全文获取类型
收费全文 | 960篇 |
免费 | 27篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 43篇 |
大气科学 | 94篇 |
地球物理 | 272篇 |
地质学 | 345篇 |
海洋学 | 67篇 |
天文学 | 116篇 |
综合类 | 6篇 |
自然地理 | 49篇 |
出版年
2021年 | 10篇 |
2020年 | 10篇 |
2019年 | 7篇 |
2018年 | 13篇 |
2017年 | 19篇 |
2016年 | 26篇 |
2015年 | 22篇 |
2014年 | 29篇 |
2013年 | 42篇 |
2012年 | 29篇 |
2011年 | 42篇 |
2010年 | 47篇 |
2009年 | 42篇 |
2008年 | 33篇 |
2007年 | 39篇 |
2006年 | 33篇 |
2005年 | 36篇 |
2004年 | 26篇 |
2003年 | 22篇 |
2002年 | 29篇 |
2001年 | 28篇 |
2000年 | 20篇 |
1999年 | 19篇 |
1998年 | 10篇 |
1997年 | 9篇 |
1996年 | 8篇 |
1995年 | 14篇 |
1994年 | 14篇 |
1993年 | 13篇 |
1991年 | 19篇 |
1990年 | 13篇 |
1989年 | 11篇 |
1988年 | 9篇 |
1987年 | 15篇 |
1986年 | 11篇 |
1985年 | 9篇 |
1984年 | 7篇 |
1983年 | 9篇 |
1982年 | 8篇 |
1981年 | 11篇 |
1980年 | 11篇 |
1979年 | 8篇 |
1978年 | 8篇 |
1976年 | 11篇 |
1975年 | 10篇 |
1971年 | 7篇 |
1966年 | 8篇 |
1964年 | 8篇 |
1956年 | 7篇 |
1954年 | 7篇 |
排序方式: 共有992条查询结果,搜索用时 18 毫秒
71.
Ohne Zusammenfassung
Mitteilung Nr. 84 相似文献
72.
Summary Simultaneous measurements of the electrical conductivity of air inside and outside of buildings have been performed with continuously recording electronic instruments of high sensitivity and short time constant. It appears that the electrical conductivity, a measure of the natural ionization of air, is one atmospheric-electric parameter that can manifest itself inside occupied buildings without appreciable difference in physical character from outside values.The probable importance of these experimental results for the field of bioclimatology is pointed out and the possibility is discussed that the electrical conductivity of air might be one of the searched—for parameters in associating physiological phenomena with weather changes.
With 1 Figure.
Publication No. 25 of the Institute of Geophysics, University of California at Los Angeles. The research reported in this paper has been sponsored in part by the Geophysics Research Directorate of the Air Force Cambridge Research Center, Air Research and Development Command, under Contract No. AF 19(122)-254. 相似文献
Zusammenfassung Gleichzeitige Messungen der luftelektrischen Leitfähigkeit im Freien und innerhalb von Gebäuden wurden mit kontinuierlich registrierenden Röhreninstrumenten von großer Empfindlichkeit und kurzer Zeitkonstante durchgeführt. Es wurde gefunden, daß die Leitfähigkeit als Maß der natürlichen Luftionisierung eine luftelektrische Größe darstellt, die ohne wesentliche physikalische Beeinflussung in bewohnte Gebäude einzudringen vermag.Die mögliche Bedeutung dieser experimentellen Ergebnisse für das Gebiet der Bioklimatologie wird angedeutet und die Wahrscheinlichkeit diskutiert, daß die luftelektrische Leitfähigkeit einen der noch unbestimmten Faktoren des Zusammenhanges physiologischer Erscheinungen mit Wetterveränderungen darstellen könnte.
Résumé Des instruments électroniques à enregistrement continu de haute fidelité et ayant une constante de courte durée ont permis de prendre des mesures simultanées de la conductivité électrique de l'air à l'intérieur et à l'extérieur de bâtiments. Il semble que la conductivité électrique, mesure de l'ionisation naturelle de l'air, soit un paramètre de l'électricité atmosphérique qui peut se manifester à l'intérieur de bâtiments habités sans différence appréciable de caractéristiques physiques avec celles des valeurs extérieures.L'importance probable de ces résultats expérimentaux dans le champ de la bioclimatologie est indiquée, et la possibilité que la conductivité atmosphérique puisse être un des paramètres recherchés dans l'association des phénomènes physiologiques avec des changements du temps est étudiée.
With 1 Figure.
