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排序方式: 共有182条查询结果,搜索用时 15 毫秒
51.
52.
含水大陆下地壳的部分熔融:大别山C型埃达克岩成因探讨 总被引:4,自引:0,他引:4
根据大陆下地壳的成分、含水基性岩体系部分熔融的基本原理和实验岩石学资料,本文对大陆下地壳的熔融机制展
开了讨论,并在此基础上对比实验熔体与大别山C 型埃达克岩的成分,进而探讨约束源岩成分、熔融的温压条件和部分熔
融程度。研究结果表明,大陆下地壳总体上是中- 基性(SiO2 50%~60% )和含少量水的,在缺乏流体相条件下伴随含水
矿物脱水的部分熔融是下地壳产生含水长英质熔体和无水残留体的主要机制。角闪岩在中等压力下(1.0~1.2 GPa,相当于
35~40 km)理论上能够产生石榴石含量超过~20% 的熔融残余,从而使得与之平衡的长英质熔体具有低Y,高Sr/Y 和La/Yb
比值等埃达克岩特征。基于水活度模型和变质基性岩p -t 相图的估算显示,含有40%~60% 角闪石的源岩(含水0.8%~1.2%)
在~950 ℃能够得到最大为15%~20% 的熔体,该熔体分数满足熔体分离的要求。大别山C型埃达克岩主要为高钾钙碱性系
列(K2O 3.5%~5%),与实验熔体成分的对比可知,其无法由低钾源岩在合理的部分熔融程度形成。根据钾在角闪岩部分熔
融过程过表现为强不相容元素的原理,利用合理假设的残余体组合得到的分配系数,估算K2O 含量为~1% 的源岩在熔融程
度为15%~20% 的情况下能够得到类似大别山C 型埃达克岩成分的熔体。 相似文献
53.
Resumé Les donées moyennes relatives à deux années de mesures continues du radon à 1.5–30 et 100 m au-dessus du sol sont présentées sous forme de variations diurnes standard; ces dernières sont étudiées par une analyse de Fourier (amplitude et phase). On précise l'évolution des variations au cours du cycle annuel.Le but de l'étude des donées moyennes étant d'accéder aux informations relatives à la variation diurne des échanges, on a recherché des relations entre la variation diurne standard des concentrations et celles des échanges; d'autre part on a défini des critères, déduits des paramètres météorologiques, classiques susceptibles de caracteriser l'intensité de la variation diurne des échanges.
Equipe de Recherche Associée au CNRS, No. 378. 相似文献
Continuous measurement of radon concentrations at, 1.5, 30 and 100 m has been carried out for 2 years, from October 1966 to October 1968. The mean diurnal variations of the concentrations are characterized in a simple manner using a Fourier analysis, revealing the diurnal and annual waves, and showing the variations with altitude of the radon concentrations. The amplitude of this diurnal wave can be considered as representative of the mean diurnal variation of the intensity of the vertical exchange processes.This method of analysis is applied to the study of influence of standard meteorological elements measured at the site on the diurnal variation of the exchanges. Additional indicators are derived from temperature, humidity and wind (speed and direction) measurements, and their daily cycles (mean winds, mean direction, temperature diurnal variation amplitude...) are shown to be related to the cycles of radon concentrations.The mean diurnal variations of the radon concentrations classified according to several meteorological parameters are used to characterize the intensity of mixing, in terms of a mixing coefficient.This characterization is achieved both from the average gradients (local value) and from the diurnal wave at the soil.
Equipe de Recherche Associée au CNRS, No. 378. 相似文献
54.
Streck Martin J. Dungan Michael A. Malavassi E. Reagan Mark K. Bussy Francois 《Bulletin of Volcanology》2002,64(5):316-327
Bulletin of Volcanology - The bulk composition of magma erupted from Volcán Arenal has remained nearly constant (SiO2 = 53.6–54.9&;nbsp;wt%; MgO = 5.0–4.5&;nbsp;wt%) during... 相似文献
55.
