全文获取类型
收费全文 | 302篇 |
免费 | 45篇 |
国内免费 | 368篇 |
专业分类
测绘学 | 12篇 |
大气科学 | 99篇 |
地球物理 | 76篇 |
地质学 | 278篇 |
海洋学 | 122篇 |
天文学 | 45篇 |
综合类 | 39篇 |
自然地理 | 44篇 |
出版年
2024年 | 14篇 |
2023年 | 48篇 |
2022年 | 24篇 |
2021年 | 27篇 |
2020年 | 18篇 |
2019年 | 9篇 |
2018年 | 17篇 |
2017年 | 24篇 |
2016年 | 12篇 |
2015年 | 29篇 |
2014年 | 95篇 |
2013年 | 47篇 |
2012年 | 15篇 |
2011年 | 16篇 |
2010年 | 24篇 |
2009年 | 24篇 |
2008年 | 24篇 |
2007年 | 26篇 |
2006年 | 25篇 |
2005年 | 35篇 |
2004年 | 21篇 |
2003年 | 15篇 |
2002年 | 17篇 |
2001年 | 13篇 |
2000年 | 29篇 |
1999年 | 8篇 |
1998年 | 6篇 |
1997年 | 9篇 |
1996年 | 10篇 |
1995年 | 6篇 |
1994年 | 10篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1991年 | 3篇 |
1990年 | 7篇 |
1989年 | 2篇 |
1987年 | 1篇 |
排序方式: 共有715条查询结果,搜索用时 31 毫秒
61.
Wen-Feng Luo Jun Yang Lang Cui Xiang Liu Zhi-Qiang Shen 《中国天文和天体物理学报》2007,7(5):611-619
We present quasi-simultaneous VLBI images of the GHz-Peaked-Spectrum radio source OQ 208 obtained with the Very Long Baseline Array at 1.4,1.7,2.3,5.0,8.4,15.4GHz and the European VLBI Network at 6.7 GHz.The low frequency(1.4,1.7 and 2.3GHz)ob- servations reveal a weak and extended steep-spectrum component at about 30mas away at position angle-110°,which may be a remnant emission.The radio structure of OQ 208 con- sists of two mini-lobes at 5.0,6.7,8.4 and 15.4 GHz.Our spectral analysis further confirms that the southwest lobe undergoes free-free absorption and finds that the free-free absorption is stronger in the inner region.By fitting the 8.4 GHz images from 1994 to 2005,we obtain a separation speed of 0.031±0.006 mas yr~(-1)between the two mini-lobes.This indicates a jet proper motion of 0.105±0.020 c and a kinematic age of 219±42 yr for the radio source. 相似文献
62.
Phylogenomic analysis of transcriptomic sequences of mitochondria and chloroplasts for marine red algae (Rhodophyta) in China 总被引:1,自引:1,他引:0
JIA Shangang WANG Xumin QIAN Hao LI Tianyong SUN Jing WANG Liang YU Jun LI Xingang YIN Jinlong LIU Tao WU Shuangxiu 《海洋学报(英文版)》2014,33(2):86-93
The chloroplast and mitochondrion of red algae (Phylum Rhodophyta) may have originated from different endosymbiosis. In this study, we carried out phylogenomic analysis to distinguish their evolutionary lin-eages by using red algal RNA-seq datasets of the 1 000 Plants (1KP) Project and publicly available complete genomes of mitochondria and chloroplasts of Rhodophyta. We have found that red algae were divided into three clades of orders, Florideophyceae, Bangiophyceae and Cyanidiophyceae. Taxonomy resolution for Class Florideophyceae showed that Order Gigartinales was close to Order Halymeniales, while Order Graci-lariales was in a clade of Order Ceramials. We confirmed Prionitis divaricata (Family Halymeniaceae) was closely related to the clade of Order Gracilariales, rather than to genus Grateloupia of Order Halymeniales as reported before. Furthermore, we found both mitochondrial and chloroplastic genes in Rhodophyta under negative selection (Ka/Ks〈1), suggesting that red algae, as one primitive group of eukaryotic algae, might share joint evolutionary history with these two organelles for a long time, although we identified some dif-ferences in their phylogenetic trees. Our analysis provided the basic phylogenetic relationships of red algae, and demonstrated their potential ability to study endosymbiotic events. 相似文献
63.
