全文获取类型
收费全文 | 2217篇 |
免费 | 384篇 |
国内免费 | 530篇 |
专业分类
测绘学 | 113篇 |
大气科学 | 354篇 |
地球物理 | 598篇 |
地质学 | 1175篇 |
海洋学 | 249篇 |
天文学 | 99篇 |
综合类 | 299篇 |
自然地理 | 244篇 |
出版年
2024年 | 7篇 |
2023年 | 40篇 |
2022年 | 98篇 |
2021年 | 138篇 |
2020年 | 101篇 |
2019年 | 108篇 |
2018年 | 144篇 |
2017年 | 124篇 |
2016年 | 132篇 |
2015年 | 125篇 |
2014年 | 159篇 |
2013年 | 104篇 |
2012年 | 131篇 |
2011年 | 144篇 |
2010年 | 169篇 |
2009年 | 129篇 |
2008年 | 96篇 |
2007年 | 100篇 |
2006年 | 102篇 |
2005年 | 74篇 |
2004年 | 63篇 |
2003年 | 62篇 |
2002年 | 57篇 |
2001年 | 61篇 |
2000年 | 64篇 |
1999年 | 88篇 |
1998年 | 86篇 |
1997年 | 73篇 |
1996年 | 54篇 |
1995年 | 58篇 |
1994年 | 47篇 |
1993年 | 33篇 |
1992年 | 33篇 |
1991年 | 27篇 |
1990年 | 25篇 |
1989年 | 16篇 |
1988年 | 16篇 |
1987年 | 13篇 |
1986年 | 11篇 |
1985年 | 4篇 |
1984年 | 3篇 |
1983年 | 6篇 |
1982年 | 2篇 |
1981年 | 1篇 |
1958年 | 3篇 |
排序方式: 共有3131条查询结果,搜索用时 15 毫秒
411.
致密砂岩油储层的脆性研究是致密砂岩油地震预测的重要内容,需要引入合适的脆性指数来建立致密砂岩油储层的脆性评价标准。本文首先构建了各向异性致密砂岩油地震岩石物理模型;依据该模型进行了各向异性介质弹性常数的脆性敏感性分析,建立了新的脆性指数;并分别从脆性敏感性定量分析、岩石物理响应特征分析以及交汇图分析三个方面系统研究了新脆性指数在致密砂岩油脆性预测上的适用性。分析结果表明,新脆性指数较其它传统脆性指数,不仅其脆性敏感性高,而且更适合于致密砂岩油储层"甜点"区的脆性预测。 相似文献
412.
尼泊尔8.1级地震建筑物震害遥感提取与分析 总被引:2,自引:2,他引:0
2015年4月25日尼泊尔发生的8.1级地震,造成重大人员伤亡与经济损失。在地震前、后灾区高分遥感影像分析处理基础上,结合现场实地调查,对灾区房屋建筑及其震害程度进行了遥感解译,编制了地震灾区房屋建筑震害分布图。结果分析表明:尼泊尔地震灾区影像上显示的建筑物震害分布与该区域房屋结构类型、主余震位置和区域活动构造分布密切相关。其中,房屋较为严重倒塌区域主要分布在8.1级主震和7.5级余震震中附近,但这两个区域并没有相连;居民点建筑物个别倒塌的居民地则连成一个区域。影像上显示的建筑物倒塌区域,与多数8级巨大地震比较,总体上极震区震害偏轻,但在南南西(垂直于破裂方向)上展布较宽。这一特征与引发该地震的印度与欧亚大陆板块边缘活动断裂在深部呈近似于平行地表的低角度断层面破裂引起的地震动能量在地表相对较宽而低的分布特征是一致的。 相似文献
413.
414.
415.
质疑了"前兆异常"原定义存在的与观测资料和预测实践不符合的缺陷,给出了异常、前兆及干扰的新定义。"异常"与"前兆"是两个完全不同的概念,异常不仅与地震有关,而且与地壳构造变动和相关自然现象也有关;地震前兆则是系由多种内因性和外因性异常构成的预测信息体系;干扰因素仅是偶然的、局部的人为因素。讨论了新老定义之间的差异、新定义的事实依据、地下水等手段今后需解决的关键性任务、现实地震预测能力的有限性等问题;提出了我国地震预报工作的重点应做"战略转移",并且需对我国几十年地震预报探索的科学思路、积累震例、预报实例和研究成果做"再清理"和"再研究"等建议。 相似文献
416.
