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   5922篇
  免费   230篇
  国内免费   88篇
测绘学   168篇
大气科学   736篇
地球物理   1442篇
地质学   1975篇
海洋学   549篇
天文学   749篇
综合类   22篇
自然地理   599篇
  2021年   59篇
  2020年   64篇
  2019年   86篇
  2018年   124篇
  2017年   117篇
  2016年   156篇
  2015年   144篇
  2014年   202篇
  2013年   323篇
  2012年   242篇
  2011年   263篇
  2010年   191篇
  2009年   304篇
  2008年   285篇
  2007年   262篇
  2006年   220篇
  2005年   188篇
  2004年   196篇
  2003年   189篇
  2002年   181篇
  2001年   133篇
  2000年   136篇
  1999年   113篇
  1998年   107篇
  1997年   91篇
  1996年   84篇
  1995年   83篇
  1994年   74篇
  1993年   63篇
  1992年   60篇
  1991年   67篇
  1990年   64篇
  1989年   58篇
  1988年   55篇
  1987年   64篇
  1986年   43篇
  1985年   74篇
  1984年   82篇
  1983年   73篇
  1982年   70篇
  1981年   79篇
  1980年   66篇
  1979年   59篇
  1978年   41篇
  1977年   61篇
  1976年   70篇
  1975年   52篇
  1974年   61篇
  1973年   53篇
  1972年   29篇
排序方式: 共有6240条查询结果,搜索用时 781 毫秒
991.
Ohne Zusammenfassung  相似文献   
992.
Ohne Zusammenfassung  相似文献   
993.
Ohne Zusammenfassung  相似文献   
994.
995.
The records of two large stock and station agents, Loan & Mercantile Agency in Dunedin and Wright Stephenson in Invercargill, allowed us to track the timing, nature, magnitude and rate of landscape change in southern New Zealand between 1896 and 1920. This period extends from the final years of subdivision of large estates, and includes closer settlement, the shift from pastoral farming to intensive agriculture, growth of dairying, and increasing mechanisation of agriculture. These changes are reflected in clients’ annual expenditures on capital items such as fencing and building materials, tools and implements, materials for drains.  相似文献   
996.
997.
998.
The hydroclimatology of the southeastern USA (AL, GA, NC, SC, and TN) is analyzed from a holistic perspective, including multiple climate drivers. Monthly precipitation modeled by the PRISM group and runoff data (1952–2011) from 18 basins are analyzed using a single-field based principal component’s analysis. Results indicate that the Atlantic Multidecadal Oscillation and El Niño-Southern Oscillation are the main atmospheric drivers of hydroclimate variability in the region, sometimes operating at several months’ lag. Their influence is the strongest in the fall through spring, which corresponds with the dry season in the southern parts of the study area thereby increasing pressure on already limited water resources. The Arctic Oscillation, North Atlantic Oscillation, and Pacific-North American patterns vary on shorter-term bases, and also show a significant, but temporally more sporadic influence. Insight is also brought to the ongoing discussion, confirming the disassociation of the Arctic and North Atlantic Oscillation. Findings can be used in water resources forecasting, giving an indication of expected water volumes several months ahead.  相似文献   
999.
Avoiding dangerous climate change will require a rapid transition away from fossil fuels. By some estimates, global consumption and production of fossil fuels—particularly coal and oil—will need to end almost entirely within 50 years. Given the scale of such a transition, nations may need to consider policies that constrain growth in fossil fuel supplies in addition to those that reduce demand. Here, we examine the emissions implications of a supply-constraining measure that was rapidly gaining momentum in the United States (US) under the Obama administration: ceasing the issuance of new leases for fossil fuel extraction on federal lands and waters. Such a measure could reduce global carbon dioxide emissions by an estimated 280 million tons annually by 2030, comparable to that of other major climate policies adopted or considered by the Obama administration. Our findings suggest that measures to constrain fossil fuel supply—though not currently viable in a US Trump administration—deserve further consideration at subnational levels in the US or by other countries now, and by future US administrations.  相似文献   
1000.
Theoretical and Applied Climatology - The daily rainfall data at 13 stations over the Central Highlands (CH) Vietnam were collected for the period 1981–2014. Two different sets of criteria...  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