全文获取类型
收费全文 | 47382篇 |
免费 | 9797篇 |
国内免费 | 13662篇 |
专业分类
测绘学 | 5559篇 |
大气科学 | 8617篇 |
地球物理 | 10943篇 |
地质学 | 25641篇 |
海洋学 | 7357篇 |
天文学 | 1545篇 |
综合类 | 4813篇 |
自然地理 | 6366篇 |
出版年
2024年 | 240篇 |
2023年 | 802篇 |
2022年 | 2328篇 |
2021年 | 2709篇 |
2020年 | 2195篇 |
2019年 | 2634篇 |
2018年 | 2774篇 |
2017年 | 2539篇 |
2016年 | 2774篇 |
2015年 | 2788篇 |
2014年 | 3048篇 |
2013年 | 3241篇 |
2012年 | 3372篇 |
2011年 | 3405篇 |
2010年 | 3464篇 |
2009年 | 3259篇 |
2008年 | 3223篇 |
2007年 | 3018篇 |
2006年 | 2583篇 |
2005年 | 2356篇 |
2004年 | 1699篇 |
2003年 | 1480篇 |
2002年 | 1453篇 |
2001年 | 1481篇 |
2000年 | 1509篇 |
1999年 | 1649篇 |
1998年 | 1245篇 |
1997年 | 1177篇 |
1996年 | 1073篇 |
1995年 | 924篇 |
1994年 | 798篇 |
1993年 | 715篇 |
1992年 | 580篇 |
1991年 | 451篇 |
1990年 | 346篇 |
1989年 | 311篇 |
1988年 | 278篇 |
1987年 | 161篇 |
1986年 | 150篇 |
1985年 | 106篇 |
1984年 | 114篇 |
1983年 | 81篇 |
1982年 | 72篇 |
1981年 | 59篇 |
1980年 | 35篇 |
1979年 | 43篇 |
1978年 | 13篇 |
1977年 | 11篇 |
1958年 | 30篇 |
1954年 | 14篇 |
排序方式: 共有10000条查询结果,搜索用时 234 毫秒
941.
GPS滑坡监测专用的Gquicks软件 总被引:6,自引:0,他引:6
介绍了Guicks软件的数学模型,Gquicks软件的结构和功能.经实测检测检验,当基准点与监测点之间距离在3km内,用20分钟GPS观测值,Gquicks软件解算的水平精度可达±2-3mm,垂直精度可达±4-6mm.Gquicks软件不仅适用于GPS滑坡变形监测,也可应用于其他变形监测领域. 相似文献
942.
基于虚拟监控技术的机器人系统 总被引:2,自引:0,他引:2
介绍了一种虚拟现实技术(VR)与智能机器人监控技术协同作业的机器人系统,该系统使用虚拟现实技术建造具有良好交互性的人机界面,并且结合智能机器人监控技术,实现了虚拟监控操作。通过机器人系统,将虚拟操作结果作为一个整体对象投射到工作现场,完成了实际作业,并以水下机器人检查钻井平台水下部分的焊缝工作为背景,说明了本系统各种功能的实现过程。 相似文献
943.
基于网络的机器人跨平台远程实时控制 总被引:2,自引:0,他引:2
提出了一种基于网络的多层次结构的跨平台远程实时控制框架,它由智能与人机交互层、运动规划层、运动控制层和伺服控制层构成,并基于该框架完成了一套单机器人远程实时控制系统,进行了远程视觉控制试验。试验表明,该控制系统运行稳定,实时性强。 相似文献
944.
945.
高职教育是GIS人才培养的重要组成部分。本文通过介绍职教GIS专业的建设,探索GIS实践教学与实践基地建设模式、方法及对人才培养的影响。 相似文献
946.
Ya. N. Pavlyuchenkov B. M. Shustov V. I. Shematovich D. S. Wiebe Zhi-Yun Li 《Astronomy Reports》2003,47(3):176-185
We consider radiative transfer in C18O, HCO+, and CS molecular lines in a spherically symmetrical, coupled, dynamical and chemical model of a prestellar core whose evolution is determined by ambipolar diffusion. Theoretical and observed line profiles are compared for the well-studied core L1544, which may be a collapsing protostellar cloud. We study the relationship between the line shapes and model parameters. The structure of the envelope and kinematic parameters of the cloud are the most important factors determining the shape of the lines. Varying the input model parameters for the radiative transfer—the kinetic temperature and microturbulent velocity—within the limits imposed by observations does not result in any substantial variations of the line profiles. The comparison between the model and observed spectra indicates that L1544 displays a flattened structure, and is viewed at an oblique angle. A two-dimensional model is needed to reproduce this structure. 相似文献
947.