417.
Natural Hazards - Inner Mongolia, located in the northern China, is a natural disaster-prone region. This study is dedicated to making a comprehensive and quantitative analysis of the... 相似文献
418.
<正>1 Introduction Shale formations bear abundant mineral resource and*unconventional petroleum resource,and the unconventional petroleum resource that contain in the shale formation should be integrated and researched. 相似文献
419.
LIU Jingdong JIANG Youlu LIU Xinshe YANG Zhiwei HOU Xiangdong ZHU Rongwei WEN Caixi WANG Feiyan 《《地质学报》英文版》2017,91(4):1363-1379
We clarified three stages of dolomitization and secondary changes by studying the petrology and geochemistry characteristics of dolomite from the Ma55–Ma510 sub-members of the Ordovician Majiagou Formation in the Jingxi area in the Ordos Basin: (1) Syngenetic microbial dolomitization is characterized by formation of dolomite with a mainly micrite structure and horse tooth-shape dolomite cements. (2) Seepage reflux dolomitization during the penecontemporaneous period superposed adjustment functions such as recrystallization and stabilization in the middle-deep burial stage, forming dolomites mainly consisting of micro crystal and powder crystal structure. (3) Powder dolomite, fine dolomite, and medium-coarse crystalline dolomite formed in pores and fractures in the middle-deep burial stage. The secondary concussive transgression-regression under a regressive background is an important condition for the occurrence of many stages of dolomitization in the study area. The basin was an occlusive epicontinental sea environment in the Ma5 member of the Ordovician Majiagou Formation sedimentary period. In the sediments, sulfate content was high, which is conducive to the preservation of microbial activity and microbial dolomitization. Micritic dolomite formed by microbial dolomitization provides good migration pathways for seepage reflux dolomitization. Affected by evaporation seawater with increased Mg/Ca ratio, seepage reflux dolomitization was widely developed and formed large-scale dolomite, and underwater uplifts and slopes are favorable areas for dolomite. In the middle-deep burial stage, dolomitizing fluid in the stratum recrystallized or stabilized the previous dolomite and formed a small amount of euhedral dolomite in the pores and fractures. 相似文献
420.
Liu Yi nan Sun Fengxia Cui Yueju Pan Xiaodong Ma Mingzhi Zhang Xin Du Jianguo 《地球科学进展》2017,32(8):810-817
The hydrochemical types and origins of underground water in Songyuan and vicinity, Liaoning Province were discussed based on the hydrochemical composition, δD and δ18O. The water samples from eight wells were collected 4 times during 2014 to 2015. The main ion concentrations of water were analyzed with an Ion Chromatography. Isotopic compositions of hydrogen and oxygen were analyzed with the Liquid Water Isotope Analyzer. The mineralization (TDS) of the water ranged from 125.4 mg/L to 19 350.9 mg/L. Values of δD and δ18O ranged from -71.7‰ to -98.1‰ and from -9.0‰ to -12.5‰, respectively. The isotopic data indicated that the water originated from meteorological precipitation. The chemical compositions of Taolaizhao phreatic water were influenced by the human activity while the other water samples collected from artesian well were less affected by the human activity. Water in Changling, Dongdashi, Taohaotai, Qianan and Ningjiang were characterized by HCO3-Na with low TDS values. Such chemical types of water with fluctuations of Na+, SO 4 2 - and δ18O drift were resulted from dissolving silicate minerals and adding surfactant during oil exploitation. Fresh water in Fuyu well was Cl-Na type, which was influenced by acid injection during oil exploitation. Water in Qianguo well was characterized by Cl-Na type with TDS up to 19 350.9 mg/L, the obvious fluctuations of hydrogen and oxygen isotopes and increasing ion concentrations in the Qianguo well may be caused by the earthquakes that occurred in the sampling duration. The results will provide the background of hydrochemistry, and will be of benefit to monitoring earthquake and certificating seismic-chemical anomalies in the future. 相似文献