全文获取类型
收费全文 | 604篇 |
免费 | 34篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 16篇 |
大气科学 | 45篇 |
地球物理 | 143篇 |
地质学 | 191篇 |
海洋学 | 66篇 |
天文学 | 122篇 |
综合类 | 2篇 |
自然地理 | 55篇 |
出版年
2021年 | 11篇 |
2020年 | 10篇 |
2019年 | 11篇 |
2018年 | 20篇 |
2017年 | 21篇 |
2016年 | 26篇 |
2015年 | 16篇 |
2014年 | 16篇 |
2013年 | 36篇 |
2012年 | 12篇 |
2011年 | 27篇 |
2010年 | 17篇 |
2009年 | 32篇 |
2008年 | 31篇 |
2007年 | 21篇 |
2006年 | 20篇 |
2005年 | 33篇 |
2004年 | 24篇 |
2003年 | 27篇 |
2002年 | 15篇 |
2001年 | 11篇 |
2000年 | 14篇 |
1999年 | 15篇 |
1998年 | 7篇 |
1997年 | 5篇 |
1996年 | 7篇 |
1995年 | 5篇 |
1994年 | 3篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1991年 | 6篇 |
1990年 | 3篇 |
1989年 | 7篇 |
1988年 | 2篇 |
1987年 | 6篇 |
1986年 | 4篇 |
1985年 | 13篇 |
1984年 | 6篇 |
1983年 | 10篇 |
1982年 | 5篇 |
1981年 | 9篇 |
1980年 | 9篇 |
1979年 | 6篇 |
1978年 | 10篇 |
1977年 | 2篇 |
1976年 | 6篇 |
1975年 | 9篇 |
1974年 | 5篇 |
1973年 | 7篇 |
1971年 | 2篇 |
排序方式: 共有640条查询结果,搜索用时 93 毫秒
561.
562.
563.
The pressure and temperature history of the Tertiary Shimanto belt of south-west Japan has been elucidated by analysing fluids trapped in quartz crystals which grew syn-kinematically along late-stage brittle faults. The samples come from three areas that span the Paleogene exposures on the Muroto Peninsula of Shikoku Island. Applying microthermometric and laser Raman microsampling techniques to coeval water-rich and carbonic fluid inclusions, we have constrained the pressure and temperature conditions that accompanied a widespread and kinematically distinct phase of deformation. The results suggest elevated geothermal gradients during late-stage deformation, conditions that are in disaccord with previous plate reconstructions that have depicted old, thermally mature Pacific crust subducting beneath Eurasia during the early to middle Tertiary. These conditions can most easily be accounted for by including an additional plate boundary in the western Pacific during Paleogene time. Plate reconstructions that include the Kula plate in this region are therefore consistent with our findings. In addition, our results provide clues to the conditions that likely accompany seismogenic deformation at active convergent plate boundaries. 相似文献
564.
565.
The City West Urban Strategy is concerned with redevelopment in part of inner metropolitan Sydney. Such plans should not be seen in isolation, but in a wider temporal and spatial context. Pyrmont and Ultimo have been undergoing significant socioeconomic changes for a decade and this trend is likely to be reinforced and intensified if the Strategy is implemented. Also the recent and projected changes are consistent with a global pattern of restructuring in urban waterfront areas where former port and industrial functions have declined. 相似文献
566.
Quentin A. Parker A. Acker D. J. Frew M. Hartley A. E. J. Peyaud F. Ochsenbein S. Phillipps D. Russeil S. F. Beaulieu M. Cohen J. Köppen B. Miszalski D. H. Morgan R. A. H. Morris M. J. Pierce A. E. Vaughan 《Monthly notices of the Royal Astronomical Society》2006,373(1):79-94
We present the Macquarie/AAO/Strasbourg Hα Planetary Nebula Catalogue (MASH) of over 900 true, likely and possible new Galactic planetary nebulae (PNe) discovered from the AAO/UKST Hα survey of the southern Galactic plane. The combination of depth, resolution, uniformity and areal coverage of the Hα survey has opened up a hitherto unexplored region of parameter space permitting the detection of this significant new PN sample. Away from the Galactic bulge the new PNe are typically more evolved, of larger angular extent, of lower surface brightness and more obscured (i.e. extinguished) than those in most previous surveys. We have also doubled the number of PNe in the Galactic bulge itself and although most are compact, we have also found more evolved examples. The MASH catalogue represents the culmination of a seven-year programme of identification and confirmatory spectroscopy. A key strength is that the entire sample has been derived from the same, uniform observational data. The 60 per cent increase in known Galactic PNe represents the largest ever incremental sample of such discoveries and will have a significant impact on many aspects of PN research. This is especially important for studies at the faint end of the PN luminosity function which was previously poorly represented. 相似文献
567.
