全文获取类型
收费全文 | 766篇 |
免费 | 20篇 |
国内免费 | 15篇 |
专业分类
测绘学 | 22篇 |
大气科学 | 60篇 |
地球物理 | 171篇 |
地质学 | 355篇 |
海洋学 | 38篇 |
天文学 | 111篇 |
综合类 | 3篇 |
自然地理 | 41篇 |
出版年
2022年 | 5篇 |
2021年 | 7篇 |
2020年 | 7篇 |
2019年 | 8篇 |
2018年 | 6篇 |
2017年 | 12篇 |
2016年 | 20篇 |
2015年 | 12篇 |
2014年 | 25篇 |
2013年 | 37篇 |
2012年 | 28篇 |
2011年 | 24篇 |
2010年 | 31篇 |
2009年 | 34篇 |
2008年 | 23篇 |
2007年 | 39篇 |
2006年 | 28篇 |
2005年 | 23篇 |
2004年 | 26篇 |
2003年 | 25篇 |
2002年 | 29篇 |
2001年 | 25篇 |
2000年 | 18篇 |
1999年 | 21篇 |
1998年 | 15篇 |
1997年 | 14篇 |
1996年 | 23篇 |
1995年 | 16篇 |
1994年 | 10篇 |
1993年 | 10篇 |
1992年 | 11篇 |
1991年 | 9篇 |
1990年 | 12篇 |
1989年 | 19篇 |
1988年 | 9篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1985年 | 5篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 6篇 |
1981年 | 10篇 |
1980年 | 8篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1975年 | 7篇 |
1973年 | 5篇 |
1971年 | 4篇 |
1966年 | 5篇 |
1958年 | 5篇 |
排序方式: 共有801条查询结果,搜索用时 31 毫秒
731.
Wolfgang Krauß 《Ocean Dynamics》1958,11(5):194-207
Zusammenfassung Es werden die wesentlichsten Beobachtungsergebnisse über das Auftreten interner Wellen im Ozean angeführt. Sämtliche Messungen erfassen entweder nur die Periode oder nur die Wellenlänge. Der Charakter der gefundenen Wellen ist daher nicht immer eindeutig festzustellen. Auch läßt sich nicht in jedem Fall entscheiden, ob die beobachteten Schwankungen durch Wellen, Wirbel oder turbulente Vorgänge erzeugt worden sind. Am Kontinentalabhang scheinen stehende Wellen aufzutreten.Periodenanalysen haben insbesondere auf interne Gezeiten und Trägheitsschwingungen geführt; Messungen der Wellenlänge ergeben im nördlichen Nordatlantischen Ozean Werte von 25–50 km. Die maximale Amplitude, welche registriert wurde, beträgt 300 m. Schwankungen von mehreren hundert Metern im Gezeitenrhythmus und eventuell mit größeren (bisher unbekannten) Perioden, welche durch meteorologische Vorgänge erzwungen Werden könnten, scheinen im nördlichen Nordatlantischen Ozean sehr häufig zu sein. In den niederen Breiten, in denen allein längere Ankerstationen durchgeführt worden sind, hat man demgegenüber meist nur geringe Amplituden beobachtet.
Die Untersuchungen auf Anton Dohrn wurden gemeinsam mit Dr. H. Griesseier und Dr. O. Czepa, Institut für Physikalische Hydrographie der Deutschen Akademie der Wissenschaften zu Berlin, durchgeführt. Für die aufschlußreiche Diskussion über die Deutung der Beobachtungsresultate sei auch an dieser Stelle beiden Herren gedankt. 相似文献
Internal waves of great amplitudePart 2: Observations
Summary The principal results deduced from observations of internal waves within the ocean are presented. Each of the measurements in question describes either the period or the wave length; hence, it follows that the nature of the detected waves cannot, in every case, be determined without ambiguity. Besides, it is not always possible to ascertain whether the observed variations are due to waves, vorticity or turbulence. Standing waves seem to occur at the continental slope.The analysis of periods, in particular, led to the suggestion that internal tides and inertia oscillations may predominate; according to measurements carried out in the northern North Atlantic Ocean, the wave lengths vary from 25 to 50 km. The maximal amplitude recorded is 300 metres. Variations of several hundred metres in accordance with the tidal rhythm and, possibly, with (still unknown) periods of some importance which may be conditioned by meteorological processes, seem to be of frequent occurrence in the northern North Atlantic Ocean. To the contrary, small amplitudes were observed in the low latitudes — the sole regions where long-time observations from anchor stations were carried out.
