全文获取类型
收费全文 | 1464篇 |
免费 | 299篇 |
国内免费 | 393篇 |
专业分类
测绘学 | 137篇 |
大气科学 | 221篇 |
地球物理 | 328篇 |
地质学 | 869篇 |
海洋学 | 227篇 |
天文学 | 26篇 |
综合类 | 124篇 |
自然地理 | 224篇 |
出版年
2024年 | 23篇 |
2023年 | 37篇 |
2022年 | 86篇 |
2021年 | 133篇 |
2020年 | 107篇 |
2019年 | 132篇 |
2018年 | 110篇 |
2017年 | 109篇 |
2016年 | 123篇 |
2015年 | 102篇 |
2014年 | 112篇 |
2013年 | 95篇 |
2012年 | 99篇 |
2011年 | 94篇 |
2010年 | 76篇 |
2009年 | 79篇 |
2008年 | 85篇 |
2007年 | 56篇 |
2006年 | 47篇 |
2005年 | 44篇 |
2004年 | 34篇 |
2003年 | 30篇 |
2002年 | 29篇 |
2001年 | 26篇 |
2000年 | 22篇 |
1999年 | 35篇 |
1998年 | 37篇 |
1997年 | 30篇 |
1996年 | 25篇 |
1995年 | 20篇 |
1994年 | 27篇 |
1993年 | 35篇 |
1992年 | 14篇 |
1991年 | 14篇 |
1990年 | 6篇 |
1989年 | 6篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有2156条查询结果,搜索用时 15 毫秒
121.
扇三角洲沉积体系及其与油气聚集关系 总被引:23,自引:2,他引:21
扇三角洲沉积体系是断陷盆地中极为发育的一种沉积体系,主要由扇三角洲平原组合、扇三角洲前缘组合和前三角洲沉积构成,可识别出9种成因相。受沉积物供给速率、可容空间增长速率及盆缘断裂产状等因素控制可划分出退积型、加积型、前积型、陡坡型和缓坡型5种扇三角洲类型。位于扇三角洲平原的辫状分流河道砂体及其位于扇三角洲前缘的与之有成因联系的水下分流河口坝、洪水型重力流砂体等物性好,可以构成优质储层。含油性勘探成果亦证实各主力油层段平面上主要分布于扇三角洲前缘及分流间湾区,小部分位于扇三角洲平原区。受埋藏深度和成岩场的影响,不同地区、不同层位主力油层段的物性与岩性相关性各异。因此,应用沉积体系分布与油气聚集规律挖掘剩余油层及进行远景区预测是有效的与可行的。 相似文献
122.
煅烧高岭土的开发与应用 总被引:3,自引:0,他引:3
本文主要介绍了高岭土煅烧反应机理和煅烧过程中高岭土的结构变化以及煅烧高岭土在电缆、造纸、涂料、耐火材料及化学工业等领域的实际应用。 相似文献
123.
Chai Chizhang Zhang Weiqi and Jiao DechengSeismological Bureau of Ningxia Hui Autonomous Region Yinchuan China 《中国地震研究》1998,(4)
Through detailed field mapping, the tectonic deformation in the front area of the Tianjingshan fault zone is discussed in this paper. The result shows that there are two Quaternary thrust (oblique) fault-fold belts, namely: the Miaoshan and Hongjianshan fault-fold belts, in the front area of the south wall's strike-slip movement of the Tianjingshan fault zone. The Hejiakouzi Quaternary anticline, which is a part of the Miaoshan fault-fold belt, is mainly discussed. It is pointed out that the fold began to grow in the middle part near Hejiakouzi in the mid-late stage of middle Pleistocene epoch and then gradually developed towards the ends in late Quaternary. Based on the Cenozoic structural features, the genesis of the Miaoshan and Hongjianshan fault-fold belts and the kinematic relation they bear with the Tianjingshan fault zone are analyzed. 相似文献
124.
用自然类比法对1998年1月10日张北─尚义6.2级地震序列类型和震后趋势进行了早期判断,找出了与之最相似的四个序列是1976年9月23日巴音木仁6.2级地震(S17)、1996年5月3日包头6.4级地震(558)、1985年4月18日禄劝6.3级地震(S34)和1984年5月21日南黄海6.0级地震(S33)。由此判断张北地震序列为主震余震型,推算最大余震震级应在4.3~4.7之间,一个月内4级以上余震数可能在11~22次之间。实测结果张北地震最大余震震级4.6,一个月内4级以上余震数18次,均在预测范围内。 相似文献
125.
