全文获取类型
收费全文 | 2363篇 |
免费 | 364篇 |
国内免费 | 461篇 |
专业分类
测绘学 | 108篇 |
大气科学 | 60篇 |
地球物理 | 743篇 |
地质学 | 1252篇 |
海洋学 | 224篇 |
天文学 | 9篇 |
综合类 | 324篇 |
自然地理 | 468篇 |
出版年
2024年 | 4篇 |
2023年 | 26篇 |
2022年 | 66篇 |
2021年 | 72篇 |
2020年 | 79篇 |
2019年 | 77篇 |
2018年 | 73篇 |
2017年 | 55篇 |
2016年 | 55篇 |
2015年 | 58篇 |
2014年 | 96篇 |
2013年 | 107篇 |
2012年 | 105篇 |
2011年 | 94篇 |
2010年 | 84篇 |
2009年 | 98篇 |
2008年 | 119篇 |
2007年 | 169篇 |
2006年 | 163篇 |
2005年 | 145篇 |
2004年 | 151篇 |
2003年 | 153篇 |
2002年 | 110篇 |
2001年 | 116篇 |
2000年 | 120篇 |
1999年 | 83篇 |
1998年 | 100篇 |
1997年 | 101篇 |
1996年 | 84篇 |
1995年 | 79篇 |
1994年 | 69篇 |
1993年 | 61篇 |
1992年 | 46篇 |
1991年 | 39篇 |
1990年 | 23篇 |
1989年 | 19篇 |
1988年 | 29篇 |
1987年 | 19篇 |
1986年 | 21篇 |
1985年 | 4篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1979年 | 4篇 |
1978年 | 2篇 |
1977年 | 2篇 |
1954年 | 4篇 |
排序方式: 共有3188条查询结果,搜索用时 437 毫秒
91.
Study on distribution characteristics of strong earthquakes in Sichuan-Yunnan area and their geological tectonic background 总被引:2,自引:0,他引:2
Introduction Both Sichuan and Yunnan are provinces with more earthquakes. Based on catalogue of strong earthquakes in China compiled by the Prediction Department of China Earthquake Administration, there are 639 M5.0 earthquakes during 26 B.C.~A.D. 2001. Among them, 475 are M=5.0~5.9 events, 124 are M=6.0~6.9 events, 39 are M=7.0~7.9 events, and one is M=8 event occurred in Sichuan and Yunnan area. Here is one of the areas where seismic activities are most active in China. Sichuan-Yun… 相似文献
92.
对板块说应持分析态度,既充分肯定它的创见,又要看到其不足。张文佑倡导的断块说强调地质演化中的陆洋地壳转化,即拉张造洋、挤压造陆。近年来提出的开合说,继承了板块说、断块说和新地槽-地台说的合理内核。笔者认为,断块-开合大地构造说是中国大地构造研究中有代表性的思潮。本文概括了其基本观点,强调了开合中的多模式、多旋回和非封闭性、不可逆性。 相似文献
93.
The paper introduces the horizontal crustal movement obtained from GPS observations in the regional networks (including the
basic network and the fiducial network) of the Crustal Movement Observation Network of China (CMONOC) carried out in 1999
and 2001. This paper is characterized by the acquisition of the horizontal displacement velocities during the period from
1999 to 2001 at the observation stations in the regional networks with datum definition of a group of stable stations with
small mutual displacements in east China. Based on the most detailed map of horizontal crustal movement in Chinese mainland,
the division of blocks, their displacements and deformations are studied. An approach to analysis of the intensity of the
horizontal crustal deformation is proposed. The general characteristics of the recent horizontal crustal movement in Chinese
mainland and that before the Kunlunshan earthquake of M=8.1 on November 14, 2001 are analyzed.
Foundation item: The National Development and Programming Project for Key Basic Research (95-13-03-07). 相似文献
94.
This article has two purposes. Firstly, a validation exercise of the modal summation technique for the computation of synthetic
strong-motion records is performed for two regions of Europe (Umbria-Marche and south Iceland), using a variety of region
specific crustal structure models, by comparing the predicted ground motion amplitudes with observed motions. It is found
that the rate of decay of ground motions is well predicted by the theoretical decay curves but that the absolute size of the
ground motions is underpredicted by the synthetic time-histories. This is thought to be due to the presence of low-velocity
surface layers that amplify the ground motions but are not included in the crustal structure models used to compute the synthetic
time-histories.
Secondly, a new distance metric based on the computed theoretical decay curves is introduced which should have the ability
to model the complex decay of strong ground motions. The ability of this new distance metric to reduce the associated scatter
in empirically derived equations for the estimation of strong ground motions is tested. It is found that it does not lead
to a reduction in the scatter but this is thought to be due to the use of crustal structure models that are not accurate or
detailed enough for the regions studied.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
95.
Introduction The Earth′s crust deforms in the regional tectonic stress field. Borehole strain observation isone important means for studies on the crustal deformation and the stress field. QIU and ZHANG(2002) have introduced the current situation of borehole strain observation in China. OutsideChina, early in September of 1968, Sacks of Carnegie Institution of Washington and Evertson ofUniversity of Texas firstly invented a borehole dilatometer in the world (Sacks, Evertson, 197… 相似文献
96.
