全文获取类型
收费全文 | 446篇 |
免费 | 12篇 |
国内免费 | 2篇 |
专业分类
测绘学 | 10篇 |
大气科学 | 24篇 |
地球物理 | 97篇 |
地质学 | 171篇 |
海洋学 | 28篇 |
天文学 | 82篇 |
自然地理 | 48篇 |
出版年
2021年 | 6篇 |
2020年 | 11篇 |
2019年 | 6篇 |
2018年 | 6篇 |
2017年 | 10篇 |
2016年 | 12篇 |
2015年 | 7篇 |
2014年 | 12篇 |
2013年 | 25篇 |
2012年 | 14篇 |
2011年 | 10篇 |
2010年 | 15篇 |
2009年 | 25篇 |
2008年 | 12篇 |
2007年 | 12篇 |
2006年 | 15篇 |
2005年 | 12篇 |
2004年 | 11篇 |
2003年 | 13篇 |
2002年 | 17篇 |
2001年 | 6篇 |
2000年 | 8篇 |
1999年 | 5篇 |
1998年 | 6篇 |
1997年 | 6篇 |
1996年 | 6篇 |
1995年 | 5篇 |
1992年 | 8篇 |
1989年 | 3篇 |
1988年 | 4篇 |
1987年 | 3篇 |
1984年 | 7篇 |
1983年 | 6篇 |
1982年 | 3篇 |
1977年 | 4篇 |
1976年 | 7篇 |
1975年 | 9篇 |
1974年 | 5篇 |
1973年 | 6篇 |
1970年 | 4篇 |
1962年 | 4篇 |
1961年 | 3篇 |
1960年 | 6篇 |
1959年 | 4篇 |
1956年 | 3篇 |
1955年 | 4篇 |
1952年 | 3篇 |
1940年 | 3篇 |
1937年 | 4篇 |
1936年 | 3篇 |
排序方式: 共有460条查询结果,搜索用时 375 毫秒
451.
Geoffrey M. Morrison Sonia Yeh Anthony R. Eggert Christopher Yang James H. Nelson Jeffery B. Greenblatt Raphael Isaac Mark Z. Jacobson Josiah Johnston Daniel M. Kammen Ana Mileva Jack Moore David Roland-Holst Max Wei John P. Weyant James H. Williams Ray Williams Christina B. Zapata 《Climatic change》2015,131(4):545-557
452.
T. Marke W. Mauser A. Pfeiffer G. Zängl D. Jacob U. Strasser 《Environmental Earth Sciences》2014,71(11):4849-4868
In the current study, two regional climate models (MM5 and REMO) driven by different global boundary conditions (the ERA40 reanalysis and the ECHAM5 model) are one-way coupled to the uncalibrated hydrological process model PROMET to analyze the impact of global boundary conditions, dynamical regionalization and subsequent statistical downscaling (bilinear interpolation, correction of subgrid-scale variability and combined correction of subgrid-scale variability and bias) on river discharge simulation. The results of 12 one-way coupled model runs, set up for the catchment of the Upper Danube (Central Europe) over the historical period 1971–2000, prove the expectation that the global boundaries applied to force the RCMs strongly influence the accuracy of simulated river discharge. It is, however, noteworthy that all efficiency criteria in case of bias corrected MM5 simulations indicate better performance under ERA40 boundaries, whereas REMO-driven hydrological simulations better correspond to measured discharge under ECHAM5 boundaries. Comparing the hydrological results achievable with MM5 and REMO, the application of bias-corrected MM5 simulations turned out to allow for a more accurate simulation of discharge, while the variance in simulated discharge in most cases was better reflected in case of REMO forcings. The correction of subgrid-scale variability within the downscaling of RCM simulations compared to a bilinear interpolation allows for a more accurate simulation of discharge for all model configurations and all discharge criteria considered (mean monthly discharge, mean monthly low-flow and peak-flow discharge). Further improvements in the hydrological simulations could be achieved by eliminating the biases (in terms of deviations from observed meteorological conditions) inherent in the driving RCM simulations, regardless of the global boundary conditions or the RCM applied. In spite of all downscaling and bias correction efforts described, the RCM-driven hydrological simulations remain less accurate than those achievable with spatially distributed meteorological observations. 相似文献
453.
