全文获取类型
收费全文 | 258篇 |
免费 | 11篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 8篇 |
大气科学 | 13篇 |
地球物理 | 44篇 |
地质学 | 72篇 |
海洋学 | 19篇 |
天文学 | 53篇 |
自然地理 | 61篇 |
出版年
2024年 | 2篇 |
2020年 | 2篇 |
2019年 | 7篇 |
2018年 | 7篇 |
2017年 | 7篇 |
2016年 | 9篇 |
2015年 | 3篇 |
2014年 | 4篇 |
2013年 | 10篇 |
2012年 | 7篇 |
2011年 | 13篇 |
2010年 | 16篇 |
2009年 | 12篇 |
2008年 | 13篇 |
2007年 | 10篇 |
2006年 | 20篇 |
2005年 | 11篇 |
2004年 | 9篇 |
2003年 | 8篇 |
2002年 | 7篇 |
2001年 | 6篇 |
2000年 | 4篇 |
1999年 | 11篇 |
1998年 | 5篇 |
1997年 | 5篇 |
1996年 | 4篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1990年 | 1篇 |
1989年 | 2篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 2篇 |
1981年 | 6篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 3篇 |
1977年 | 2篇 |
1976年 | 4篇 |
1975年 | 2篇 |
1974年 | 5篇 |
1973年 | 2篇 |
1972年 | 3篇 |
1971年 | 3篇 |
1969年 | 1篇 |
1964年 | 1篇 |
排序方式: 共有270条查询结果,搜索用时 15 毫秒
51.
Bohdan Kochtubajda Ronald E. Stewart Mike D. Flannigan Barrie R. Bonsal Charles Cuell Curtis J. Mooney 《大气与海洋》2019,57(1):73-90
Weather and climate are major factors influencing worldwide wildfire activity. This study assesses surface and atmospheric conditions associated with the 2014 extreme wildfires in the Northwest Territories (NWT) of Canada. Hot and dry conditions led to the NWT experiencing the most severe wildfire season in its recorded history. The season included a record number of cloud-to-ground lightning flashes and set a record for area burned. Lightning was the dominant ignition source and accounted for about 95% of the wildfires. Prolonged periods of smoke led to dramatic reductions in visibility, frequent road closures, and reduced air quality resulting in numerous health alerts. Temporal and spatial patterns of lightning characteristics in 2014, derived from Canadian Lightning Detection Network data, were different from those in other years with, for example, far more positive flashes from 0600 to 1200?utc (midnight to 6:00 am local time). The highest fraction of positive cloud-to-ground flashes (43.1%) occurred in the smoke-dominated North Slave region, which was more than in the Dehcho, South Slave, or Sahtu regions. Mid-tropospheric atmospheric circulation over a large region that included the NWT was classified into the six most common summer patterns. Results showed that ridging and ridge displacements occurred more frequently during 2014 although lightning was associated with all circulation patterns. This study has advanced the understanding of the roles of weather, lightning, and mid-tropospheric circulation patterns associated with extreme wildfires in northwestern Canada. 相似文献
52.
Y. Futaana S. Barabash M. Holmström E. Kallio H. Gunell R. Lundin M. Yamauchi J.D. Winningham J.R. Sharber A.J. Coates D.O. Kataria P. Riihelä H. Koskinen J. Luhmann D. Williams C.C. Curtis B.R. Sandel M. Carter A. Fedorov S. Orsini M. Maggi P. Bochsler N. Krupp M. Fränz C. Dierker 《Icarus》2006,182(2):424-430
The neutral particle detector (NPD) on board Mars Express has observed energetic neutral atoms (ENAs) from a broad region on the dayside of the martian upper atmosphere. We show one such example for which the observation was conducted at an altitude of 570 km, just above the induced magnetosphere boundary (IMB). The time of flight spectra of these ENAs show that they had energies of 0.2-2 keV/amu, with an average energy of ∼1.1 keV/amu. Both the spatial distribution and the energy of these ENAs are consistent with the backscattered ENAs, produced by an ENA albedo process. This is the first observation of backscattered ENAs from the martian upper atmosphere. The origin of these ENAs is considered to be the solar wind ENAs that are scattered back by collision processes in the martian upper atmosphere. The particle flux and energy flux of the backscattered ENAs are and , respectively. 相似文献
53.
Alternative Places of Detention (APODs) are a new way of detaining asylum seekers in Australia. The establishment of APODs creates a new formal structure of belonging in Australia which challenges everyday practices of belonging and senses of belonging at the local and national scale. This paper examines practices of belonging which emerged following the establishment of the Inverbrackie APOD in Woodside, South Australia. Using a critical discourse analysis approach, informed by the insights of theories of performativity, this research explores the competing stories of two broadly defined groups (opponents and supporters of Inverbrackie) engaged in a dialogue about asylum seekers, refugees, immigration detention and belonging. While opposition to the APOD was vocal and frequent in the lead-up to the establishment of the detention centre, once the Inverbrackie APOD became operational opponents’ voices began to fade. On the other hand, supporters continued to say things—and more importantly continued to do things—to nurture belonging for asylum seekers in Inverbrackie, Woodside, and Australia. 相似文献
54.
