全文获取类型
收费全文 | 687篇 |
免费 | 12篇 |
国内免费 | 17篇 |
专业分类
测绘学 | 9篇 |
大气科学 | 43篇 |
地球物理 | 140篇 |
地质学 | 256篇 |
海洋学 | 53篇 |
天文学 | 139篇 |
自然地理 | 76篇 |
出版年
2021年 | 3篇 |
2020年 | 6篇 |
2019年 | 4篇 |
2018年 | 14篇 |
2017年 | 12篇 |
2016年 | 25篇 |
2015年 | 17篇 |
2014年 | 12篇 |
2013年 | 26篇 |
2012年 | 18篇 |
2011年 | 29篇 |
2010年 | 20篇 |
2009年 | 35篇 |
2008年 | 26篇 |
2007年 | 32篇 |
2006年 | 30篇 |
2005年 | 24篇 |
2004年 | 37篇 |
2003年 | 26篇 |
2002年 | 20篇 |
2001年 | 21篇 |
2000年 | 19篇 |
1999年 | 15篇 |
1998年 | 19篇 |
1997年 | 17篇 |
1996年 | 13篇 |
1995年 | 12篇 |
1994年 | 4篇 |
1993年 | 7篇 |
1992年 | 16篇 |
1991年 | 12篇 |
1990年 | 6篇 |
1989年 | 4篇 |
1988年 | 4篇 |
1987年 | 8篇 |
1986年 | 3篇 |
1985年 | 8篇 |
1984年 | 13篇 |
1983年 | 12篇 |
1982年 | 8篇 |
1981年 | 8篇 |
1980年 | 11篇 |
1979年 | 5篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1975年 | 9篇 |
1974年 | 7篇 |
1972年 | 3篇 |
1964年 | 2篇 |
排序方式: 共有716条查询结果,搜索用时 15 毫秒
711.
Theoretical and Applied Climatology - Atmospheric rivers (ARs) are channels of high water vapor flux that transport moisture from low to higher latitudes on synoptic timescales. In areas of... 相似文献
712.
Glen R. Harris David M. H. Sexton Ben B. B. Booth Mat Collins James M. Murphy 《Climate Dynamics》2013,40(11-12):2937-2972
This paper describes a Bayesian methodology for prediction of multivariate probability distribution functions (PDFs) for transient regional climate change. The approach is based upon PDFs for the equilibrium response to doubled carbon dioxide, derived from a comprehensive sampling of uncertainties in modelling of surface and atmospheric processes, and constrained by multiannual mean observations of recent climate. These PDFs are sampled and scaled by global mean temperature predicted by a Simple Climate Model (SCM), in order to emulate corresponding transient responses. The sampled projections are then reweighted, based upon the likelihood that they correctly replicate observed historical changes in surface temperature, and combined to provide PDFs for 20 year averages of regional temperature and precipitation changes to the end of the twenty-first century, for the A1B emissions scenario. The PDFs also account for modelling uncertainties associated with aerosol forcing, ocean heat uptake and the terrestrial carbon cycle, sampled using SCM configurations calibrated to the response of perturbed physics ensembles generated using the Hadley Centre climate model HadCM3, and other international climate model simulations. Weighting the projections using observational metrics of recent mean climate is found to be as effective at constraining the future transient response as metrics based on historical trends. The spread in global temperature response due to modelling uncertainty in the carbon cycle feedbacks is determined to be about 65–80 % of the spread arising from uncertainties in modelling atmospheric, oceanic and aerosol processes of the climate system. Early twenty-first century aerosol forcing is found to be extremely unlikely to be less than ?1.7 W m?2. Our technique provides a rigorous and formal method of combining several lines of evidence used in the previous IPCC expert assessment of the Transient Climate Response. The 10th, 50th and 90th percentiles of our observationally constrained PDF for the Transient Climate Response are 1.6, 2.0 and 2.4 °C respectively, compared with the 10–90 % range of 1.0–3.0 °C assessed by the IPCC. 相似文献
713.
Carolynn M. Harris James W. McClelland Tara L. Connelly Byron C. Crump Kenneth H. Dunton 《Estuaries and Coasts》2017,40(1):50-62
Shallow estuarine lagoons characterize >70 % of the eastern Alaskan Beaufort Sea coastline and, like temperate and tropical lagoons, support diverse and productive biological communities. These lagoons experience large variations in temperature (?2 to 14 °C) and salinity (0 to >45) throughout the year. Unlike lower latitude coastal systems, transitions between seasons are physically extreme and event-driven. On Arctic coastlines, a brief summer open-water period is followed by a 9-month ice-covered period that concludes with a late-spring sea ice breakup and intense freshwater run-off. From 2011 to 2014, we examined interannual variations in water column physical structure (temperature, salinity, and δ18O) in five lagoons that differ with respect to their degree of exchange with adjacent marine waters and magnitude of freshwater inputs. Temperature, salinity, and source water composition (calculated using a salinity and δ18O mixing model) were variable in space and time. During sea ice breakup in June, water column δ18O and salinity measurements showed that low salinity waters originated from meteoric inputs (50–80 %; which include river inputs and direct precipitation) and sea ice melt (18–51 %). Following breakup, polar marine waters became prevalent within a mixed water column over the summer open-water period within all five lagoons (26–63 %). At the peak of ice-cover extent and thickness in April, marine water sources dominated (75–87 %) and hypersaline conditions developed in some lagoons. Seasonal runoff dynamics and differences in lagoon geomorphology (i.e., connectivity to the Beaufort Sea) are considered key potential drivers of observed salinity and source water variations. 相似文献
714.