DONG Yunpeng ZHANG Guowei ZHAO Xia YAO Anping & LIU Xiaoming The Key Laboratory of Continental Dynamics Ministry of Education Department of Geology Northwest University Xi抋n China 《中国科学D辑(英文版)》2004,(4)
Being a composite collisional orogen between North China and South China blocks, the Qinling orogenic belt is the key to understand the composite combination, prolonged evolutionary history and their continental dynamics. The main suture between north and south Qinling, called Shangdan suture zone (SDSZ), had been studied in detail for about twenty years. Recently, another suture zone, called Mianl黣 suture zone (MLSZ), has been identified in the Qinling Mountains. It is characterized b… 相似文献
97.
中国西北盆山地区地壳结构及其演化 总被引:2,自引:0,他引:2
根据新疆及其它相关地学断面所获资料,论述了中国西北盆山构造地区的地壳结构,已有资料表明,在中国西北盆山地区,山脉和盆地具有明显不同的地壳结构,它们的地壳厚度不同,表现为山区地壳厚,具有明显的山根:盆地区地壳厚度小,同时地壳分层和各层的组分也有所差异,这些地壳本身结构性的差异,以及它们所受到的应力状态和热状态的不同,就是小区各种构造活动产生的根源,最后从区内地质构造形成过程讨论了区内地壳不同结构形成的演化历史。 相似文献
98.
岩石Kaiser效应测地应力原理中的若干问题研究 总被引:3,自引:0,他引:3
该文通过对几种不同类型岩石的实验研究,提出了关于在围压条件下影响岩石Kaiser效应的若干问题,分析了它们的声发射特征,为深部地应力测量提供了一种新的解决方法。 相似文献
99.
FREZZOTTI MARIA-LUCE; PECCERILLO ANGELO; ZANON VITTORIO; NIKOGOSIAN IGOR 《Journal of Petrology》2004,45(1):3-26
Quartz-rich xenoliths in lavas and pyroclastic rocks from VulcanoIsland, part of the Aeolian arc, Italy, contain silicic meltinclusions with high SiO2 (7380 wt %) and K2O (36wt %) contents. Two types of inclusions can be distinguishedbased on their time of entrapment and incompatible trace element(ITE) concentrations. One type (late, ITE-enriched inclusions)has trace element characteristics that resemble those of themetamorphic rocks of the Calabro-Peloritano basement of theadjacent mainland. Other inclusions (early, ITE-depleted) havevariable Ba, Rb, Sr and Cs, and low Nb, Zr and rare earth element(REE) contents. Their REE patterns are unfractionated, witha marked positive Eu anomaly. Geochemical modelling suggeststhat the ITE-depleted inclusions cannot be derived from equilibriummelting of Calabro-Peloritano metamorphic rocks. ITE-enrichedinclusions can be modelled by large degrees (>80%) of meltingof basement gneisses and schists, leaving a quartz-rich residuerepresented by the quartz-rich xenoliths. Glass inclusions inquartz-rich xenoliths represent potential contaminants of Aeolianarc magmas. Interaction between calc-alkaline magmas and crustalanatectic melts with a composition similar to the analysed inclusionsmay generate significant enrichment in potassium in the magmas.However, ITE contents of the melt inclusions are comparablewith or lower than those of Vulcano calc-alkaline and potassicrocks. This precludes the possibility that potassic magmas inthe Aeolian arc may originate from calc-alkaline parents throughdifferent degrees of incorporation of crustal melts. KEY WORDS: melt inclusions; crustal anatexis; magma assimilation; xenoliths; Vulcano Island 相似文献
100.
KERR ANDREW C.; TARNEY JOHN; KEMPTON PAMELA D.; PRINGLE MALCOLM; NIVIA ALVARO 《Journal of Petrology》2004,45(9):1877-1906
The fault-bounded Bolívar Ultramafic Complex (BUC) onthe eastern fringes of the Western Cordillera of Colombia wastectonically accreted onto the western coast of South Americain the late Cretaceousearly Tertiary, along with pillowbasalts of the CaribbeanColombian Oceanic Plateau (CCOP).The complex consists of a lower sequence of ultramafic cumulates,successively overlain by layered and isotropic gabbroic rocks.The gabbros grade into, and are intruded by, mafic pegmatitesthat consist of large magnesiohornblende and plagioclase crystals.These pegmatites yield a weighted mean 40Ar39Ar step-heatingage of 90·5 ± 0·9 Ma and thus coincidewith the timing of peak CCOP volcanism. The chemistry of theBUC is not consistent with a subduction-related origin. However,the similarity in SrNdPbHf isotopes betweenthe CCOP and the BUC, in conjunction with their indistinguishableages, suggests that the BUC is an integral part of the plume-derivedCCOP. The parental magmas of the Bolívar complex wereprobably hydrous picrites that underwent 2030% crystallization.The residual magmas from this fractionation contained 相似文献