The West Kunlun orogenic belt is located at the conjunction of the paleo-Asian tectonic system and the Tethys tectonic system.
Petrological and mineralogical studies of the Early Cambrian metamorphic surface crust in this region have shown that in case
the metamorphism reached low-temperature granulate facies, the typical mineral assemblage is biotite-garnet-silimanite-K feldspar-plagioclase-quartz.
The peak metamorphic temperatures are within the range of 720–740°C and the pressure is 0.6 GPa ±. Three types of metamorphic
zircon have been detected in the metamorphic rocks: the complex inclusion-bearing type ; the early relic zircon inclusion-bearing
type; and the inclusion-free type. SHRIMP age determination of these three types of metamorphic zircon have revealed that
these zircons were formed principally during 400–460 Ma, indicating that pre-Cambrian metamorphic surface crust rocks underwent
low-temperature granulite facies metamorphism during the Caledonian. In combination with the geological characteristics of
this region, it is considered that when the oceanic basin was closed, there occurred intense intracontinental subduction (type
A), bringing part of the Early Cambrian metamorphic basement in this region downwards to the lower crust. Meanwhile, there
were accompanied with tectonic deformation at deep levels and medium- to high-grade metamorphism. This study provided important
chronological and mineralogical evidence for the exploration of the evolutionary mechanism and process of the West Kunlun
Early Paleozoic.
Part of the results from the research project “ Research on the West Kunlun pre-Cambrian tectonic events” under the program
“ Research on the important geological problems of China’ s pre-Cambrian” (No. 200113900070) sponsored by the China National
Geological Surveying Bureau. 相似文献
948.
Detailed palaeomagnetic and rock magnetic analyses provide improved palaeomagnetic results from 23 sites in the Borgmassivet intrusions in the Ahlmannryggen region of Dronning Maud Land, East Antarctica. These intrusions are of similar age to their host, the ca. 1130 Ma Ritscherflya Supergroup (RSG). A mean direction of D=235.4°, I=−7.6° with k=45.9 and α95=4.5° was obtained from this study. When combined with previously reported results from 11 sites in the same region, including sites from the Ritscherflya Supergroup, it gives an overall mean direction for 34 sites from the igneous suite with D=236.5°, I=−3.6°, k=27.9 and α95=4.8°. Isothermal remanent magnetization (IRM) experiments on several specimens suggest magnetite or titanomagnetite as the primary remanence carrier, while high temperature magnetic susceptibility experiments indicate the presence of single domain particles. These observations, together with field evidence and the high coercivities and unblocking temperatures, support a primary origin for the observed characteristic remanence. The Borgmassivet palaeomagnetic pole lies at 54.5°E, 8.3°N with A95=3.3°. If Antarctica is moved to its Gondwanan position adjacent to southeast Africa, the Borgmassivet pole (BM) coincides with that of the African well-established, well-dated (1100 Ma) Umkondo Large Igneous Province pole, supporting the hypothesis that the Grunehogna craton of Dronning Maud Land was part of the Kalahari craton of southern Africa at ca. 1100 Ma. 相似文献
949.
The coal-bearing, alternating marine and non-marine Longzhaogou Group in eastern Heilongjiang, northeastern China, has long been considered as Jurassic, or mainly Jurassic, in age. However, recent studies have demonstrated that the ammonites and dinoflagellate cysts are of Early Cretaceous age. This has now been confirmed by new radiolarian evidence. The radiolarian fauna recovered from the upper Qihulin Formation of the Longzhaogou Group consists of nine poorly preserved species referable to nine genera. Novixitus is a Cretaceous genus, and the specimens of Archaeodictyomitra sp. and Xitus sp. recovered resemble A. vulgaris Pessagno and X. spicularius (Aliev), respectively. 相似文献
950.