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排序方式: 共有357条查询结果,搜索用时 15 毫秒
311.
Paul R. Mahaffy Mehdi Benna Todd King Daniel N. Harpold Robert Arvey Michael Barciniak Mirl Bendt Daniel Carrigan Therese Errigo Vincent Holmes Christopher S. Johnson James Kellogg Patrick Kimvilakani Matthew Lefavor Jerome Hengemihle Ferzan Jaeger Eric Lyness John Maurer Anthony Melak Felix Noreiga Marvin Noriega Kiran Patel Benito Prats Eric Raaen Florence Tan Edwin Weidner Cynthia Gundersen Steven Battel Bruce P. Block Ken Arnett Ryan Miller Curt Cooper Charles Edmonson J. Thomas Nolan 《Space Science Reviews》2015,196(1-4):49-77
312.
M. C. De Sanctis A. Coradini E. Ammannito G. Filacchione M. T. Capria S. Fonte G. Magni A. Barbis A. Bini M. Dami I. Ficai-Veltroni G. Preti VIR Team 《Space Science Reviews》2011,163(1-4):329-369
The Dawn spectrometer (VIR) is a hyperspectral spectrometer with imaging capability. The design fully accomplishes Dawn’s scientific and measurement objectives. Determination of the mineral composition of surface materials in their geologic context is a primary Dawn objective. The nature of the solid compounds of the asteroid (silicates, oxides, salts, organics and ices) can be identified by visual and infrared spectroscopy using high spatial resolution imaging to map the heterogeneity of asteroid surfaces and high spectral resolution spectroscopy to determine the composition unambiguously. The VIR Spectrometer—covering the range from the near UV (0.25 μm) to the near IR (5.0 μm) and having moderate to high spectral resolution and imaging capabilities—is the appropriate instrument for the determination of the asteroid global and local properties. VIR combines two data channels in one compact instrument. The visible channel covers 0.25–1.05 μm and the infrared channel covers 1–5.0 μm. VIR is inherited from the VIRTIS mapping spectrometer (Coradini et al. in Planet. Space Sci. 46:1291–1304, 1998; Reininger et al. in Proc. SPIE 2819:66–77, 1996) on board the ESA Rosetta mission. It will be operated for more than 2 years and spend more than 10 years in space. 相似文献
313.
We present a methodology that provides traceable analysis from stakeholders’ needs to prioritized goals for human space exploration. We first construct a network to represent the stakeholder environment of NASA’s human exploration efforts, then assess the intensity of these stakeholder needs, and build a numerical model to represent the flow of value in the network. The underlying principle is that as a rational actor, NASA should invest its resources in creating outputs that provide the greatest return of support to it. We showcase this methodology, seeded with test data, the results of which suggests that the most important outputs of the exploration endeavor are human and robotic exploration firsts and science data, but also include funding to the science community, providing interesting NASA mission event content directly to the public and to the media, and commercial contracts. We propose that goals should be structured to ensure these value outputs, and be written in such as way as to convey the subsequent creation of value in the network. The goals derived in this manner suggest that the majority of the value created by human space exploration derives from campaign level design, rather than from operation of transportation elements. There would be higher assurance that these value outputs would be delivered if a responsible official or entity within the exploration function was specifically tasked with ensuring stakeholder value creation. 相似文献
314.
A. A. Baranov A. F. B. de Prado V. Yu. Razumny Anatoly A. BaranovJr. 《Cosmic Research》2011,49(3):269-279
Four types of optimal solutions are demonstrated to exist for transfers (time of flight is not fixed) between close near-circular
coplanar orbits. One solution is realized with the help of fixed orientation of the propulsion system (PS) along a transversal
in the orbital coordinate system. Another is reached at fixed orientation of the PS in the inertial coordinate system. The
third and fourth types of solutions change the PS orientation in the process of executing the maneuver. Regions of existence
are established for all types of solutions, and algorithms for determination of parameters of these maneuvers are suggested.
The algorithms were used to calculate parameters of the maneuvers of transfer from a launching orbit to a working Sun-synchronous
orbit, and to calculate the maneuvers of supporting the parameters of such an orbit in a specified range. 相似文献
315.
316.
美国国防部的"先进概念技术验证"(ACTD)计划,主要用来验证新型采购方式与信息技术的快速发展相适应的兼容性,并通过开发利用已经或正在成熟的技术来解决一些迫切的重要军用装备问题."联合蓝军态势报告"技术的成功应用是其中一个典型例子. 相似文献
317.