The Cambrian sediments in Howth and Ireland's Eye to the northeast of Dublin have been mapped and the submarine deltaic Censure Group and the overlying Nose of Howth Group, which consists of interbedded turbidites and olistostromes, have been distinguished. Large scale sedimentary disruption has accompanied detachment of quartzitic sandstone beds in the Censure Group, where the bases of detached blocks have slump features while their tops generally do not. This contrasts with the chaotic sedimentary breccias in the olistostromes of the Nose of Howth Group. Blocks in the Censure and Nose of Howth Groups are up to 450 m and 700 m across respectively. The turbidies have come from the southeast and east whereas the slumping appears to have been generated from the southwest. Slumping during sedimentation was followed closely by large-scale folding and sliding of sedimentary or tectono-sedimentary origin, and the bulk appearance of the sediments is due to these sedimentary and tectono-sedimentary mechanisms. The main structure is an easterly facing, steep plunging syncline which locally is associated with a poorly preserved cleavage. This structure predated the main penetrative cleavage which is not axial planar to it. 相似文献
454.
阿拉斯加北极地区的工程设计和施工经验及教训 总被引:6,自引:7,他引:6
阿拉斯加北极地区位于布鲁克斯山以北, 白令海峡以东的北坡地区, 属北极海洋性气候区. 区内寒冷( -10 ~ -6 ℃)、连续多年冻土厚度多在200~300 m, 局部达700 m. 地表湖塘和冰楔多边形广泛分布. 阿拉斯加北极地区的工程建筑活动主要为海军部和商业石油勘探、开发和运输服务. 从20世纪40年代以来, 尽管有不少的曲折和教训, 但成功和可以借鉴的经验很多. 最成功的例子当数普如道湾油气田开发、阿里亚斯卡输油管道工程及其相应的环境保护措施. 工程师为了成功和经济地在北极地区修筑和运行工程设施, 必须从"冷"处着想, 并付诸计划和行动. 设计和施工的工程师必须保持实事求是、不断创新精神, 而不拘泥于中纬度地区的教育、培训, 或行业传统. 从工程勘察、设计到施工阶段, 工程师和从事环境研究的科学家必须密切合作. 工程师需要知道环境参数, 制约因素和可利用的机会; 环境科学家需要知道工程师的施工设计和问题, 理解工程限制条件、设备工作能力, 以及备选方案的经济学问题. 这些相互理解只能在密切合作中形成, 并能创造工程经济效益和奇迹. 相似文献
455.
Unconventional PGE occurrences and PGE mineralization in the Great Dyke: metallogenic and economic aspects 总被引:4,自引:0,他引:4
B. Stribrny F. -W. Wellmer K. -P. Burgath T. Oberthür M. Tarkian T. Pfeiffer 《Mineralium Deposita》2000,35(2-3):260-280
Platinum group elements (PGE) are strategic materials because 96–99% of the world production is derived from just five mining
districts and because they cannot be replaced as catalysts in many chemical processes. In order to lessen the strategic character
of PGE, both conventional deposits and unconventional PGE mineralizations were investigated in an attempt to locate viable
deposits which would diversify the supplier base. In the Great Dyke, conventional PGE mineralization occurs in the form of
pristine sulfide ores mined underground and oxidic surface ores. New observations such as bimodal distributions of the PGE
in the Main Sulfide Zone (MSZ), elevated Pt/Pd ratios in the oxidized MSZ compared to the sulfidic part and distinct differences
between the platinum group mineral (PGM) assemblages of the MSZ and stream sediments of adjacent rivers emphasize the fact
that even though the Great Dyke seems to be the second or third largest PGE occurrence in the world, the complicated PGE distributions
and supergene redistributions should be kept in mind during planning and mine operation. Investigations of unconventional
PGE occurrences in ophiolites, Alaskan-type intrusions, porphyry copper deposits and in the Kupferschiefer show that economically
exploitable PGE concentrations can be expected in a broader variety of host rocks than considered favourable in the past.
In the Albanian Mirdita ophiolite average contents of 860 ppb Pt and 60 ppb Pd were detected. Flotation concentrates of porphyry
copper deposits, for example from Mamut, Malaysia, Santo Tomas, Philippines, Elacite, Bulgaria, and Ok Tedi, Papua New Guinea,
contain between 827 and 1860 ppb Pd + Pt. In selected profiles of the Polish Kupferschiefer average contents of 255 ppb Pt,
94 ppb Pd, 2.4 ppm Au and 13.0 ppm Ag were analysed. The distribution of the PGE resources in the world and the annual production
rates, however, underline the fact that the chances for a significant change in the supplier base are relatively low. The
Bushveld Complex will remain the largest producer, followed by Noril'sk-Talnakh, Sudbury and Stillwater. If the operations
in the Great Dyke reach their planned capacities, the Great Dyke will rank in third place among the PGE-producing deposits
in the world.
Received: 12 September 1998 / Accepted: 7 December 1999 相似文献
456.
