全文获取类型
收费全文 | 593篇 |
免费 | 79篇 |
国内免费 | 120篇 |
专业分类
航空 | 390篇 |
航天技术 | 227篇 |
综合类 | 76篇 |
航天 | 99篇 |
出版年
2024年 | 2篇 |
2023年 | 6篇 |
2022年 | 9篇 |
2021年 | 18篇 |
2020年 | 20篇 |
2019年 | 34篇 |
2018年 | 56篇 |
2017年 | 38篇 |
2016年 | 29篇 |
2015年 | 22篇 |
2014年 | 28篇 |
2013年 | 25篇 |
2012年 | 32篇 |
2011年 | 36篇 |
2010年 | 34篇 |
2009年 | 44篇 |
2008年 | 50篇 |
2007年 | 37篇 |
2006年 | 52篇 |
2005年 | 41篇 |
2004年 | 24篇 |
2003年 | 29篇 |
2002年 | 12篇 |
2001年 | 12篇 |
2000年 | 18篇 |
1999年 | 8篇 |
1998年 | 10篇 |
1997年 | 10篇 |
1996年 | 9篇 |
1995年 | 10篇 |
1994年 | 14篇 |
1993年 | 5篇 |
1992年 | 4篇 |
1991年 | 4篇 |
1990年 | 6篇 |
1989年 | 2篇 |
1984年 | 2篇 |
排序方式: 共有792条查询结果,搜索用时 453 毫秒
101.
介绍了一种新型电工钢片磁性能无损检测传感器及其测量原理 ,同时讨论了该传感器的设计原则并给出了典型数据及仿真测试结果 相似文献
102.
S.W. Kahler B.R. Ragot 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
A current serious limitation on the studies of solar energetic particle (SEP) events is that their properties in the inner heliosphere are studied only through in situ spacecraft observations. Our understanding of spatial distributions and temporal variations of SEP events has come through statistical studies of many such events over several solar cycles. In contrast, flare SEPs in the solar corona can be imaged through their radiative and collisional interactions with solar fields and particles. We suggest that the heliospheric SEPs may also interact with heliospheric particles and fields to produce signatures which can be remotely observed and imaged. A challenge with any such candidate signature is to separate it from that of flare SEPs. The optimum case for imaging high-energy (E > 100 MeV) heliospheric protons may be the emission of π0-decay γ-rays following proton collisions with solar wind (SW) ions. In the case of E > 1 MeV electrons, gyrosynchrotron radio emission may be the most readily detectible remote signal. In both cases we may already have observed one or two such events. Another radiative signature from nonthermal particles may be resonant transition radiation, which has likely already been observed from solar flare electrons. We discuss energetic neutrons as another possible remote signature, but we rule out γ-ray line and 0.511 MeV positron annihilation emission as observable signatures of heliospheric energetic ions. We are already acquiring global signatures of large inner-heliospheric SW density features and of heliosheath interactions between the SW and interstellar neutral ions. By finding an appropriate observable signature of remote heliospheric SEPs, we could supplement the in situ observations with global maps of energetic SEP events to provide a comprehensive view of SEP events. 相似文献
103.
Daniel Gómez 《Space Science Reviews》2006,122(1-4):231-238
104.
磁性液体,是由固体的磁性粒子分散到载体(液体)中形成的一种胶体溶液,此种深夜既有液体的流动性,又具有磁性,是一种新型的磁性材料,本文对磁性液体的制造方法,及其存在的条件,进行了研究与探讨,并简单介绍了磁性液体的性质及其应用前景。 相似文献
105.
The spectral and polarization properties of thermal cyclotron radio emission from a hot coronal loop with a current along the axis are computed. The magnetic field is supposed to have a component along the loop axis as well as a poloidal part due to the current, both components being of comparable magnitude. In this specific configuration a helical magnetic field is present with a remarkable minimum of its absolute value along the loop axis and a maximum at its periphery. The presence of one or two maxima of magnetic field value along the line of sight results in increasing optical thickness of the gyroresonance layers at appropriate frequencies in the microwave band and, therefore, in enhanced radio emission at those harmonics which are optically thin (for example,s=4). These cannot be observed in models with the commonly employed magnetic field configuration (longitudinal along the loop axis).We show that the frequency spectrum of thermal cyclotron radiation from a hot coronal loop with a helical magnetic field differs from that of the standards-component source (with smooth frequency characteristics and polarization corresponding toe-mode) in that plenty of fine structures (line-like features and cut-offs) are present and theo-mode is prevalent in some frequency intervals. The enhanced radio emission at high harmonics and the complicated form of frequency spectrum in the model considered imply that some microwave sources, which are poorly explained in traditional models of solar active regions, may be associated with helical magnetic fields in hot coronal loops. Computations allow one to indicate spectral and polarizational peculiarities of local sources testifying to the presence of a helical magnetic field. 相似文献
106.
José Luis Ballester 《Space Science Reviews》2005,121(1-4):105-113
Prominence seismology is a rapidly developing topic which seeks to infer the internal structure and properties of solar prominences
from the study of its oscillations. An extensive observational background about oscillations in quiescent solar prominences
has been gathered during the last 70 years. These observations point out the existence of two different types of oscillations:
Flare-induced oscillations (winking filaments) which affect the whole prominence and are of large amplitude and small amplitude
oscillations which seem to be of local nature. From the theoretical point of view, few models have been set up to explain
the phenomenon of winking filaments while, on the contrary, for small amplitude oscillations a large number of models trying
to explain the observed features have been proposed. 相似文献
107.
Nat Gopalswamy 《Space Science Reviews》2006,124(1-4):145-168
Interplanetary coronal mass ejections (ICMEs) originating from closed field regions on the Sun are the most energetic phenomenon
in the heliosphere. They cause intense geomagnetic storms and drive fast mode shocks that accelerate charged particles. ICMEs
are the interplanetary manifestations of CMEs typically remote-sensed by coronagraphs. This paper summarizes the observational
properties of ICMEs with reference to the ordinary solar wind and the progenitor CMEs. 相似文献
108.
Magnetic reconnection is a universal phenomenon where energy is efficiently converted from the magnetic field to charged particles
as a result of global magnetic topology changes during which earlier separated plasma regions become magnetically connected.
While the reconnection affects large volumes in space most of the topology changes and of the energization occur within small
localized regions. Regions of special importance are the X-region and the separatrix region. The understanding of the microphysics
of these regions is crucial for the overall understanding of the reconnection. The Earth magnetosphere is the best environment
where the details of these regions can be studied in situ. We summarize their main properties and discuss recent spacecraft observations. 相似文献
109.
V.M. Lipunov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,3(10-12)
The general aproach is considered which describs the evolution of neutron stars in terms of their interaction with surrounding matter. All possible states of neutron stars are classified from this point of view. Classification and evolution of binaries contaning neutron stars are also considered. 相似文献
110.
P. Mszros 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,3(10-12)
The key radiative processes are discussed, numerical methods of magnetized radiative transfer are presented, and these are considered in their application to X-ray pulsar models. 相似文献