Vagues internes de grande amplitude2e Partie: Observations
Résumé Le travail suivant présente des résultats dérivés des observations de vagues internes rencontrées à l'intérieur des océans. Chacune des mesures en question décrit soit la période, soit la longueur d'onde, d'où vient que la nature des vagues rencontrées ne peut pas, toujours, être décrite sans ambiguïté. En outre, il est souvent difficile de décider si les variations observées sont dues à des vagues, à des tourbillons ou à des processus turbulents. Des ondes stationnaires semblent être présentes sur le talus continental.Desanalyses des périodes, en particulier, nous ont conduit à supposer que prédominent des marées internes et des oscillations d'inertie; selon des mesures entreprises dans la partie septentrionale de l'Atlantique Nord on y a rencontré des ondes entre 25 et 50 km de longueur. L'amplitude maximale y enregistrée est de 300 mètres. Des ondes variant de plusieurs cent mètres en longueur suivant le rythme des marées et, peut-être, selon des périodes importantes (encore inconnues), qui pourraient être causées par des procès météorologiques semblent se présenter très souvent dans la partie nord de l'Océan Atlantique Nord. Au contraire, des amplitudes insignifiantes se trouvent souvent dans les basses latitudes — les seules régions où on a fait jusqu'ici des observations à longue durée à bord des bâtiments mouillés.
Die Untersuchungen auf Anton Dohrn wurden gemeinsam mit Dr. H. Griesseier und Dr. O. Czepa, Institut für Physikalische Hydrographie der Deutschen Akademie der Wissenschaften zu Berlin, durchgeführt. Für die aufschlußreiche Diskussion über die Deutung der Beobachtungsresultate sei auch an dieser Stelle beiden Herren gedankt. 相似文献
732.
Wolfgang Krauß 《Ocean Dynamics》1958,11(1):26-30
Zusammenfassung Die Untersuchungen mit Anton Dohrn im April 1957 bestätigen in den wesentlichen Zügen das aus dem Material der Jahre 1929–1933 gewonnene Bild über die ozeanische Zirkulation im Seegebiet zwischen Island und Grönland.
Recent hydrographic investigations made on board the Anton Dohrn in the Icelandic Sea (Denmark Strait)
Summary The investigations made on board the research ship Anton Dohrn in April 1957 essentially confirm the conception of the oceanic circulation in the sea area between Iceland and Greenland formed after the observational material obtained in 1929/33.
Récentes recherches hydrographiques effectuées à bord de l' «Anton Dohrn» en mer d'Islande (Détroits de Danemark)
Résumé Les recherches, effectuées à bord du navire explorateur «Anton Dohrn», en avril 1957, vérifient essentiellement la conception, formée sur les données d'observation de 1929/33, de la circulation océanique dans les parages compris entre l'Islande et le Groenland.相似文献
733.
Phase transitions and associated domains of meteoritic troilite (FeS) have been studied by means of transmission electron microscopy (TEM). Three polymorphs have been found, two of which can be described by superstructures of the NiAs-type structure (A, C subcell). The P \(\overline 6\) 2c (√3A, 2C) polymorph, stable at room temperature, displays antiphase domains with the displacement vector 1/3< \(\overline {\text{1}}\) 10>. In situ heating experiments showed that the P \(\overline 6\) 2c polymorph changes at temperatures of 115°–150° C into an orthorhombic pseudohexagonal transitional phase with the probable space group Pmcn (A,√3A, C). It contains antiphase domains with the displacement vector 1/2 [110] and twins with a threefold twin-axis parallel c. When heated above 210° C the transitional phase transforms into the high-temperature modification with NiAs structure (P6 3/mmc). All observed phase transitions are reversible. The occurrence of antiphase and twin domains, respectively, agrees with the symmetry reductions involved in the subsolidus phase transitions. This is demonstrated by group-subgroup relationships among the space groups P6 3/mmc, Pmcn, and P \(\overline 6\) 2c. 相似文献
734.
735.
