全文获取类型
收费全文 | 3901篇 |
免费 | 537篇 |
国内免费 | 339篇 |
专业分类
测绘学 | 57篇 |
大气科学 | 27篇 |
地球物理 | 887篇 |
地质学 | 1579篇 |
海洋学 | 272篇 |
天文学 | 1482篇 |
综合类 | 120篇 |
自然地理 | 353篇 |
出版年
2024年 | 17篇 |
2023年 | 51篇 |
2022年 | 55篇 |
2021年 | 86篇 |
2020年 | 77篇 |
2019年 | 103篇 |
2018年 | 83篇 |
2017年 | 87篇 |
2016年 | 116篇 |
2015年 | 109篇 |
2014年 | 193篇 |
2013年 | 207篇 |
2012年 | 184篇 |
2011年 | 159篇 |
2010年 | 157篇 |
2009年 | 284篇 |
2008年 | 267篇 |
2007年 | 338篇 |
2006年 | 248篇 |
2005年 | 222篇 |
2004年 | 184篇 |
2003年 | 188篇 |
2002年 | 165篇 |
2001年 | 141篇 |
2000年 | 159篇 |
1999年 | 153篇 |
1998年 | 150篇 |
1997年 | 95篇 |
1996年 | 99篇 |
1995年 | 63篇 |
1994年 | 61篇 |
1993年 | 40篇 |
1992年 | 47篇 |
1991年 | 20篇 |
1990年 | 50篇 |
1989年 | 30篇 |
1988年 | 32篇 |
1987年 | 18篇 |
1986年 | 11篇 |
1985年 | 8篇 |
1984年 | 3篇 |
1982年 | 2篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1978年 | 4篇 |
1954年 | 3篇 |
排序方式: 共有4777条查询结果,搜索用时 15 毫秒
261.
磁力勘探与岩性测深理论基础的对比 总被引:1,自引:0,他引:1
首先概括了岩性测深技术的理论基础和物性基础要点,强调电偶极子场是岩性测深技术的基本理论。然后通过电偶极子场与磁偶极子场的类比,以及岩性测深与磁力勘探的对比,提出了一条研究岩性测深技术理论基础及正演计算的思路。 相似文献
262.
Li ChuanXin Guo ZhaoJie Meng ZiFang Li HaiYan Zhang ZhiCheng Wu ChaoDong 《中国科学D辑(英文版)》2007,50(4):544-554
Analyses of rock-magnetic properties of Neogene sediments of the Taxihe section, northern Tianshan Mountains, show that the section can be classified into three categories including lacustrine facies, fluvial facies and alluvial facies, which correspond to the lower, middle and upper of the Taxihe section respectively. The magnetic minerals of the lacustrine facies may be affected by the process of weath- ering, lithogenesis and biolithogenesis besides the source of the sediments. The natural remanence intensities are between 10-3 A/m and 10-2 A/m. The minerals are dominated by magnetite and the high coercive magnetic mineral may be goethite. The magnetic grains are the mixture of PSD SD or SD SP. The natural remanence intensities of the strata of fluvial facies are between 10-2 A/m and 10-1 A/m, about ten times that of the lacustrine facies. The magnetic minerals are mainly magnetite and hematite, and the magnetic grains are mainly PSD. The characteristic remanence (ChRM) carriers are magnetites. In the alluvial facies, the natural remanence intensities are mostly less than 1×10-2 A/m. The magnetic minerals of the series are dominated by magnetite and hematite, almost the same as the fluvial facies. But the difference is that most of the stepwise demagnetization can reveal two components and the ChRM carriers are hematites. The magnetic grains are PSD in terms of the hysteresis parameters. 相似文献
263.
H. Greiner-Mai J. Hagedoorn L. Ballani I. Wardinski D. Stromeyer R. Hengst 《Studia Geophysica et Geodaetica》2007,51(4):491-513
We investigate the temporal behaviour of the axial component of the electromagnetic core-mantle coupling torque that is associated
with the poloidal part of the geomagnetic field observable at the Earth surface. For its computation, we use different models
of the geomagnetic field, expanded into spherical harmonics (Wardinski and Holme, 2006; Sabaka et al., 2004), and the mantle
conductivity. The geomagnetic field, which we have to know at the core-mantle boundary for the associated computations, will
be inferred from the field at the Earth surface by the non-harmonic field continuation through a conducting mantle shell.
The aims of this investigation are (i) to check how sensitive is the computation of the torque with respect to the different
geomagnetic field models, (ii) to check its dependence on the spherical harmonic degree n, and (iii) to determine the difference
between the mechanical torque derived from the observed length-of-day variations (atmospheric influence subtracted) and the
poloidal electromagnetic torque in dependence on the assumed conductivity. To use the non-harmonic field continuation for
the torque calculation and to obtain an insight into the influence of the different geomagnetic field models on the EM torques
are the major aspects of this paper.
grm@gfz-potsdam.de 相似文献
264.
265.
