全文获取类型
收费全文 | 1764篇 |
免费 | 86篇 |
国内免费 | 32篇 |
专业分类
测绘学 | 41篇 |
大气科学 | 186篇 |
地球物理 | 407篇 |
地质学 | 642篇 |
海洋学 | 139篇 |
天文学 | 288篇 |
综合类 | 5篇 |
自然地理 | 174篇 |
出版年
2023年 | 6篇 |
2022年 | 9篇 |
2021年 | 33篇 |
2020年 | 35篇 |
2019年 | 26篇 |
2018年 | 54篇 |
2017年 | 45篇 |
2016年 | 77篇 |
2015年 | 50篇 |
2014年 | 72篇 |
2013年 | 114篇 |
2012年 | 57篇 |
2011年 | 105篇 |
2010年 | 87篇 |
2009年 | 105篇 |
2008年 | 91篇 |
2007年 | 102篇 |
2006年 | 101篇 |
2005年 | 69篇 |
2004年 | 66篇 |
2003年 | 53篇 |
2002年 | 55篇 |
2001年 | 44篇 |
2000年 | 33篇 |
1999年 | 38篇 |
1998年 | 30篇 |
1997年 | 19篇 |
1996年 | 20篇 |
1995年 | 18篇 |
1994年 | 14篇 |
1993年 | 18篇 |
1992年 | 9篇 |
1991年 | 19篇 |
1990年 | 16篇 |
1989年 | 16篇 |
1987年 | 13篇 |
1986年 | 19篇 |
1985年 | 9篇 |
1984年 | 6篇 |
1983年 | 16篇 |
1982年 | 13篇 |
1981年 | 14篇 |
1980年 | 12篇 |
1979年 | 9篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1976年 | 7篇 |
1975年 | 8篇 |
1974年 | 7篇 |
1973年 | 6篇 |
排序方式: 共有1882条查询结果,搜索用时 15 毫秒
971.
Eric Buffetaut 《地学学报》1989,1(1):69-74
The Late Cretaceous (mainly Campanian and Maastrichtian) non-marine vertebrate faunas of Europe contain archosaurian reptiles which belong to groups otherwise known mainly or only from the southern ('Gondwanan') continents. They include titanosaurid sauropods, abelisaurid theropods, and trematochampsid crocodilians. The occurrence of these forms together with others of 'Asiamerican' affinities gives the Late Cretaceous vertebrate faunas of Europe a peculiar composition, which makes them clearly different from the well-known faunas from western North America and Central Asia. The Gondwanan dinosaurs and crocodilians from Europe provide evidence of faunal interchange across the Tethys Sea during the Cretaceous, possibly via the Alboran plate, or the Apulian plate, which may have functioned as 'stepping-stones', especially during periods of low sea level. 相似文献
972.
973.
Wang-Hong Yang R. James Kirkpatrick Norma Vergo John McHone Tryggvi I. Emilsson Eric Oldfield 《Meteoritics & planetary science》1986,21(1):117-124
High-resolution solid-state silicon-29 nuclear magnetic resonance spectroscopy using “magic-angle” sample-spinning can readily detect the presence of the high pressure silica polymorphs coesite and stishovite in whole-rock samples from a Meteor Crater, Arizona, impact sample, and yields accurate coesite/stishovite ratios. Such determinations are being carried out by partially suppressing (saturating) intense quartz signals (which have long spin-lattice relaxation times) by means of short experimental recycle-times. This method enhances the signal-to-noise ratios of coesite and stishovite (which have relatively short spin-lattice relaxation times). For the sample examined, the coesite/stishovite ratio is about 27. 相似文献
974.
975.
Earth Motion Caused by Local Atmospheric Pressure Changes 总被引:4,自引:0,他引:4
G. G. Sorrells John A. McDonald Z. A. Der Eugene Herrin 《Geophysical Journal International》1971,26(1-4):83-98
Summary Observations have been made of the local atmospheric pressure field and the long-period seismic noise fields both on the surface of the Earth and in a mine at a depth of 183 metres. The observations show that during windy intervals and in the period range 20–100 s there is a strong correlation between local atmospheric pressure changes and the noise recorded by a vertical seismograph located on the surface. In contrast, over the same range of periods there is no correlation between the seismic noise recorded in the mine and local atmospheric pressure changes except during the passage of acoustic waves. It is shown that the noise in this pass band is not due to the buoyant response of the seismograph, but is caused by the motion of the Earth responding to atmospheric pressure changes. 相似文献
976.
