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91.
Brad E. Tucker 《Astrophysics and Space Science》2011,335(1):223-230
Type Ia Supernova (SN Ia) are a powerful, albeit not completely understood, tool for cosmology. Gaps in our understanding
of their progenitors and detailed physics can lead to systematic errors in the cosmological distances they measure. We use
UV data in two context to help further our understanding of SN Ia progenitors and physics. We analyze a set of nearly 700
light curves, and find no signature of the shock heating of a red giant companion, predicted by Kasen (Astrophys. J. 708:1025,
2010), casting doubt as to frequency of this SN Ia channel. We also use UV imaging of high redshift host galaxies of SN Ia to
better understand the environments which SN Ia occur. We show that some high-z elliptical galaxies have current star formation, hindering efforts to use them as low-extinction environments. We show cosmological
scatter of SN distances at large effective radii in their hosts is significantly reduced, and argue this is due to the smaller
amounts of dust affecting the SN Ia. Finally, we find a two component dependence of SN distance measurements as a function
of their host galaxy’s FUV-V color. This indicates that both the age and metallicity/mass of the host galaxy maybe important
ingredients in measuring SN Ia distances. 相似文献
92.
Decaying mountain ranges often show a surprisingly dynamic pattern of landscape evolution. Although one might expect a simple, monotonic decline in relief over time, evidence from several inactive mountain ranges shows alternating sequences of deposition and erosion in the associated basins, suggesting variations in relief and exhumation rate in the ranges themselves. Examples include the Southern Rocky Mountains, the Pyrenees, the European Alps and the Atlas Mountains. In this paper, we explore the possible origins of post‐orogenic landscape dynamics using a simple mathematical model of a mountain range and an adjacent foreland basin. The analysis highlights the importance of mass balance. In particular, a switch from basin exhumation to renewed sedimentation requires either an increase in sediment influx from the range or a decrease in sediment outflux beyond the basin margin. Although it is widely understood that post‐orogenic changes in erosion and sediment flux can have multiple causes (including climate change, regional tectonic uplift or tilting, or exhumation of variable lithologies), an important implication of our analysis is that the impact of such changes must differ in sign or magnitude between the range and the basin to be recorded. This requirement places an important constraint on viable explanations for alternating sequences of deposition and erosion in a decaying mountain‐basin pair. 相似文献
93.
Abigail L. Langston Gregory E. Tucker Robert S. Anderson Suzanne P. Anderson 《Applied Geochemistry》2011
Understanding the relationship between subsurface flow paths on hillslopes and chemical weathering of bedrock is fundamental to understanding the timing and mechanisms that weather bedrock to saprolite. The link between chemical weathering of bedrock and contact time with reactive water along flow paths motivates this study. Water drives the chemical alteration of rock into saprolite, yet connected porosity generally declines with depth into the weathered profile. Saprolite formation, therefore, reflects coupled weathering and permeability development over time. This study uses numerical modeling and soil-moisture monitoring to explore the hydrology of the unsaturated zone and the influence of fracture density, hillslope gradient, and permeability contrasts within the saprolite development horizon on saprolite development. 相似文献
94.
Our knowledge about the lunar environment is based on a large volume of ground-based, remote, and in situ observations. These observations have been conducted at different times and sampled different pieces of such a complex system as the surface-bound exosphere of the Moon. Numerical modeling is the tool that can link results of these separate observations into a single picture. Being validated against previous measurements, models can be used for predictions and interpretation of future observations results. 相似文献
95.
96.
L. Golub E. DeLuca G. Austin J. Bookbinder D. Caldwell P. Cheimets J. Cirtain M. Cosmo P. Reid A. Sette M. Weber T. Sakao R. Kano K. Shibasaki H. Hara S. Tsuneta K. Kumagai T. Tamura M. Shimojo J. McCracken J. Carpenter H. Haight R. Siler E. Wright J. Tucker H. Rutledge M. Barbera G. Peres S. Varisco 《Solar physics》2007,243(1):63-86
The X-ray Telescope (XRT) of the Hinode mission provides an unprecedented combination of spatial and temporal resolution in solar coronal studies. The high sensitivity
and broad dynamic range of XRT, coupled with the spacecraft’s onboard memory capacity and the planned downlink capability
will permit a broad range of coronal studies over an extended period of time, for targets ranging from quiet Sun to X-flares.
This paper discusses in detail the design, calibration, and measured performance of the XRT instrument up to the focal plane.
The CCD camera and data handling are discussed separately in a companion paper. 相似文献
97.
T.H. Torsvik R.D. Tucker L.D. Ashwal L.M. Carter B. Jamtveit K.T. Vidyadharan & P. Venkataramana 《地学学报》2000,12(5):220-224
A U–Pb zircon age of 91.2 ± 0.2 Myr from western India (St. Mary islands) confidently links India with the Late Cretaceous magmatic province in Madagascar (≈ 84–92 Ma), and the U–Pb age is within analytical error of the U–Pb age of the Analalava gabbro pluton (91.6 ± 0.3 Myr) in northeastern Madagascar. Palaeomagnetic data from India and Madagascar allow us to postulate a new India–Madagascar fit (Euler latitude = 14.24°, longitude = 38.8° and rotation angle = –69.2°). This fit is applicable to the Late Cretaceous, directly prior to and during the early phase of Madagascar–India separation. In our Late Cretaceous reconstruction, south-west India runs roughly subparallel with the first known break-up related magnetic anomaly (A34); it maintains a close connection between Mada-gascar and India, but places India slightly rotated compared to the eastern margin of Madagascar and more northerly compared with some reconstructions. St. Mary magmatism is linked to the initial break-up between India and Madagascar, and magmatism probably resulted from rift-related extensional processes initially induced by the Marion hotspot underlying southern Madagascar during the Late Cretaceous. 相似文献
98.
99.
A grain mobility model of post-depositional realignment 总被引:1,自引:0,他引:1
P. Tucker 《Geophysical Journal International》1980,63(1):149-163
100.
Theoretical and Applied Climatology - Daily synoptic maps for May–September 1966 have shown the presence of a persistent wind shift or convergence zone, the Afar Convergence Zone (ACZ),... 相似文献