Publication No. 25 of the Institute of Geophysics, University of California at Los Angeles. The research reported in this paper has been sponsored in part by the Geophysics Research Directorate of the Air Force Cambridge Research Center, Air Research and Development Command, under Contract No. AF 19(122)-254. 相似文献
73.
J. Fischer M.L. Luhman S. Satyapal M.A. Greenhouse G.J. Stacey C.M. Bradford S.D. Lord J.R. Brauher S.J. Unger P.E. Clegg H.A. Smith G. Melnick J.W. Colbert M.A. Malkan L. Spinoglio P. Cox V. Harvey J.-P Suter V. Strelnitski 《Astrophysics and Space Science》1999,266(1-2):91-98
Based on far-infrared spectroscopy of a small sample of nearbyinfrared-bright and ultraluminous infrared galaxies (ULIRGs) with theISO Long Wavelength Spectrometer we find adramatic progression in ionic/atomic fine-structure emission line andmolecular/atomic absorption line characteristics in these galaxiesextending from strong [O III]52,88 m and [N III]57 m lineemission to detection of only faint [C II]158 m line emissionfrom gas in photodissociation regions in the ULIRGs. The molecularabsorption spectra show varying excitation as well, extending fromgalaxies in which the molecular population mainly occupies the groundstate to galaxies in which there is significant population in higherlevels. In the case of the prototypical ULIRG, the merger galaxy Arp220, the spectrum is dominated by absorption lines of OH, H2O, CH,and [O I]. Low [O III]88 m line flux relative to the integratedfar-infrared flux correlates with low excitation and does not appear tobe due to far-infrared extinction or to density effects. A progressiontoward soft radiation fields or very dusty H II regions may explainthese effects. 相似文献
74.
Gerhard Hahn Claes-Ingvar Lagerkvist 《Celestial Mechanics and Dynamical Astronomy》1987,43(1-4):285-302
Numerical integrations of 26 orbits of planet-crossing astetoids of Apollo-Amor type have been performed, in a solar system model including the perturbations by the planets from Venus to Neptune. The 15:th order RADAU integrator (Everhart, 1985) has been used. Orbits for the asteroids 433 Eros, 887 Alinda, 1036 Ganymed, 1221 Amor, 1580 Betulia, 1627 Ivar, 1685 Toro, 1862 Apollo, 1863 Antinous, 1864 Daedalus, 1865 Cerberus, 1915 Quetzalcoatl and 1916 Boreas have been integrated over 100 000 years forward in time and for 1866 Sisyphus, 2102 Tantalus, 2201 Oljato, 2329 Orthos, 3360 1981 VA, 3552 1983 SA, 1981 EJ30, 1985 PA, 1985 WA, 1986 DA 1986 JK and 1986 RA a period of about 33 000 years has been covered. The orbital evolutions of these asteroids are discussed. This work is part of a larger study of the long-term orbital evolution of planet-crossing asteroids and will be continued within the project SPACEGUARD (Milani et al., 1987). 相似文献
75.
Wolf Tietze Gerhard Kortum W. R. Mead T. K. Poiker C. Paddick George Kish A. Njøs H. Mensching V. Haarmann Uzo M. Igbozurike M. M. Yoshino Mushtaqur Rahman Lage Wahlström J. Connell Kazimierz Dziewonski Wayland R. Swain J. Humlum G. W. Lüttig Haruko Kishimoto Mai Britt E. Mørk 《GeoJournal》1982,6(3):270-280
76.
It is shown that endogenic lava flow processes can be identified by their characteristic effects on lunar crater size distributions without necessarily being able to recognise individual flows on the photographs studied. The thickness of lava flows or a series of flows can be estimated from these crater size distribution characteristics. The lava flow histories of the Apollo landing sites 11, 12 and 15 are discussed in detail. The thicknesses of the most recent (3–3.4 × 109 years ago) flows there and of the youngest flows in an area in south-west Mare Imbrium (3 × 109 years) are found to range between 30 and 60 m. The subsequent flow episodes at the landing sites showing up in the crater size distributions can be related to differences in the radiometric ages of the respective lunar rocks. 相似文献
77.
