全文获取类型
收费全文 | 113746篇 |
免费 | 6320篇 |
国内免费 | 6738篇 |
专业分类
测绘学 | 3358篇 |
大气科学 | 12626篇 |
地球物理 | 24405篇 |
地质学 | 44773篇 |
海洋学 | 10083篇 |
天文学 | 19920篇 |
综合类 | 3280篇 |
自然地理 | 8359篇 |
出版年
2022年 | 1231篇 |
2021年 | 1511篇 |
2020年 | 1488篇 |
2019年 | 1606篇 |
2018年 | 5274篇 |
2017年 | 4967篇 |
2016年 | 4427篇 |
2015年 | 2351篇 |
2014年 | 2989篇 |
2013年 | 4741篇 |
2012年 | 3928篇 |
2011年 | 6245篇 |
2010年 | 5960篇 |
2009年 | 6882篇 |
2008年 | 5888篇 |
2007年 | 6222篇 |
2006年 | 3528篇 |
2005年 | 3524篇 |
2004年 | 3367篇 |
2003年 | 3297篇 |
2002年 | 2910篇 |
2001年 | 2513篇 |
2000年 | 2711篇 |
1999年 | 2904篇 |
1998年 | 2621篇 |
1997年 | 2598篇 |
1996年 | 2283篇 |
1995年 | 2086篇 |
1994年 | 1918篇 |
1993年 | 1699篇 |
1992年 | 1466篇 |
1991年 | 1221篇 |
1990年 | 1303篇 |
1989年 | 1112篇 |
1988年 | 1010篇 |
1987年 | 1069篇 |
1986年 | 934篇 |
1985年 | 1106篇 |
1984年 | 1233篇 |
1983年 | 1164篇 |
1982年 | 1068篇 |
1981年 | 1025篇 |
1980年 | 868篇 |
1979年 | 827篇 |
1978年 | 867篇 |
1977年 | 780篇 |
1976年 | 745篇 |
1975年 | 685篇 |
1974年 | 695篇 |
1973年 | 706篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
J. Drimmel 《Meteorology and Atmospheric Physics》1964,14(2):213-217
Zusammenfassung Die bisher ungeklärte Winter-Anomalie der D-Schicht sowie die explosionsartigen Erwärmungen der Hochstratosphäre im Winter können durch Staubpartikel interplanetaren Ursprungs (Meteorströme) hervorgerufen werden. Eine Anlagerung von Elektronen an die Staubteilchen in der Exosphäre bewirkt das Einfangen der kleinsten Partikel durch das erdmagnetische Feld und verhindert so ihr Verglühen in der Ionosphäre. Durch Sedimentation und turbulente Diffusion gelangt der Meteorstaub bis in die Ozonosphäre, wo er oxydiert wird und so eine plötzliche Wärmeentwicklung zur Folge hat. Die angelagerten Elektronen exosphärischen Ursprungs können bei zeitgerechter Photoablösung elektromagnetische Wellen dämpfen und so die Winter-Anomalie der D-Schicht hervorrufen.
Summary The winter-anomaly of the ionospheric D-region for which no sufficient explanation existed up to now, as well as the explosive warming of the high stratosphere in wintertime are possibly caused by dust particles of inter-planetary origin (meteoric showers). The attachment of electrons on the dust particles in the exosphere causes the magnetic field of the earth to catch the smallest particles and so they do not evaporate in the ionosphere. By sedimentation and turbulent diffusion the meteoric dust reaches the ozonosphere where it is oxidized, which is followed by a sudden development of heat. After photo-detachment in due time the formerly attached electrons of exospheric origin are able to damp electro-magnetic waves and by this they cause the winter-anomaly of the D-region.
Résumé L'anomalie de la couche D — inexplicable jusqu'ici — ainsi que les hausses prodigieusement rapides de la température de la haute stratosphère, deux phénomènes particuliers de l'hiver, peuvent être provoquées par des particules de poussière d'origine interplanétaire (courants de météorites). Des électrons adhérant, dans l'exosphère, aux grains de poussière permettent l'entraînement des plus petites particules par le champ magnétique terrestre et empèchent ainsi leur désintégration dans l'ionosphère. Par sédimentation et diffusion turbulente, la poussière cosmique parvient ensuite jusque dans l'ozonosphère où elle est oxydée. Il en résulte alors un dégagement subit de chaleur. Les électrons d'origine exosphérique adhérant à la poussière cosmique peuvent atténuer, s'ils s'en détachent en temps opportun sous l'effet du rayonnement solaire, les ondes électromagnétiques et provoquer ainsi l'anomalie d'hiver de la couche D.相似文献
962.
D. J. Schove 《Pure and Applied Geophysics》1963,55(1):249-261
Summary The geometry of the principal Upper High (near the Indian Occean) in the 300–100 mb layer appears to account for the Southern Oscillation (S.O.), and models of its behaviour are presented. Significant features of these models include the equatorial points of upper convergence (C) and divergence (D), a pressure discontinuity (CNDS) forming «arcs» and an «enclosure» around the high, and, lastly, encircling «crescents» both outside and inside the enclosure. The geography of the seasonal sucession can thus—in a qualitative manner—be interpreted in the light of known wind and contour patterns near the tropopause. With a few general principles, the established empirical rules of long-range forecasting then follow by deduction. The models and the terminology are useful likewise in the interpretation of solar-terrestrial relations and of climatic fluctuations. 相似文献
963.