Ben Harte John J. Gurney Jeffrey W. Harris 《Contributions to Mineralogy and Petrology》1980,72(2):181-190
Olivine, orthopyroxene and garnet grains belonging to the peridotitic suite of mineral inclusions in natural diamonds typically show compositions poorer in Ca and Al and richer in Mg and Cr than the same minerals in peridotite nodules in kimberlite. Other features suggest the crystallisation of diamonds from magmas of kimberlitic affinities, and it is suggested that the genesis of peridotitic suite diamonds is linked with that of a CO2-bearing magma. It is shown that the generation of kimberlitic magma from common garnet-peridotite (with 5 wt.% clinopyroxene) in the presence of CO2 may rapidly remove by melting all Ca-rich solid phases (clinopyroxene and/or carbonate). Further melting may form liquids in equilibrium with olivine, orthopyroxene, and garnet with the distinctive compositions of the diamond inclusions. The amount of melting and CO2 necessary for the loss of clinopyroxene (and/or carbonate) are estimated at approximately 5.0 wt.% and 0.5 wt.% respectively. 相似文献
715.
Yuenyong Panjasawatwong Leonid V. Danyushevsky Anthony J. Crawford Keith L. Harris 《Contributions to Mineralogy and Petrology》1995,118(4):420-432
An experimental investigation of plagioclase crystallization in broadly basaltic/andesitic melts of variable Ca# (Ca/(Ca+Na)*100)
and Al# (Al/(Al+Si)*100) values and H2O contents has been carried out at high pressures (5 and 10 kbar) in a solid media piston-cylinder apparatus. The H2O contents of glasses coexisting with liquidus or near-liquidus plagioclases in each experiment were determined via an FTIR
spectroscopic technique. This study has shown that melt Ca# and Al#, H2O content and crystallization pressure all control the composition of liquidus plagioclase. Increasing melt Ca# and Al# increase
An content of plagioclase, whereas the effect of increasing pressure is the opposite. However, the importance of the role
played by each of these factors during crystallization of natural magmas varies. Melt Ca# has the strongest control on plagioclase
An content, but melt Al# also exerts a significant control. H2O content can notably increase the An content of plagioclase, up to 10 mol % for H2O-undersaturated melts, and 20 mol % for H2O-saturated melts. Exceptionally calcic plagioclases (up to An100) in some primitive subduction-related boninitic and related rocks cannot be attributed to the presence of the demonstrated
amounts of H2O (up to 3 wt %). Rather, they must be due to the involvement of extremely refractory (CaO/Na2O>18) magmas in the petrogenesis of these rocks. Despite the refractory nature of some primitive MORB glasses, none are in
equilibrium with the most calcic plagioclase (An94) found in MORB. These plagioclases were likely produced from more refractory melts with CaO/Na2O = 12–15, or from melts with exceptionally high Al2O3(>18%). Magmas of appropriate compositions to crystallize these most calcic plagioclases are sometimes found as melt inclusions
in near liquidus phenocrysts from these rocks, but are not known among wholerock or glass compositions. The fact that such
melts are not erupted as discrete magma batches indicates that they are effectively mixed and homogenized with volumetrically
dominant, less refractory magmas. The high H2O contents (∼ 6 wt%) in some high-Al basaltic arc magmas may be responsible for the existence of plagioclases up to An95 in arc lavas. However, an alternative possibility is that petrogenesis involving melts with abnormally high CaO/Na2O values (> 8) may account for the presence of highly anorthitic plagioclases in these rocks.
Received: 31 August 1993 / Accepted: 20 May 1994 相似文献
716.
基于微扰理论,研究了内部存在一个同轴圆柱扰动体时圆柱谐振腔共振频率的偏移问题.其中,圆柱谐振腔的边侧面是刚性的,上下底面应力自由.经过推导,得出了圆柱扰动体存在时谐振腔的声势与共振频率的表达式.在此基础上,分析了谐振腔与圆柱扰动体各种参数对谐振腔共振频率的影响.数值模拟结果表明,谐振腔的共振频率受扰动体在谐振腔中的位置影响较大.圆柱谐振腔的共振频率在圆柱扰动体居中时是最大值,并且其共振频率对扰动体的声速敏感;当扰动体在谐振腔两端时,谐振腔共振频率是最小值,并且其对扰动体的密度敏感.最后,通过数值模拟结果和实验测量结果之间的对比,发现两者的基本变化趋势是吻合的. 相似文献