全文获取类型
收费全文 | 9744篇 |
免费 | 2024篇 |
国内免费 | 2542篇 |
专业分类
测绘学 | 836篇 |
大气科学 | 1978篇 |
地球物理 | 2640篇 |
地质学 | 5040篇 |
海洋学 | 1197篇 |
天文学 | 392篇 |
综合类 | 1007篇 |
自然地理 | 1220篇 |
出版年
2024年 | 43篇 |
2023年 | 160篇 |
2022年 | 518篇 |
2021年 | 538篇 |
2020年 | 449篇 |
2019年 | 584篇 |
2018年 | 627篇 |
2017年 | 562篇 |
2016年 | 638篇 |
2015年 | 551篇 |
2014年 | 582篇 |
2013年 | 635篇 |
2012年 | 590篇 |
2011年 | 562篇 |
2010年 | 563篇 |
2009年 | 537篇 |
2008年 | 520篇 |
2007年 | 486篇 |
2006年 | 370篇 |
2005年 | 352篇 |
2004年 | 306篇 |
2003年 | 293篇 |
2002年 | 386篇 |
2001年 | 415篇 |
2000年 | 356篇 |
1999年 | 412篇 |
1998年 | 346篇 |
1997年 | 284篇 |
1996年 | 249篇 |
1995年 | 233篇 |
1994年 | 206篇 |
1993年 | 188篇 |
1992年 | 164篇 |
1991年 | 114篇 |
1990年 | 92篇 |
1989年 | 84篇 |
1988年 | 78篇 |
1987年 | 45篇 |
1986年 | 36篇 |
1985年 | 34篇 |
1984年 | 26篇 |
1983年 | 21篇 |
1982年 | 13篇 |
1981年 | 14篇 |
1980年 | 9篇 |
1979年 | 9篇 |
1978年 | 7篇 |
1976年 | 3篇 |
1958年 | 12篇 |
1954年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
961.
机载激光雷达已成为快速、精确、高密度采集地形数据的有效手段,尤其在高速公路等范围狭长的区域体现明显.本文涵盖了数据采集和数据预处理等在外业采集时的关键技术,首先探讨了数据采集前的准备工作,包括检校场的选择、航线的设计、控制点的布设等重要步骤;然后说明了数据采集中的测量工作;最后讨论了数据检查工作,包括航线和激光数据的生成、数据的补漏.通过实验发现,该过程科学实用且精度满足实际生产要求,能够为今后激光数据处理流程化操作提供借鉴. 相似文献
962.
针对航空重力测量的原始扰动数据,本文介绍了数据处理的一般流程,内容包括原始数据检查、零点漂移校正、平均高程面归算、交叉点搜寻、内符合精度评价、离散数据的格网化等方面,详细说明了每一步数据处理的理论模型,并通过工程实例对计算结果进行了讨论和分析,为今后开展大规模航空重力测量业务作出一定的尝试和探索. 相似文献
963.
964.
提出了一种对灰色-马尔科夫链预测模型的状态区间取值修正方法.考虑实测值在状态区间中的位置分布情况作为先验知识,对状态区间的端点重新定权,修正预测值在状态区间中的取值,从而获得更高精度的预测结果.结合某建筑物的实测沉降数据,与原始GM(1,1)、残差修正G M(1,1)、灰色-马尔科夫链预测模型进行对比,结果表明:本文预测模型精度更高,状态区间取值修正方法对灰色-马尔科夫链的精度改善有一定的实用性. 相似文献
965.
966.
967.
Although it has been shown that the potential of tight‐sand gas resources is large, the research into the mechanisms of hydrocarbon charging of tight sandstone reservoirs has been relatively sparse. Researchers have found that there is a force balance during hydrocarbon charging, but discriminant models still have not been established. Based on the force balance conditions observed during gas migration from source rocks to tight sandstone reservoirs, a calculation formula was established. A formula for identifying effective source rocks was developed with the gas expulsion intensity as the discrimination parameter. The critical gas expulsion intensity under conditions of various burial depths, temperatures, and pressures can be obtained using the calculation formula. This method was applied in the Jurassic tight sandstone reservoirs of the eastern Kuqa Depression, Tarim Basin, and it was calculated that the critical expulsion intensity range from 6.05 × 108 m3/km2 to 10.07 × 108 m3/km2. The critical gas charging force first increases with depth and later decreases with greater depths. The distribution range of effective gas source rocks and total expelled gas volume can be determined based on this threshold. This method provides new insight into and method for predicting favourable tight‐sand gas‐bearing regions and estimating their resource potentials. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
968.
Tao Hu Xiongqi Pang Sa Yu Xulong Wang Hong Pang Jigang Guo Fujie Jiang Weibing Shen Qifeng Wang Jing Xu 《Geological Journal》2016,51(6):880-900
Combined with the actual geological settings, tight oil is the oil that occurs in shale or tight reservoirs, which has permeability less than 1 mD and is interbedded with or close to shale, including tight dolomitic oil and shale oil. The Fengcheng area (FA), at the northwest margin of the Junggar Basin, northwest China, has made significant progress in the tight oil exploration of the Fengcheng (P1f) Formation recently, which indicates that the tight oil resources have good exploration prospects. Whereas the lack of recognition of hydrocarbon generation and expulsion characteristics of Permian P1f source rocks results in the misunderstanding of tight oil resource potential. Based on the comprehensive analysis of geological and geochemical characteristics of wells, seismic inversion, sedimentary facies, tectonic burial depth, etc., the characteristics of P1f source rocks were investigated, and the horizontal distributions of the following aspects were predicted: the thickness of source rocks, abundance and type of organic matter. And on this basis, an improved hydrocarbon generation potential methodology together with basin simulation techniques was applied to unravel the petroleum generation and expulsion characteristics of P1f source rocks in FA. Results show that the P1f source rocks distribute widely (up to 2039 km2), are thick (up to 260 m), have high total organic content (TOC, ranging from 0.15 to 4 wt%), are dominated by type II kerogen and have entered into low mature–mature stage. The modeling results indicate that the source rocks reached hydrocarbon generation threshold and hydrocarbon expulsion threshold at 0.5% Ro and 0.85% Ro and the comprehensive hydrocarbon expulsion efficiency was about 46%. The amount of generation and expulsion from the P1f source rocks was 31.85 × 108 and 15.31 × 108 t, respectively, with a residual amount of 16.54 × 108 t within the source rocks. Volumetrically, the geological resource of shale oil is up to 15.65 × 108 t. Small differences between the amounts calculated by the volumetric method compared with that by hydrocarbon generation potential methodology may be due to other oil accumulations present within interbedded sands associated with the oil shales. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
969.
新型GPS探空仪与业务GTS1 2探空仪对比分析 总被引:1,自引:0,他引:1
2012年8月,中国气象局气象探测中心在广东阳江开展自动探空系统新型GPS探空仪比对试验,对比分析其技术改进后的准确性,试验结果表明:温度测量性明显优于GTS1 2型探空仪。湿度测量结果与RS92型探空仪一致性较好,系统误差在15%RH内,标准偏差在12%RH内。气压系统误差全量程在±10 hPa内,标准偏差在08 hPa内。位势高度系统误差在±20 gpm以内,标准偏差在70 gpm内。GPS定位测风性能优于GTS1 2型探空仪配合L波段二次测风雷达测风性能结果。 相似文献
970.
Zhe Yuan Deng-Hua Yan Zhi-Yong Yang Jun Yin Yong Yuan 《Theoretical and Applied Climatology》2015,122(3-4):755-769