全文获取类型
收费全文 | 602篇 |
免费 | 14篇 |
国内免费 | 1篇 |
专业分类
测绘学 | 11篇 |
大气科学 | 55篇 |
地球物理 | 148篇 |
地质学 | 203篇 |
海洋学 | 34篇 |
天文学 | 114篇 |
自然地理 | 52篇 |
出版年
2021年 | 9篇 |
2020年 | 7篇 |
2019年 | 11篇 |
2018年 | 7篇 |
2017年 | 6篇 |
2016年 | 11篇 |
2015年 | 17篇 |
2014年 | 13篇 |
2013年 | 24篇 |
2012年 | 12篇 |
2011年 | 16篇 |
2010年 | 23篇 |
2009年 | 30篇 |
2008年 | 32篇 |
2007年 | 19篇 |
2006年 | 20篇 |
2005年 | 18篇 |
2004年 | 24篇 |
2003年 | 14篇 |
2002年 | 26篇 |
2001年 | 19篇 |
2000年 | 21篇 |
1999年 | 15篇 |
1998年 | 6篇 |
1997年 | 12篇 |
1996年 | 12篇 |
1995年 | 13篇 |
1994年 | 12篇 |
1993年 | 5篇 |
1991年 | 8篇 |
1990年 | 9篇 |
1989年 | 8篇 |
1988年 | 4篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 4篇 |
1984年 | 10篇 |
1983年 | 6篇 |
1982年 | 8篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1979年 | 14篇 |
1978年 | 9篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1975年 | 8篇 |
1974年 | 5篇 |
1973年 | 9篇 |
1972年 | 7篇 |
1944年 | 4篇 |
排序方式: 共有617条查询结果,搜索用时 187 毫秒
61.
P.A. Wood 《Geoforum》1974,5(3):19-27
British regional problems increasingly emphasize the need to understand the exploitation and movement of all factors of production between different parts of the country. This paper reviews evidence, from work sponsored by the National Institute of Economic and Social Research, on the significance for the standard regions of capital investment, interregional capital flows and regional investment multipliers. A high level of economic interdependence allows the effects of investment to become widely spread throughout the British space economy. This limits the power of capital expenditure to lead growth in the region where it takes place. Studies of the spatial implications of capital investment should therefore form part of more general appraisals of factor supply and demand changes and their effects on the decisions of different investing agencies (including government). Two distinctive themes for the geographical study of capital investment are suggested: the examination of relationships between investment projects by different agencies at appropriate sub-regional scales; and the ways in which established patterns of physical capital stock may influence the expenditure of new, mobile funds. 相似文献
62.
63.
O. Reimer P. F. Michelson R. A. Cameron S. W. Digel D. J. Thompson K. S. Wood 《Astrophysics and Space Science》2007,309(1-4):523-526
Gamma-ray astrophysics depends in many ways on multiwavelength studies. The Gamma-ray Large Area Space Telescope (GLAST) Large
Area Telescope (LAT) Collaboration has started multiwavelength planning well before the scheduled 2007 launch of the observatory.
Some of the high-priority multiwavelength needs include: (1) availability of contemporaneous radio and X-ray timing of pulsars;
(2) expansion of blazar catalogs, including redshift measurements; (3) improved observations of molecular clouds, especially
at high galactic latitudes; (4) simultaneous broad-band blazar monitoring; (5) characterization of gamma-ray transients, including
gamma ray bursts; (6) radio, optical, X-ray and TeV counterpart searches for reliable and effective sources identification
and characterization. Several of these activities are needed to be in place before launch.
相似文献
64.
Compared to hydrograph recession analysis, which is widely applied in engineering hydrology, the quantitative assessment of stream salinity with time (i.e. the salinograph) has received significantly less attention. In particular, while in many previous hydrological studies an inverse relationship between hydrograph and salinograph responses is apparent, the concept of salinity accession (the inversely related salinity counterpart to hydrograph recession) has not been introduced nor quantitatively evaluated in previous literature. In this study, we conduct a mathematical analysis of salinograph accession, and determine new quantitative relationships between salinity accession and hydrograph recession parameters. An equation is formulated that reproduces the general trend in salinity accession. A salinity accession parameter kc is then introduced and is shown to be the ratio of direct runoff to total stream flow recession parameters: kr/k. The groundwater recession parameter kg was estimated using a simple and rapid method that uses both salinograph and hydrograph data. Salinity accession type‐curves illustrate that under certain conditions, the relative steepness of individual salinographs is dependent upon the ratio of groundwater salinity to direct runoff salinity: Cg/Cr. The salinity accession algorithms are applied to two contrasting field settings: Scott Creek, South Australia and Sandy Creek, northern Queensland, Australia. It was found that kg > k during periods of obvious stream flow recession, for the events analysed. Salinograph accession behaviour was fairly similar for both sites, despite contrasting environments. Using assumed end‐member salinities for groundwater and direct runoff based upon field observations, the behaviour of kc from the Scott Creek site was approximately reproduced by varying the initial groundwater to runoff flow ratio: Qg0/Qr0, within reasonable parameter ranges. The use of salinograph information when used in addition to standard hydrograph analyses provided useful information on recession characteristics of stream components. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
65.
66.
67.
