全文获取类型
收费全文 | 1485篇 |
免费 | 214篇 |
国内免费 | 248篇 |
专业分类
测绘学 | 27篇 |
大气科学 | 119篇 |
地球物理 | 185篇 |
地质学 | 620篇 |
海洋学 | 660篇 |
天文学 | 1篇 |
综合类 | 101篇 |
自然地理 | 234篇 |
出版年
2024年 | 1篇 |
2023年 | 7篇 |
2022年 | 26篇 |
2021年 | 31篇 |
2020年 | 28篇 |
2019年 | 63篇 |
2018年 | 39篇 |
2017年 | 42篇 |
2016年 | 47篇 |
2015年 | 57篇 |
2014年 | 62篇 |
2013年 | 64篇 |
2012年 | 71篇 |
2011年 | 75篇 |
2010年 | 67篇 |
2009年 | 85篇 |
2008年 | 93篇 |
2007年 | 93篇 |
2006年 | 91篇 |
2005年 | 81篇 |
2004年 | 102篇 |
2003年 | 90篇 |
2002年 | 78篇 |
2001年 | 67篇 |
2000年 | 59篇 |
1999年 | 52篇 |
1998年 | 48篇 |
1997年 | 33篇 |
1996年 | 18篇 |
1995年 | 36篇 |
1994年 | 25篇 |
1993年 | 20篇 |
1992年 | 20篇 |
1991年 | 12篇 |
1990年 | 11篇 |
1989年 | 5篇 |
1988年 | 5篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1985年 | 13篇 |
1984年 | 19篇 |
1983年 | 29篇 |
1982年 | 32篇 |
1981年 | 36篇 |
1980年 | 1篇 |
排序方式: 共有1947条查询结果,搜索用时 31 毫秒
991.
上扬子西部滇东、黔西茅口组之上多为峨眉山玄武岩所覆盖,长期以来人们一直认为两者不存在沉积间断和地层剥蚀。作者通过野外实地考察和室内综合研究首次系统地厘定上扬子西部茅口组顶部的古喀斯特地貌,其形态多种多样,包括起伏不平的古剥蚀面、溶蚀洼地、溶斗、峰林、溶丘、洞穴以及洞穴充填物和古剥蚀面上红壤土。古喀斯特地貌在一个地区的地质发展中具有重要的意义,它代表了一次地壳上升运动。本区古喀斯特的系统研究不仅丰富了中国古喀斯特研究的内容,而且对确定云南地区东吴运动的存在和峨眉山地幔柱的活动提供了重要佐证。 相似文献
992.
福建沿海山区县,由于受地形地貌、地质条件、气候条件、高密度人口居住环境等综合因素的影响,发生地质灾害具有点多、面广、规模小、危害性大、突发性强等共同特点,安溪县就是一个典型。安溪县国土资源局,多年来经过实践摸索、探讨研究,在工作中不断总结提高.建立了一套行之有效的“安溪地质灾害预防工作模式”。有效地扭转了原先被动防灾的不利局面.逐步走上主动预防的新路子.最大程度地避免了地质灾害的发生。 相似文献
993.
Longwave Measurements for the Coast of British Columbia and Improvements to the Tsunami Warning Capability 总被引:1,自引:0,他引:1
A few years ago the Canadian Hydrographic Service initiated a major upgrade toall tide gauges and tsunami stations on the coast of British Columbia (B.C.). Thisprogram was undertaken to address shortcomings of the earlier digital systems andwas driven by concerns about emergency response continuity in the year 2000. By1999, thirteen tide gauge stations had been installed and were operational. Three ofthese stations (Tofino, Winter Harbour, and Langara) were selected for use as tsunamiwarning stations. Several years of continuous, high quality data have now been collectedat these stations and used for analysis of long waves in the tsunami frequency band.Careful examination of these data revealed two weak tsunamis recorded by severalB.C. stations: a distant tsunami of June 23, 2001 generated by the Peru Earthquake(Mw = 8.4), and a local tsunami of October 12, 2001 induced by the Queen Charlotte Earthquake (Mw = 6.3$). Spectral characteristics of these two tsunamis are compared with the spectral characteristics of long waves generated by a strong storm (October, 2000) and of ordinary background oscillations. The topographic admittance functions (frequency responses) constructed for all stations showed that most of them (in particular, Winter Harbour, Tofino, Bamfield, Port Hardy, and Victoria) have strong resonance at periods from 2.5 to 20 min, indicating that these locations are vulnerable to relatively high-frequency tsunamis. The Winter Harbour station also has two strong resonant peaks with periods of 30 and 47 min and with amplification factors of about 7. The estimated source functions show very clear differences between long waves associated with the seismic source (typical periods 10–30 min) and those generated by a storm, which typically have shorter periods and strong energy pumping from high-frequencies due to non-linear interaction of wind waves. 相似文献
994.
