全文获取类型
| 收费全文 | 566篇 |
| 免费 | 115篇 |
| 国内免费 | 120篇 |
专业分类
| 测绘学 | 44篇 |
| 大气科学 | 104篇 |
| 地球物理 | 197篇 |
| 地质学 | 227篇 |
| 海洋学 | 74篇 |
| 天文学 | 5篇 |
| 综合类 | 65篇 |
| 自然地理 | 85篇 |
出版年
| 2024年 | 9篇 |
| 2023年 | 21篇 |
| 2022年 | 30篇 |
| 2021年 | 61篇 |
| 2020年 | 47篇 |
| 2019年 | 29篇 |
| 2018年 | 67篇 |
| 2017年 | 61篇 |
| 2016年 | 55篇 |
| 2015年 | 42篇 |
| 2014年 | 46篇 |
| 2013年 | 40篇 |
| 2012年 | 40篇 |
| 2011年 | 52篇 |
| 2010年 | 22篇 |
| 2009年 | 43篇 |
| 2008年 | 21篇 |
| 2007年 | 27篇 |
| 2006年 | 19篇 |
| 2005年 | 20篇 |
| 2004年 | 7篇 |
| 2003年 | 14篇 |
| 2002年 | 7篇 |
| 2001年 | 5篇 |
| 2000年 | 2篇 |
| 1999年 | 2篇 |
| 1997年 | 1篇 |
| 1996年 | 5篇 |
| 1990年 | 4篇 |
| 1983年 | 2篇 |
排序方式： 共有801条查询结果，搜索用时 15 毫秒
31.
The rational use of drilling parameters is a hot issue in the field of geotechnical engineering and geological engineering. A new method, for evaluating the bearing capacity of soils using drilling parameters was proposed. First, through the mechanical analysis of the drill bit, the preconditions and theoretical formulas for calculating the bearing capacity of soils using the bit’s torque are clearly defined. Next, drilling tests and dynamic cone penetration tests were performed on miscellaneous fill, silty clay, sandy clay, medium coarse sand and gravel sand, and the empirical formula for calculating the bearing capacity of these soils were given. Then, using the new method and the empirical formula, the bearing capacity of the soil under the roadbed was examined. The test results show that the bit’s torque is a good parameter for the evaluation of the bearing capacity of the soil. Finally, the application scope of the new method and the empirical formula is discussed, and the subsequent research directions are pointed out. 相似文献
32.
Tao Zhang Wutian Cai Yingzhi Li Tingting Geng Zhiyin Zhang Yonggao Lv Miao Zhao Jinwei Liu 《Arabian Journal of Geosciences》2018,11(17):510
In order to study the major ion chemistry and controls of groundwater, 65 groundwater samples were collected and their major ions measured from wells within Lhasa River Basin. Groundwater has the characteristics of slightly alkaline and moderate total dissolved solid (TDS). TDS concentration ranged from 122.0 to 489.9 mg/L with a median value of 271.2 mg/L. Almost all the groundwater samples suited for drinking and irrigation. The major cations of groundwater are Ca2+ and Mg2+, accounting for 59.6 and 31.3% of the cations, respectively. Meanwhile, HCO3? and SO42? constituted about 56.7 and 36.9% of the anions, respectively, in Lhasa River Basin. The hydrochemical type of groundwater is HCO3-SO4-Ca-Mg. The chemical composition of groundwater samples located in the middle of Gibbs model, which indicates that the major chemical process of groundwater is controlled by rock weathering. Carbonate weathering was the dominant hydro-geochemical process controlling the concentration of major ions in groundwater within Lhasa River Basin, but silicate weathering also plays an important role. 相似文献
33.
