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521.
分布于宁镇地区的下蜀黄土年代标尺研究薄弱.我们以镇江大港钻孔岩芯的下蜀黄土为例,探讨了下蜀黄土记录地磁场相对古强度的可靠性.岩石磁学的实验显示,下蜀黄土大体上符合估计相对古强度对沉积物的要求.以低频磁化率()作为天然剩磁(NRM300)的归一化因子,我们获得了下蜀黄土记录的地磁场相对古强度变化.通过与邻区和全球的单个及合成曲线的对比,我们发现大港钻孔岩芯的相对古强度记录展现出主要的全球偶极场的变化特征,因而可用于建立下蜀黄土的年代标尺.新的年代标尺表明,大港钻孔的磁化率年代序列与北方黄土无法直接对比,证实了该地点的下蜀黄土磁化率变化机制与北方的不同.大港钻孔下蜀黄土的沉积速率与磁化率相关,低风尘沉积速率对应低磁化率,是降水增加所导致的结果.沉积速率与磁化率年代序列显示,下蜀黄土记录的本区季风变化过程可分为4个阶段.阶段Ⅳ(819~700ka)对应中更新世转型阶段,东亚季风降水较少.阶段Ⅲ(700~412ka)对应中更新世的大间冰期,东亚季风降水最多.阶段Ⅱ(412~197ka)时东亚季风降水减少,较阶段Ⅳ略少.阶段Ⅰ(197~34ka)东亚季风降水最少.因此,中更新世气候转型后,长时间尺度东亚季风降水持续减少,可能受全球温度阶段性降低驱动. 相似文献
522.
523.
本文分析了1980 、1984 和1989 年SMM 卫星观测到的140 次日冕物质抛射(CME) 事件在时空分布上与“冕洞边缘结构”、耀斑爆发和爆发日珥等事件的相关关系结果表明, CME 事件与日冕边缘结构的关系最密切此外, CME与赤道冕洞具有同步的长期演化关系由此认为, 冕洞边缘结构对CME的可能贡献是不可忽视的 相似文献
524.
A comparison and analysis of airborne gravimetry results from two strapdown inertial/DGPS systems 总被引:2,自引:0,他引:2
In September 1996 the University of Calgary tested a combination of strapdown inertial navigation systems and differential
global positioning system (DGPS) receivers for their suitability to determine gravity at aircraft flying altitudes. The purpose
of this test was to investigate the long-term accuracy and repeatability of the system, as well as its potential for geoid
and vertical gradient of gravity determination. The test took place during a 3-day period in the Canadian Rocky Mountains
over a single 100 × 100 km area which was flown with 10-km line spacing. Two flights were done at 4350 m in E–W and N–S profile
directions, respectively, and one at 7300 m with E–W profiles. Two strapdown inertial systems, the Honeywell LASEREF III and
the Litton-101 Flagship, were flown side by side. Comparison of the system estimates with an upward-continued reference showed
root-mean-square (RMS) agreement at the level of 3.5 mGal for 90- and 120-s filter lengths. The LASEREF III, however, performed
significantly better than the Litton 101 for shorter filtering periods of 30 and 60 s. A comparison between the two systems
results in an RMS agreement of 2.8 and 2.3 mGal for the 90- and 120-s filters. The better agreement between the two systems
is mainly due to the fact that the upward-continued reference has not been filtered identically to the system gravity disturbance
estimates. Additional low-frequency differences seem to point to an error in the upward-continued reference. Finally, an analysis
of crossover points between flight days for the LASEREF III shows a standard deviation of 1.6 mGal, which is near the noise
level of the INS and GPS data. Further improvements to the system are possible, and some ideas for future work are briefly
presented.
Received: 17 March 1998 / Accepted: 1 February 1999 相似文献
525.
航空重力测量中厄特弗斯改正的计算与误差分析 总被引:3,自引:0,他引:3
基于航空重力测量基本数学模型,导出了椭球近似的厄特弗斯改正公式;以一组实测数据,对厄特弗斯改正的计算与平滑方法进行了分析和比较。此外,给出了简单的误差估计模型。 相似文献
526.
