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   617篇
  免费   145篇
  国内免费   1159篇
测绘学   18篇
大气科学   214篇
地球物理   244篇
地质学   995篇
海洋学   190篇
综合类   201篇
自然地理   59篇
  2024年   47篇
  2023年   163篇
  2022年   55篇
  2021年   82篇
  2020年   75篇
  2019年   97篇
  2018年   53篇
  2017年   76篇
  2016年   63篇
  2015年   128篇
  2014年   201篇
  2013年   157篇
  2012年   49篇
  2011年   47篇
  2010年   53篇
  2009年   52篇
  2008年   59篇
  2007年   56篇
  2006年   67篇
  2005年   69篇
  2004年   56篇
  2003年   32篇
  2002年   27篇
  2001年   35篇
  2000年   41篇
  1999年   25篇
  1998年   9篇
  1997年   3篇
  1996年   5篇
  1995年   4篇
  1994年   2篇
  1993年   4篇
  1992年   5篇
  1991年   1篇
  1990年   5篇
  1989年   1篇
  1988年   3篇
  1986年   3篇
  1985年   1篇
  1984年   1篇
  1983年   2篇
  1980年   1篇
  1979年   2篇
  1976年   1篇
  1943年   1篇
  1941年   1篇
  1937年   1篇
排序方式: 共有1921条查询结果,搜索用时 15 毫秒
991.
中国北部辽东湾表层沉积物中PAHs源解析和生态风险评价   总被引:1,自引:0,他引:1  
研究于2014年和2015年对辽东湾表层沉积物中16种多环芳烃(PAHs)的来源和生态风险状况进行了调查和评估。辽东湾表层沉积物中16种PAHs的含量范围为88.5-347 ng/g,高值区主要分布在辽东湾中部海域。对辽东湾各站位沉积物中多环芳烃的含量进行中聚类分析结果表明,辽东湾的采样站位可分为两类,一类站位主要分布在辽东湾沉积物中部海域,另一类站位主要分布在受陆源污染较为严重的近岸海域。辽东湾表层沉积物中PAHs的来源为燃烧源和石油源的混合来源,其中燃烧源为主要来源。萘、苊、苊烯、菲、二苯并[a,h]蒽可能偶尔会引发有害生物效应;辽东湾表层沉积物为低致癌风险;辽东湾中部海域表层沉积物中PAHs的生态风险和毒性污染水平高于辽东湾近岸海域。  相似文献   
992.
Deep-water regions often have winds favorable for offshore wind turbines, and floating turbines currently show the greatest potential to exploit such winds. This work established proper scaling laws for model tests, which were then implemented in the construction of a model wind turbine with optimally designed blades. The aerodynamic, hydrodynamic, and elastic characteristics of the proposed new multi-column tension-leg-type floating wind turbine (WindStar TLP system) were explored in the wave tank testing of a 1:50 scale model at the State Key Laboratory of Ocean Engineering at Shanghai Jiao Tong University. Tests were conducted under conditions of still water, white noise waves, irregular waves, and combined wind, wave, and current loads. The results established the natural periods of the motion, damping, motion response amplitude operators, and tendon tensions of the WindStar TLP system under different environmental conditions, and thus could serve as a reference for further research.  相似文献   
993.
994.
1 IntroductionOstracodaisoneofthelargestgroupsoftheCrus-tacea (M artin and Davis, 2001), and the num bersofliving speciesofostracodesconsistof7 500. OneofthefrustratingaspectsforOstracodastudyisunstabili-tyofthehigherclassification status (Schram, 1986),w…  相似文献   
995.
Tethys tectonic system has experienced a long-term evolution history, including multiple Wilson cycles; thus, it is an ideal target for analyzing plate tectonics and geodynamics. Tethyan evolution is typically characterized by a series of continental blocks that separated from the Gondwana in the Southern Hemisphere, drifted northward, and collided and accreted with Laurasia in the Northern Hemisphere. During this process, the successive opening and closing of multistage Tethys oceans(e.g.,Proto...  相似文献   
996.
The Tethyan domain hosts the world’s most abundant hydrocarbon and Mississippi Valley-type(MVT) Pb-Zn resources. The relations among organic matter-rich sediments, MVT Pb-Zn mineralization, and the Tethyan tectonic evolution history are an important scientific issue. The data of paleogeographic reconstruction indicate that the Proto-, Paleo-, and NeoTethys oceans mainly lay in low latitude areas between 30°N and 45°S. The high temperature and precipitation and the lack of sea water overturning i...  相似文献   
997.
Seasonal differences of temperature are crucial components of the Earth’s climate system.However,the relatively short observational record,especially for East Asia,has limited progress in understanding seasonal differences.In this study,we identify ten tree-ring chronologies separately correlated with local winter(December-February)temperatures and twelve different tree-ring chronologies separately correlated with summer(June-August)temperatures across East Asia.Using these discrete seasonal tre...  相似文献   
998.
Polymetallic sulfides present in mid-ocean ridges(MORs) have become important strategic resources for humans, and a scientific metallogenic model is necessary for the investigation and exploration of these resources. Compared to fast-and slow-spreading MORs, ultraslow-spreading MORs show substantial differences in magma supply, tectonic activity, and oceanic crust structures. However, information on hydrothermal circulation and a metallogenic model related to sulfides along the ultraslow-spreadi...  相似文献   
999.
Since Shi et al. proposed that the climate in the drylands of Northwest China experienced a significant transition from a “warming and drying” trend to a “warming and wetting” trend in the 1980s, researchers have conducted numerous studies on the variations in precipitation and humidity in the region and even in arid Central Asia. In particular, the process of the “warming and wetting” trend by using obtained measurement data received much attention. However, there remain uncertainties about whe...  相似文献   
1000.
On September 5, 2022, a strong MS6.8 earthquake struck the Luding area in the Kangding-Moxi segment of the Xianshuihe fault zone, which is the northern boundary of the Sichuan-Yunnan rhombic block, causing considerable casualties. The Bamei-Kangding segment of the Xianshuihe fault zone, which is located only tens of kilometers away from the Luding earthquake, has hosted frequent moderate to strong earthquakes in history and is a dangerous earthquake-prone zone. Therefore, it is critical to inves...  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