全文获取类型
收费全文 | 76篇 |
免费 | 10篇 |
国内免费 | 21篇 |
专业分类
测绘学 | 6篇 |
大气科学 | 22篇 |
地球物理 | 26篇 |
地质学 | 17篇 |
海洋学 | 6篇 |
天文学 | 23篇 |
综合类 | 3篇 |
自然地理 | 4篇 |
出版年
2022年 | 1篇 |
2020年 | 3篇 |
2019年 | 6篇 |
2017年 | 2篇 |
2016年 | 4篇 |
2015年 | 4篇 |
2014年 | 7篇 |
2013年 | 4篇 |
2012年 | 2篇 |
2011年 | 1篇 |
2010年 | 1篇 |
2009年 | 6篇 |
2008年 | 7篇 |
2007年 | 13篇 |
2006年 | 1篇 |
2005年 | 6篇 |
2004年 | 4篇 |
2003年 | 3篇 |
2002年 | 4篇 |
2001年 | 4篇 |
2000年 | 4篇 |
1999年 | 8篇 |
1997年 | 2篇 |
1996年 | 1篇 |
1995年 | 1篇 |
1994年 | 1篇 |
1992年 | 1篇 |
1991年 | 4篇 |
1990年 | 1篇 |
1984年 | 1篇 |
排序方式: 共有107条查询结果,搜索用时 140 毫秒
91.
通过1991年6月6日共生太阳白光耀斑(WLF)的射电运动IV型爆发及其伴随现象(包括耀斑后环、爆发衰减相的射电脉动、多波段射电辐射和太阳物质抛射等)观测资料的分析,定性地探讨了WLF的起源、加热机制和发射地点的问题.假设了WLF和射电运动IV型射电爆发可能有共同起源的低日冕电子加速区,讨论了WLF的能量传输可能是通过二步加速过程,即来自低日冕的非热电子沉降能量于色球层,产生色球层的压缩波或向下的辐射场进而使上光球层温度增加导致WLF此外,提出WLF可能会伴有耀斑后环和射电精细结构的对应物. 相似文献
92.
Y. Lu E. Vintzileou G. -F. Zhang T. P. Tassios 《Soil Dynamics and Earthquake Engineering》1999,18(2):709
In the area of reduced-scale model testing, increasing the size of model structures as a means of improving the model performance is often inhibited by the capacity limitation of the available seismic testing facilities. This was the case in a recent experimental programme conducted at NTUA in which several 1:5.5-scale model frames were tested on an earthquake simulator. In order to improve the model reliability, the following measures were taken: strictly obeying the geometric scaling in almost all aspects; using deformed bars as model reinforcement; and using stone-aggregate microconcrete for constructing the models, etc. To evaluate the effectiveness of these measures, a parallel column test programme was conducted in which duplicates of typical columns in the test model frames were prepared, along with those of large sizes following similitude laws. The column specimens were tested under reversals of lateral load. Besides the scale effects, general rules regarding the influences of transverse confinement and axial force on the ductility and strength of columns were also confirmed on the small-scale model columns. 相似文献
93.
耗能减震技术研究及应用的新进展 总被引:23,自引:5,他引:18
本文总结了耗能减震技术近年来的研究与应用情况,主要包括各种新型耗能减震装置的原理、性能及应用。文中介绍了有关国家耗能减振技术标准发展的情况,提出了该项技术今后应加强研究的若干问题,并预测了其发展前景。 相似文献
94.
We consider the damping mechanisms for the radial oscillations of solar coronal loops in the approximation of a thin magnetic flux tube. We show that the free tube oscillations can have a high Q if the plasma density inside the magnetic flux tube is much higher than the density outside. We analyze the effect of radial coronal-loop magnetic-field oscillations on the modulation of the microwave radiation from solar flares. In the case of a nonthermal gyrosynchrotron mechanism, the fluxes from optically thin and optically thick sources are modulated in antiphase. Based on our model, we diagnose the flare plasma. For the event of May 23, 1990, we estimate the spectral index for accelerated electrons, α≈4.4, and the magnetic-field strength in the region of energy release, B≈190 G. 相似文献
95.
活的非可培养状态霍乱弧菌的复苏 总被引:1,自引:0,他引:1
将活的非可培养状态的霍乱弧菌(EITor生物型)注入兔肠结扎段中,通过兔肠可以使休眠的霍乱弧菌复苏,恢复成为可培养状态.复苏的霍乱弧菌具有很强的毒力,使兔肠结扎段肿胀、积水、内壁紫红色并出现溃疡。结扎段积液中含有约109cells/ml细菌。 相似文献
96.