Phase relationships on the vapor-saturated liquidus surfacein the system CaO-MgO-CO2-H2O have been deduced from data inthe systems CaO CO2-H2O, CaO-MgO-CO2, and MgO-CO2-H2O, and frompreliminary experiments in the quaternary system. These areillustrated in composition tetrahedra, and in isobaric sectionsthrough the petrogenetic model. The univariant PT curve forthe beginning of melting lies between 625? C and 600? C in thepressure range 10 bars to 4 kilobars, in the presence of a vaporphase rich in H2O. The curve is divided into three sectionsby two invariant points, each section having a different primarymagnesian phase involved in the melting reaction. Periclaseoccurs on the low-pressure section (less than about 1 kilobar),and with increasing pressure first brucite and then dolomitebecome stable on the liquidus. The pressure of the second invariantpoint, above which dolomite is stable on the liquidus, is notknown. The effect of FeO as an additional component is considered.Processes of crystallization resulting from changes in temperature,in pressure, and in the composition of the vapor phase are discussed.These processes are applied to the crystallization and differentiationof carbonatite magmas, and the reverse processes involving fusionare applied to the metamorphism of dolomites. Crystallizationdifferentiation of a carbonatite magma could produce the sequenceof intrusion observed at some carbonatite complexes: calcitics?vite, followed by ankeritic s?vite, and finally sideriticcarbonatite. Partial melting may occur during the thermal metamorphismof dolomites, but melting is unlikely during regional metamorphism. 相似文献
964.
F. Steinhauser W. Mörikofer J. Drimmel Peter Steinhauser 《Meteorology and Atmospheric Physics》1965,15(2):251-264
Ohne Zusammenfassung 相似文献
965.
J. A. Eden 《The Photogrammetric Record》1966,5(27):150-169
Some of the advantages and disadvantages of super-wide angle photography are discussed. Special reference is made to photography of an area in Bechuanaland, when airborne profile recorder and horizon camera were used in conjunction with aerial photography. Data from these ancillary aids were used in the subsequent adjustment procedure. The paper concludes with an account of analytical bridging using super-wide angle photography and a monocomparator. 相似文献
966.
967.
968.
969.
The long-wave outgoing radiation, effective cloudiness equal to the product of the total cloud amount by their optical density,
and the sea-surface temperature determined from the satellites are used to determine the annual course of the components of
external heat balance on the sea surface whose climatic anomalies, parallel with the meridional heat and water transfer in
the ocean-atmosphere system, specify the intraannual and interannual large-scale variations of weather in different regions
of the Earth. The development of these studies is connected with the progress of satellite hydrophysics because the data obtained
from the space become sufficiently exact, regular, and global. The increase in the existing data array on the external heat
balance of the oceans from ∼15–20 to 100 yr and more would promote the solution of the problem of oscillations of Earth's
climate. We present examples of coordinated numerical analysis of the heat balance of the upper (0–100 m ) layer of the Black
Sea performed on the basis of the shipborne and satellite data.
__________
Translated from Morskoi Gidrofizicheskii Zhurnal, No. 6, pp. 59–75, November–December, 2007. 相似文献
970.
Isotopic variation of fishes in freshwater and estuarine zones of a large subtropical coastal lagoon
A.M. Garcia D.J. Hoeinghaus J.P. Vieira K.O. Winemiller 《Estuarine, Coastal and Shelf Science》2007,73(3-4):399-408
We used stable C and N isotope ratios of tissues from 29 fish species from a large subtropical lagoon in southern Brazil to examine spatial variability in isotopic composition and vertical trophic structure across freshwater and estuarine habitats. Nitrogen isotope ratios indicated a smooth gradation in trophic positions among species, with most fishes occupying the secondary and tertiary consumer level. Fish assemblages showed a significant shift in their carbon isotopic signatures between freshwater and estuarine sites. Depleted carbon signatures (from −24.7‰ to −17.8‰) were found in freshwater, whereas more enriched signatures (from −19.1‰ to −12.3‰) were obtained within the estuarine zone downstream. Based on our survey of the C3 and C4 plants and isotopic values for phytoplankton and benthic microalgae reported for ecosystems elsewhere, we hypothesized that the observed δ13C differences in the fish assemblage between freshwater and estuarine sites is due to a shift from assimilating organic matter ultimately derived from C3 freshwater marsh vegetation and phytoplankton at the freshwater site (δ13C ranging from −25‰ to −19‰), to C4 salt-marsh (e.g. Spartina) and widgeon grass (Ruppia maritima), benthic microalgae and marine phytoplankton at the estuarine sites (from −18‰ to −12‰). Our results suggested that fish assemblages are generally supported by autochthonous primary production. Freshwater fishes that likely were displaced downstream into the estuary during periods of high freshwater discharge had depleted δ13C values that were characteristic of the upper lagoon. These results suggest that spatial foodweb subsidies can occur within the lagoon. 相似文献