全文获取类型
收费全文 | 222篇 |
免费 | 25篇 |
国内免费 | 160篇 |
专业分类
测绘学 | 5篇 |
大气科学 | 66篇 |
地球物理 | 72篇 |
地质学 | 176篇 |
海洋学 | 51篇 |
天文学 | 14篇 |
综合类 | 6篇 |
自然地理 | 17篇 |
出版年
2021年 | 4篇 |
2020年 | 4篇 |
2019年 | 9篇 |
2018年 | 14篇 |
2017年 | 10篇 |
2016年 | 9篇 |
2015年 | 10篇 |
2014年 | 12篇 |
2013年 | 28篇 |
2012年 | 10篇 |
2011年 | 22篇 |
2010年 | 19篇 |
2009年 | 18篇 |
2008年 | 24篇 |
2007年 | 9篇 |
2006年 | 17篇 |
2005年 | 13篇 |
2004年 | 8篇 |
2003年 | 11篇 |
2002年 | 14篇 |
2001年 | 8篇 |
2000年 | 8篇 |
1999年 | 3篇 |
1997年 | 7篇 |
1996年 | 6篇 |
1995年 | 3篇 |
1992年 | 4篇 |
1991年 | 5篇 |
1990年 | 4篇 |
1988年 | 3篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1977年 | 2篇 |
1975年 | 3篇 |
1966年 | 2篇 |
1965年 | 3篇 |
1964年 | 3篇 |
1963年 | 3篇 |
1959年 | 2篇 |
1950年 | 2篇 |
1948年 | 2篇 |
1942年 | 7篇 |
1938年 | 3篇 |
1934年 | 9篇 |
1928年 | 4篇 |
1926年 | 6篇 |
1925年 | 3篇 |
1924年 | 4篇 |
1923年 | 2篇 |
1922年 | 2篇 |
排序方式: 共有407条查询结果,搜索用时 984 毫秒
51.
In a commemorable evening—I believe it was in the early part of December, 1933—when I happened to discuss the problem of Pleistocene climate in China with the late Dr. Davidson Black, I informed him, without 相似文献
52.
GEOLOGY OF KENKOU ON THE HUNAN-KWANGTUNG BORDER AND ITS BEARING TO THE OROGENY OF THE NANLING RANGES
INTRODUCTION In the winter of 1932 and the spring of 1933, the Nanling Mountain ranges covering the borders of Hunan, Kwangtung, Kwangsi and Kueichou were studied by the members of the National Research Institute of Geology, 相似文献
53.
Eleven years ago when this society held its Third General Meeting I had the opportunity of calling your attention to certain strange deposits and topographical features that came under my notice in certain parts of North China. I showed you a number of striated boulders that could not be attributed to mere 相似文献
54.
Since the publication of the Fusulinidae of North China much information has been obtained from the southern seas of this country of the Carboniferous and Permian Periods. We are now in the position to form a birds eye 相似文献
55.
J. ZINN J. WREN R. WHITAKER J. SZYMANSKI D. O. Revelle W. PRIEDHORSKY J. HILLS G. GISLER S. FLETCHER D. CASPERSON J. BLOCH R. BALSANO W. T. ARMSTRONG C. AKERLOF R. KEHOE T. McKAY B. LEE M. C. KELLEY R. E. SPALDING S. MARSHALL 《Meteoritics & planetary science》1999,34(6):1007-1015
Abstract— This paper describes the coordinated results of several sets of measurements of two Leonid meteor fireballs over northern New Mexico at 1:32 and 3:06 MST, respectively, on the night of 1998 November 17. The measurements included visible band photometry on both events, as well as filtered 5890 Å all-sky images of the Na airglow. Also, for the 3:06 a.m. event, we obtained an infrasound measurement of the hydrodynamic yield. For the 1:32 a.m. event, we obtained a set of visible band charge-coupled device (CCD) camera images of the meteor train for times extending to 30 min after the initial impact. The measurement results have been combined to derive an optical efficiency for the intense early-time optical flash, and the total explosion yields and masses for both of the meteors. We have also done a set of numerical radiation, hydrodynamic, and chemistry computations to investigate the nature and distribution of the long-lasting airglow. We attribute the brightest visible airglow to atomic O 5577 Å line emission, with additional contributions from atomic Na emission and NO2 chemiluminescence. The near-infrared atmospheric bands of molecular O2 should be very strong as well. All of the band emissions are expected to show a hollow limb-brightened structure. 相似文献
56.