Andrzej A. Zdziarski Marek Gierliski A. R. Rao S. V. Vadawale Joanna Mikoajewska 《Monthly notices of the Royal Astronomical Society》2005,360(3):825-838
We present an exhaustive analysis of five broad-band observations of GRS 1915+105 in two variability states, χ and ω, observed simultaneously by the Proportional Counter Array (PCA) and High-Energy X-ray Timing Experiment (HEXTE) detectors aboard the Rossi X-ray Timing Explorer , and the Oriented Scintillation Spectrometer Experiment (OSSE) detector aboard the Compton Gamma-ray Observatory . We find all the spectra well fitted by Comptonization of disc blackbody photons, with very strong evidence for the presence of a non-thermal electron component in the Comptonizing plasma. Both the energy and the power spectra in the χ state are typical of the very high/intermediate state of black hole binaries. The spectrum of the ω state is characterized by a strong blackbody component Comptonized by thermal electrons and a weak non-thermal tail. We then calculate rms spectra (fractional variability as functions of energy) for the PCA data. We accurately model the rms spectra by coherent superposition of variability in the components implied by the spectral fits, namely a less variable blackbody and more variable Comptonization. The latter dominates at high energies, resulting in a flattening of the rms at high energies in most of the data. This is also the case for the spectra of the quasi-periodic oscillations present in the χ state. Then, some of our data require a radial dependence of the rms of the disc blackbody. We also study the distance to the source, and find d ≃ 11 kpc as the most likely value, contrary to a recent claim of a much lower value. 相似文献
568.
A computer correlation technique was used to deduce the spreading history of the Mid-Atlantic Ridge from 5 magnetic profiles between 28°S and 43°S. In general, several possible histories are indicated for each profile involving changes of spreading rate and faulting, some of which are easily overlooked by the visual method. The only spreading history that was consistent will all the profiles required spreading at approximately 2.2 cm yr-1 from 11 m.y.b.p. to approximately 5.5 m.y.b.p., followed by a decrease in rate to 1.7 cm yr-1 relative to the Vine (1966) magnetic reversal model based on the South Pacific. Comparison of the data with other reported spreading rate discontinuities suggests that the South Pacific may be reponsible for the reported spreading rate changes. 相似文献
569.
Philomène A. Verlaan Author Vitae David S. Cronan Author Vitae Charles L. Morgan Author Vitae 《Progress in Oceanography》2004,63(3):125-158
Regional variation of Mn, Fe, Co, Ni and Cu in ferromanganese oxides (nodules and crusts) in the central south Pacific is related to primary productivity, oxygen minimum layer, and calcium carbonate compensation depth. The largely latitudinal influence of these environmental parameters on nodule and crust composition reflects their predominantly latitudinal variation. Primary productivity is the principal regional environmental control, influencing diagenetic enrichment of these elements in nodules through its effect, mediated by the CCD, on supply and concentration of labile organic matter vs. carbonate remains to the sediments. It influences hydrogenetic enrichment of these elements in nodules and crusts through its effect, mediated by the oxygen minimum layer (mainly in the case of crusts), on their export from surface waters.The elements’ varying susceptibility to being scavenged or organically bound influences the contrasting composition of diagenetic vs. hydrogenetic ferromanganese oxides, which is further influenced by depth. Hydrogenesis is the fundamental process governing nodule and crust formation, superimposed on which is diagenesis under specific circumstances; both are subject to intermittent interruption, diminution and augmentation by changes in environmental parameters. Application of regionally operative environmental controls locally explains local compositional variations and helps refine exploration criteria for economically viable nodules and crusts. 相似文献
570.