全文获取类型
收费全文 | 11722篇 |
免费 | 2110篇 |
国内免费 | 2195篇 |
专业分类
测绘学 | 249篇 |
大气科学 | 600篇 |
地球物理 | 3185篇 |
地质学 | 6665篇 |
海洋学 | 1521篇 |
天文学 | 1758篇 |
综合类 | 605篇 |
自然地理 | 1444篇 |
出版年
2024年 | 34篇 |
2023年 | 109篇 |
2022年 | 266篇 |
2021年 | 369篇 |
2020年 | 388篇 |
2019年 | 442篇 |
2018年 | 394篇 |
2017年 | 418篇 |
2016年 | 472篇 |
2015年 | 439篇 |
2014年 | 564篇 |
2013年 | 625篇 |
2012年 | 538篇 |
2011年 | 600篇 |
2010年 | 539篇 |
2009年 | 810篇 |
2008年 | 833篇 |
2007年 | 889篇 |
2006年 | 851篇 |
2005年 | 711篇 |
2004年 | 699篇 |
2003年 | 637篇 |
2002年 | 572篇 |
2001年 | 472篇 |
2000年 | 529篇 |
1999年 | 474篇 |
1998年 | 438篇 |
1997年 | 310篇 |
1996年 | 283篇 |
1995年 | 285篇 |
1994年 | 222篇 |
1993年 | 191篇 |
1992年 | 135篇 |
1991年 | 105篇 |
1990年 | 94篇 |
1989年 | 89篇 |
1988年 | 54篇 |
1987年 | 49篇 |
1986年 | 25篇 |
1985年 | 18篇 |
1984年 | 15篇 |
1983年 | 7篇 |
1982年 | 6篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1979年 | 7篇 |
1978年 | 3篇 |
1954年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
991.
The spinel solid solution was found to exist in the whole range between Fe3O4 and γ-Fe2SiO4 at over 10 GPa. The resistivity of Fe3−
x
Si
x
O4 (0.0<x<0.288) was measured in the temperature range of 80∼300 K by the AC impedance method. Electron hopping between Fe3+ and Fe2+ in the octahedral site of iron-rich phases gives a large electric conductivity at room temperature. The activation energy
of the electron hopping becomes larger with increasing γ-Fe2SiO4 component. A nonlinear change in electric conductivity is not simply caused by the statistical probability of Fe3+–Fe2+ electron hopping with increasing the total Si content. This is probably because a large number of Si4+ ions occupies the octahedral site and the adjacent Fe2+ keeping the local electric neutrality around Si4+ makes a cluster, which generates a local deformation by Si substitution.
The temperature dependence of the conductivity of solid solutions indicates the Verwey transition temperature, which decreases
from 124(±2) K at x=0 (Fe3O4) to 102(±5) K at x=0.288, and the electric conductivity gap at the transition temperature decreases with Si4+ substitution.
Received: 15 March 2000 / Accepted: 4 September 2000 相似文献
992.
Wang Siyuan Xiao Qibing Zeng Jianguo Faculty of Earth Resources China University of Geosciences Wuhan 《中国地质大学学报(英文版)》2001,12(1)
-,The well-known Suichang silvengold field is located inZhejiang Province of SOutheast China. It is the largest silver-gold deposit associated with copper and zinc in the Cathaysianmetallogenic province.There are a series of silver-gold dePOsits in the shear zonesof Proterozoic gneiss terrene, Suichang region. The volcanicapparatus at Mesozoic has complicated rpineralization. Respectively, there are two pieces of understanding on the origin ofore-formigg nuid: (l ) metamorphic fluid (Lia… 相似文献
993.
