全文获取类型
收费全文 | 715篇 |
免费 | 156篇 |
国内免费 | 204篇 |
专业分类
测绘学 | 44篇 |
大气科学 | 102篇 |
地球物理 | 215篇 |
地质学 | 466篇 |
海洋学 | 122篇 |
天文学 | 35篇 |
综合类 | 38篇 |
自然地理 | 53篇 |
出版年
2024年 | 2篇 |
2023年 | 11篇 |
2022年 | 11篇 |
2021年 | 12篇 |
2020年 | 20篇 |
2019年 | 27篇 |
2018年 | 16篇 |
2017年 | 28篇 |
2016年 | 23篇 |
2015年 | 28篇 |
2014年 | 36篇 |
2013年 | 41篇 |
2012年 | 38篇 |
2011年 | 58篇 |
2010年 | 39篇 |
2009年 | 74篇 |
2008年 | 68篇 |
2007年 | 68篇 |
2006年 | 54篇 |
2005年 | 45篇 |
2004年 | 36篇 |
2003年 | 37篇 |
2002年 | 40篇 |
2001年 | 33篇 |
2000年 | 17篇 |
1999年 | 22篇 |
1998年 | 39篇 |
1997年 | 32篇 |
1996年 | 23篇 |
1995年 | 18篇 |
1994年 | 22篇 |
1993年 | 16篇 |
1992年 | 11篇 |
1991年 | 6篇 |
1990年 | 4篇 |
1989年 | 10篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 1篇 |
排序方式: 共有1075条查询结果,搜索用时 15 毫秒
311.
312.
Using Artificial Neural Networks to Predict the Presence of Overpressured Zones in the Anadarko Basin,Oklahoma 总被引:1,自引:0,他引:1
Constantin Cranganu 《Pure and Applied Geophysics》2007,164(10):2067-2081
Many sedimentary basins throughout the world exhibit areas with abnormal pore-fluid pressures (higher or lower than normal
or hydrostatic pressure). Predicting pore pressure and other parameters (depth, extension, magnitude, etc.) in such areas
are challenging tasks. The compressional acoustic (sonic) log (DT) is often used as a predictor because it responds to changes
in porosity or compaction produced by abnormal pore-fluid pressures. Unfortunately, the sonic log is not commonly recorded
in most oil and/or gas wells. We propose using an artificial neural network to synthesize sonic logs by identifying the mathematical
dependency between DT and the commonly available logs, such as normalized gamma ray (GR) and deep resistivity logs (REID).
The artificial neural network process can be divided into three steps: (1) Supervised training of the neural network; (2)
confirmation and validation of the model by blind-testing the results in wells that contain both the predictor (GR, REID)
and the target values (DT) used in the supervised training; and 3) applying the predictive model to all wells containing the
required predictor data and verifying the accuracy of the synthetic DT data by comparing the back-predicted synthetic predictor
curves (GRNN, REIDNN) to the recorded predictor curves used in training (GR, REID). Artificial neural networks offer significant
advantages over traditional deterministic methods. They do not require a precise mathematical model equation that describes
the dependency between the predictor values and the target values and, unlike linear regression techniques, neural network
methods do not overpredict mean values and thereby preserve original data variability. One of their most important advantages
is that their predictions can be validated and confirmed through back-prediction of the input data. This procedure was applied
to predict the presence of overpressured zones in the Anadarko Basin, Oklahoma. The results are promising and encouraging. 相似文献
313.
Remote sensing and GIS for artificial recharge study, runoff estimation and planning in Ayyar basin, Tamil Nadu, India 总被引:4,自引:0,他引:4
This paper focuses on artificial groundwater recharge study in Ayyar basin, Tamil Nadu, India. The basin is covered by hard crystalline rock and overall has poor groundwater conditions. Hence, an artificial recharge study was carried out in this region through a project sponsored by Tamil Nadu State Council for Science and Technology. The Indian Remote Sensing satellite 1A Linear Imaging Self Scanning Sensor II (IRS 1A LISS II) satellite imagery, aerial photographs and geophysical resistivity data were used to prioritize suitable sites for artificial recharge and to estimate the volume of aquifer dimension available to recharge. The runoff water available for artificial recharge in the basin is estimated through Soil Conservation Service curve number method. The land use/land cover, hydrological soil group and storm rainfall data in different watershed areas were used to calculate the runoff in the watersheds. The weighted curve number for each watershed is obtained through spatial intersection of land use/land cover and hydrological soil group through GeoMedia 3.0 Professional GIS software. Artificial recharge planning was derived on the basis of availability of runoff, aquifer dimension, priority areas and water table conditions in different watersheds in the basin. 相似文献
314.
系统论和非线性方法为石油地球物理勘探注入了新的动力。本文试通过分形理论结合人工神经网络方法对测井资料进行解释,对油气分布进行平面成像预测。 相似文献
315.
Offshore oil platforms and fouling communities in the southern Arabian Gulf (Abu Dhabi) 总被引:1,自引:0,他引:1
Stachowitsch M Kikinger R Herler J Zolda P Geutebrück E 《Marine pollution bulletin》2002,44(9):853-860
This study examined the fouling organisms on the legs of offshore oil platforms at two sites in the southern Arabian Gulf (offshore Abu Dhabi, United Arab Emirates). 100% of the metal structures was colonized by encrusting organisms. Both the number of individuals and the total biomass tended to decrease with depth. The total weight of dead shells always exceeded that of living organisms. Sessile filter feeders dominated the biomass, whereas small mobile forms had the largest number of individuals. The biomass at the deeper platform (22 m) was dominated by bivalves, barnacles and bryozoans, while polychaetes and amphipods had the greatest number of individuals. Biomass values here ranged from 1 g/0.1 m2 at 20 m to 147 g/0.1 m2 at 5 m; the corresponding individual numbers were 266 (20 m) and 11,814 indiv./0.1 m2 (5 m). The results at the shallower platform (11 m) differed in several respects: barnacles clearly dominated over bivalves, and sponges exceeded byrozoans, while total individual numbers fell due to a decline in polychaete dominance. Biomass values here ranged from 84 g/0.1 m2 at 10 m to 153 g/0.1 m2 at 0 m; the corresponding individual numbers were 695 (10 m) and 3,125 indiv./0.1 m2 (0 m). The potential role of such fouling communities on artificial structures in the Gulf is discussed. 相似文献
316.
317.
根据断裂动力学理论及弹性P波与裂缝相互作用的分析,利用混凝土的动态断裂韧度,研究了大体积混凝土深层或贯穿裂缝在爆炸应力波P波作用下的扩展,得到了含裂缝混凝土的安全质点振动速度,并讨论了P波频率及其入射角对安全质点振动速度的影响。结果表明,频率越低、入射角越大的应力波对混凝土裂缝的扩展作用越大,频率为10 Hz垂直入射条件下,混凝土裂缝不扩展的安全质点振动速度仅为0.95 cm/s,与水利水电工程施工组织设计手册中规定的混凝土重力坝、混凝土闸墩等大体积混凝土结构的安全振速5 cm/s有较大差距,含裂缝混凝土更加容易被破坏。 相似文献
318.
319.
320.