全文获取类型
收费全文 | 279篇 |
免费 | 51篇 |
国内免费 | 97篇 |
专业分类
测绘学 | 30篇 |
大气科学 | 100篇 |
地球物理 | 29篇 |
地质学 | 102篇 |
海洋学 | 72篇 |
天文学 | 4篇 |
综合类 | 29篇 |
自然地理 | 61篇 |
出版年
2024年 | 1篇 |
2023年 | 6篇 |
2022年 | 17篇 |
2021年 | 25篇 |
2020年 | 20篇 |
2019年 | 30篇 |
2018年 | 19篇 |
2017年 | 15篇 |
2016年 | 22篇 |
2015年 | 19篇 |
2014年 | 12篇 |
2013年 | 24篇 |
2012年 | 22篇 |
2011年 | 16篇 |
2010年 | 16篇 |
2009年 | 17篇 |
2008年 | 24篇 |
2007年 | 8篇 |
2006年 | 15篇 |
2005年 | 14篇 |
2004年 | 7篇 |
2003年 | 5篇 |
2002年 | 7篇 |
2001年 | 6篇 |
2000年 | 7篇 |
1999年 | 9篇 |
1998年 | 10篇 |
1997年 | 2篇 |
1996年 | 5篇 |
1995年 | 5篇 |
1994年 | 4篇 |
1993年 | 1篇 |
1992年 | 4篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1988年 | 3篇 |
1987年 | 3篇 |
1958年 | 1篇 |
排序方式: 共有427条查询结果,搜索用时 15 毫秒
1.
In model inter-comparisons one major obstacle is the format of the reported data. To facilitate the analysis of the results from the different models they should all be reported in the same format. This requires that the format is flexible enough to be easily implemented into the different land surface schemes. It should also be fault tolerant and allow a few consistence checks to avoid erroneous data to be submitted. The present note describes such a format developed for the PILPS project. After discussing the aim of this new format we present the routines which are used to write and read data. Finally two applications are described which allow the user to perform a number of consistency checks on the data. 相似文献
2.
参考鳗鲡等鱼类线粒体 DNA序列进行了中国花鲈线粒体 DNA细胞色素 b基因片断的引物设计、PCR扩增及其序列测定。得到中国花鲈的碱基序列为 4 10 bp,其 A、T、G、C含量分别为 10 1bp(2 4 .6 3% )、112 bp(2 7.32 % )、72 bp(17.56 % )、12 5bp(30 .4 9% ) ,与鳗鲡等其他鱼类相同基因片断序列碱基含量相似。 相似文献
3.
4.
树木年轮与其根部土壤化学元素含量的相关性 总被引:5,自引:0,他引:5
运用树木年轮学方法研究了北京南郊土壤环境中元素含量随时间序列演变的规律。依据吸收系数研究了相同土壤类型上生长的不同树种对12种化学元素的吸收状况,结果表明不同树种对元素的吸收情况不同。Zn、Cd和P3个元素吸收系数较高。对杨树年轮及其根部土壤中9种化学元素(Na、K、Cu、Zn、As、Sr、Cd、Ba、Pb)的相关性研究结果表明,年轮中元素的含量与其根土中对应元素的含量呈正相关。采用对数线性相关模式(1gC’=a 1gC+b),根据逐年年轮中Cu、Zn、As、Cd、Ba、Pb 6种化学元素的含量,反演6种元素在土壤中的逐年(1982-2004年)演变状况。本技术方法能为追溯近代城市化几十年以来的环境污染变迁历史、预测未来污染演变趋势提供更为丰富和科学的信息。 相似文献
5.
Based on remote sensing information sources including B/W aerial photos of 1983, pseudo-color aerial photos of 1992 and JERS-1/OPS VNIR image of 1996, vegetation types of Yingbazha, in the middle reaches of the Tarim River Basin in Xinjiang, China are mapped using ARC/INFO and related software. The changes in vegetation areas and distribution conditions are analyzed. As a result of natural and human influences, vegetation changes have temporal and spatial characteristics. According to the principles of landscape ecology and geographical information science, the landscape changes are indicated. Moreover, the remote sensing and GIS techniques are integrated to study vegetation and its landscape. 相似文献
6.
