全文获取类型
收费全文 | 362篇 |
免费 | 51篇 |
国内免费 | 51篇 |
专业分类
测绘学 | 16篇 |
大气科学 | 38篇 |
地球物理 | 102篇 |
地质学 | 164篇 |
海洋学 | 30篇 |
天文学 | 13篇 |
综合类 | 37篇 |
自然地理 | 64篇 |
出版年
2024年 | 5篇 |
2023年 | 8篇 |
2022年 | 13篇 |
2021年 | 17篇 |
2020年 | 13篇 |
2019年 | 11篇 |
2018年 | 13篇 |
2017年 | 16篇 |
2016年 | 22篇 |
2015年 | 14篇 |
2014年 | 26篇 |
2013年 | 19篇 |
2012年 | 26篇 |
2011年 | 22篇 |
2010年 | 23篇 |
2009年 | 20篇 |
2008年 | 20篇 |
2007年 | 11篇 |
2006年 | 4篇 |
2005年 | 15篇 |
2004年 | 8篇 |
2003年 | 10篇 |
2002年 | 17篇 |
2001年 | 5篇 |
2000年 | 7篇 |
1999年 | 16篇 |
1998年 | 9篇 |
1997年 | 4篇 |
1996年 | 9篇 |
1995年 | 13篇 |
1994年 | 6篇 |
1993年 | 7篇 |
1992年 | 9篇 |
1991年 | 8篇 |
1990年 | 7篇 |
1989年 | 3篇 |
1988年 | 3篇 |
1987年 | 1篇 |
1985年 | 1篇 |
1982年 | 2篇 |
1958年 | 1篇 |
排序方式: 共有464条查询结果,搜索用时 0 毫秒
101.
44 samples of the Jilin meteorite were analyzed by various laboratories for spallogenic, radiogenic, and trapped rare gases. A non-uniform distribution has been found for the rare gases of different origins. There have been found correlations among the spallogenic rare gases, with apparent depth effects. 43 samples were analyzed for their cosmogenic radionuclides60Co,26Al,36Cl,40K,53Mn,54Mn, and22Na. Correlations have been found between60Co and53Mn and between60Co and21Ne. The Jilin meteorite has a complex history of cosmic-ray irradiation. According to the two-stage model and the other fragments have a burying depth two stages,T 1=11 m.y. andT 2=0.3 m.y. The burying depth of all samples in the parent body can be obtained by the content of21Ne. Jilin meteorite No. 1 is located 20–142 cm from the surface, No. 4 ranges from 106–134 cm, and the other fragments have a burying depth between 15 and 150 cm. The equation of the reference plane for the surface of the 1-stage Jilin meteoroid is 0.24x+0.81y+0.53z+0.5=0. Use can also be made of60Co to determine the burying depth of all samples in the 2-stage Jilin meteoroid (under a geometry of 4π), and further to restore the preatmospheric form and size of the parent body. During its atmospheric passage, the Jilin had an ablation rate of ca. 30%. On the basis of the two-stage model and the concentration of21Ne and60Co in the samples, we propose a scheme to restore the relative position of all samples in the parent body. 12 sample-distribution regions can be sketched out. Also can be restored the relative position of all the samples in the parent body during the two stages. 相似文献
102.
Song Xuexin Xu Qingsheng Guo Yuemin Mao Xueying Ouyang Hong Institute of Mineral Deposits Chinese Academy of Geological Sciences Beijing Institute of High Energy Physics Chinese Academy of Sinices Beijing 《《地质学报》英文版》1997,71(3):263-272
REE ratios and patterns for massive pyrite ore and massive cuprous pyrite ore ofthe Baiyinchang orefield are quite similar to those for quartz keratophyritic tuff and quartzalbitophyre of the same orefield. However, massive cuprous pyrite ore of the Ashele Cu-Zn de-posit is similar to basalt-diabase of the same district in REE geochemistry. Comparison of theChinese VMS ores with those from Rio Tinto, Spain and Que River, Australia, in REEgeochemistry has been made. REE ratios and patterns of bedded-massive and massive ores ofthe Changba-Lijiagou Zn-Pb deposit, the second largest SEDEX deposit in China are similarto those of their host rocks, the Qinling shales of Devonian age and the Changba adamellite.The three types of ore and their host rocks of the Dongshengmiao pyrite (pyrrhotite)-Zn-Pbdeposit have parallel REE ratios and patterns. 相似文献
103.
Summary Two numerical experiments were performed for sensitivity study of surface albedo, one was a control run in which the albedo values for snow-free surfaces were prescribed as constant; the other was a sensitivity run in which an albedo with seasonal variation was incorporated into the model show that the simulation of precipitation is sensitive to the surface albedo variations, especially those over Eastern Asia and the Sahara. Changes in surface albedo also have an impact on the monthly mean sea level pressure, especially on the July-mean Western Pacific subtropical high. Surface air temperature decreased over most of the Eastern Asia but increases over most of the Antarctica in July.With 6 Figures 相似文献
104.
