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31.
A 1.2 m snow pit was recovered on July 29th, 2009 from the Bogda Glacier, eastern Tianshan (天山). The sample site temperature of -9.6 ℃ indicates that the unique glaciochemical re-cord was well preserved and suitable for the reconstruction of air pollution levels in this previously un-explored region. Samples were analyzed for major ions (Na+, K+, Ca2+, Mg2+, NH4+, Cl-, SO42-, NO3-, HCOO-, and CH3COO-). NO3- and SO42- were characterized by significant high levels of pollution con-centration. Most air masses ...  相似文献   
32.
Magmatic rocks from the pre-Mesozoic basements of the Sambuco and Maggia nappes have been dated by U–Pb zircon ages with the LA-ICPMS technique. Several magmatic events have been identified in the Sambuco nappe. The mafic banded calc-alkaline suite of Scheggia is dated at 540 Ma, an age comparable to that of mafic rocks in the Austroalpine Silvretta nappe. The Sasso Nero peraluminous augengneiss has an age of 480–470 Ma, like many other “older orthogneisses” in Alpine basement units. It hosts a large proportion of inherited zircons, which were dated around 630 Ma, a Panafrican age indicating the Gondwanan affiliation of the Sambuco basement. The calc-alkaline Matorello pluton yielded ages around 300 Ma, similar to numerous Late Carboniferous intrusions in other basement units of the Lower Penninic (Monte Leone, Antigorio, Verampio) and Helvetic domains (Gotthard and other External Crystalline Massifs). Associated lamprophyric dykes are slightly younger (300–290 Ma), like similar dykes sampled in gneiss blocks included in the sedimentary cover of the underlying Antigorio nappe (290–285 Ma). The Cocco granodiorite and Rüscada leucogranite, both intruding the basement of the neighbouring Maggia nappe, yielded ages of ca. 300–310 Ma, identical within errors to the age of the Matorello pluton. They are significantly older than former age determinations. This age coincidence, coupled with remarkable petrologic similarities between the Cocco and Matorello granodiorites, strongly suggests paleogeographic proximity of the Sambuco and Maggia nappes in Late Carboniferous times. In recent publications these two nappes have been interpreted as belonging to distinct Mesozoic paleogeographic domains: “European” for Sambuco and “Briançonnais” for Maggia, separated by the “Valais” oceanic basin. In this case, the similarity of the Matorello and Cocco intrusions would demonstrate the absence of any significant transcurrent movement between these two continental domains. Alternatively, according to a more traditional view, Sambuco and Maggia might belong to a single large Alpine tectonic unit.  相似文献   
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简平  杨巍然 《地质学报》2000,74(3):259-264
熊店榴辉岩产于大别山西部苏家河构造混杂岩带内,是典型的高压一超高压中温榴辉岩。作者应用岩学结合阴极发光和扫描电镜方法,较系统地研究了榴辉岩中锆石在岩石中的赋存状态、内部结构及表面特征。锆石主要产于石榴子石等变质矿物内,与主晶界面清晰,具有多晶面等变质锆石特有形貌特征,内部均或发育变质生长结构,从而说明它们是变质作用的产物。SHRIMP分析表明,锆石^206Pb/^238U年龄为335~424Ma,  相似文献   
35.
Three major types of Ordovician intrusive-related gold-copper deposits are recognized in central-west New South Wales, Australia: porphyry, skarn and high sulphidation epithermal deposits. These deposits are mainly distributed within two Ordovician volcano-intrusive belts of the Lachlan Fold Belt: the Orange-Wellington Belt and the Parkes-Narromine Belt. Available isotopic age data suggest that mineralization of the three types of deposits is essentially coeval with the Ordovician intrusive rocks (480-430 Ma).Porphyry gold-copper deposits can be further divided into two groups. The first group is associated with monzonite showing shoshonitic features, represented by Cadia and Goonumbla. The second group is associated with diorite and dacite, including the Copper Hill and Cargo gold-copper deposits. Gold skarn is associated with Late Ordovician (430-439 Ma) monzonitic intrusive complexes in the Junction Reefs area (Sheahan-Grants, Frenchmans, and Cor-nishmens), Endeavour 6, 7 and 44, Big and Little Cadia  相似文献   
36.