The analysis of the Th/U ratio in meteorites and the evolutionary ages of globular clusters favour values of the cosmic age of (19±5)×109 yr. This evidence together with a Hubble parameterH
0>70 km s–1 Mpc–1=(14×109 yr)–1 cannot be reconciled in a Friedmann model with =0. It requires a cosmological constant in the order of 10–56 cm–2, equivalent to a vacuum density
v
=10–29 g cm–3
The Friedmann-Lemaître models (>0) with a hot big-bang have been calculated. They are based on a present value of the baryonic matter density of
0=0.5×10–30 g cm–3 as derived from the primordial4He and2H abundances.For a Hubble parameter ofH
0=75 km s–1 Mpc–1, our analysis favours a set of models which can be represented by a model with Euclidean metric (density parameter 0=1.0, deceleration parameterq
0=–0.93, aget
0=19.7×109 yr) and by a closed model with perpetual expansion (0=1.072,q
0=–1.0, aget
0=21.4×109 yr). A present density parameter close to one can indeed be expected if the conjecture of an exponential inflation of the very early universe is correct.The possible behaviour of the vacuum density is demonstrated with the help of Streeruwitz' formula in the context of the closed model with an inflationary phase at very early times. 相似文献
736.
737.
738.
René Hudec Pavel Spurný Jan Florián Jaroslav Boček Miloš Tichý Jana Tichá Libor Vyskočil Wolfgang Wenzel Scott Barthelmy Thomas Cline Niels Gehrels Gerald Fishman Chryssa Kouveliotou Charles Meegan Asen Mutafov 《Experimental Astronomy》1997,7(4):319-323
We present first preliminary results obtained with the European Observation Network consisting of 9 observatories in the Czech Republic, Germany and Bulgaria. We also discuss related problems such as the background of unknown variable stars and suggest a strategy for work in this area. 相似文献
739.
Wolfgang Siebel 《International Journal of Earth Sciences》1995,84(2):384-398
Petrochemical and Rb-Sr, K-Ar and Sm-Nd isotopic data presented for the Mitterteich granite provide information on whole rock and mineral compositional characteristics, intrusion and cooling history, and protolith nature and put further constraints on the Variscan magmatic evolution in north-east Bavaria.The compositional characteristics classify the Mitterteich granite as a peraluminous (monzo-)granite (SiO2 67.3–73.5 wt.% ). Values for K2O/Na2O (> 1.2 and Al2O3/(CaO + N2O + K2O) (>1.1) are in the range of S-type granites. The rare earth elements show fractionated chondrite-normalized patterns (La
N
/Yb
N
=24–19) with negative Eu anomalies (Eu
N
/Eu
N
*=0.35–0.19). The micas have restricted ranges of major element composition, but reveal notable variations in trace element concentrations. Different biotite fractions of single specimens show a trend to lower concentrations of compatible elements in the finer fraction which can be explained as a result of asynchronous growth during the fractionation process. The PT conditions of crystallization of the magma based on muscovite and biotite is 600–640°C at 3 kbar. Regression of the whole rock samples gives an isochron corresponding to a 87Rb-87Sr age of 310 ± 7 Ma, initial 87Sr/86Sr of 0.7104±0.0010 (2 errors) and MSWD =0.03. Muscovite and biotite yield concordant K-Ar ages between 310 and 308 Ma, indicating a fast cooling rate of the granite intrusion. Nd
T310values average –4.2±1.0. Nd model ages of 1.4 Ga suggest a source region of mid-Proterozoic age.The Rb-Sr isochron age and initial Sr ratio of the Mitterteich granite are indistinguishable from those of the adjacent Falkenberg granite, establishing a genetic link. However, the K-Ar mica ages suggest that the Mitterteich granite must have undergone a faster uplift or cooling history than Falkenberg. Confronted with the geochronological record of granite emplacement in north-east Bavaria, the new results substantiate the view of three key periods of magmatic activity around 330–325, 315–305 and 290 Ma. 相似文献
740.
Abstract. Two species of cerithid prosobranchs live on a sand flat in Bermuda. At low tide during day light Batillaria minima is found on the surface whereas Cerithium lutosum remains buried in the sediment. This correlates with much higher lethal and coma temperatures, as well as much greater resistance to desiccation, of the former species. However, at other diurnal or tidal stages the two species co-occur in the same layer of sand. Despite greater resistance to physical factors the population of B. minima seems to be declining since in 1980 juveniles of this species were rare on Tuckers Town Flat whereas the population of C. lutosum was thriving. 相似文献