55.
Curtis M. Oldenburg Jennifer L. Lewicki Lehua Pan Laura Dobeck Lee Spangler 《Environmental Earth Sciences》2010,60(2):241-250
A numerical experiment was carried out to test whether the patchy CO2 emission patterns observed at the Zero Emissions Research and Technology release facility are caused by the presence of packers
that divide the horizontal injection well into six CO2-injection zones. A three-dimensional model of the horizontal well and cobble–soil system was developed and simulations using
TOUGH2/EOS7CA were carried out. Simulation results show patchy emissions for the seven-packer (six-injection-zone) configuration
of the field test. Numerical experiments were then conducted for the cases of 24 packers (23 injection zones) and an effectively
infinite number of packers. The time to surface breakthrough and the number of patches increased as the number of packers
increased suggesting that packers and associated along-pipe flow are the origin of the patchy emissions. In addition, it was
observed that early breakthrough occurs at locations where the horizontal well pipe is shallow and installed mostly in soil
rather than the deeper cobble. In the cases where the pipe is installed at shallow depths and directly in the soil, higher
pipe gas saturations occur than where the pipe is installed slightly deeper in the cobble. It is believed this is an effect
mostly relevant to the model rather than the field system and arises through the influence of capillarity, permeability, and
pipe elevation of the soil compared to the cobble adjacent to the pipe. 相似文献
56.
Read (1934b) described the mineralogy and regional setting of spectacularly zoned ultrabasic bodies occurring in Unst, Shetland. Chemical and phase compositional data are presented here for a selection of samples taken from each of the several monomineralic zones.The phase sequence and elemental distribution are discussed in some detail since both are complicated. It is shown that virtually all distributional features may be explained on the basis of a diffusion model: transport most probably having occurred via aqueous solutions in pore space.The present configurations represent frozen reaction intermediates. Controls upon the nature and extent of reaction are analysed. Certain features may be explained on the basis of local equilibrium thermodynamics. These arguments, however, are inadequate. Fairly simple kinetic considerations lead to a much more satisfactory analysis.Some of the problems associated with concepts of element mobility are discussed briefly. 相似文献
57.
R. C. Bhandari L. F. Curtis U. C. Shukla 《Journal of the Indian Society of Remote Sensing》1976,4(1-2):37-41
LANDSAT-MSS data in the form of a false colour composite image at a scale of 1:250,000 has been used to produce terrain unit maps of parts of north west India. The area of study consisted of central and southern districts of Haryana State. It has been possible to obtain a qualitative assessment of land use patterns and surface hydrology by means of visual Interpretation. The boundaries between differeat terrain units and moisture regimes were clearly discernible It is felt that comparative studies of false colour infrared imagery over a period of time can provide valuable Information for those engaged in reclamation schemes. In particular, the data can be used to plan reclamation of salt affected and waterlogged lands in semi-arid zones of states like Haryana. 相似文献
58.
59.
Major, minor and trace element concentrations have been measured in all the volumetrically significant minerals from the L-6 chondrites Alfianello, Colby (WI) and Leedey. Most of the elements show the compositional uniformity observed in other studies. However, REE, Co and Ni are distinctly different in their abundances and their phase distributions in each of the three meteorites. Such differences must manifest differing physical and chemical conditions involved in the formation of each of the three rocks. The distributions of REE and Ni between various phases are compatible with models which assume equilibrium between presently coexisting minerals. Such a model demonstrates how plausible differences in temperature and Ni content of metallic minerals could produce the observed differences in Ni abundances in olivine and clinopyroxene from each of the three chondrites.REE are too abundant in the minerals to have been produced by crystal-liquid fractionation from a magma of whole rock composition.Alkali element abundances are incompatible with a model of closed system equilibration of the meteorites. Rb is underabundant in feldspar relative to Na when compared to the equilibrium model predictions. A portion of the Cs seems to be included in feldspar by diadochic substitution, however, significant amounts are randomly associated with other minerals, perhaps by incorporation into lattice defects and at interstices. Partial loss of this nonfeldspathic Cs may be responsible for the large range of Cs abundances observed in chondrites. 相似文献
60.
The Silurian succession in the Tortworth Inlier includes strata belonging to the three main divisions of the System. The Upper Llandovery, which rests unconformably on Tremadoc beds, consists of about 700 ft. (213 m.) of fine-grained sandstones, mudstones and shales with two igneous bands. The Wenlock Series is represented by some 800 ft. (244 m.) of mudstones, siltstones and calcareous sandstones with impersistent limestone bands at various horizons. The Ludlow succession is incomplete, but at least 300 ft. (91 m.) of mudstones, siltstones and fine-grained sandstones are present, and they pass up conformably into the Downtonian. 相似文献