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   38851篇
  免费   628篇
  国内免费   240篇
测绘学   754篇
大气科学   2580篇
地球物理   7635篇
地质学   14063篇
海洋学   3545篇
天文学   8720篇
综合类   87篇
自然地理   2335篇
  2022年   257篇
  2021年   441篇
  2020年   499篇
  2019年   576篇
  2018年   1011篇
  2017年   1013篇
  2016年   1079篇
  2015年   582篇
  2014年   1034篇
  2013年   1851篇
  2012年   1191篇
  2011年   1629篇
  2010年   1441篇
  2009年   1797篇
  2008年   1630篇
  2007年   1688篇
  2006年   1556篇
  2005年   1058篇
  2004年   1074篇
  2003年   1112篇
  2002年   996篇
  2001年   868篇
  2000年   797篇
  1999年   724篇
  1998年   717篇
  1997年   723篇
  1996年   588篇
  1995年   572篇
  1994年   501篇
  1993年   453篇
  1992年   409篇
  1991年   424篇
  1990年   437篇
  1989年   391篇
  1988年   369篇
  1987年   400篇
  1986年   415篇
  1985年   508篇
  1984年   545篇
  1983年   542篇
  1982年   496篇
  1981年   454篇
  1980年   429篇
  1979年   408篇
  1978年   375篇
  1977年   384篇
  1976年   344篇
  1975年   353篇
  1974年   340篇
  1973年   370篇
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
231.
Geotectonics - The South Anyui Fold System was formed at the end of the Early Cretaceous at the site of a closed oceanic basin as a result of the collision of the Chukotka microcontinent with the...  相似文献   
232.
Astronomy Reports - An algorithm has been developed for finding the global minimum of a multidimensional error function by fitting model spectral maps into observed ones. Principal component...  相似文献   
233.
Ermash  A. A.  Pilipenko  S. V.  Mikheeva  E. V.  Lukash  V. N. 《Astronomy Reports》2021,65(12):1194-1210
Astronomy Reports - Within the framework of the model of the extragalactic background created earlier by the authors, the factors influencing the statistical properties of the confusion noise have...  相似文献   
234.
Mathematical Geosciences - Manually interpreting multivariate drill hole data is very time-consuming, and different geologists will produce different results due to the subjective nature of...  相似文献   
235.
Solar System Research - Ionizing radiation is one of the main factors that destroy biomolecules in extraterrestrial conditions. The effects of radiation depend on the conditions of the exposure...  相似文献   
236.
Izvestiya, Atmospheric and Oceanic Physics - We analyze our concepts about ocean dynamics and, in particular, internal waves. Our concepts have changed over the 50 years after the Polygon-70...  相似文献   
237.
Izvestiya, Atmospheric and Oceanic Physics - A method for retrieving sea wave spectra from space images of high spatial resolution has been developed for various conditions of wave generation based...  相似文献   
238.
Photometric properties of deep Tautenburg Schmidt plates in the UBV system over the whole field and over a wide range of stellar magnitudes are discussed. Different reduction models based on the calibration curve alone and with additional terms containing colour and plate coordinates are considered. With the filter-emulsion combinations used the Johnson UBV system can be reproduced quite well by the Tautenburg telescope. The accuracy of photometric data can be improved if geometrical terms are taken into account. For deep plates with a significant effect of background nebulosity a supplementary term is to be included in the reduction model. The polynomial coefficients vary in dependence on spectral bands and individual properties of each plate.  相似文献   
239.
In south Cumbria, Permo-Triassic breccias and conglomerates (‘brockram’) are exposed only at Rougholme Point on the Cartmel peninsula. In 1973 the Institute of Geological Sciences Humphrey Head borehole penetrated 257 m of brockram before entering probable Upper Carboniferous sediments. The brockram consists of pebbles of carbonate, chert and basalt in a matrix of haematite-stained quartz sand. Carbonate and chert fragments were derived from the upper part of the Carboniferous Limestone sequence exposed today nearby. Basalt clasts were derived from lavas, which appear to have cooled in a subaqueous environment, at least in part. They were locally derived and are the only certain evidence for Carboniferous volcanic activity in south Cumbria. As volcanic fragments increase in abundance towards the base of the borehole they must have been derived from the top of the succession being eroded and are probably of Brigantian age. Carbonate fragments were dolomitized soon after incorporation in the brockram, probably by saline fluids derived from the evaporative Zechstein Sea. The dolomitization was incomplete, leaving remnant limestone cores to clasts which were subsequently dissolved. The resultant vugs were infilled by dolomite, calcite and gypsum cements, which have been partially weathered from outcropping brockram, leaving hollow pebbles.  相似文献   
240.
Adaptation is a key concept in long‐term human adjustments to climate change. Despite the centrality of human decisions and actions in adaptation, much of the climate change literature is thin on humanities and social science which are the primary approaches for understanding human activity. This situation is particularly pronounced in Louisiana's discussions about its disappearing coast line where research has concentrated in understanding biophysical processes and solutions prioritize short‐term adaptations. This paper reviews the relationship of adaptation and long‐term transitions in the global change discussion and traces how disjointed adaptations in coastal Louisiana have contributed to a perilous environmental situation there. It proposes a shift from discrete adaptations to efforts that incorporate interrelated biophysical and human adaptations that can sustain long‐term transitions.  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