Ruth Soto Antonio M. Casas-Sainz Juan J. Villalaín Beln Oliva-Urcia 《Tectonophysics》2007,445(3-4):373-394
In this work we analyse and check the results of anisotropy of magnetic susceptibility (AMS) by means of a comparison with palaeostress orientations obtained from the analysis of brittle mesostructures in the Cabuérniga Cretaceous basin, located in the western end of the Basque–Cantabrian basin, North Spain. The AMS data refer to 23 sites including Triassic red beds, Jurassic and Lower Cretaceous limestones, sandstones and shales. These deposits are weakly deformed, and represent the syn-rift sequence linked to basins formed during the Mesozoic and later inverted during the Pyrenean compression. The observed magnetic fabrics are typical of early stages of deformation, and show oblate, triaxial and prolate magnetic ellipsoids. The magnetic fabric seems to be related to a tectonic overprint of an original, compaction, sedimentary fabric. Most sites display a NE–SW magnetic lineation that is interpreted to represent the stretching direction of the Early Cretaceous extensional stage of the basin, without recording of the Tertiary compressional events, except for sites with compression-related cleavage.Brittle mesostructures include normal faults, calcite and quartz tension gashes and joints, related to the extensional stage. The results obtained from joints and tension gashes show a dominant N–S to NE–SW, and secondary NW–SE, extension direction. Paleostresses obtained from fault analysis (Right Dihedra and stress inversion methods) indicate NW–SE to E–W, and N–S extension direction. The results obtained from brittle mesostructures show a complex pattern resulting from the superposition of several tectonic processes during the Mesozoic, linked to the tectonic activity related to the opening of the Bay of Biscay during the Early Cretaceous. This work shows the potential in using AMS analysis in inverted basins to unravel its previous extensional history when the magnetic fabric is not expected to be modified by subsequent deformational events. Brittle mesostructure analysis seems to be more sensitive to far-field stress conditions and record longer time spans, whereas AMS records deformation on the near distance, during shorter intervals of time. 相似文献
266.
首先应用MATLAB语言,编制了多边形法计算基底界面深度的程序,计算了一条基底界面深度。以区域地质资料和物性资料为依据,对黑龙江省虎林市幅1∶20万重磁场进行了综合分析。根据虎林盆地布格异常和区域场特征,结合重力异常和航磁异常等综合资料,按结晶基底起伏状态,将虎林盆地划分为3个隆起区,2个凹陷区。应用Sufer软件以及3D成图技术恢复出盆地基底起伏界面全貌。 相似文献
267.
C. G. Campbell & P. M. Heptinstall 《Monthly notices of the Royal Astronomical Society》1998,301(2):558-568
A full numerical solution is found for the effect of a strongly magnetic star on its accretion disc, for the case of magnetic buoyancy diffusion. As in the previously considered case of turbulent diffusion, the disc becomes disrupted when magnetic and viscous stresses become comparable. A magnetically induced temperature elevation leads to electron scattering opacity and radiation pressure becoming significant far from the stellar surface, with consequent viscous instability and vertical disruption of the disc. This, together with the previous turbulent case, suggests that such a disruption mechanism owing to strongly magnetic accretors is generally operable. 相似文献
268.
Gavin Ramsay & Peter J. Wheatley 《Monthly notices of the Royal Astronomical Society》1998,301(1):95-100
We present low–medium resolution optical spectroscopy of the eclipsing AM Her system MN Hya (RX J0929–24). We determine the magnetic field strength at the primary accretion region of the white dwarf to be 42 MG from the spacing of cyclotron features visible during π ∼ 0.4–0.7. From spectra taken during the eclipse we find that the secondary has an M3–4 spectral type. Combined with the eclipse photometry of Sekiguchi, Nakada &38; Bassett and an estimate of the interstellar extinction we find a distance of ∼300–700 pc. We find unusual line variations at π ∼ 0.9: Hα is seen in absorption and emission. This is at the same point in the orbital phase at which a prominent absorption dip is seen in soft X-rays. 相似文献
269.
L. Burderi A. R. King & G. A. Wynn 《Monthly notices of the Royal Astronomical Society》1998,300(4):1127-1130
Lorimer et al. have recently reported that the spin-down age (∼7 × 109 yr) of the low-mass binary pulsar PSR J1012+5307 is much higher than the cooling age (3 × 108 yr) of its white dwarf companion. The proposed solutions for this discrepancy are outlined and discussed. In particular, the revised cooling age estimate proposed by Alberts et al. agrees with data from other low-mass binary pulsar systems if a transition to the 'classical' cooling regime occurs between ∼0.14 and ∼0.28 M⊙ . If this transition is excluded, PSR J1012+5307 seems to have finished its accretion phase far from the spin-up line. 相似文献
270.
INTRODUCTION~hon0ffornjcelmtSwnthebasisofthestudyonthecrustaldefonnationanddeVel0prnent,thedistributionofndnereIs,andthendnerogeneticlawr.ThegeornagneticfieklisthecomP0siterefledionoftheformati0nanddefortnationofthecrust.Sornagnct-icsLLrVeydatacomPriseirnPortantbasisfordelincatingthearchiteCtonicelements,dCtendningtheirboundarylines,andanalopngthesanndarystrudriineachelernent,whicharetthernaintasks0fgoophySicalworkers.Thegoornagneticdelineati0nofanareahadforlongbodonequalitativeybyobs… 相似文献