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   23096篇
  免费   189篇
  国内免费   143篇
测绘学   360篇
大气科学   1218篇
地球物理   4383篇
地质学   9042篇
海洋学   2249篇
天文学   5298篇
综合类   44篇
自然地理   834篇
  2022年   265篇
  2021年   435篇
  2020年   395篇
  2019年   464篇
  2018年   950篇
  2017年   868篇
  2016年   887篇
  2015年   370篇
  2014年   778篇
  2013年   1292篇
  2012年   910篇
  2011年   1103篇
  2010年   1060篇
  2009年   1222篇
  2008年   1053篇
  2007年   1224篇
  2006年   1069篇
  2005年   571篇
  2004年   534篇
  2003年   542篇
  2002年   567篇
  2001年   514篇
  2000年   411篇
  1999年   334篇
  1998年   323篇
  1997年   332篇
  1996年   255篇
  1995年   261篇
  1994年   237篇
  1993年   182篇
  1992年   209篇
  1991年   181篇
  1990年   195篇
  1989年   187篇
  1988年   156篇
  1987年   182篇
  1986年   170篇
  1985年   205篇
  1984年   198篇
  1983年   197篇
  1982年   188篇
  1981年   172篇
  1980年   162篇
  1979年   183篇
  1978年   158篇
  1977年   142篇
  1976年   133篇
  1975年   136篇
  1974年   125篇
  1973年   166篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
This paper addresses the geochemical features of the noble metal disseminated sulfide and Timagnetite mineralization in the rocks of the Kalar group of autonomous gabbro-anorthosite massifs. The investigations suggest that this mineralization was formed in two stages. The first stage is related to the gabbroanorthosites proper and may be promising for low-sulfide PGE mineralization as well as PGE-bearing Ti-magnetite mineralization, while the second stage is linked to the ultrabasic intrusions associated with copper-nickel or chromite mineralization accompanying by PGE. The horizons of low-sulfide mineralization in the gabbro-anorthosites and copper-nickel mineralization in the dunite-pyroxenites are characterized by the Pd predominance over Pt, while the Cr-bearing and Ti-magnetite ores show the Pt predominance over Pd.  相似文献   
92.
We have estimated the upper and lower limits of sunspot activity, in terms of active day fraction during the Maunder minimum (1645–1710), using raw information on individual daily observations (Hoyt and Schatten, 1998). Establishing the relation between the sunspot activity and active day fraction after 1850, we evaluate the upper limit of annual group sunspot number during the deep Maunder minimum (1645–1700) which does not exceed 4. The earlier finding of a dominant 22-year periodicity during the Maunder minimum is verified and shown to be robust. Also we confirm that the start of the Maunder minimum was very abrupt.  相似文献   
93.
94.
95.
Based on the spore-pollen data, the mineral composition of clay rocks, analyzed structures and facies, and a general paleogeographic analysis, the sedimentation conditions and landscapes of islands located during the Late Bajocian in the region of the present-day the Crimean Mountains have been reconstructed. It is shown that the sublatitudinally elongated insular land zone had a width of 30 km, the heights of the islands were no more than 1 km, with steep mudflow-affected northern slopes and with an extensive river system on the southern slopes.  相似文献   
96.
Doklady Earth Sciences - This paper discusses sources of significant errors that occur in the course of determination of the primary environmental standard for natural waters: the maximum...  相似文献   
97.
Properly designed precast concrete cladding could potentially provide lateral stiffness, ductility, and energy dissipation for an overall building structure, especially during earthquakes. This paper describes a set of advanced connections that take advantage of the interaction between facade panels and structure (mainly due to horizontal interstorey drift) to dissipate energy, thereby reducing the response of the main structure. The results of an experimental program to characterize the hysteretic behaviour of advanced connections are presented. Design equations for the advanced connections are then calibrated against the test results, and the corresponding design charts are presented. It is anticipated that this research will lead to innovative ways of viewing the entire cladding system of a building.  相似文献   
98.
Gromov  A. O.  Nikiforov  I. I. 《Astronomy Letters》2021,47(6):357-376
Astronomy Letters - Techniques for solving the problem of constructing a Stäckel model by generalizing the potential from the equatorial plane to the entire space are considered. The initial...  相似文献   
99.
Izvestiya, Atmospheric and Oceanic Physics - The central part of the Malouralsky volcanic–plutonic belt, which includes the Manyukuyu–Vorchatinsky ore cluster, is analyzed using...  相似文献   
100.
Izvestiya, Atmospheric and Oceanic Physics - The results of the fractal analysis of a drainage network reconstructed using a digital elevation model and the structural and geomorphological analysis...  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