R. Lehmann 《Journal of Geodesy》1999,73(9):491-500
A review of recent progress and current activities towards an improved formulation and solution of geodetic boundary value
problems is given. Improvements stimulated and required by the dramatic changes of the real world of geodetic measurements
are focused upon. Altimetry–gravimetry problems taking into account various scenarios of non-homogeneous data coverage are
discussed in detail. Other problems are related to free geodetic datum parameters, most of all the vertical datum, overdetermination
or additional constraints imposed by satellite geodetic observations or models. Some brief remarks are made on pseudo-boundary
value problems for geoid determination and on purely gravitational boundary-value problems.
Received: 17 March 1999 / Accepted: 19 April 1999 相似文献
527.
表征海相烃源岩有机质成熟度的若干重要指标的对比与研究 总被引:21,自引:1,他引:20
对目前表征海相烃源岩有机质成熟度的几个重要指标(镜质体反射率,沥青反射率,镜状体反射率、动物有机碎屑反射率及牙形刺色变指数等)进行了探讨与对比,并在总结它们各自优缺点的基础上,提出了选择海相烃源岩有机质成熟度评价指标的原则,进而提出牙形刺相对荧光强度(I546)是表征海相烃源岩有机质成熟度的良好指标,其具有较广泛的适用性。 相似文献
528.
Gauss-Matuyama极性转换期间地球磁场方向和强度变化特征 总被引:13,自引:2,他引:11
粒度分析和风化强度研究表明 ,黄土高原渭南阳郭剖面黄土层L33沉积期间成壤化作用相对较弱 .在此基础上 ,为研究极性转换期间地球磁场变化特征 ,本文对黄土层L33进行了详细的岩石磁学和古地磁学研究 ,其结果表明黄土层L33的主要载磁矿物为磁铁矿和磁赤铁矿 ,并以沉积剩磁为主 ;由逐步热退磁确定的特征剩磁 (ChRM )揭示了G M(Gauss Matuyama)极性转换过程的持续时间为 9 43± 0 64ka;在G M极性转换之前 ,地球磁场曾发生过持续时间为 2 2± 0 1 3ka的短极性漂移事件 ;相对强度研究表明 ,G M极性转换期间地球磁场强度减弱 . 相似文献
529.
A comparison of stable platform and strapdown airborne gravity 总被引:3,自引:1,他引:2
C. L. Glennie K. P. Schwarz A. M. Bruton R. Forsberg A. V. Olesen K. Keller 《Journal of Geodesy》2000,74(5):383-389
To date, operational airborne gravity results have been obtained using either a damped two-axis stable platform gravimeter
system such as the LaCoste and Romberg (LCR) S-model marine gravimeter or a strapdown inertial navigation system (INS), showing
comparable accuracies. In June 1998 three flight tests were undertaken which tested an LCR gravimeter and a strapdown INS
gravity system side by side. To the authors' knowledge, this was the first time such a comparison flight was undertaken. The
flights occurred in Disko Bay, off the west coast of Greenland. Several of the flight lines were partly flown along existing
shipborne gravity profiles to allow for an independent source of comparison of the results. The results and analysis of these
flight tests are presented. The measurement method and error models for both the stable platform and strapdown INS gravity
systems are presented and contrasted. An intercomparison of gravity estimates from both systems is given, along with a comparison
of the individual estimates with existing shipborne gravity profiles. The results of the flight tests show that the gravity
estimates from the two systems agree at the 2–3 mGal level, after the removal of a linear bias. This is near the combined
noise level of the two systems. It appears that a combination of both systems would provide an ideal airborne gravity survey
system, combining the excellent bias stability of the LCR gravimeter with the higher dynamic range and increased spatial resolution
of the strapdown INS.
Received: 3 June 1999 / Accepted: 30 November 1999 相似文献
530.
大宗物质供销区位的定量分析及其引伸 总被引:2,自引:1,他引:2
大宗物资供销区位的一般提法是:设有某大宗物资(如粮食、煤炭、原油),其产地是A_1, A_2,……,A_m,共m个,产量分别是a_1,a_2,……,a_m个单位(如 t,10~4×0.5kg);另有n个销地B_1,B_2,……B_n,销量分别为b_1,b_2,……,b_n。产销是平衡的,同时产地与销地之间的运输距离与运输方式已知,即单位货物的运输费用已知。 相似文献