An advanced method of automated seismic phase picking and exact location and magnitude determination of swarm micro-earthquakes from local network data is presented. The phase picker is applied in two steps: first, S-wave groups are identified using a polarisation detector, and then corresponding P-wave groups are searched for. The times of maximum P- and S-amplitudes are then used as starting points for the determination of accurate P- and S-arrival times. The maximum S-wave amplitudes are utilised for determining local magnitudes. The whole procedure is checked by simultaneous preliminary hypocentre location providing estimates of local magnitudes and a compatibility check of the candidate P- and S-phases. The closest station to the earthquake cluster is used as a master, and the phase search at the remaining stations is governed by the P- and S-phases identified at the master station. Thanks to the use of apriori information on the approximate position of hypocentres, the procedure is also capable of picking the individual P- and S-phases of sequences of overlapping swarm events. The performance of the procedure was tested by comparison of the automatically and interactively created catalogues of the January 1997 NW-Bohemia micro-earthquake swarm. With stations located at epicentral distances between 0 and 20 km, the difference between hypocentre coordinates obtained by automatic and interactive processing did not exceed 80 m for 86% events. All events above magnitude 0.5 were identified, and the automatically determined polarity of first P-wave motion proved to be correct in 89% of them. 相似文献
78.
Matthias?AuerEmail author Gerhard?H.?Eisbacher 《International Journal of Earth Sciences》2003,92(2):210-227
The Northern Calcareous Alps (NCA) of southern Bavaria and northern Tyrol constitute a carbonate-dominated polyphase fold-thrust wedge; together with its Grauwacken Zone Basement, it is the northernmost part of the far-travelled Upper Austroalpine thrust complex of the Eastern Alps. The present geometry developed in several kinematic stages. Jurassic extensional faults that affected large parts of the NCA and their basement originated when the main part of the NCA was still located southeast of the Central Alpine Ötztal-Silvretta complex. These faults and related facies transitions influenced the later style of detachment of the NCA thrust sheets. Mid to Late Cretaceous detachment, thrust-sheet stacking and motion over the Central Alpine complex are registered in clastic deposits of syntectonic basins. The latest Cretaceous to Cenozoic NNE- to N-directed motion of the NCA towards Europe in front of the Central Alpine complex created another set of significant contraction structures, which at depth overprinted all previous structures. During Cretaceous to Cenozoic deformation, the NCA experienced about 80 km of shortening, i.e., about 73% along the TRANSALP Profile. The European basement and autochthonous Mesozoic cover beneath the allochthonous NCA thrust sheets and flysch complexes seem to have remained relatively undeformed. 相似文献
79.
Gerhard?SchmiedlEmail author Maria?Scherbacher Angela?A.?Bruch Bogomir?Jelen James?H.?Nebelsick Christoph?Hemleben Volker?Mosbrugger Helena?Rifelj 《International Journal of Earth Sciences》2002,91(1):123-132
Several sections from the uppermost Eocene and Oligocene of northern Slovenia have been investigated with respect to sedimentary facies, foraminiferal assemblages, stable isotopes, carbonate microfacies, and palynology. The main objective was to reconstruct the paleoenvironmental history of the Paleogene Paratethys in this region of the eastern Alpine realm. The sediments exhibit a transgressive succession beginning with conglomerates, sandstones, and mudstones of fluvial and lacustrine origin followed by carbonates and muddy marls indicating marine conditions. The foraminiferal faunal changes from brackish to shallow marine to deeper marine assemblages and the distribution of the palynofloras corroborate the sedimentological results. Microfacies analysis of the limestones shows a wide variation of shallow water, generally mud-rich facies dominated by coralline algae, foraminifera, and corals. Microfaunas adapted to low-oxygen conditions indicate temporal sluggish bottom-water circulation which can be associated with high fresh-water fluxes. These results are discussed as reflecting both the global sea-level rise during the Early Oligocene and the regional tectonic and climatic evolution. 相似文献
80.
Korzennik SG Brown TM Fischer DA Nisenson P Noyes RW 《The Astrophysical journal》2000,534(2):L147-L150
We present deep Hubble Space Telescope (HST) imaging, as well as ground-based imaging and spectroscopy, of the optical afterglow associated with the long-duration gamma-ray burst GRB 990712 and its host galaxy. The data were obtained 48-123 days after the burst occurred. The magnitudes of the host (R=21.9, V=22.5) and optical afterglow (R=25.4, V=25.8, 47.7 days after the burst) favor a scenario in which the optical light follows a pure power-law decay with an index of alpha approximately -1.0. We find no evidence for a contribution from a supernova like SN 1998bw. This suggests that either there are multiple classes of long-duration gamma-ray bursts or that the peak luminosity of the supernova was more than 1.5 mag fainter than SN 1998bw. The HST images and EFOSC2 spectra indicate that the gamma-ray burst was located in a bright, extended feature (possibly a star-forming region) 1.4 kpc from the nucleus of a 0.2L*B galaxy at z=0.434, possibly a Seyfert 2 galaxy. The late-time afterglow and host galaxy of GRB 990712 bear some resemblance to those of GRB 970508. 相似文献