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   56697篇
  免费   1002篇
  国内免费   574篇
测绘学   1424篇
大气科学   4732篇
地球物理   11473篇
地质学   20448篇
海洋学   4624篇
天文学   12067篇
综合类   129篇
自然地理   3376篇
  2021年   396篇
  2020年   461篇
  2019年   486篇
  2018年   1154篇
  2017年   1143篇
  2016年   1458篇
  2015年   855篇
  2014年   1395篇
  2013年   2802篇
  2012年   1551篇
  2011年   2096篇
  2010年   1809篇
  2009年   2423篇
  2008年   2091篇
  2007年   1973篇
  2006年   2037篇
  2005年   1590篇
  2004年   1571篇
  2003年   1518篇
  2002年   1512篇
  2001年   1356篇
  2000年   1370篇
  1999年   1118篇
  1998年   1079篇
  1997年   1157篇
  1996年   974篇
  1995年   927篇
  1994年   891篇
  1993年   741篇
  1992年   761篇
  1991年   729篇
  1990年   744篇
  1989年   706篇
  1988年   681篇
  1987年   777篇
  1986年   714篇
  1985年   840篇
  1984年   925篇
  1983年   958篇
  1982年   867篇
  1981年   807篇
  1980年   797篇
  1979年   725篇
  1978年   720篇
  1977年   663篇
  1976年   594篇
  1975年   587篇
  1974年   641篇
  1973年   614篇
  1972年   390篇
排序方式: 共有10000条查询结果,搜索用时 62 毫秒
951.
952.
953.
954.
In order to provide new data on the neotectonics and geodynamic properties of western Syria, studies of marine terraces have been carried out. The most attention was paid to the lower terraces in the range of 3–5 to 30–35 m above sea level, because they have more complete distributions along the shore. The lower terraces were examined along the coastal area from Tartus to Latakia, and along the carbonate cliff on Arwad Island. Seven 230Th/U dates for these terraces are in the range of 85–130 ka, suggesting the age interval of the last interglacial (MIS 5). New dates on the lower terraces provide a basis for stratigraphical and geomorphological interpretation as well as neotectonic reconstruction. According to the geomorphological data and lithological composition of those terraces, two main uplifted blocks can be established. One coincides with the Latakia block, and another corresponds to the western margin of the Banias volcanic plateau. These blocks are divided by a subsided structure corresponding to the Nahr el Kebir graben. The amplitude of neotectonic uplifting in the Latakia and Banias blocks reaches 15–20 m for the Late Pleistocene.  相似文献   
955.
956.
957.
The history of the discovery of hot gas in galaxies is briefly reviewed, and the main properties of this gas described, emphasizing the need to refine these properties, in particular, the mass of the gas. It is proposed to do this via observations of the Sunyaev-Zel’dovich (SZ) effect due to hot gas in the coronas of elliptical galaxies. The absolute and relative perturbations of the spectrum of the cosmic microwave background (CMB) radiation due to scattering of the CMB photons by electrons with a Maxwellian energy distribution are calculated. The possibility of observing the SZ effect is demonstrated using three elliptical galaxies as examples. The kinematic SZ effect arising due to the peculiar motions and rotations of the galaxies is also accessible to observations. Together with X-ray data, such observations would enable refinement of the properties of gas in galaxies, and also yield additional information about the rotation of galaxies, possible accretion flows in the galactic gas, and hot galactic winds.  相似文献   
958.
The intensity of postmagmatic processes in the Botuobinskaya pipe kimberlites was estimated from the calculated content of normative secondary quartz (Q). Several simple algorithms are proposed to calculate the Q content from chemical analyses of kimberlites. Ten groups of altered kimberlites have been recognized from the Q contents. The contents of MgO, some trace elements, and LREE in the groups, the contents of Cr and Ca of crimson garnets, the diamond contents of kimberlites, and the average weight of diamonds decrease as the Q content increases. It is shown that the negative SiO2–MgO correlation is the most effective indicator of the postmagmatic alteration of kimberlites. As the degree of their secondary alteration increases, the kimberlites transform into an assemblage of quartz and clay minerals enriched in some trace elements and almost completely lacking REE and diamonds.  相似文献   
959.
Relations between indoor and soil gas radon were experimentally studied in villages of the Baikal region. On the basis of the obtained data, the soil-to-indoor radon ratio was calculated, which can be used for prediction of radon pollution in buildings of the same kind.  相似文献   
960.
Climatic changes in southeastern Transbaikalia in the Middle and Late Holocene and their influence on alluvial sedimentation environments are reconstructed from the results of study of the Ilya floodplain sediments (Alkhanai National Park). At the beginning of the Subboreal period, the regional climate became more arid, which led to a significant increase in steppe species communities in the landscapes. Intense climate aridization also took place at the beginning and at the end of the Subatlantic period of the Holocene. The alluvial-sedimentation rate increased during the weakening of aridization and decreased during cooling and the intensification of aridization. The obtained regional data are compared with data on the adjacent areas and the global climatic changes in the Northern Hemisphere.  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