57.
正Dear Members of the Editorial Board,Contributors and Friends of EEEV,To commemorate the tenth anniversary of the Wenchuan earthquake disaster,the journal of Earthquake Erngineering and Engineering Vibratiorn will publish special sections with invited papers in 2018.We sincerely appreciate the contributions from the following experts:Professor Akira WADA,and Professor Kuo-Chun CHANG. 相似文献
58.
In general, geologically speaking, it has been noted that if the formation of coal took place during the Permo-Carboniferous period, its volatile matter will al ways be less than 30% when analized, and the contrary is usually the case for coal created during the Tertiary and Jurassic, these having more than 40%. 相似文献
59.
Fuel consumption in fisheries is a primary concern because of its effects on the environment and the costs incurred by fishermen. Many studies have been conducted to reduce the fuel consumption in fishing operations. Fuel consumption due to fishing gear during a fishing operation is generally related to the hydrodynamic resistance on the gear. This means that fuel consumption is proportional to the drag created by the towing speed. Based on numerical methods, this study suggests a new approach to reduce fuel consumption in fisheries. The results of the simulation are in good agreement with those of model experiments. The total as well as partial resistance forces on the gear are calculated by simulation. The simulation results suggest improved materials and gear structure for reducing the hydrodynamic forces on the gear while maintaining gear performance. The method for assessing the gear performance involves measuring the height and width of the net mouth. Furthermore, this study investigates the efficiency of a low-energy trawl from an economic point of view. The findings of this study will be useful in reducing greenhouse gas (GHG) emissions in fishing operations, and thereby contribute toward lowering fishing costs by saving fuel. 相似文献
60.
2008汶川地震之后,多个研究组对龙门山的新生代剥蚀历史进行了研究,但是在龙门山推覆构造带中段,剥蚀历史研究主要集中在彭灌杂岩,而彭灌杂岩东侧(即中央断裂下盘)的热年代学资料相对缺乏,其剥蚀历史还比较模糊.对于彭灌杂岩东侧岩体的新生代剥蚀历史研究,不仅可以了解龙门山推覆构造带的新生代断层活动历史,而且对于青藏高原东缘的新生代隆升机制具有重要约束作用.在前人热年代学研究基础上,在龙门山推覆构造带中段中央断裂和前山断裂附近补充了一些裂变径迹样品.采用外探测器法(external detector method)对样品进行裂变径迹分析,实验测试在台湾中正大学裂变径迹实验室完成.实验获得了6个锆石裂变径迹和6个磷灰石裂变径迹年龄.前山断裂上盘,AFT(磷灰石裂变径迹)年龄以小鱼洞断裂为界存在明显的差异,其中小鱼洞断裂以南的样品AFT年龄为39Ma,小鱼洞断裂以北的4个AFT年龄介于6—8 Ma之间.研究揭示出中央断裂和前山断裂的新生代活动性以NW向小鱼洞断裂为界存在较大差异:距今8Ma以来,小鱼洞断裂以北,中央断裂和前山断裂的平均垂向滑动速率分别为约0.1mm·a-1和约0.55mm·a-1;小鱼洞断裂以南,平均垂向滑动速率则分别为约0.55mm·a-1和约0.1mm·a-1.低温热年代学方法获得的断层新生代垂向滑动速率与汶川地震断层垂向同震位移分布基本一致.前山断裂(小鱼洞断裂以北)距今8 Ma以来北西-南东向水平缩短量达到8~12km,表明地壳缩短是造成龙门山抬升和剥蚀的重要因素之一.本研究结论不支持下地壳增厚模型对于龙门山隆升的解释. 相似文献