首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   680篇
  免费   27篇
  国内免费   34篇
测绘学   10篇
大气科学   70篇
地球物理   236篇
地质学   160篇
海洋学   148篇
天文学   56篇
综合类   31篇
自然地理   30篇
  2023年   3篇
  2022年   7篇
  2021年   12篇
  2020年   16篇
  2019年   9篇
  2018年   18篇
  2017年   28篇
  2016年   34篇
  2015年   27篇
  2014年   40篇
  2013年   48篇
  2012年   40篇
  2011年   51篇
  2010年   52篇
  2009年   45篇
  2008年   51篇
  2007年   39篇
  2006年   20篇
  2005年   30篇
  2004年   13篇
  2003年   18篇
  2002年   24篇
  2001年   3篇
  2000年   9篇
  1999年   7篇
  1998年   12篇
  1997年   3篇
  1996年   2篇
  1995年   8篇
  1994年   2篇
  1993年   4篇
  1992年   8篇
  1991年   4篇
  1990年   5篇
  1989年   2篇
  1988年   4篇
  1986年   2篇
  1983年   3篇
  1982年   2篇
  1981年   3篇
  1980年   3篇
  1979年   4篇
  1978年   2篇
  1977年   4篇
  1976年   2篇
  1974年   3篇
  1962年   2篇
  1954年   3篇
  1949年   1篇
  1933年   1篇
排序方式: 共有741条查询结果,搜索用时 15 毫秒
81.
We present the results of a study of galaxy activity in two merging binary clusters (A168 and A1750) using the Sloan Digital Sky Survey (SDSS) data supplemented with the data in the literature. We have investigated the merger histories of A168 and A1750 by combining the results from a two-body dynamical model and X-ray data. In A168, two subclusters appear to have passed each other and to be coming together from the recent maximum separation. In A1750, two major subclusters appear to have started interaction and to be coming together for the first time. We find an enhanced concentration of the galaxies showing star formation (SF) or active galactic nuclei (AGN) activity in the region between two subclusters in A168, which were possibly triggered by the cluster merger. In A1750, we do not find any galaxies with SF/AGN activity in the region between two subclusters, indicating that two major subclusters are in the early stage of merging.  相似文献   
82.
The few known γ-ray binary systems are all associated with variable radio and X-ray emission. The TeV source HESS J0632+057, apparently associated with the Be star MWC 148, is plausibly a new member of this class. Following the identification of a variable X-ray counterpart to the TeV source we conducted Giant Metrewave Radio Telescope (GMRT) and Very Large Array (VLA) observations in 2008 June–September to search for the radio counterpart of this object. A point-like radio source at the position of the star is detected in both 1280-MHz GMRT and 5-GHz VLA observations, with an average spectral index, α, of ∼0.6. In the VLA data there is significant flux variability on ∼month time-scales around the mean flux density of ≈0.3 mJy. These radio properties (and the overall spectral energy distribution) are consistent with an interpretation of HESS J0632+057 as a lower power analogue of the established γ-ray binary systems.  相似文献   
83.
84.
Acta Geochimica - In this study, we investigated the chemical composition of dissolved solids in the Ca River basin, North-Central Vietnam. Water samples were collected from August 2017 to July...  相似文献   
85.
Kerimov  V. Yu.  Leonov  M. G.  Osipov  A. V.  Mustaev  R. N.  Hai  Vu Nam 《Geotectonics》2019,53(1):42-59
Geotectonics - The paper considers the origin of hydrocarbon accumulations within the Pre-Cenozoic basement of the Vietnam shelf. It is shown that the formation of hydrocarbon deposits is...  相似文献   
86.
Ku  Jeong Eun  Lee  Sung Il  Kim  Doo Nam 《Ocean Science Journal》2021,56(4):413-423
Ocean Science Journal - Age and growth of southern bluefin tuna (SBT, Thunnus maccoyii) were estimated based on otoliths collected by Korean tuna longline vessels in the Atlantic and Indian Oceans...  相似文献   
87.
88.
F.J.TSENG  C.S.Ho 《地质学报》1949,(Z1):127-134,181,182
I. INTRODUCTION Bordering the SW margin of the Red Basin of Szechuan runs a roughly N-S mountain range which includes such mountains as Washan, Omeishan and Talliangshan (Pl. I) and for the sake of convenience is designated with the name of Liangshan Range. Among these mountains only the geology of the Omeishan region is fairly well known in consequence of the works done by many a geologist; of the Washan region, though had been visited by  相似文献   
89.
To efficiently and effectively monitor and mitigate air pollution in the urban environment, it is of paramount importance to integrate into a unified whole air pollutant concentration databases coming from different sources including the ground-based stations, mobile sensors, remote sensing, atmospheric-chemical-transport models and social media for the analysis and unraveling of the complex air pollution processes in space and time. This study constructs and implements for the first time a prototype of the fully integrated air pollution decision support system (APDSS) that put together in an integrated manner all relevant multi-scale, multi-type and multi-source data for decision-making on urban air pollution. The prototype contains the main system that handles the multi-source, multi-type and multi-scale databases, queries, visualization and data mining algorithms and the integrated modules that individually and holistically capitalize on the power of the ground-based stations, ground and aerial mobile sensors, satellite-borne remote-sensing technologies, atmospheric-chemical-transport models and social media. It renders a solid scientific foundation and system development methodology for the study of the spatiotemporal air pollution profiles crucial to the mitigation of urban air pollution. Real-life applications of the prototype are employed to illustrate the functionality of the APDSS.  相似文献   
90.
Sub-cellular perturbations in the lysosomal compartment of molluscan haemocytes were examined in mussels (Perna viridis), collected along a pollution gradient. The neutral red technique was validated using a well defined contamination gradient among indigenous populations from five stations along Tolo Harbour, Hong Kong. Condition indices (shell length:dry tissue wt) and tissue metal concentrations were also measured in an attempt to identify a relationship between contamination level and adverse physiological effects. Correlations were found between lysosomal retention time and condition along the pollution gradient. There were significant differences between mussels collected from stations on offshore islands and those collected from inner harbour sites (p < 0.05). There was, however, little correlation between metal concentrations and retention time or condition (p > 0.05).  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号