全文获取类型
收费全文 | 260篇 |
免费 | 4篇 |
国内免费 | 5篇 |
专业分类
测绘学 | 3篇 |
大气科学 | 3篇 |
地球物理 | 34篇 |
地质学 | 137篇 |
海洋学 | 8篇 |
天文学 | 77篇 |
自然地理 | 7篇 |
出版年
2022年 | 1篇 |
2021年 | 5篇 |
2020年 | 1篇 |
2019年 | 2篇 |
2018年 | 18篇 |
2017年 | 11篇 |
2016年 | 17篇 |
2015年 | 6篇 |
2014年 | 9篇 |
2013年 | 18篇 |
2012年 | 11篇 |
2011年 | 14篇 |
2010年 | 3篇 |
2009年 | 11篇 |
2008年 | 11篇 |
2007年 | 8篇 |
2006年 | 6篇 |
2005年 | 10篇 |
2004年 | 3篇 |
2003年 | 1篇 |
2002年 | 5篇 |
2001年 | 6篇 |
2000年 | 1篇 |
1999年 | 1篇 |
1998年 | 4篇 |
1997年 | 1篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1994年 | 4篇 |
1993年 | 5篇 |
1992年 | 7篇 |
1991年 | 1篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 3篇 |
1982年 | 7篇 |
1981年 | 4篇 |
1980年 | 4篇 |
1979年 | 6篇 |
1978年 | 5篇 |
1977年 | 1篇 |
1969年 | 1篇 |
1917年 | 1篇 |
1907年 | 1篇 |
排序方式: 共有269条查询结果,搜索用时 31 毫秒
81.
Osman Demircan 《Astrophysics and Space Science》1980,72(2):281-286
This is a continuation of a previous paper which appeared in this journal (Demircan, 1980b) and aims at ascertaining some other relations between the integral transforms of the light curves of eclipsing binary systems. The appropriate use of these relations should facilitate the numerical computations for an analysis of eclipsing binary light curves by different Fourier techniques. 相似文献
82.
Osman Demircan 《Astrophysics and Space Science》1980,67(2):375-386
The aim of the present paper is to deduce relations between the integral transformsA
2m, B2m,andF
1,2 of the light curves of eclipsing binary systems. The integral transformsA
2m, B2m,andF
1,2 have been related to one another by means of finite or rapidly converging infinite summations obtained by integrations of the series expansions of trigonometric functions. 相似文献
83.
84.
Kivanc Zorlu M. Celal Tunusluoglu Tolga Gorum Hakan A. Nefeslioglu Ali Yalcin Dilek Turer Candan Gokceoglu 《Environmental Earth Sciences》2011,62(8):1685-1693
The Cappadocia region has unique geomorphological features resulting from differential erosional processes which make it very attractive to tourists. Besides the fairy chimneys for which the area is best known, there are also impressive buttes and mesas. Buttes and mesas are formed in regions having flat-lying strata in which the uppermost levels are composed of well-cemented limestones and granular ignimbrites, whereas the lower parts and slopes consist of low-durability tuff and ignimbrites. This durability difference results in serious rockfall events. This study involves two-dimensional rockfall analyses in and near the Avanos, Zelve, and Çavusini areas, where volcano-sedimentary units of Neogene age outcrop, to provide a rockfall hazard map in which areas of tourism activity are also considered. 相似文献
85.