Wei‐Xin Lv Hao‐Ming Yin Meng‐Shu Liu Fang Huang Hui‐Min Yu 《Geostandards and Geoanalytical Research》2021,45(1):245-256
A dry ashing method is commonly used to remove organic material from samples prior to geochemical analysis. In the course of this study, the Cd isotope ratios of a series of soil and plant reference materials and samples were studied to evaluate the effect of the dry ashing method on measurement results of Cd isotope ratios. The samples were pre‐treated using the dry ashing method and high‐pressure bomb for comparison. The results show that the digestion using high‐pressure bombs did not lead to Cd loss, but using the dry ashing method would cause different proportions of Cd loss. The whole range of Cd isotope difference between two methods was from ?0.07‰ to 3.01‰. There was also an obvious difference in measured Cd isotope ratios from the same leaf sample pre‐treated independently by the dry ashing method, indicating that the amount of Cd loss and the effect on Cd isotope measurement during dry ashing is related to the properties of the samples. Therefore, dry ashing may not be appropriate for the removal of organic material in Cd isotope ratio measurement, especially for samples with high organic contents. The δ114/110Cd values of reference materials NIST SRM 1573a and GSD‐30 are reported for the first time in this study. 相似文献
34.
Landslides - Talus slopes play an important role in landscape evolution in some mid-altitude mountains. In this study, we analyzed talus slope activity on Xiaowutai Mountain in the Northern Taihang... 相似文献
35.
36.
喜马拉雅中—新生代地层沉积于印度被动大陆边缘,三叠系沉积物物源分析是冈瓦纳大陆裂解和古地理研究的重要载体.特提斯喜马拉雅东段上三叠统涅如组碎屑岩的物质来源和沉积背景具有较大的争议,本次研究采集隆子县斗玉乡晚三叠世粉砂质板岩进行碎屑锆石U-Pb年代学和全岩主微量元素地球化学分析.涅如组碎屑锆石年龄具有两个明显的峰值:206～224Ma(峰值213 Ma)和462～567Ma(峰值512 Ma),表明涅如组沉积时代为晚三叠世诺利期.涅如组w(SiO2)含量较低(平均值为57.7％),w(Al2O3)值较高(17.2％),轻稀土元素富集,重稀土元素亏损,轻稀土/重稀土元素平均值为8.1.高场强元素中Nb,Ta,Ti亏损,Zr,Hf,Th,U富集;大离子亲石元素中Ba,Sr亏损,Rb和K富集.综合分析认为源区岩石以酸性岩浆岩为主.本次研究认为上三叠统涅如组浊流相沉积形成于裂谷环境,代表新特提斯洋的打开;标志着拉萨板块从冈瓦纳大陆北缘裂解,并开始向北漂移. 相似文献
37.
38.
平流层和中层大气研究的进展 总被引：16，自引：4，他引：12
平流层和中层大气研究是20世纪70年代以来持续得到大气科学界和日地物理界共同关注的研究前沿.中国科学界在文化大革命结束后立即抓住这一前沿作为发展重点之一.20多年来,中国科学院大气物理研究所等单位较为系统地开展了这一方向的研究,并在一些方面进行了前沿性的工作.作者着重介绍以下几方面的进展:(1)平流层和中层大气探测设施与探测方法;(2)大气臭氧、平流层气溶胶的监测与分析;(3)行星波在中层大气环流与大气臭氧分布中的作用;(4)重力波在中层大气的传播特征与作用;(5)平流层-对流层交换的动力物理与化学问题. 相似文献
39.
飞机航迹分析是飞机云物理和大气环境探测中进行飞行探测资料整合中的一项重要工作，在GPS航迹资料分析中，资料的不连续和经纬度数据进制换算是飞机探测作业分析中常遏的问题。根据北京2004年增蓄型飞机人工增雨探测作业试验期间GPS航迹数据特点，通过Matlab分析讨论其中的问题，利用Matlab良好的矩阵运算功能，对航迹经纬度数据进行换算，并根据航迹记录时间的连续性特点，提出了对不恰当、丢失和重复数据的判断分析方法。分析使用表明，在飞机探测作业航迹分析中，Matlab可以很方便地进行数据分析处理，并能将结果进行多维可视化显示。 相似文献
40.
结合学习中国气象事业发展战略研究成果,深入分析了县级气象局的基本状况、社会地位以及存在的困难和问题与中国气象事业发展战略要求的差距,阐述了当前适合县级气象局发展的思路和对策. 相似文献