全文获取类型
收费全文 | 2429篇 |
免费 | 394篇 |
国内免费 | 522篇 |
专业分类
测绘学 | 307篇 |
大气科学 | 406篇 |
地球物理 | 379篇 |
地质学 | 1487篇 |
海洋学 | 299篇 |
天文学 | 47篇 |
综合类 | 130篇 |
自然地理 | 290篇 |
出版年
2024年 | 13篇 |
2023年 | 32篇 |
2022年 | 48篇 |
2021年 | 86篇 |
2020年 | 85篇 |
2019年 | 139篇 |
2018年 | 68篇 |
2017年 | 149篇 |
2016年 | 170篇 |
2015年 | 155篇 |
2014年 | 209篇 |
2013年 | 152篇 |
2012年 | 128篇 |
2011年 | 136篇 |
2010年 | 130篇 |
2009年 | 157篇 |
2008年 | 146篇 |
2007年 | 156篇 |
2006年 | 137篇 |
2005年 | 128篇 |
2004年 | 104篇 |
2003年 | 85篇 |
2002年 | 108篇 |
2001年 | 95篇 |
2000年 | 65篇 |
1999年 | 67篇 |
1998年 | 68篇 |
1997年 | 65篇 |
1996年 | 49篇 |
1995年 | 35篇 |
1994年 | 32篇 |
1993年 | 24篇 |
1992年 | 22篇 |
1991年 | 21篇 |
1990年 | 17篇 |
1989年 | 17篇 |
1988年 | 9篇 |
1987年 | 2篇 |
1986年 | 8篇 |
1985年 | 3篇 |
1984年 | 9篇 |
1983年 | 4篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有3345条查询结果,搜索用时 31 毫秒
81.
抚顺盆地超厚煤层的沉积条件分析 总被引:11,自引:0,他引:11
根据抚顺盆地早第三纪超厚煤层中异常丰富的成因标志,论证了一种与河流、风暴作用有关的陆相超厚煤层形成新机制-湖成异地-微异地混合堆积机制。在这一新机制中,由风暴上升流(也许还有地震)触发的水下重力流及风暴回流,既驱动湖滨泥炭沼泽和三角洲上的有机碎屑及无机碎屑进入湖泊中心区,又造成泥炭碎屑在较深水环境的再次堆积,从而使其中无机碎屑与泥炭碎屑有效地分离。 相似文献
82.
应用直流电法仪在井下进行了工作面巷道底板电测深和掘进头超前探测,查清了工作面底板水层的富水性和掘进头前头的地质构造及含水情况。目前,大部分探测结果已得到生产实践的证实。 相似文献
83.
本文利用在乌鲁木齐河山区流域所建立的树轮年表,重建了乌鲁木齐河山区流域360年上年7月~当年3月的平均径流量。校准方程的相关系数为0.670,交叉检验的误差缩减值达0.366。在重建的360年径流量的变化中,有4个偏丰期和3个偏枯期,第2,3两个偏丰期与乌鲁木齐河河源1号冰川的两次冰进期相对应。对重建径流量的丰枯频率分析发现,平水年份出现最多,偏枯水年份多于偏丰水年份约5.8%,特枯水年没有出现,特丰水年出现6次,约占1.7%。这表明360年来径流量变化基本上稳定。 相似文献
84.
The 3 310-m-high Chia-min Lake records the climatic history since 4 ka B. P. in Taiwan. The warm/wet period before 2.2 ka
B.P. seemed to correspond to the later part of the Holocene Megathermal, and the cold/dry period during 0–2.2 ka B. P. corresponded
to the Katathermal. Before the termination of the Megathermal, an especially warm and humid segment (2.2–2.4 ka B. P.) emerged.
The paleoclimatic records from Yuen-yang and Chi-tsai Lakes support the notion that the Megathermal in Taiwan terminated during
2—2.3 ka B. P. A warm segment (820–1 320 AD) in the Katathermal could be considered the Medieval Warm Period. The climate
turned cold and dry after 1 320 AD and this indicated the onset of the Little Ice Age. These paleoclimatic variations are
also in good agreement with those recorded in Great Ghost Lake. 相似文献
85.