邛崃西部地区须家河组二段气藏储层预测技术研究 总被引:3,自引:0,他引:3
川西地区须家河组是四川盆地重要的油气勘探开发层系,是区内寻找大中型气田的重要目标.而须家河组储层纵横向变化很大,储层非均质性极强.通过对须家河组沉积相的研究,从区域上掌握地区沉积环境和砂体展布特点,重点解剖邛西构造须家河组二段储层的测井、地震响应特征,建立储层地球物理模型,开展以须家河组二段为主的储层预测技术攻关研究,进而预测储层有利区带,优选钻探目标,终于获得高产天然气流. 相似文献
995.
The profile crossing the west Kunlun region cov-ers the area between the Tarim Basin and the Kara-korum Fault, which is the highest (~5000 m a.s.l.) andthe most narrow part (400—500 km from north tosouth) of the Tibetan Plateau, thus attracting great at-tention of the geological community because of itsunique tectonic features. The Geological Bureau of Xinjiang Uygur Auton-omous Region and Chinese Academy of Sciences(CAS) carried out mineral exploration and geologicalmapping in th… 相似文献
996.
Abstract The evolution of volcanism in Sumatra and Java during Tertiary and Quaternary time can be divided into three phases: (i) lava flows of the Early Tertiary event (43–33 Ma) consisting of island arc tholeiites; followed by (ii) eruption of tholeiitic pillow basalt at the beginning of the Late Tertiary (11 Ma); and succeeded by (iii) medium-K calc-alkaline magmatism in the Pliocene and Quaternary. The present available field data on the occurrence of Paleogene volcanic rocks and subsurface data in south Sumatra and northern west Java indicate a much larger area of distribution of the volcanic rocks than previously recognized. Because the eastward continuation of the northern west Java volcanic rocks had not been found, early investigators were inclined to assume that they continued to south Kalimantan. In contrast, the early Tertiary volcanic rocks that occupy the south coast of Java can be traced further east as far as Flores. The occurrence of Paleogene volcanics in south Sumatra and northern west Java can be interpreted as a Paleogene volcanic arc that was presumably related to the late Cretaceous–Paleogene trench parallel to Sumatra and west Java due to subduction of the Indian Plate toward the northeast (Meratus trend). 相似文献
997.
998.
Taking west Jilin Province as an example, this paper put forward the assessment index of salinization, and based on it, the authors present the distribution characteristics of saline-alkali soil in the 1980s and the 1990s in west Jilin and analyze its physical and chemical properties in detail. The developing tendency of salinization was also inferred by comparing the saline-alkali soil of the 1980s with that of the 1990s. Finally, the natural and human factors leading to salinization are analyzed. 相似文献
999.
1000.
The west sandy land of the Northeast China Plain is located in the eastern huge sandy belt of mid-latitude in Eurasia and the eastern fringe of desertified land with best bio-climatic conditions in China. With rapid economic development, the deterioration of eco-environment has occurred and the desertification becomes very obvious. The first part of this paper studies the regional differences of landscape patterns and explores the regional differences of desertification. The second part aims to reveal the dynamics of desertification in the 1990s by using NOAA/AVHRR data and thematic data in GIS database. This work lays a scientific basis for the rehabilitation and development of the sandy lands. 相似文献