64.
65.
Impact of Anthropogenic Heat Release on Regional Climate in Three Vast Urban Agglomerations in China简 总被引:5,自引:0,他引:5
We simulated the impact of anthropogenic heat release (AHR) on the regional climate in three vast city agglomerations in China using the Weather Research and Forecasting model with nested high-resolution modeling.Based on energy consumption and high-quality land use data,we designed two scenarios to represent no-AHR and current-AHR conditions.By comparing the results of the two numerical experiments,changes of surface air temperature and precipitation due to AHR were quantified and analyzed.We concluded that AHR increases the temperature in these urbanized areas by about 0.5℃-1℃,and this increase is more pronounced in winter than in other seasons.The inclusion of AHR enhances the convergence of water vapor over urbanized areas.Together with the warming of the lower troposphere and the enhancement of ascending motions caused by AHR,the average convective available potential energy in urbanized areas is increased.Rainfall amounts in summer over urbanized areas are likely to increase and regional precipitation patterns to be altered to some extent. 相似文献
66.
How many sutures in the southern Central Asian Orogenic Belt:Insights from East Xinjiang-West Gansu(NW China)? 总被引:1,自引:0,他引:1
Wenjiao Xiao ;Chunming Han ;Wei Liul ;Bo Wan ;Ji'en Zhang ;Song jian Ao ;Zhiyong Zhang ;Dongfang Song ;Zhonghua Tian ;Jun Luo 《地学前缘(英文版)》2014,5(4):525-536
How ophiolitic mèlanges can be defined as sutures is controversial with regard to accretionary orogenesis and continental growth.The Chinese Altay,East junggar,Tianshan,and Beishan belts of the southern Central Asian Orogenic Belt(CAOB) in Northwest China,offer a special natural laboratory to resolve this puzzle.In the Chinese Altay,the Erqis unit consists of ophiolitic melanges and coherent assemblages,forming a Paleozoic accretionary complex.At least two ophiolitic melanges(Armantai,and Kelameili) in East Junggar,characterized by imbricated ophiolitic melanges,Nb-enriched basalts,adakitic rocks and volcanic rocks,belong to a Devonian-Carboniferous intra-oceanic island arc with some Paleozoic ophiolites,superimposed by Permian arc volcanism.In the Tianshan,ophiolitic melanges like Kanggurtag,North Tianshan,and South Tianshan occur as part of some Paleozoic accretionary complexes related to amalgamation of arc terranes.In the Beishan there are also several ophiolitic melanges,including the Hongshishan,Xingxingxia-Shibangjing,Hongliuhe-Xichangjing,and Liuyuan ophiolitic units.Most ophiolitic melanges in the study area are characterized by ultramafic,mafic and other components,which are juxtaposed,or even emplaced as lenses and knockers in a matrix of some coherent units.The tectonic settings of various components are different,and some adjacent units in the same melange show contrasting different tectonic settings.The formation ages of these various components are in a wide spectrum,varying from Neoproterozoic to Permian.Therefore we cannot assume that these ophiolitic melanges always form in linear sutures as a result of the closure of specific oceans.Often the ophiolitic components formed either as the substrate of intra-oceanic arcs,or were accreted as lenses or knockers in subduction-accretion complexes.Using published age and paleogeographic constraints,we propose the presence of (1) a major early Paleozoic tectonic boundary that separates the Chinese Altay-East Junggar multiple subduction system 相似文献
67.
Please?refer?to?the?attachment(s)?for?more?details. 相似文献
68.
69.
ZHANG Chao DENG Jun YANG Liqiang WANG Zhongliang GUO Linnan LIU Yu ZHANG Liang LIU Yue LIU Xiangdong 《地质学报》2014,88(Z2):1584-1585
Please?refer?to?the?attachment(s)?for?more?details. 相似文献
70.
正1 Introduction The main production of Yabulai salt lake was original salt and recycled salt many years ago.After decade’s production,the sale lake resource is more and more deficient.Glauber's salt and magnesium salt are concentrated in brine now.It could affect the quality of the salt.In recent years,research had done much work to 相似文献