Ben De Mol Max Kozachenko Andy Wheeler Hugo Alvares Jean-Pierre Henriet Karine Olu-Le Roy 《International Journal of Earth Sciences》2007,96(1):103-120
High-resolution seismic profiles, swath bathymetry, side-scan sonar data and video imageries are analysed in this detailed
study of five carbonate mounds from the Belgica mound province with special emphasis on the well-surveyed Thérèse Mound. The
selected mounds are located in the deepest part of the Belgica mound province at water depths of 950 m. Seismic data illustrate
that the underlying geology is characterised by drift sedimentation in a general northerly flowing current regime. Sigmoidal
sediment bodies create local slope breaks on the most recent local erosional surface, which act as the mound base. No preferential
mound substratum is observed, neither is there any indication for deep geological controls on coral bank development. Seismic
evidence suggests that the start-up of the coral bank development was shortly after a major erosional event of Late Pliocene–Quaternary
age. The coral bank geometry has been clearly affected by the local topography of this erosional base and the prevailing current
regime. The summits of the coral banks are relatively flat and the flanks are steepest on their upper slopes. Deposition of
the encased drift sequence has been influenced by the coral bank topography. Sediment waves are formed besides the coral banks
and are the most pronounced bedforms. These seabed structures are probably induced by bottom current up to 1 m/s. Large sediment
waves are colonised by living corals and might represent the initial phase of coral bank development. The biological facies
distribution of the coral banks illustrate a living coral cap on the summit and upper slope and a decline of living coral
populations toward the lower flanks. The data suggest that the development of the coral banks in this area is clearly an interaction
between biological growth processes and drift deposition both influenced by the local topography and current regime. 相似文献
457.
Ground temperatures from four of the seven extensively studied highway cross-sections near Gulkana/Glennallen,Alaska during 1954~1962,were chosen to better understand the impacts of highway construction on warm permafrost.Both the thawing of permafrost and seasonal frost action impacted on road surface stability for about 6 years until the maximum summer thaw reached about 3 m in depth.Seasonal frost action caused most of the ensuing stability problems.Unusually warm summers and the lengths of time required to re-freeze the active layer were far more important than the average annual air temperatures in determining the temperatures of the underlying shallow permafrost,or the development of taliks.The hypothesized climate warming would slightly and gradually deepen the active layer and the developed under-lying talik,but its effect would be obscured by unusually warm summers,by warmer than usual winters,and by the vari-able lengths of time of the zero curtains.At least one period of climate mini-cooling in the deeper permafrost during the early 20th century was noted. 相似文献
458.
The simplest magnetic model for the upper 20 km of crust in central Ireland is of two layers. A thin, weakly magnetic upper layer carrying a number of magnetic bodies that can be related to surface geology overlies a magnetic crustal zone whose gross magnetization increases towards the north. The deeper trace of the lapetus Suture in central Ireland forms the boundary between a more magnetic northern crustal area and a less magnetic southern area. A pre-Carboniferous major dextral offset of this suture boundary occurs in the Limerick area. The suture is traced beneath the Dingle peninsula in the far south-west of Ireland. In east-central Ireland, between the Iapetus Suture and Southern Upland Line, the crust contains a large, south-dipping magnetic body with no surface expression, which produces the Virginia magnetic anomaly. The development of magnetic bodies — in particular, volcanic rocks of Carboniferous age — has been controlled by regional stress patterns. The major volcanic centre at Limerick lies at the intersection of two major Caledonian block fault systems just to the north of the surface trace of the Hercynian Front. 相似文献
459.
Juliane Scheder Friederike Bungenstock Kristin Haynert Anna Pint Frank Schlütz Peter Frenzel Achim Wehrmann Helmut Brückner Max Engel 《第四纪科学杂志》2022,37(1):71-85
In light of global warming and rising relative sea level (RSL), detailed reconstructions of RSL histories and their controlling processes are essential in order to manage coastal-protection challenges. This study contributes to unravelling Holocene RSL change on the East Frisian North Sea coast in high resolution and with a new approach for the German Bight. For the first time, a transfer function (vertical error: 29.7 cm ? ~11% of the mean tidal range) for RSL change based on a combined training set of benthic foraminifers and ostracods from the back-barrier tidal basin of Spiekeroog is applied to the Holocene record of the back-barrier tidal basin of Norderney. The resulting RSL curve for the Norderney tidal basin is corrected for decompaction and shows a deceleration in RSL rise between 6000 and 5000 cal bp. The smallest possible error envelope (~1 m) results from the good suitability of salt-marsh layers between 5000 and 4000 cal bp. The RSL curve provides an approach towards the closure of the common data gap of peat-based curves for the southern North Sea related to a lack of basal peats in the youngest age range, and verifies regional differences in glacial isostatic adjustment. 相似文献
460.