J. A. McSaveney P. R.Wood M. Scholz J. C. Lattanzio K. H. Hinkle 《Monthly notices of the Royal Astronomical Society》2007,378(3):1089-1100
High-dispersion near-infrared spectra have been taken of seven highly evolved, variable, intermediate-mass (4–6 M⊙ ) asymptotic giant branch (AGB) stars in the Large Magellanic Cloud and Small Magellanic Cloud in order to look for C, N and O variations that are expected to arise from third dredge-up and hot-bottom burning. The pulsation of the objects has been modelled, yielding stellar masses, and spectral synthesis calculations have been performed in order to derive abundances from the observed spectra. For two stars, abundances of C, N, O, Na, Al, Ti, Sc and Fe were derived and compared with the abundances predicted by detailed AGB models. Both stars show very large N enhancements and C deficiencies. These results provide the first observational confirmation of the long-predicted production of primary nitrogen by the combination of third dredge-up and hot-bottom burning in intermediate-mass AGB stars. It was not possible to derive abundances for the remaining five stars: three were too cool to model, while another two had strong shocks in their atmospheres which caused strong emission to fill the line cores and made abundance determination impossible. The latter occurrence allows us to predict the pulsation phase interval during which observations should be made if successful abundance analysis is to be possible. 相似文献
68.
The energy balance over land and oceans: an assessment based on direct observations and CMIP5 climate models 总被引:2,自引:0,他引:2
69.
M. M. Bisi A. R. Breen B. V. Jackson R. A. Fallows A. P. Walsh Z. Mikić P. Riley C. J. Owen A. Gonzalez-Esparza E. Aguilar-Rodriguez H. Morgan E. A. Jensen A. G. Wood M. J. Owens M. Tokumaru P. K. Manoharan I. V. Chashei A. S. Giunta J. A. Linker V. I. Shishov S. A. Tyul’bashev G. Agalya S. K. Glubokova M. S. Hamilton K. Fujiki P. P. Hick J. M. Clover B. Pintér 《Solar physics》2010,265(1-2):49-127
We report the results of a multi-instrument, multi-technique, coordinated study of the solar eruptive event of 13 May 2005. We discuss the resultant Earth-directed (halo) coronal mass ejection (CME), and the effects on the terrestrial space environment and upper Earth atmosphere. The interplanetary CME (ICME) impacted the Earth’s magnetosphere and caused the most-intense geomagnetic storm of 2005 with a Disturbed Storm Time (Dst) index reaching ?263 nT at its peak. The terrestrial environment responded to the storm on a global scale. We have combined observations and measurements from coronal and interplanetary remote-sensing instruments, interplanetary and near-Earth in-situ measurements, remote-sensing observations and in-situ measurements of the terrestrial magnetosphere and ionosphere, along with coronal and heliospheric modelling. These analyses are used to trace the origin, development, propagation, terrestrial impact, and subsequent consequences of this event to obtain the most comprehensive view of a geo-effective solar eruption to date. This particular event is also part of a NASA-sponsored Living With a Star (LWS) study and an on-going US NSF-sponsored Solar, Heliospheric, and INterplanetary Environment (SHINE) community investigation. 相似文献
70.
D. Howell I. G. Wood D. P. Dobson A. P. Jones L. Nasdala J. W. Harris 《Contributions to Mineralogy and Petrology》2010,160(5):705-717
The pressure and temperature conditions of formation of natural diamond can be estimated by measuring the residual stress
that an inclusion remains under within a diamond. Raman spectroscopy has been the most commonly used technique for determining
this stress by utilising pressure-sensitive peak shifts in the Raman spectrum of both the inclusion and the diamond host.
Here, we present a new approach to measure the residual stress using quantitative analysis of the birefringence induced in
the diamond. As the analysis of stress-induced birefringence is very different from that of normal birefringence, an analytical
model is developed that relates the spherical inclusion size, R
i, host diamond thickness, L, and measured value of birefringence at the edge of the inclusion,
\Updelta n(R\texti )\textav \Updelta n(R_{\text{i}} )_{\text{av}} , to the peak value of birefringence that has been encountered; to first order
\Updelta n\textpk = (3/4)(L/R\texti ) \Updelta n(R\texti )\textav \Updelta n_{\text{pk}} = (3/4)(L/R_{\text{i}} ) \, \Updelta n(R_{\text{i}} )_{\text{av}} . From this birefringence, the remnant pressure (P
i) can be calculated using the photoelastic relationship
\Updelta n\textpk = - (3/4)n3 q\textiso P\texti \Updelta n_{\text{pk}} = - (3/4)n^{3} q_{\text{iso}} P_{\text{i}} , where q
iso is a piezo-optical coefficient, which can be assumed to be independent of crystallographic orientation, and n is the refractive index of the diamond. This model has been used in combination with quantitative birefringence analysis
with a MetriPol system and compared to the results from both Raman point and 2D mapping analysis for a garnet inclusion in
a diamond from the Udachnaya mine (Russia) and coesite inclusions in a diamond from the Finsch mine (South Africa). The birefringence
model and analysis gave a remnant pressure of 0.53 ± 0.01 GPa for the garnet inclusion, from which a source pressure was calculated
as 5.7 GPa at 1,175°C (temperature obtained from IR analysis of the diamond host). The Raman techniques could not be applied
quantitatively to this sample to support the birefringence model; they were, however, applied to the largest coesite inclusion
in the Finsch sample. The remnant pressure values obtained were 2.5 ± 0.1 GPa (birefringence), 2.5 ± 0.3 GPa (2D Raman map),
and 2.5–2.6 GPa (Raman point analysis from all four inclusions). However, although the remnant pressures from the three methods
were self-consistent, they led to anomalously low source pressure of 2.9 GPa at 1,150°C (temperature obtained from IR analysis)
raising serious concerns about the use of the coesite-in-diamond geobarometer. 相似文献