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   251541篇
  免费   5235篇
  国内免费   3239篇
测绘学   6921篇
大气科学   18954篇
地球物理   52463篇
地质学   87076篇
海洋学   21162篇
天文学   54575篇
综合类   990篇
自然地理   17874篇
  2021年   2155篇
  2020年   2571篇
  2019年   2822篇
  2018年   3331篇
  2017年   2999篇
  2016年   5597篇
  2015年   4183篇
  2014年   6896篇
  2013年   14196篇
  2012年   6396篇
  2011年   7629篇
  2010年   6669篇
  2009年   9329篇
  2008年   8194篇
  2007年   7618篇
  2006年   9617篇
  2005年   7650篇
  2004年   7590篇
  2003年   7068篇
  2002年   6689篇
  2001年   5976篇
  2000年   5885篇
  1999年   4808篇
  1998年   4845篇
  1997年   4631篇
  1996年   4214篇
  1995年   4310篇
  1994年   3999篇
  1993年   3742篇
  1992年   3500篇
  1991年   3525篇
  1990年   3620篇
  1989年   3327篇
  1988年   3169篇
  1987年   3707篇
  1986年   3251篇
  1985年   4121篇
  1984年   4632篇
  1983年   4307篇
  1982年   4231篇
  1981年   3850篇
  1980年   3601篇
  1979年   3435篇
  1978年   3439篇
  1977年   3225篇
  1976年   2966篇
  1975年   2902篇
  1974年   2864篇
  1973年   3056篇
  1972年   1989篇
排序方式: 共有10000条查询结果,搜索用时 93 毫秒
991.
992.
993.
994.
995.
996.
997.
Abstract

Sea-level allowances at 22 tide-gauge sites along the east coast of Canada are determined based on projections of regional sea-level rise for the Representative Concentration Pathway 8.5 (RCP8.5) from the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5) and on the statistics of historical tides and storm surges (storm tides). The allowances, which may be used for coastal infrastructure planning, increase with time during the twenty-first century through a combination of mean sea-level rise and the increased uncertainty of future projections with time. The allowances show significant spatial variation, mainly a consequence of strong regionally varying relative sea-level change as a result of glacial isostatic adjustment (GIA). A methodology is described for replacement of the GIA component of the AR5 projection with global positioning system (GPS) measurements of vertical crustal motion; this significantly decreases allowances in regions where the uncertainty of the GIA models is large. For RCP8.5 with GPS data incorporated and for the 1995–2100 period, the sea-level allowances range from about 0.5?m along the north shore of the Gulf of St. Lawrence to more than 1?m along the coast of Nova Scotia and southern Newfoundland.  相似文献   
998.
The impacts of AMSU-A and IASI (Infrared Atmospheric Sounding Interferometer) radiances assimila-tion on the prediction of typhoons Vicente and Saola (2012) are studied by using the ensemble transform ...  相似文献   
999.
Identifying regions sensitive to external radiative changes, including anthropogenic (sulphate aerosols and greenhouse gases) and natural (volcanoes and solar variations) forcings, is important to formulate actionable information at multi-year time-scales. Internally-generated climate variability can overcome this radiative forcing, especially at regional level, so that detecting the areas for this potential dominance is likewise critical for decadal prediction. This work aims to clarify where each contribution has the largest effect on North Atlantic sea surface temperature (SST) predictions in relation to the Atlantic multi-decadal variability (AMV). Initialized decadal hindcasts and radiatively-forced historical simulations from the fifth phase of the Climate Model Intercomparison Project are analysed to assess multi-year skill of the AMV. The initialized hindcasts reproduce better the phase of the AMV index fluctuations. The radiatively-forced component consists of a residual positive trend, although its identification is ambiguous. Initialization reduces the inter-model spread when estimating the level of AMV skill, thus reducing its uncertainty. Our results show a skilful performance of the initialized hindcasts in capturing the AMV-related SST anomalies over the subpolar gyre and Labrador Sea regions, as well as in the eastern subtropical basin, and the inability of the radiatively-forced historical runs to simulate the horseshoe-like AMV signature over the North Atlantic. Initialization outperforms empirical predictions based on persistence beyond 1–4 years ahead, suggesting that ocean dynamics play a role in the AMV predictability beyond the thermal inertia. The initialized hindcasts are also more skilful at reproducing the observed AMV teleconnection to the West African monsoon. The impact of the start date frequency is also described, showing that the standard of 5-year interval between start dates yields the main features of the AMV skill that are robustly detected in hindcasts with yearly start date sampling. This work updates previous studies, complementing them, and concludes that skilful initialized multi-model forecasts of the AMV-related climate variability can be formulated, improving uninitialized projections, until 3–6 years ahead.  相似文献   
1000.
A set of micro pulse lidar(MPL)systems operating at 532 nm was used for ground-based observation of aerosols in Shanghai in 2011.Three typical particulate pollution events(e.g.,haze)were examined to determine the evolution of aerosol vertical distribution and the planetary boundary layer(PBL)during these pollution episodes.The aerosol vertical extinction coefficient(VEC)at any given measured altitude was prominently larger during haze periods than that before or after the associated event.Aerosols originating from various source regions exerted forcing to some extent on aerosol loading and vertical layering,leading to different aerosol vertical distribution structures.Aerosol VECs were always maximized near the surface owing to the potential influence of local pollutant emissions.Several peaks in aerosol VECs were found at altitudes above 1 km during the dust-and bioburning-influenced haze events.Aerosol VECs decreased with increasing altitude during the local-polluted haze event,with a single maximum in the surface atmosphere.PM2.5 increased slowly while PBL and visibility decreased gradually in the early stages of haze events;subsequently,PM2.5 accumulated and was exacerbated until serious pollution bursts occurred in the middle and later stages.The results reveal that aerosols from different sources impact aerosol vertical distributions in the atmosphere and that the relationship between PBL and pollutant loadings may play an important role in the formation of pollution.  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