地震前兆复杂性成因机理研究的讨论(一):地震前兆复杂性的表现形式 总被引:10,自引:2,他引:8
通过国内外成功与失败的震例分析,介绍了地震前兆共性的一面,如在台网具有一定监测能力的地区,如果发生6级以上地震,震前总能或多或少地观测到异常现象。地震越大震前异常越多,分布越广,持续时间越长,异常幅度也较大,同时章着重对前兆复杂性的表现形式进行了较系统的归纳,整理,主要从以下几方面进行了分析,异常与地震关系的不确定性,主要表现在除了“有异常有地震”和“无异常无地震”的理论情况外,还存在“有异常无 相似文献
126.
INTRODUCTIONInhighlyextendedregions(β>1.5-2)suchastheBasinandRangeProvinceandpasivemargins,extensionaltectonicsystemischaract... 相似文献
127.
An Arctic Ocean eddy in sub-surface layer is analyzed in this paper by use of temperature,salinity and current profiles data obtained at an ice camp in the Canada Basin during the second Chinese Arctic Expedition in summer of 2003.In the vertical temperature section,the eddy shows itself as an isolated cold water block at depth of 60 m with a minimum temperature of-1.5℃,about 0.5℃ colder than the ambient water.Isopycnals in the eddy form a pattern of convex,which indicates the eddy is anticyclonic.Although maximum velocity near 0.4 m s-1 occurs in the current records observed synchronously,the current pattern is far away from a typical eddy.By further analysis,inertial frequency oscillations with amplitudes comparable with the eddy velocity are found in the sub-surface layer currents.After filter the inertial current and mean current,an axisymmetric current pattern of an eddy with maximum velocity radius of 5 km is obtained.The analysis of the T-S characteristics of the eddy core water and its ambient waters supports the conclusion that the eddy was formed on the Chukchi Shelf and migrated northeastward into the northern Canada Basin. 相似文献
128.
This paper studies the relative motion of satellite formation flying in arbitrary elliptical orbits with no perturbation.
The trajectories of the leader and follower satellites are projected onto the celestial sphere. These two projections and
celestial equator intersect each other to form a spherical triangle, in which the vertex angles and arc-distances are used
to describe the relative motion equations. This method is entitled the reference orbital element approach. Here the dimensionless
distance is defined as the ratio of the maximal distance between the leader and follower satellites to the semi-major axis
of the leader satellite. In close formations, this dimensionless distance, as well as some vertex angles and arc-distances
of this spherical triangle, and the orbital element differences are small quantities. A series of order-of-magnitude analyses
about these quantities are conducted. Consequently, the relative motion equations are approximated by expansions truncated
to the second order, i.e. square of the dimensionless distance. In order to study the problem of periodicity of relative motion,
the semi-major axis of the follower is expanded as Taylor series around that of the leader, by regarding relative position
and velocity as small quantities. Using this expansion, it is proved that the periodicity condition derived from Lawden’s
equations is equivalent to the condition that the Taylor series of order one is zero. The first-order relative motion equations,
simplified from the second-order ones, possess the same forms as the periodic solutions of Lawden’s equations. It is presented
that the latter are further first-order approximations to the former; and moreover, compared with the latter more suitable
to research spacecraft rendezvous and docking, the former are more suitable to research relative orbit configurations. The
first-order relative motion equations are expanded as trigonometric series with eccentric anomaly as the angle variable. Except
the terms of order one, the trigonometric series’ amplitudes are geometric series, and corresponding phases are constant both
in the radial and in-track directions. When the trajectory of the in-plane relative motion is similar to an ellipse, a method
to seek this ellipse is presented. The advantage of this method is shown by an example. 相似文献
129.
采用Ronge-Kutta射线追踪法对地震勘探中几个典型地质模型的地震波射线路径和旅行时计算的实例和效果进行分析。将Ronge-Kutta射线追踪模拟的结果与程函方程计算的时距曲线结果进行对比,验证了Ronge-Kutta射线追踪法的易实现性和程函方程有限差分旅行时算法的强稳定性,表明Ronge-Kutta射线追踪法在复杂构造区域进行地震射线路径和旅行时计算时能得到较好的模拟效果。 相似文献
130.
"三旧"改造是广东省特有的改造模式,也是未来城市可持续发展战略的重要组成部分.为了全面掌握"三旧"改造用地的工作情况,实现对"三旧"改造项目有效地动态监控,项目采用地理信息系统(GIS)、三维可视化、倾斜摄影、云计算等先进技术,构建了"三旧"改造数据库,搭建了"三旧"改造信息管理平台,并阐述平台实现的相关关键技术.实践表明,平台在改造项目批后、改造项目建设进度等方面起到良好的监控和管理作用,实现了"三旧"改造的精细化管理. 相似文献