Yousif Osman Mohammad 《Arabian Journal of Geosciences》2011,4(1-2):69-83
Two types of serpentinized peridotites are distinguished within the Northwest Zagros Thrust Zone (NW-ZTZ) in Kurdistan region of Iraq. One is found as lower members of ophiolite sequences, such as the Mawat and Penjwin ophiolites of the upper Cretaceous age. The other is represented by intraformational isolated serpentinite bodies in Betwat, Qaladeza, and Qalander areas within the Walash–Naopurdan volcano-sedimentary unit of the Paleocene to Eocene paleo-arc tectonic setting. Serpentinites within the NW-ZTZ consist mainly of lizardite and chrysotile, with subordinate amounts of syn-serpentinization magnetite, carbonates, chromium chlorite, tremolite, and talc as secondary minerals, and olivine, clinopyroxene, and chromian spinel as primary minerals. Minor antigorite is also found in the sheared serpentinites often found in ophiolite sequences. Petrological and geochemical studies of serpentinites from the NW-ZTZ show that, of the original protoliths of serpentinites, those associated with ophiolites are residual depleted harzburgite and dunite. The $ {\text{Cr}}\# \left( {{{ = {\text{ Cr}}} \mathord{\left/ {\vphantom {{ = {\text{ Cr}}} {\left( {{\text{Cr}} + {\text{Al}}} \right){\text{ atomic ratio}}}}} \right. \kern-0em} {\left( {{\text{Cr}} + {\text{Al}}} \right){\text{ atomic ratio}}}}} \right) $ of chromian spinel is more than 0.6, and the forsterite content of olivine is 91–92. On the other hand, the original protolith of isolated serpentinite bodies is less depleted harzburgite or depleted lherzolite, which has spinel with Cr# less than 0.6 and olivine with 90–91 forsterite contents. Whole rock chemistry of major, trace, and rare earth elements shows that the serpentinites of ophiolite sequences are depleted in CaO, Al2O3, and SiO2, Sr, and Zr, and are enriched in MgO, Ni, and Cr, in comparison with the isolated serpentinites. Cr# of the disseminated unaltered chromian spinels indicates that the serpentinites of both types had been originated from the supra-subduction zone tectonic setting; the serpentinites of ophiolite sequences obducted and thrusted over the continental margin during the obduction of the Tethyth oceanic crust onto the Arabian continental margin during the upper Cretaceous period. Isolated serpentinite bodies represent serpentinized forearc mantle wedge peridotites emplaced by diapiric upwelling into non-accretionary forearc tectonic settings during the Paleocene to Eocene age. 相似文献
86.
Reservoir Quality Assessment of the Upper Permian Chhidru Formation,Salt and Surghar Ranges,Pakistan
Muhammad ZAHIR Muhammad AWAIS Mukhtiar GHANI Mohibullah MOHIBULLAH Osman SALAD HERSI Irfan U. JAN Sajjad AHMAD Hamid IQBAL 《《地质学报》英文版》2021,95(6):2120-2137
The Late Permian succession of the Upper Indus Basin in northeastern Pakistan is represented by the carbonate-dominated Zaluch Group, which consists of the Amb, Wargal and Chhidru formations, which accumulated on the southwestern shelf of the Paleo-Tethys Ocean, north of the hydrocarbon-producing Permian strata of the Arabian Peninsula. The reservoir properties of the mixed clastic-carbonate Chhidru Formation (CFm) are evaluated based on petrography, using scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDX) and x-ray diffraction (XRD) techniques. The diagenetic features are recognized, ranging from marine (isopachous fibrous calcite, micrite), through meteoric (blocky calcite-I, neomorphism and dissolution) to burial (poikilotopic cement, blocky calcite-II-III, fractures, fracture-filling, and stylolites). Major porosity types include fracture and moldic, while inter- and intra-particle porosities also exist. Observed visual porosity ranges from 1.5%–7.14% with an average of 5.15%. The sandstone facies (CMF-4) has the highest average porosity of 10.7%, whereas the siliciclastic grainstone microfacies (CMF-3) shows an average porosity of 5.3%. The siliciclastic mudstone microfacies (CMF-1) and siliciclastic wacke-packestone microfacies (CMF-2) show the lowest porosities of 4.8% and 5.0%, respectively. Diagenetic processes like cementation, neomorphism, stylolitization and compaction have reduced the primary porosities; however, processes of dissolution and fracturing have produced secondary porosity. On average, the CFm in the Nammal Gorge, Salt Range shows promise and at Gula Khel Gorge, Trans-Indus, the lowest porosity. 相似文献
87.
The secular terms of the first-order planetary Hamiltonian is determined, by two methods, in terms of the variables of H. Poincaré, neglecting powers higher than the second in the eccentricity-inclination. 相似文献
88.
89.
This paper deals with the problem of T‐bar penetration. New kinematically admissible velocity fields are derived from elastic solutions of incompressible material using Airy stress function. These velocity fields are used to obtain upper bounds to collapse loads. Two particular solutions are presented, one for a rough contact surface between the T‐bar and soil and the other for a smooth contact surface. The merit of the solutions is that within the boundaries of the velocity field, the soil is required to shear compatibly and continuously. Therefore, these solutions can easily be combined with the strain path method to estimate rate and softening effects. Analysis including consideration of strain rate effect showed that the new mechanisms predict, under certain conditions, lower values than previously published upper bound solutions. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
90.
Osman M. Kamel 《Earth, Moon, and Planets》1990,49(3):259-267
We construct the outline of a third order secular theory for the four major planets. We apply the Hori-Lie technique to solve the problem. We take into consideration both parts of the perturbing function. Our canonical variables are those of H. Poincaré. Our periodic terms are the only 2:5 and 1:2 critical terms of J-S and U-N respectively. Terms of degree higher than the second in the Poincaré canonical variables H, K, P, Q are neglected. 相似文献