The responses of the climate system to increase of atmospheric carbon dioxide(CO_2)arestudied by using a new version of the Bureau of Meteorological Research Centre(BMRC)globalcoupled general circulation model(CGCM).Two simulations are run:one with atmospheric CO_2concentration held constant at 330 ppm,the other with a tripling of atmospheric CO_2(990 ppm).Results from the 41-year control coupled integration are applied to analyze the mean state,seasonal cycle and interannual variability in the model.Comparisons between the greenhouseexperiment and the control experiment then provide estimations of the influence of increased CO_2on climate changes and climate variability.Especially discussed is the question on whether theclimate changes concerned with CO_2 inerease will impact interannual variability in tropical Pacific,such as ENSO.  相似文献   
37.
河南省是我国乃至世界上最重要的恐龙蛋化石产地之一,具有含蛋层位多、数量大、类型全、原始状态保存好以及可供研究的K/T界线等特点。据初步统计,已有7科、10属、19种之多,且与霸王龙、鸭咀龙、蜥脚类及轮藻、孢粉、痕迹化石等共生。本文评述了恐龙蛋化石的分类系统、地层划分与时代、古生态特征及古气候等,并论述了恐龙绝灭的问题。  相似文献   
38.
Radiometric measurements of hemispherical surface reflectance and long-wave irradiance are required to quantify the broadband albedo and the outgoing thermal radiation. These observations are typically integrated with eddy covariance measurements of sensible and latent heat fluxes to characterize the surface energy budget. While the aerodynamic footprint has been widely investigated, the geometry of the hemispherical radiometric footprint over plant canopies has been rarely tackled. In the present work, the size and shape of the hemispherical radiometric footprint are formalized for a bare surface and in presence of a vegetation cover. For this purpose, four idealized canopies are analyzed and the dependency of the radiometric footprint on leaf area index and canopy height is explored. Besides, the radiometric footprint is compared with the aerodynamic footprint in conditions of neutral stability. It was observed that almost 100% of the hemispherical radiometric signal originates within a distance of a few radiometer heights, while only about 50–80% of the cumulative aerodynamic signal is generated within a distance of about 20 sensor heights. In order to achieve comparable extensions of the footprint areas, hemispherical radiometric measurements should therefore be taken about 6–15 times higher than turbulent flux ones, depending on the vegetation type. The analysis also highlights that the size of the radiative footprint decreases at increasing leaf area index, whereas the aerodynamic footprint shows an opposite behavior. For the abovementioned reasons, this work may support the interpretation of energy flux measurements and the optimal design of eddy covariance stations located in heterogeneous sites.  相似文献   
39.
French meteorological data provide some information on wind direction since 1890. Since 1951, wind speed and direction have been digitised every three hours in many stations. The Brest tide gauge has recorded hourly sea levels since 1860, thus enabling hourly surges to be calculated and studied. This set of data has been organised into a data base and analysed in order to recognize evolution and trends. Strong winds are increasing in frequency in the western part of Brittany and decreasing in Normandy and Pays de Loire. Surges associated with these winds do present a slight decreasing trend. A more precise analysis allows to distinguish between southerly winds, which are slightly decreasing, and strong winds from other directions, which display a more or less important increase in frequency. The analysis shows trends that may be linked to the global circulation pattern, and that result in a new spatial distribution of winds on western France.  相似文献   
40.
1 .IntroductionNumericalmodelsmostwidelyusedforseaenvironmentandsedimenttransportfocusonsolvingseriesofdifferentialequations .Theinputandoutputofanumericalmodelareconsideredasdecisivefactors .Butinrealitythecausesofnaturaleventssuchasmeteorological,astronomical,oceanograph ic ,geomorphologicandgeophysicalfactorsarerandom .Therearemanyuncertaintiesinvolvedininputfactorsinnumericalmodels .Correspondinglytheoutputsofnumericalmodelsarealsorandom .There fore ,theoutputparametersofnumericalmodelsca…  相似文献   
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