Chemical and physical processes in the outer solar nebula are reviewed. It is argued that the outer nebula was a chemically
active environment with UV photochemistry and ion-molecule chemistry in its low density regions and grain-catalyzed chemistry
in Jovian protoplanetary subnebulae. Presolar material was altered to greater or lesser extent by these spatially and temporally
variable processes, which mimic many features of interstellar chemistry. Experiments, models, and observations are recommended
to address the questions of presolar versus nebular dominance in the outer solar nebula and of how to distinguish interstellar
and nebular sources of cometary volatiles.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
318.
Mark Nelson William F. Dempster John P. Allen 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
Closed ecological systems are desirable for a number of purposes. In space life support systems, material closure allows precious life-supporting resources to be kept inside and recycled. Closure in small biospheric systems facilitates detailed measurement of global ecological processes and biogeochemical cycles. Closed testbeds facilitate research topics which require isolation from the outside (e.g. genetically modified organisms; radioisotopes) so their ecological interactions and fluxes can be studied separate from interactions with the outside environment. But to achieve and maintain closure entails solving complex ecological challenges. These challenges include being able to handle faster cycling rates and accentuated daily and seasonal fluxes of critical life elements such as carbon dioxide, oxygen, water, macro- and mico-nutrients. The problems of achieving sustainability in closed systems for life support include how to handle atmospheric dynamics including trace gases, producing a complete human diet, recycling nutrients and maintaining soil fertility, the maintenance of healthy air and water and preventing the loss of critical elements from active circulation. In biospheric facilities, the challenge is also to produce analogues to natural biomes and ecosystems, studying processes of self-organization and adaptation in systems that allow specification or determination of state variables and cycles which may be followed through all interactions from atmosphere to soils. Other challenges include the dynamics and genetics of small populations, the psychological challenges for small isolated human groups and backup technologies and strategic options which may be necessary to ensure long-term operation of closed ecological systems. 相似文献
319.
Vytenis M. Vasyliūnas 《Space Science Reviews》2011,158(1):91-118
Many widely used methods for describing and understanding the magnetosphere are based on balance conditions for quasi-static
equilibrium (this is particularly true of the classical theory of magnetosphere/ionosphere coupling, which in addition presupposes
the equilibrium to be stable); they may therefore be of limited applicability for dealing with time-variable phenomena as
well as for determining cause-effect relations. The large-scale variability of the magnetosphere can be produced both by changing
external (solar-wind) conditions and by non-equilibrium internal dynamics. Its developments are governed by the basic equations
of physics, especially Maxwell’s equations combined with the unique constraints of large-scale plasma; the requirement of
charge quasi-neutrality constrains the electric field to be determined by plasma dynamics (generalized Ohm’s law) and the
electric current to match the existing curl of the magnetic field. The structure and dynamics of the ionosphere/magnetosphere/solar-wind
system can then be described in terms of three interrelated processes: (1) stress equilibrium and disequilibrium, (2) magnetic
flux transport, (3) energy conversion and dissipation. This provides a framework for a unified formulation of settled as well
as of controversial issues concerning, e.g., magnetospheric substorms and magnetic storms. 相似文献
320.
William Marshall Mark Shirley Zachary Moratto Anthony Colaprete Gregory Neumann David Smith Scott Hensley Barbara Wilson Martin Slade Brian Kennedy Eric Gurrola Leif Harcke 《Space Science Reviews》2012,167(1-4):71-92
The Lunar CRater Observations and Sensing Satellite (LCROSS) mission impacted a spent Centaur rocket stage into a permanently shadowed region near the lunar south pole. The Sheperding Spacecraft (SSC) separated ~9 hours before impact and performed a small braking maneuver in order to observe the Centaur impact plume, looking for evidence of water and other volatiles, before impacting itself. This paper describes the registration of imagery of the LCROSS impact region from the mid- and near-infrared cameras onboard the SSC, as well as from the Goldstone radar. We compare the Centaur impact features, positively identified in the first two, and with a consistent feature in the third, which are interpreted as a 20 m diameter crater surrounded by a 160 m diameter ejecta region. The images are registered to Lunar Reconnaisance Orbiter (LRO) topographical data which allows determination of the impact location. This location is compared with the impact location derived from ground-based tracking and propagation of the spacecraft’s trajectory and with locations derived from two hybrid imagery/trajectory methods. The four methods give a weighted average Centaur impact location of ?84.6796°, ?48.7093°, with a 1σ uncertainty of 115 m along latitude, and 44 m along longitude, just 146 m from the target impact site. Meanwhile, the trajectory-derived SSC impact location is ?84.719°, ?49.61°, with a 1σ uncertainty of 3 m along the Earth vector and 75 m orthogonal to that, 766 m from the target location and 2.803 km south-west of the Centaur impact. We also detail the Centaur impact angle and SSC instrument pointing errors. Six high-level LCROSS mission requirements are shown to be met by wide margins. We hope that these results facilitate further analyses of the LCROSS experiment data and follow-up observations of the impact region. 相似文献