Sun Jinzhong College of Engineering Technology China University of Geosciences Beijing Tan Hanhua Guizhou Institute of Communication Design Guiyang Qi Shengwen Institute of Geology Chinese Academy of Sciences Beijing 《中国地质大学学报(英文版)》2001,12(2)
INTRODUCTIONBecauseofitssimpleoperationandlowcostaswellaseffec tivenessformanyprojects ,heavytampinghasbeenusedwidelyintheworld (Qianetal.,1986 ) .However,thestrongvibrationinsoilmasscausedbyheavytampingmaybeharmfultobuildings,instrumentsandevenhumanbodiesar… 相似文献
994.
Detection of seepage paths in earth dams using self-potential and electrical resistivity methods 总被引:7,自引:0,他引:7
Earth and rockfill dams are designed to operate under steady state seepage. Anomalous seepage may be a threat to the integrity of the structure. In spite of advances made in the fields of geotechnical engineering, it is not possible to have 100% leak-proof structure. Any excessive and unplanned seepage may lead to the failure of the dam, especially in unconsolidated or fractured terrains. Geophysical methods play an important role in mapping seepage paths and monitoring the changes of the seepage with time, enabling to plan technically and economically worthwhile remedial measures. In the present paper, utilisation of electrical methods for delineation of seepage zones at two of the four Saddle dams of the Som-Kamla-Amba project, Rajasthan State, India; which is founded on heterogeneous rock mass, is discussed. Electrical resistivity method was used to delineate zones favourable for seepage, whereas, self-potential (SP) method was used to delineate the seepage paths. SP measurements have shown negative anomaly of the order of 10–20 mV in amplitude, indicating low seepage, coinciding with the seepage measurements made by the project authorities. 相似文献
995.
996.
在大地热流密度分布的基础上,研究了塔里木盆地中库尔勒-若羌和阿克苏-叶城两条剖面岩石层热结构特征.由岩石层P波速度分布转换成生热率剖面,用二维数值模型获得了岩石层热结构和热状态特征.结果表明,塔里木盆地壳幔边界温度的高低与其埋深密切相关.居里等温面深度大,地幔热流密度较低.岩石层厚度变化与其新生代期间挠曲过程密切相关.在岩石层温度分布基础上,确定了深部脆-韧性过渡带深度和岩石层屈服强度,表明塔里木盆地岩石层相对较冷,且具有刚性的地球动力学特征. 相似文献
997.
998.
Therelationshipsbetwenearthquakesandpositionsofthesunandmoon(Ⅱ)——Sometemporalcharacteristicsoftheaftershocksequencesofstronge... 相似文献
999.
The Geothermal Study of the Mid-Segment of the Tancheng-Lujiang Fault Zone and Its Neighboring Region 总被引:1,自引:0,他引:1
In this paper,25 new terrestrial heat flow values newly observed along the mid-segment of the Tancheng-Lujiang fault zone are listed.With these geothermal data and 37 other terrestrial heat flow values(previously published),we describe the distribution features of terrestrial heat flows in the area.In this research,the two-dimensional temperature structure from the surface to lithospheric bottom of the Huaibei-Sixian-Jinhu profile is inferred by using the finite-element method and the temperature and heat flow of sedimentary,granitic,and basaltic layers is calculated. 相似文献
1000.
Preliminary Study on Two Newly-Generated Seismotectonic Zones in North and Southwest China 总被引:1,自引:0,他引:1
Xu Jie Han Zhujun Wang Chunhua and Niu LanfangInstitute of Geology State Seismological Bureau Beijing China 《中国地震研究》1996,(4)
In previous seismotectonic studies,the emphasis was placed on the inherited active fault zones.In the recent tectonic stage that essentially keeps in step with the current regional geologic environment and the stress field,however,there are also some newly generated fault zones.By studying the seismicity in North and Southwest China,it has been known that the NE-trending Tangshan-Hejian-Cixian and NW-trending Tengchong-Gengma-Lancang seismic zones are just two newly generated fault zones.As distinguished from the inherited fault zones,they are called the newly generated seismotectonic zones.This paper deals with the existence of these two seismogenic zones from their seismicity and geological structures,gives a preliminary analysis of their characteristics,and shows their significance. 相似文献