We present a numerical simulation of drag partition over rough surfaces. A computational fluid dynamics model is applied with high resolution to simulatingturbulent flows over arrays of roughness elements positioned on asmooth surface. The skin drag on the surface and the pressure drag on the roughnesselements are computed. The simulated drag partition compares well with wind-tunnelmeasurements and theoretical estimates for similar rough surfaces. This confirms that the computational approach offers an alternative to wind-tunnel and field experiments in studying drag and drag partition. The model is then applied to studying drag partition over rough surfaces with various roughness configurations. It is shown that drag partition depends not only on the magnitude of the roughness frontal area but also on the sizes and arrangement of roughness elements, because (1) the pressure drag coefficient is sensitive to roughness-element dimensions and (2) the arragement of roughness elements lead to different interferences of turbulent wakes. The impact ofthe latter factor is not insignificant. 相似文献
7.
云南省东北部拱王山第四纪冰川遗迹研究 总被引:7,自引:6,他引:7
云南省东北部的拱王山海拔3100m以上的山地发生过第四纪冰川作用,典型的冰川遗迹集中分布在轿子山峰附近和妖精塘-牛洞坪两个地区,遗存的冰川地貌主要有冰斗,冰蚀岩盆和侧碛堤。根据冰川地貌的组合特征,以及它们生成的先后顺序,将拱王山第四纪冰川作用划分为末次冰期的倒数第二期冰期。 相似文献
8.
In the geological evolution of the Tarim Basin, many transgressions and relictions happened. So there have been plentiful sources of salt. Moreover, because of uttermost drought, a lot of salt has been deposited. It is possible to find potash salt in this area. In our fieldwork, we have found salt and brine in western Tarim Basin. Based on a geological survey and the characteristics of sedimentary facies and paleogeography, this paper deals with the geochemical parameters and discusses the possibility of formation of potash salt in terms of the chemical analyses of samples collected from western Tarim Basin. Results of brine analysis lead to some conclusions: most of these salt brines have eluviated from very thick halite beds, mainly chloridetype salt and this kind of halite does not reach the stage of potash deposition in all aspects; WKSL (Wukeshalu) occupies a noticeable place, and we should attach importance to this district because there have been some indicators of the occurrence of potash deposits as viewed from the contents of Br and K. Finally, low Br contents are recognized in the Tarim Basin as a result of salt aggradation, and this point of view has been proved by the results of this experiment and the data available. It cannot depend upon the index of Br to judge the evolution stage of halite. We must look for other facies of potash except marine facies. 相似文献
9.
WU Yaping ZHU Yuanlin GUO Chunxiang SU Qiang & MA Wei . School of Civil Engineering Lanzhou Jiaotong University Lanzhou China . State Key Laboratory of Frozen Soil Engineering Cold Arid Regions Environmental Engineering Research Institute Chinese Academy of Sciences Lanzhou China 《中国科学D辑(英文版)》2005,48(7)
In the construction of Qinghai-Tibet railway,to avoid diseases caused by frost heave and thaw col-lapse of frozen ground,besides the normal bridges over the rivers,a lot of dry bridge structures have been built to replace subgrade in the regions of high tem-perature and high ice content frozen soil.So,the problems on forming mechanism of bearing capacity of pile foundation in cold regions already become one of hot spot problems in frozen soil engineering.Freezing force and frost heave force ar… 相似文献
10.
Correlation Fractal and Multifractal Characteristics of Seismic Activity in the Taiwan Area, China 总被引:2,自引:0,他引:2
XU Jiandong HUANG Jianf WEI Fuquan YAN Yunpeng LI Yaping LIN Chien-te Institute of Geology China Earthquake Administration Beijing Chin Earthquake Administration of Fujian Province Fuzhou Fujian China China Aero Geophysical Survey Remote Sensing for Land Resources Beijing China Leader University Tainan Taiwan China 《《地质学报》英文版》2005,79(2):225-232
Based on the analysis of newly collected data of plate tectonics, distribution of active faults and crustal deformation, the Taiwan area is divided into two seismic regions and six seismic belts. Then, correlation fractal dimensions of all the regions and belts are calculated, and the fractal characteristics of hypocenteral distribution can be quantitatively analyzed. Finally, multifractal dimensions Dq and f(α) are calculated by using the earthquake catalog of the past 11 years in the Taiwan area. This study indicates that (1) there exists a favorable corresponding relationship between spatial images of seismic activity described with correlation fractal dimension analysis and tectonic settings; (2) the temporal structure of earthquakes is not single but multifractal fractal, and the pattern of Dq variation with time is a good indicator for predicting strong earthquake events. 相似文献