspects of 40Ar/39Ar dating.  相似文献   
9.
Very-high-resolution (VHR) seismic and magnetic investigations were carried out over a chemical munition dumpsite in the Bornholm Basin, south-western Baltic Sea. The main goal of the investigations was to image the shallow internal structure of the dumpsite and to map the lateral and vertical distribution of the dumped war material. The shallow geology was imaged in great detail on the seismic data. Seven seismic–stratigraphic units were identified, related to different stages in the Holocene and late-glacial history. A large number of diapir-like features were observed that most likely represent fluid expulsion phenomena. Four shipwrecks were identified in the dumpsite area. The wrecks have partly sunk into the soft upper sediments, their height above the sea floor reaching no more than 2 m. Seismic and magnetic data indicate the presence of a large number of buried objects. In most cases there is a good correlation between the seismic and magnetic data sets. The objects are generally buried no deeper than 1 to 2 m. Their size varies between 1.5 and 5 m, occasionally up to 10 m. Shallow pits in the sea bed are likely due to the impact of dumping. The data confirm the wide variety of dumped war material ranging from bombs and shells to encasements and containers. The distribution of the buried objects seems rather heterogeneous, with locally high object concentrations surrounded by areas of lower object density. The results of this case study demonstrate the benefit of complementary, concurrent geophysical investigations for munition dumpsite research. Finally this will yield a better assessment of the current status of the dumpsite and the possible ecological risks related to the dumped war material.  相似文献   
10.
Summary 1) It is confirmed that in filtered, nucleus-free air, in a polyethylene balloon, if irradiated by sunglight, an immediate large number of condensation nuclei appear. — 2) The nucleus count rises to about 35. 000/cm3 and if the irradiation is continued does not increase, but decreases. This decreased is accelerated in the dark. — 3) Less intensive sunlight as when the sun was covered by clouds, gives slower and smaller increases. — 4) The same was observed if, instead of air, inducstrial oxygen or nitrogen was used. — 5) Traces of H2S increase the sun effect enormously. — 6) Traces of NH3 also increase it, but less than H2S. — 7) SO2 filtered through cottonwool gave also in the dark nuclei, which then decreased in number. — 8) It is supposed that H2S is oxydized by the photochemical action of the sun's visible spectrum to SO2 SO3 SO4 which is a nucleus. With NH3 the formation of (NH3)2 SO4 is probable. But no direct proof is given that these are the actual impurities which explain the sun's action on air. It is calculated that dilutions of 10–15 of an impurity of the type of H2S can quantitatively explain the sun effect. — 9) The work ofAitken is extensively quoted, who noticed, 50 years ago, the «fog produced by sun».
Zusammenfassung 1) Es wird bestätigt, dass Sonnen-Bestrahlung von filtrierter kernfreier Luft, welche in einem Polyethylen-Ballon aufbewahrt ist, zum Entstehen einer hohen Zahl von Kondensations Kernen führt. — 2) Die Kernzahl steigt auf etwa 35 000/cm3. Wird die Bestrahlung fortgesetzt, dann steigt sie nicht weiter sondern nimmt ab. Die Abnahme wird im Dunkeln beschleunigt. — 3) Durch Wolken abgeschwächtes Sonnenlicht gibt eine langsamere, weniger grosse Kernbildung. — 4) Dieselben Beobachtungen wurden mit industriellem Sauerstroff und Stickstoff auch gemacht. — 5) Spuren von H2S verstärken den Sonneneffekt enorm. — 6) Spuren von NH3 verstärken ihn auch, jedoch weniger. — 7) SO2 Gas, gefiltert durch Baumwollfilter giebt auch im Dunkeln schon Kerne, deren Zahl dann wieder abnimmt. — 8) Es wird angenommen, das H2S durch photochemische Wirkung des sichtbaren Sonnenlichtes oxidiert wird zu SO2 SO3 SO4 welch letzteres bereits als H2HO4 ein Kondensationskern ist. Mit NH3)2 SO4 Kondensationskerne gebildet werden. Es sind jedoch keine direkten Beweise dafür vorhanden, dass diese Gase die Verunreinigungen der atmosphärischen Luft sind, welche den Sonnenffekt geben. Es wird aber berechnet, dass schon Verdünnungen von 10–15 eine Verunreinigung H2S den Sonnen-Effekt erklären. — 9)Aitken's Werk, der bereits vor 50 Jahren von « durch Sonne verursachten Nebel « sprach, wird gewürdigt.


From the Clima-physiological Laboratory of St. Moritz-Bad.  相似文献   
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