Magnetic Anomalies on the Tree Trunks 总被引:2,自引:0,他引:2
Kletetschka Gunther Žila Vojtěch Wasilewski Peter J. 《Studia Geophysica et Geodaetica》2003,47(2):371-379
Magnetic measurements of soil and tree bark adjacent to a busy highway revealed a significant variation in the concentration of magnetic particles with distance from the highway. Further more, forest-facing tree-bark contains significantly more magnetic particles than road-facing tree-bark. Magnetic particles were detected both on the bark of the maple trees and in the first centimeter of the soil cover (O/A horizon). Stability of saturation isothermal magnetization (SIRM) and hysteresis parameters of the soil indicates the presence of single domain (SD/PSD) magnetic carriers. Measurements of the tree bark hysteresis parameters and SIRM detect a significant lower coercivity component that we interpret to be an indication of more abundant pseudo-single domain (PSD) type magnetic grains. Magnetic measurements around the perimeters of eight tree trunks reveal magnetic carriers whose distribution is antipodal to the source direction (highway). We interpret our observation by adopting an air circulation model, where suspended PSD/SD particles are carried in the air stream. The air stream from the heavy traffic lowers the amount of moisture on the tree trunk surfaces facing the highway and thus reduces an adhesive potential on this side. Therefore, more particles can stay on the moist side of the trunk protected from the direct airflow. 相似文献
97.
Oliver Montenbruck Yago Andres Heike Bock Tom van Helleputte Jose van den Ijssel Marc Loiselet Christian Marquardt Pierluigi Silvestrin Pieter Visser Yoke Yoon 《GPS Solutions》2008,12(4):289-299
The global navigation satellite system receiver for atmospheric sounding (GRAS) on MetOp-A is the first European GPS receiver
providing dual-frequency navigation and occultation measurements from a spaceborne platform on a routine basis. The receiver
is based on ESA’s AGGA-2 correlator chip, which implements a high-quality tracking scheme for semi-codeless P(Y) code tracking
on the L1 and L2 frequency. Data collected with the zenith antenna on MetOp-A have been used to perform an in-flight characterization
of the GRAS instrument with focus on the tracking and navigation performance. Besides an assessment of the receiver noise
and systematic measurement errors, the study addresses the precise orbit determination accuracy achievable with the GRAS receiver.
A consistency on the 5 cm level is demonstrated for reduced dynamics orbit solutions computed independently by four different
agencies and software packages. With purely kinematic solutions, 10 cm accuracy is obtained. As a part of the analysis, an
empirical antenna offset correction and preliminary phase center correction map are derived, which notably reduce the carrier
phase residuals and improve the consistency of kinematic orbit determination results.
相似文献
Oliver MontenbruckEmail: |
98.
本文采用中国地区基于卫星观测的植被光合有效辐射资料(FPAR)和月平均气候数据(1982-2000年)来分析中国区域陆面植被与气温、降水的反馈作用.通过计算和分析超前滞后相关系数和反馈系数发现:春、夏季FPAR超前气温一个月相关系数在全国大部分地区为负值,反映出植被生长旺盛,可以降低局地气温.春、秋两季气温与FPAR的同期相关系数较大.夏季降水超前FPAR一个月的正相关性反映出夏季降水对于植被生长存在促进作用.在中国长江流域以南区域,植被对于气温的反馈系数为一致正值,可达0.5 ℃(0.1FPAR)-1;在30°N以北区域显示出一致的负反馈,可达-0.42 ℃(0.1FPAR)-1.FPAR对降水全年反馈系数全国区域平均可达-2.12 cm month-1(0.1FPAR)-1.不同植被类型、不同季节的植被反馈效应也存在差异.植被反馈系数可以用来验证动态植被模式计算的植被大气反馈作用. 相似文献
99.
100.
Emmanouil Rovithis Emmanouil Kirtas Kyriazis Pitilakis 《Bulletin of Earthquake Engineering》2009,7(3):719-736
Seismic soil-pile interaction is evaluated in this study based on back-calculated p-y loops constructed from sampled data
of pile bending moments. Fundamental properties of p-y loops are implemented to derive distributed springs and dashpots, thereby
quantifying soil-pile interaction in the realm of a Beam on Dynamic Winkler Foundation modeling. The procedure is validated
by means of well-documented centrifuge tests of a single pile supported structure founded on a two-layer soil profile that
comprises of soft clay overlying dense sand. Two shaking levels of a real earthquake motion applied at the base of the soil
profile were examined and the generated seismic p-y loops were compared to cyclic p-y curves commonly used in pile design
practice. The results demonstrate the strong influence of intensity of the input motion on seismic p-y loops while cyclic
p-y curves established for soft clays tend to overestimate soil stiffness under strong excitation. Typical sets of recorded
and computed structural response are presented, denoting the ability of the BDWF model related to p-y loops in reproducing
adequately fundamental aspects of seismic soil-pile interaction. 相似文献