大别山太湖地区榴辉岩峰期变质条件与构造意义 总被引:3,自引:6,他引:3
大别山太湖地区曾被作为“冷”、“热”榴辉岩带的交界处所在,我们对大别山太湖地区的进行了1:10000地质填图,并详细研究了该地区榴辉岩的岩相学和矿物成分变化,以及KD值、峰期变质P-T条件。研究表明榴辉岩自南向北可分为三类:①朱家冲型榴辉岩;②大坝型榴辉岩;③金河桥型榴辉岩。其中朱家冲型榴辉岩和金河桥型榴辉岩显示出明显的温度、压力差异,它们形成的P-T条件分别为:P=2.14GPa、T=563℃和P=3.76GPa、T=791℃。大坝型榴辉岩的峰期变质P-T条件差别较大,在柯石英-石英相变线附近徘徊,变质环境相当于高压一超高压过渡环境。朱家冲型榴辉岩与大坝型榴辉岩分别对应于前人所划分的“冷”、“热”榴辉岩,并且两者在峰期,变质温、压条件上是连续变化的,没有明显的温、压间断。因此,我们认为本区所谓的“冷”、“热”榴辉岩带界线是不存在的。 相似文献
86.
本文论述了冀中坳陷-黄骅坳陷馆陶组热储砂岩、底部砾岩、砂砾岩的发育、孔隙度及热水水质的差异性,对热储出水特征进行了探讨,提出了馆陶组热储成井的基本条件,对冀中坳陷-黄骅坳陷馆陶组热储成井具有一定的指导意义。 相似文献
87.
88.
Sébastien J. Stemmler Stéphanie Loyaux-Lawniczak Jacques Berthelin 《Comptes Rendus Geoscience》2004,336(13):1171-1179
Iron-reducing activity of autochthonous bacteria from two temporary hydromorphic soils is evaluated by the study of iron reductive dissolution, as a function of water content. The release of ferrous iron in solution is coupled to the mineralization of soil organic carbon. Water soil saturation is not necessary for iron reductive dissolution, since the highest dissolution is obtained for a wet, but not water-saturated soil (100% of water holding capacity WHC), and dissolution is also very high in a soil at 75% WHC. To cite this article: S.J. Stemmler et al., C. R. Geoscience 336 (2004). 相似文献
89.
Thermodynamic conditions of framework grain dissolution of clastic rocks and its application in Kela 2 gas field 总被引:2,自引:2,他引:2
LAI Xingyun YU Bingsong CHEN Junyuan CHEN Xiaolin LIU Jianqing MEI Mingxiang JING Weiguang & CHENG Suhua School of Earth Sciences Mineral Resources China University of Geosciences Beijing China Key Laboratory of Lithospheric Tectonics Deep-level Process Exploration of Ministry of Education Beijing China 《中国科学D辑(英文版)》2005,48(1):21-31
Feldspar and clastic debris are the most important constituent framework grains of sedimentary clastic rocks and their chemical dissolution plays an essential role in the formation and evolution of the secondary pore in the reservoir rocks. On the basis of thermodynamic phase equilibrium, this study investigates the chemical equilibrium relationships between fluid and various plagioclase and K-feldspar in diagenesis of the sediments, particularly, the impact of temperature and fluid compositions (pH, activity of K+, Na+, Ca2+ and so on) on precipitation and dissolution equilibria of feldspars. Feldspar is extremely easily dissolved in the acid pore water with a low salinity when temperature decreases. The dissolution of anorthite end-member of plagioclase is related to the Ca content of the mineral and the fluid, higher Ca either in the mineral or in the fluid, easier dissolution of the feldspar. Moreover, the dissolution of albite end-member of plagioclase is related to Na of both the mineral and fluid, 相似文献
90.
A precise monitoring of snow surface height in the region of Lambert Glacier basin-Amery Ice Shelf,East Antarctica 总被引:2,自引:0,他引:2
I.Allison 《中国科学D辑(英文版)》2005,48(1):100-111
The net surface snow accumulation on the Antarctic ice sheet is determined by a combination of precipitation, sublimation and wind redistribution. We present a one-year record of hourly snow-height measurements at LGB69 (70°50'S, 77°04'E, 1850 m a.s.l.). east side of Lambert Glacier basin (LGB), and 4 year record at G3 (70°53'S, 69°52'E, 84 m a.s.l.), Amery Ice Shelf (AIS). The measurements were made with ultrasonic sensors mounted on automatic weather stations installed at two sites. The snow accumulation at LGB69 is approximately 70 cm. Throughout the winter, between April and September, there was little change in surface snow height (SSH) at the two sites. The negative SSH change is due to densification at LGB69, and is due to both ablation and densification at G3. The strongest accumulation at two sites occurred during the period between October and March (accounting for 101.6% at LGB69), with four episodic increasing events occurring during 2002 for LGB69, and eight events during 1999-2002 for G 相似文献