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991.
Shueh-Jung?Lin Wuu-Liang?HuangEmail author 《Contributions to Mineralogy and Petrology》2004,147(5):604-614
The kinetics of the calcite to aragonite transformation have been investigated using synthetic polycrystalline calcite aggregates, with and without additional minerals present. The reaction progresses as a function of time were measured at four temperature/pressure conditions: (1) 550 °C/1.86 GPa; (2) 600 °C/2.11 GPa; (3) 650 °C/2.11 GPa, and (4) 700 °C/2.29 GPa. Experiments reveal that Mg-calcite and Fe-calcite transforms to aragonite at considerably slower rates than pure calcite, and that Sr-bearing calcite and calcite + quartz aggregates transform at significantly higher rates than pure calcite. The reaction progresses vs. time data for pure calcite were fitted to Cahns grain-boundary nucleation and interface-controlled growth model. Evidence for interface-controlled growth is provided by petrographic observations of grain boundaries. The activation energy for aragonite growth from the synthetic polycrystalline calcite determined in this study is significantly lower than that previously determined from a natural marble. The discrepancy in rates and activation energy may be attributed to the nature of grain boundaries, to deformational strain or the presence of impurities in the studied samples, and likely to uncertainties in experimental conditions. The results of this study imply that the variation of local petrologic conditions, in addition to temperature, pressure and grain size, may play an important role in determining the rates for the calcite to aragonite transformation in nature.Editorial responsibility: W. Schreyer 相似文献
992.
M. L. Kaplan J. J. Charney K. T. WaightIII K. M. Lux J. D. Cetola A. W. Huffman A. J. Riordan S. D. Slusser M. T. Kiefer P. S. Suffern Y.-L. Lin 《Meteorology and Atmospheric Physics》2006,94(1-4):235-270
Summary In this paper, we will focus on the real-time prediction of environments that are predisposed to producing moderate-severe
(hazardous) aviation turbulence. We will describe the numerical model and its postprocessing system that is designed for said
prediction of environments predisposed to severe aviation turbulence as well as presenting numerous examples of its utility.
The purpose of this paper is to demonstrate that simple hydrostatic precursor circulations organize regions of preferred wave
breaking and turbulence at the nonhydrostatic scales of motion. This will be demonstrated with a hydrostatic numerical modeling
system, which can be run in real time on a very inexpensive university computer workstation employing simple forecast indices.
The forecast system is designed to efficiently support forecasters who are directing research aircraft to measure the environment
immediately surrounding turbulence.
The numerical model is MASS version 5.13, which is integrated over three different grid matrices in real-time on a university
workstation in support of NASA-Langley’s B-757 turbulence research flight missions. The model horizontal resolutions are 60,
30, and 15 km and the grids are centered over the region of operational NASA-Langley B-757 turbulence flight missions.
The postprocessing system includes several turbulence-related products including four turbulence forecasting indices, winds,
streamlines, turbulence kinetic energy, and Richardson numbers. Additionally there are convective products including precipitation,
cloud height, cloud mass fluxes, lifted index, and K-index. Furthermore, soundings, sounding parameters, and Froude number
plots are also provided. The horizontal cross section plot products are provided from 16,000–46,000 feet in 2,000 feet intervals.
Products are available every three hours at the 60 and 30 km grid interval and every 1.5 hours at the 15 km grid interval.
The model is initialized from the NWS ETA analyses and integrated two times a day. 相似文献
993.
抚顺市是中国重要的大型煤炭工业基地之一。由于长期的采掘施工,其采矿场和采矿坑不断扩大加深,导致了矿区及其周边地带地面不稳定性的不断加剧,且已发生了局部的地面沉降等地质灾害,给人们的生产和生活带来了直接的威胁,并严重地影响着该地区社会经济的可持续发展。本研究工作采用遥感技术手段,快速地查明该地区现有的地质灾害类型、数量及其表现形式,以及地质灾害与断裂构造的相互关系,从而为在该地区进行地质灾害防治工作提供准确可靠的依据,取得了良好的应用效果。 相似文献
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自2002~2003年度首次启用遥感技术监测黄河凌情以来,到目前已连续进行了10个年度。10个年度的生产实践表明:国产高分辨率卫星遥感数据能够有效跟踪黄河凌情的发展过程,实现黄河凌情的日动态监测、重点时段的精细监测和突发凌汛灾害时的实时监测。黄河凌情尤其在封开河阶段,日变化非常显著,中巴资源卫星作为国产高分辨率可见光民用遥感卫星的代表,以其大视场、高空间、高时间分辨率的特点,动态监测凌情,基本做到每天实现一次全覆盖监测的能力,配合其他如中国遥感卫星等高分辨率可见光、雷达数据,初步实现了凌情发展预估、开河前的河道槽蓄水量计算、封开河期间冰凌险情监测以及发生凌汛灾害时灾情信息采集与评估,为黄河防凌调度、决策会商提供了有力的技术支持。 相似文献
1000.
文章以ASP.NET技术为核心,结合使用SQL Server数据库、Visual C#语言,开发和构建了基于Web平台的地理信息系统(GIS)网络课程,实现了GIS专业知识与网站的融合;同时在外观设计上,系统运用DIV+CSS进行布局,并注重界面的友好性,方便了用户的操作。系统的实现对B/S结构系统的开发及如何将地理信息系统专业知识应用于网络课程具有借鉴意义。 相似文献