全文获取类型
收费全文 | 3545篇 |
免费 | 946篇 |
国内免费 | 857篇 |
专业分类
测绘学 | 119篇 |
大气科学 | 30篇 |
地球物理 | 444篇 |
地质学 | 4107篇 |
海洋学 | 166篇 |
天文学 | 29篇 |
综合类 | 285篇 |
自然地理 | 168篇 |
出版年
2024年 | 16篇 |
2023年 | 60篇 |
2022年 | 202篇 |
2021年 | 177篇 |
2020年 | 174篇 |
2019年 | 192篇 |
2018年 | 99篇 |
2017年 | 113篇 |
2016年 | 139篇 |
2015年 | 129篇 |
2014年 | 247篇 |
2013年 | 232篇 |
2012年 | 264篇 |
2011年 | 277篇 |
2010年 | 232篇 |
2009年 | 241篇 |
2008年 | 250篇 |
2007年 | 251篇 |
2006年 | 250篇 |
2005年 | 231篇 |
2004年 | 248篇 |
2003年 | 175篇 |
2002年 | 178篇 |
2001年 | 158篇 |
2000年 | 137篇 |
1999年 | 121篇 |
1998年 | 118篇 |
1997年 | 107篇 |
1996年 | 68篇 |
1995年 | 44篇 |
1994年 | 49篇 |
1993年 | 43篇 |
1992年 | 32篇 |
1991年 | 23篇 |
1990年 | 11篇 |
1989年 | 12篇 |
1988年 | 9篇 |
1987年 | 10篇 |
1986年 | 6篇 |
1985年 | 7篇 |
1984年 | 1篇 |
1983年 | 1篇 |
1982年 | 1篇 |
1980年 | 2篇 |
1979年 | 1篇 |
1978年 | 3篇 |
1977年 | 5篇 |
1973年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有5348条查询结果,搜索用时 875 毫秒
281.
282.
283.
结合安徽省高速公路建设工程实例,介绍瞬态瑞雷面波勘探技术在公路工程地质勘察中的应用,解决沿线高边坡、深路堑、桥梁、隧道进出口的岩土分层,给出基岩风化分带等工程地质问题,省时、省力,取得了良好的经济效益和环境效益. 相似文献
284.
285.
286.
287.
288.
高力罕凹陷为二连盆地乌尼特坳陷的一个组成部分,由有相似构造发育史的分散小湖盆(洼槽)集合而成的沉积盆地。结构复杂,表现出分割性强,多洼槽多沉积中心,岩相变化大的特点。通过对高力罕凹陷的构造特征、结构特征、沉积特征、岩性发育特征及铀成矿条件的分析,认为高力罕凹陷具有良好的铀矿找矿前景。提出该地区的找矿方向,具有一定的参考意义。 相似文献
289.
Assessment of Exploration Bias in Data-Driven Predictive Models and the Estimation of Undiscovered Resources 总被引:3,自引:0,他引:3
The spatial distribution of discovered resources may not fully mimic the distribution of all such resources, discovered and
undiscovered, because the process of discovery is biased by accessibility factors (e.g., outcrops, roads, and lakes) and by
exploration criteria. In data-driven predictive models, the use of training sites (resource occurrences) biased by exploration
criteria and accessibility does not necessarily translate to a biased predictive map. However, problems occur when evidence
layers correlate with these same exploration factors. These biases then can produce a data-driven model that predicts known
occurrences well, but poorly predicts undiscovered resources.
Statistical assessment of correlation between evidence layers and map-based exploration factors is difficult because it is
difficult to quantify the “degree of exploration.” However, if such a degree-of-exploration map can be produced, the benefits
can be enormous. Not only does it become possible to assess this correlation, but it becomes possible to predict undiscovered,
instead of discovered, resources.
Using geothermal systems in Nevada, USA, as an example, a degree-of-exploration model is created, which then is resolved into
purely explored and unexplored equivalents, each occurring within coextensive study areas. A weights-of-evidence (WofE) model
is built first without regard to the degree of exploration, and then a revised WofE model is calculated for the “explored
fraction” only. Differences in the weights between the two models provide a correlation measure between the evidence and the
degree of exploration.
The data used to build the geothermal evidence layers are perceived to be independent of degree of exploration. Nevertheless,
the evidence layers correlate with exploration because exploration has preferred the same favorable areas identified by the
evidence patterns. In this circumstance, however, the weights for the “explored” WofE model minimize this bias. Using these
revised weights, posterior probability is extrapolated into unexplored areas to estimate undiscovered deposits. 相似文献
290.
Chai Chizhang 《中国地震研究》2007,21(3):225-235
The paper introduces the steps and methods of multi-approach,multi-level exploration of buried faults in thick Quaternary sediment regions by taking the test exploration of the Yinchuan active fault as example.Based on the comprehensive analyses of previous data,we choose the Xinqushao Village of Xingqing District of Yinchuan City as the test site for the comprehensive exploration.Firstly,we adopted shallow seismic investigation with group intervals of 10m,5m and 1m to gradually trace layer by layer the master fault of the Yinchuan buried fault from a deep depth to a shallow depth where drilling could be used.Then,with composite geological profile drilling,we determined the precise location and dip angle of the fault.The drilling show the buried depth of the upper offset point is 8.3m.Finally,large-scale trenching revealed that the actual buried depth of the upper offset point of the fault is 1.5m from the ground surface and there are paleoearthquake events of 5 stages.Combined with the preliminary result of corresponding sample age,we conclude the Yinchuan buried fault is a mid to late Holocene active fault. 相似文献