Eric A. Crecelius 《Marine Chemistry》1980,8(3):245-250
The elemental solubilities of three coal fly ash samples and two coastal marine-aerosol samples in seawater are different. The coal fly ash samples were collected from the electrostatic precipitators on coal-fired power plants. The air particulates were collected by a high-volume air sampler located near the Washington coast. Samples were neutron-activated then contacted with seawater for several hours. The elements that were partially solubilized from both fly ash and aerosols included As, Sb, Se, Br and Cr. Zinc and Co were more soluble in aerosols then fly ash. 相似文献
977.
Herbert W. Schnopper Eric Silver Stephen Murray Suzanne Romaine Simon Bandler Christine Jones William Forman Norman Madden Jeffery Beeman Eugene Haller Finn Christensen Niels Westergaard Juan Fabregat Victor Reglero Alvaro Gimenez Noah Brosch Elia Liebowitz Hagai Netzer Marco Barbera Alfonso Collura Salvatore Sciortino 《Astrophysics and Space Science》2001,276(1):49-65
The X-Ray Spectroscopic Explorer (XRASE) has a unique combination of features that will make it possible to address many of NASA's scientific goals. These include how galaxy clusters form, the physics and chemistry of the ISM, the heating of stellar coronae, the amount and content of intergalactic baryonic matter, the mass of black holes and the formation of disks and jets in AGN and galactic binaries. XRASE has a thin foil, multilayered telescope with a large collecting area up to 10 keV, especially in the Fe K region (1100 cm2). Its microcalorimeter array combines high energy resolution (7 eV at 6 keV) and efficiency with a field-of-view of 26 arcmin2 . A deep orbit allows for long, continuous observations. Monitoring instruments in the optical (WOM-X), UV (TAUVEX) and hard X-RAY (GRAM) bands will offer exceptional opportunities to make simultaneous multi-wavelength observations. 相似文献
978.
The history of MODFLOW 总被引:4,自引:1,他引:3
979.
Anthony?C.?WithersEmail author Eric?J.?Essene Youxue?Zhang 《Contributions to Mineralogy and Petrology》2003,145(2):199-204
The transition between rutile and α-PbO2 structured TiO2 (TiO2II) has been investigated at 700–1,200 °C and 4.2–9.6 GPa. Hydrothermal phase equilibrium experiments were performed in the multi-anvil apparatus to bracket the phase boundary at 700, 1,000, and 1,200 °C. The equilibrium phase boundary is described by the equation: P (GPa)=1.29+0.0065 T ( °C). In addition, growth of TiO2II was observed in experiments at 500 and 600 °C, although growth of rutile was too slow to bracket unambiguously the equilibrium boundary at these temperatures. Water was not detected in either rutile or TiO2II, and dry synthesis experiments at 1,200 °C were consistent with the phase boundary determined in the fluid-bearing experiments, suggesting that the equilibrium is unaffected by the presence of water. Our bracket of the phase boundary at 700 °C is consistent with the reversed, dry experiments of Akaogi et al. (1992) and the reversals of Olsen et al. (1999). The new data suggest that the phase boundary is linear, in agreement with Akaogi et al. (1992), but in striking contrast to the phase diagram inferred by Olsen et al. (1999). The natural occurrence of TiO2II requires formation pressures considerably higher than the graphite–diamond phase boundary. 相似文献
980.
Rock-magnetic proxies of climate change from loess -paleosol sediments of the Czech Republic 总被引:6,自引:0,他引:6
Summary Rock-magnetic characteristics of late Pleistocene loess-paleosol sequences in the Czech Republic show patterns of variation
that reflect climate-related depositional and diagenetic processes which acted on the sedimentary profiles. Mass-normalized
magnetic susceptibility is high in interglacial and interstadial paleosols, while uniformly low values are measured in unweathered
loess horizons. Normalized ferrimagnetic susceptibility and anhysteretic remanent magnetization show an enhancement of ultrafine
(superparamagnetic, SP) and fine (single-domain, SD, and pseudo-single-domain, PSD) grains in chernozem paleosols correlated
with δ18O substages 5c and 5a as well as in the Holocene soil. The parabraunerde paleosol associated with peak interglacial conditions,
correlated with δ18O substage 5e, shows evidence of diagenetic loss of fine grained magnetic minerals, although coarse (multidomain, MD) grains
appear to be preserved.
Low temperature remanence behavior plus high temperature susceptibility measurements of representative samples from each lithologic
unit indicate that magnetite and maghemite are the dominant magnetic minerals within the sediments. Variations in concentration-independent
rock-magnetic parameters are therefore primarily a function of grain size variations through the profile. It is anticipated
that with additional magnetic and non-magnetic sedimentological and geochemical tests, a quantitative rock-magnetic — paleoclimate
model can be developed for the central European loess region. 相似文献