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281.
282.
B. A. Antuf’ev 《Russian Aeronautics (Iz VUZ)》2008,51(3):227-231
A problem on low vibrations of a thin spherical shell is considered. A solid of finite dimensions is discretely attached to the shell by means of an elastic rod system. The calculation examples are presented. 相似文献
283.
A capillary-driven root module for plant growth in microgravity. 总被引:2,自引:0,他引:2
S B Jones D Or 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1998,22(10):1407-1412
A new capillary-driven root module design for growing plants in microgravity was developed which requires minimal external control. Unlike existing systems, the water supply to the capillary-driven system is passive and relies on root uptake and media properties to develop driving gradients which operate a suction-induced flow control valve. A collapsible reservoir supplies water to the porous membrane which functions to maintain hydraulic continuity. Sheet and tubular membranes consisting of nylon, polyester and sintered porous stainless steel were tested. While finer pore sized membranes allow greater range of operation, they also reduce liquid flux thereby constraining system efficiency. Membrane selection should consider both the maximum anticipated liquid uptake rate and maximum operating matric head (suction) of the system. Matching growth media water retention characteristics to the porous membrane characteristics is essential for supplying adequate liquid flux and gas exchange. A minimum of 10% air-filled porosity (AFP) was necessary for adequate aeration. The capillary-driven module maintained hydraulic continuity and proper gas exchange rates for more than 80 days in a plant growth experiment. 相似文献
284.
Extraterrestrial infrastructure is key to the development of a space economy. Means for accelerating transition from today's isolated projects to a broad-based economy are considered. A large system integration approach is proposed. The beginnings of an economic simulation model are presented, along with examples of how interactions and coordination bring down costs. A global organization focused on space infrastructure and economic expansion is proposed to plan, coordinate, fund and implement infrastructure construction. This entity also opens a way to raise low-cost capital and solve the legal and public policy issues of access to extraterrestrial resources. 相似文献
285.
S. A. Mikhailov A. M. Girfanov A. B. Bochkareva A. S. Fal’ko 《Russian Aeronautics (Iz VUZ)》2007,50(4):362-367
The results of numerical and experimental study of physico-mechanical properties of composite materials are proposed and variations in rigidity characteristics of the hub working part of the hingeless type within the entire range of helicopter operational temperatures are evaluated. 相似文献
286.
C. de Jager A. Ollongren Tj. de Graaf B. J. Levin M. Tucker 《Space Science Reviews》1969,9(5):740-742
287.
ARTEMIS Mission Design 总被引:2,自引:0,他引:2
Theodore H. Sweetser Stephen B. Broschart Vassilis Angelopoulos Gregory J. Whiffen David C. Folta Min-Kun Chung Sara J. Hatch Mark A. Woodard 《Space Science Reviews》2011,165(1-4):27-57
The ARTEMIS mission takes two of the five THEMIS spacecraft beyond their prime mission objectives and reuses them to study the Moon and the lunar space environment. Although the spacecraft and fuel resources were tailored to space observations from Earth orbit, sufficient fuel margins, spacecraft capability, and operational flexibility were present that with a circuitous, ballistic, constrained-thrust trajectory, new scientific information could be gleaned from the instruments near the Moon and in lunar orbit. We discuss the challenges of ARTEMIS trajectory design and describe its current implementation to address both heliophysics and planetary science objectives. In particular, we explain the challenges imposed by the constraints of the orbiting hardware and describe the trajectory solutions found in prolonged ballistic flight paths that include multiple lunar approaches, lunar flybys, low-energy trajectory segments, lunar Lissajous orbits, and low-lunar-periapse orbits. We conclude with a discussion of the risks that we took to enable the development and implementation of ARTEMIS. 相似文献
288.
289.
R.B. Sheldon 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2000,25(12):2347-2356
It has generally been assumed that a geomagnetic storm is entirely driven by external forces—e.g., solar wind Ey = Vx × Bz, Vx, V2x (where the components of the electric field, E, the magnetic field, B, and velocity, V, are given in GSE coordinates)—which would imply that particle injections in the ring current (RC) or outer radiation belts should be highly correlated. However the data from ISTP are showing that the magnetosphere can have at least two very different responses to the same solar wind (SW) conditions: a classic, enhanced RC with Dst response, or a 1000-fold increase in the outer radiation belt MeV electrons (ORBE). August 29, October 14 and 23, 1996 are examples of Dst storms, whereas April 15, 1996 and January 10, 1997 are examples of MeV storms. It is this second response that is so deadly to some geosynchronous spacecraft, whereas geomagnetic storms are categorized by the first response. Neither of these appear to be correlated to the SW conditions driving substorms. Why should the SW energy appear in the radiation belts or the ring current independently? We hypothesize that the RC couples to the electric power available (Ey), the ORBE couple to the mechanical power available (Vx), and the Tail couples to the magnetic energy (Bz) available in the SW. The transducer for RC may be subauroral parallel potentials, the transducer for ORBE may be the cusp, while the Tail substorm transducer is yet a third independent mechanism for extracting SW energy. Evidence for this theory comes from the novel POLAR satellite that traverses the cusp, the plasmasheet and the radiation belts. 相似文献
290.
B. Gustafsson 《Space Science Reviews》1998,85(1-2):419-428
Various observable properties of the Sun are compared with those of solar-type stars. It is concluded that the Sun, to a remarkable
degree, is “solar-type”. As regards its particular mass and age, and probably its non-binarity, “anthropic” explanations may
seem in place. The possible tendency for the Sun, as compared with similar stars, to be somewhat rich in iron relative to
other elements needs further exploration. This is also true concerning its presently small micro-variability amplitude.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献