全文获取类型
收费全文 | 824篇 |
免费 | 105篇 |
国内免费 | 79篇 |
专业分类
测绘学 | 5篇 |
大气科学 | 140篇 |
地球物理 | 268篇 |
地质学 | 469篇 |
海洋学 | 51篇 |
天文学 | 2篇 |
综合类 | 26篇 |
自然地理 | 47篇 |
出版年
2024年 | 1篇 |
2023年 | 9篇 |
2022年 | 7篇 |
2021年 | 24篇 |
2020年 | 21篇 |
2019年 | 31篇 |
2018年 | 23篇 |
2017年 | 34篇 |
2016年 | 37篇 |
2015年 | 26篇 |
2014年 | 44篇 |
2013年 | 41篇 |
2012年 | 34篇 |
2011年 | 41篇 |
2010年 | 26篇 |
2009年 | 60篇 |
2008年 | 58篇 |
2007年 | 57篇 |
2006年 | 58篇 |
2005年 | 58篇 |
2004年 | 29篇 |
2003年 | 39篇 |
2002年 | 37篇 |
2001年 | 24篇 |
2000年 | 32篇 |
1999年 | 19篇 |
1998年 | 20篇 |
1997年 | 14篇 |
1996年 | 18篇 |
1995年 | 7篇 |
1994年 | 14篇 |
1993年 | 10篇 |
1992年 | 15篇 |
1991年 | 9篇 |
1990年 | 6篇 |
1989年 | 3篇 |
1988年 | 7篇 |
1987年 | 2篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1976年 | 2篇 |
排序方式: 共有1008条查询结果,搜索用时 156 毫秒
901.
云龙白洋厂银多金属矿区帚状构造带及其控矿作用 总被引:1,自引:0,他引:1
白洋厂矿区以银为主,共生、伴生铜铅锌汞,系滇西首个发现的中型独立银矿床。矿区东部断裂呈弧形弯曲,并作NNW向收敛、SE方向撒开趋势,这些弧形断裂应是一帚状构造。 相似文献
902.
叠溪地震区龙池岸坡中埋藏古沟槽的空间分布特征 总被引:4,自引:0,他引:4
围绕叠溪地震区的龙池岸坡在引水隧洞施工开挖过程中多处出现沟谷相的松散堆积物这一地质现象为线索,在多次现场地质地貌调研分析的基础上,采用甚低频电磁法现场测试和RaA氡气现场测试的验证分析,阐明了龙池岸坡中埋藏古沟槽的空间分布特征,揭示岷江河谷近期演化特征,解决引水工程施工中所关心的地质问题;通过本次研究不仅对龙池岸坡的稳定性有了新的认识,而且为类似强震区的岸坡稳定性分析提供新的思路和方法。 相似文献
903.
人工引发雷电的静态摄影及特性分析 总被引:2,自引:0,他引:2
展示和分析了人工引发雷电的近距离静态摄影照片,从中可以获取雷电某些宏观特征的有用信息。 相似文献
904.
Maximum-likelihood estimators properly represent measurement error, thus provide a statistically sound basis for evaluating the adequacy of a model fit and for finding the multivariate parameter confidence region. We demonstrate the advantages of using maximum-likelihood estimators rather than simple least-squares estimators for the problem of finding unsaturated hydraulic parameters. Inversion of outflow data given independent retention data can be treated by an extension to a Bayesian estimator. As an example, we apply the methodology to retention and transient unsaturated outflow observations, both obtained on the same medium sand sample. We found the van Genuchten expression to be adequate for the retention data, as the best fit was within measurement error. The Cramer–Rao confidence bound described the true parameter uncertainty approximately. The Mualem–van Genuchten expression was, however, inadequate for our outflow observations, suggesting that the parameters (, n) may not always be equivalent in describing both retention and unsaturated conductivity. 相似文献
905.
906.
907.
滇西龙川江盆地中南部砂岩型铀矿成矿特征及成因探讨 总被引:2,自引:0,他引:2
研究了龙川江盆地中南部的沉积特征、构造特征及含矿岩系特征,提出铀成矿与构造演化中的2个沉积间断面关系密切。通过对龙川江盆地中南部铀矿化特征的研究,在382矿床内发现了沥青铀矿、铀黑和磷钙铀矿,在381矿床发现了超显微状放射性矿物,并根据龙川江盆地中南部382矿床成矿年龄的研究,提出了龙川江盆地中南部铀矿化的多阶段成因。 相似文献
908.
Allen P. Macfarlane Andrea Förster Daniel F. Merriam Jörg Schrötter John M. Healey 《Hydrogeology Journal》2002,10(6):662-673
Aquifer properties can be evaluated by monitoring artificially stimulated fluid movements between wells, if the fluid is
heated. Changes in the temperature profile recorded in observation wells indicate the flow path of the heated fluid, which
in effect acts as a tracer. A fluid-flow experiment in the Cretaceous Dakota Formation at the Hodgeman County site, west-central
Kansas, demonstrated the advantage of using the distributed optical-fiber temperature sensing method for monitoring transient
temperature conditions in this hydrological application. The fluid flow in the aquifer was increased by producing water from
a pumping well and injecting heated water in an injection well 13 m (43 ft) distant from the pumping well. The time-temperature
series data obtained and compared with results from previous pumping tests point to interwell heterogeneity of the aquifer
and to a zone in the sandstone aquifer of high hydraulic conductivity. However, the experiment would have allowed further
clarification of aquifer heterogeneity and thermal properties if at least one observation well had been present between the
injection and production wells.
Electronic Publication 相似文献
909.
A design of a dewatering system is necessary for site improvement prior to the construction of some structures. The design
of an efficient dewatering system requires estimating the value of the in-situ coefficient of permeability. The available
relationships for estimating the permeability coefficient were developed based on limited field measurements and conditions,
and their predictions vary by several orders of magnitudes. Therefore, it was necessary to conduct field measurements of permeability
and determine the relationship that best fits these measurements prior to the design of a dewatering system for specific geological
and site conditions.
This paper presents field measurements of permeability in complex chaotic and diagenetic limestone strata. It also offers
comparative analysis of several relationships available in the literature for predicting the in-situ coefficient of permeability.
The analysis is conducted for both steady and nonsteady conditions. The results show that the coefficient of permeability
value is dependent on the water table level, which is affected by the tidal condition. The US Navy equation is shown to give
the best correlation with field measurements.
Electronic Publication 相似文献
910.