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61.
中国南极中山站位于南极拉斯曼丘陵地区(λ=76°22′E,φ=69°22′S),1991年3月至1993年2月,用LacosteET型重力仪,在这个地区进行了为期近两年的观测,取得了600多天的有效资料,经调和分析和流变模型、海潮负荷改正后得到:δo1=1.2253±0.0031,Δφo1=0.73°±0.14°;δm2=1.0785±0.0045,Δφm2=-3.55°±0.29°从资料分析的精度来看,观测资料是比较好的;但由于海潮负荷改正缺少附近海域的资料,会对最终结果造成较大的影响 相似文献
62.
63.
张清志 《沉积与特提斯地质》2001,21(2):23-30
卫星信号从GPS卫星发射到地面的过程中经过了以充满大气为介质的空间,电磁波在这种变化的介质中传播,其传播的方向、速度、强度都可能随时改变,本文简略地介绍了大气传播延迟的产生及其对GPS测量的影响,并就GAMIT软件对大气传播延迟的控制方法和所采用的改正模型做一简单介绍,并对减弱和消除大气传播延迟的方法和手段进行了讨论。 相似文献
64.
G. A. Mansilla 《Studia Geophysica et Geodaetica》2007,51(4):563-574
An investigation of the response of the mid-high, mid and low latitude critical frequency foF2 to the geomagnetic storm of
15 July 2000 is made. Ground-based hourly foF2 values (proportional to square root of peak electron density of F2-layer) from
four chains of ionospheric stations located in the geographic longitude ranges 10°W–35°E, 60°E–120°E, 130°E–170°E, 250°E–295°E
are used. Relative deviations of foF2 are considered. The main ionospheric effects for the considered storm are: long-duration
negative disturbances at mid-high latitudes in summer hemisphere in sectors where the storm onset occurred in the afternoon/night-time
hours; short-duration positive disturbances in the summer hemisphere at mid-high latitudes in the pre-sunset hours during
the end of main phase-first stage of the recovery; small and irregular negative disturbances in the low latitude winter hemisphere
which predominate during the main phase and first part of the recovery, and positive disturbances in both hemispheres at mid-high
and mid latitudes prior to the storm onset irrespective of the local time. In addition, the validity of some physical mechanisms
proposed to explain the F2 region behaviour during disturbed conditions is considered.
gus-mansilla@hotmail.com 相似文献
65.
The structure of the mid- and high-latitude ionosphere during the November 2004 storm event obtained from GPS observations 总被引:1,自引:1,他引:1
Andrzej Krankowski Irk I. Shagimuratov Lubomir W. Baran Galina Yakimova 《Acta Geophysica》2007,55(4):490-508
GPS data from the International GNSS Service (IGS) network were used to study the development of the severe geomagnetic storm
of November 7–12, 2004, in the total electron content (TEC) on a global scale. The TEC maps were produced for analyzing the
storm. For producing the maps over European and North American sectors, GPS measurements from more than 100 stations were
used. The dense network of GPS stations provided TEC measurements with a high temporal and spatial resolution. To present
the temporal and spatial variation of TEC during the storm, differential TEC maps relative to a quiet day (November 6, 2004)
were created.
The features of geomagnetic storm attributed to the complex development of ionospheric storm depend on latitude, longitude
and local time. The positive, as well as negative effects were detected in TEC variations as a consequence of the evolution
of the geomagnetic storm. The maximal effect was registered in the subauroral/auroral ionosphere during substorm activity
in the evening and night period. The latitudinal profiles obtained from TEC maps for Europe gave rise to the storm-time dynamic
of the ionospheric trough, which was detected on November 7 and 9 at latitudes below 50°N. In the report, features of the
response of TEC to the storm for European and North American sectors are analyzed. 相似文献
66.
Real‐time pseudodynamic (PSD) testing is an experimental technique for evaluating the dynamic behaviour of a complex structure. During the test, when the targeted command displacements are not achieved by the test structure, or a delay in the measured restoring forces from the test structure exists, the reliability of the testing method is impaired. The stability and accuracy of real‐time PSD testing in the presence of amplitude error and a time delay in the restoring force is presented. Systems consisting of an elastic single degree of freedom (SDOF) structure with load‐rate independent and dependent restoring forces are considered. Bode plots are used to assess the effects of amplitude error and a time delay on the steady‐state accuracy of the system. A method called the pseudodelay technique is used to derive the exact solution to the delay differential equation for the critical time delay that causes instability of the system. The solution is expressed in terms of the test structure parameters (mass, damping, stiffness). An error in the restoring force amplitude is shown to degrade the accuracy of a real‐time PSD test but not destabilize the system, while a time delay can lead to instability. Example calculations are performed for determining the critical time delay, and numerical simulations with both a constant delay and variable delay in the restoring force are shown to agree well with the stability limit for the system based on the critical time delay solution. The simulation models are also used to investigate the effects of a time delay in the PSD test of an inelastic SDOF system. The effect of energy dissipation in an inelastic structure increases the limit for the critical time delay, due to the energy removed from the system by the energy dissipation. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
67.
This paper mainly observed and analyzed the character of shear-wave splitting in rock specimens while they were in the critical state of rupture. The rock specimens for study are made of Laizhou marble from Shandong, China. A series of records were obtained from two rock specimens when they were in the critical state of rupture. The result shows that, in the critical state just before rock rupture, there may be the phenomenon of rise and fall in the time delay of shear-wave splitting, even though the load was kept constant. That is to say, the time delay of shear-wave splitting may have a falling process before rock rupture. 相似文献
68.
69.
利用两颗伴飞的Swarm A/C卫星搭载的双频GPS接收机获取的TEC数据,在两个卫星轨道平面同时对顶部电离层电子密度进行层析成像,实现对顶部电离层电子密度的三维观测.为了能够重现扰动期间电离层电子密度的空间变化特征,在正则化求解过程中,我们引入了水平矩阵H和垂直矩阵V刻画电子密度的空间变化特征,引入整体约束矩阵C以调节不同空间对电子密度相对变化的权重.数值验证结果表明我们的算法对常见的观测误差具有较强的包容性,反演计算出的电子密度平均偏差优于10%.在不同地磁活动条件下,与第三方观测数据的对比,验证了本文反演算法的可靠性.实测数据反演结果表明我们的算法不仅能够较好地重现顶部电离层子午向百公里级别的不规则结构,还能有效分辨纬向相隔~150 km的两个卫星轨道平面的电子密度差异. 相似文献
70.
The response of the azimuthal component of the ionospheric electric field to auroral arc brightening
V. Safargaleev W. Lyatsky N. G. Gazey P. N. Smith V. Kriviliov 《Annales Geophysicae》1999,18(1):65-73
We have analyzed the response of azimuthal component of the ionospheric electric field to auroral arc activity. We have chosen for analysis three intervals of coordinated EISCAT and TV observations on 18 February, 1993. These intervals include three kinds of arc activity: the appearance of a new auroral arc, the gradual brightening of the existing arc and variations of the arc luminosity. The arcs were mostly east-west aligned. In all cases, the enhancement of arc luminosity is accompanied by a decrease in the westward component of the ionospheric electric field. In contrast, an increase of that component seems to be connected with arc fading. The observed response is assumed to have the same nature as the short circuit of an external electric field by the conductor. The possible consequence of this phenomenon is discussed. 相似文献