Chen Xuezhong Yin Xiangchu Aki K Ouyang H Jin A. Song Zhiping and Wang YucangCenter tor Analysis Prediction SSB Beijing ChinaSouthern California Eanhquake Center University of Southern California Los Angeles USAInstitute of Geophysics SSB Beijing China 《中国地震研究》1996,(4)
The load/unload response ratio YQ with the geophysical parameter coda Q-1 of the crust as response is denned in this study.The variation in YQ-1 before and after the Northridge earthquake of January 17,1994(California)has been investigated by using the data of coda Q-1 with frequencies of 1.5,3.0,6.0,12.0,and 24.0 Hz in the Southern California from 1987 to 1994.It can be found that YQ-1 for coda waves with all frequencies,the frequency of 12.0 Hz excluded,ascended to a certain extent prior to the occurrence of the rnainshock and returned to normality after the main shock. 相似文献
105.
Time and tectonic setting of the Xixiang Group: Constraints from zircon U-Pb geochronology and geochemistry 总被引:4,自引:0,他引:4
The present paper reports the research development in the timing and tectonic setting of the Xixiang Group, northwestern margin
of the Yangtze block. U-Pb concordant ages of (946 ± 18) Ma and (904±18) Ma of zircons were obtained from the upper and lower
units of the Xixiang volcanic succession, respectively. Elemental and Nd isotope characteristics show that the volcanic suite
has the affinities of arc island magmatism as well as an evolution trend of tectonic setting from front-arc to back-arc. The
volcanic rocks suffered from some extensive post-stage tectono-thermal events, resulting in the resetting of their Rb-Sr isotopic
system. 相似文献
106.
1INTRODUCTIONErgodichypothesisisoneofthebasicconceptsofmoderngeomorphology.Itsuggeststhatundercertaincircumstancessamplinginspacecanbeequivalenttosamplingthroughtime;andthatspace-timetransformationsarepermissibleasaworkingtool.Thisisbasedontheassumptionthat,whenindividualmembersofapopulationoflandformsarechangingregularlythroughtime,thespatialfrequencyofoccurrenceofgiventypesoflandformsisinverselyproportionaltotheirrateofchange(Chorley,etal.,1985).TheconceptofthecycleofDavis'erosioninwhi… 相似文献
107.
地理1和选择性必修1课程内容要求之间的关系为联系基础上的进阶。整体联系体现在太阳辐射和地球自身特点共同作用下的自然带地域分异规律形成过程,是必修地理1和选择性必修1隐含的学科逻辑线索。这条内容线索也是理解“必修”二字的关键。在“必修”的基础上看“选择性”,地理1和选择性必修1内容要求之间的进阶,体现在内容构成上,从现象到规律、从单一要素到要素综合;在学习水平上,从“识记”、“领会”,提升到“领会”、“分析”水平。地理1和选择性必修1内容要求之间的联系与进阶,要求教师树立教学设计的整体意识,包括课程内容的结构化分析和教学目标的分层设计,从而在整体把握学科知识体系的基础上,有一条清晰的逐级递进、螺旋上升体现学习进阶过程的教学“路线图”。 相似文献
108.
109.
The rapid development of data mining provides a new method for water resource management, hydrology and hydroinformatics research. In the paper, based on data mining theory and technology, we analyse hydrological daily discharge time series of the Shaligunlanke Station in the Tarim River Basin in China from the year 1961 to 2000. Firstly, according to the four monthly statistics, namely mean monthly discharge, monthly maximum discharge, monthly amplitude and monthly standard deviation, K‐mean clustering was used to segment the annual process of the daily discharge. The clustering result showed that the annual process of the daily discharge can be divided into five segments: snowmelt period I (April), snowmelt period II (May), rainfall period I (June–August), rainfall period II (September) and dry period (October–December and January–March). Secondly, dynamic time warping (DTW), which is a different distance metric method from the traditional Euclidian distance metric, was used to look for similarities in the discharge process. On the basis of the similarity matrix, the similar discharge processes can be mined in each period. Thirdly, agglomerative hierarchical clustering was used to cluster and discover the discharge patterns in terms of the autoregressive model. It was found that the discharge had a close relationship with the temperature and the precipitation, and the discharge processes were more similar under the same climatic condition. Our study shows that data mining is a feasible and efficient approach to discover the hidden information in the historical hydrological data and mining the implicative laws under the hydrological process. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
110.
美国PBO计划:钻孔应变仪台网遭遇挑战 总被引:2,自引:0,他引:2
PBO(Plate Boundary Observatory)计划专门设计了一批钻孔应变仪台.网,在数百米距离内,安装2~3台仪器,以研究钻孔应变仪如何响应构造活动的信号,以及局部因素会造成何种干扰.本文收集了6个这样的台网的资料,给出了所有仪器数年的记录曲线,并对观测结果显示的地壳应变场做了简要的分析对比,发现6个试... 相似文献