Beraki Asmerom F. Morioka Yushi Engelbrecht Francois A. Nonaka Masami Thatcher Marcus Kobo Nomkwezane Behera Swadhin 《Climate Dynamics》2020,54(11):4775-4792
Climate Dynamics - The study examines the influence of external climate forcings, and atmosphere–ocean–sea–ice coupled interaction on the Southern Hemisphere (SH) atmospheric... 相似文献
56.
Roland Vanderspek Alia Atlas Tye M. Brady Geoffrey B. Crew John P. Doty Steven E. Kissel George R. Ricker Peter C. Tappan Francois Martel M. Tim Jones 《Astrophysics and Space Science》1995,231(1-2):479-482
The High Energy Transient Experiment (HETE), scheduled for launch this year, is a small satellite dedicated to multiwavelength observations of -ray and X-ray bursts. The HETE spacecraft will be equipped with gamma-ray detectors, X-ray detectors with a coded mask, and ultraviolet-sensitive CCD cameras. The UV cameras on HETE are wide-field imagers which will a) provide UV images of the regions in which -ray or X-ray bursts are detected, before, duringand after the burst, b) detect UV transients, whether associated with a high-energy transient or not, c) monitor the brightnesses of field stars for variability over a wide range of timescales, and d) serve as star trackers for HETE. In this poster, we describe the HETE UV instrumentation, control software, and data products. 相似文献
57.
板状绿柱石晶体的结构测定 总被引:12,自引:0,他引:12
自然界中绿柱石晶体多为柱状,具板状晶形的绿柱石非常少见。本文对产于四川雪宝顶云英岩晶洞中的无色透明板状绿柱石进行了精确的结构分析,并与产于阿尔泰山号伟晶岩脉中的柱状绿柱石进行了比较。与阿尔泰柱状绿柱石相比,雪面板状绿石富Li、Na,c/a值较高,为1.001,属钠-锂绿柱石或“四面体”绿柱石。本文还对这种特殊形貌柱石的形成机制进行了初步讨论,成矿流体中Li的浓度以及Si的化学形态可能是影响柱石忻驳闹 相似文献
58.
Abstract An analytical spectral model of the barotropic divergent equations on a sphere is developed using the potential-stream function formulation and the normal modes as basic functions. Explicit expressions of the coefficients of nonlinear interaction are obtained in the asymptotic case of a slowly rotating sphere, i.e. when the normal modes can be expressed as single spherical harmonics. 相似文献
59.
European Union directives as well as national legislation are placing great emphasis on the inclusion of stakeholder perspectives in the governance of risks from natural hazards. This should help decision makers formulate better policies. However, to date, there is little information on stakeholders’ perspectives with respect to landslide risk governance. This paper addresses the gap by reporting on research in Nocera Inferiore, Italy. The research is based on a documentary analysis, 43 semi-structured interviews and a survey submitted to 373 residents. The political instability, the unfairness of national funding allocation across municipalities and the residents’ lack of knowledge about risk assessment and emergency planning are some of the main barriers to effective risk governance. Moreover, there are divergent, sometimes even opposite, stakeholders’ views on several issues, such as the relevance of illegal development in risky areas. The results highlight the importance of addressing these divergent views and including the plurality of voices as a prerequisite for inclusive risk governance. The research provided essential background information for a participatory process, which was designed to support decisions on landslide risk mitigation measures in Nocera Inferiore (Linnerooth-Bayer et al. this issue). The methodology will be of more general interest to researchers and policymakers intent upon including stakeholder perspectives in natural risk governance. 相似文献
60.
Landman Willem A. Engelbrecht Francois Hewitson Bruce Malherbe Johan van der Merwe Jacobus 《Theoretical and Applied Climatology》2018,132(3-4):1153-1163
Theoretical and Applied Climatology - Multi-decadal regional projections of future climate change are introduced into a linear statistical model in order to produce an ensemble of austral... 相似文献