全文获取类型
收费全文 | 2170篇 |
免费 | 4篇 |
国内免费 | 7篇 |
专业分类
航空 | 754篇 |
航天技术 | 762篇 |
综合类 | 8篇 |
航天 | 657篇 |
出版年
2022年 | 6篇 |
2021年 | 23篇 |
2019年 | 7篇 |
2018年 | 73篇 |
2017年 | 58篇 |
2016年 | 56篇 |
2015年 | 20篇 |
2014年 | 69篇 |
2013年 | 68篇 |
2012年 | 66篇 |
2011年 | 109篇 |
2010年 | 80篇 |
2009年 | 125篇 |
2008年 | 144篇 |
2007年 | 81篇 |
2006年 | 51篇 |
2005年 | 66篇 |
2004年 | 70篇 |
2003年 | 83篇 |
2002年 | 53篇 |
2001年 | 90篇 |
2000年 | 38篇 |
1999年 | 41篇 |
1998年 | 43篇 |
1997年 | 34篇 |
1996年 | 49篇 |
1995年 | 40篇 |
1994年 | 33篇 |
1993年 | 20篇 |
1992年 | 35篇 |
1991年 | 9篇 |
1990年 | 12篇 |
1989年 | 34篇 |
1988年 | 13篇 |
1987年 | 19篇 |
1986年 | 20篇 |
1985年 | 67篇 |
1984年 | 35篇 |
1983年 | 25篇 |
1982年 | 37篇 |
1981年 | 66篇 |
1980年 | 16篇 |
1979年 | 6篇 |
1978年 | 7篇 |
1977年 | 13篇 |
1976年 | 9篇 |
1975年 | 14篇 |
1974年 | 15篇 |
1973年 | 8篇 |
1970年 | 4篇 |
排序方式: 共有2181条查询结果,搜索用时 0 毫秒
231.
Nicole D. Buckley Claude P. Champagne Adriana I. Masotti Lisa E. Wagar Thomas A. Tompkins Julia M. Green-Johnson 《Acta Astronautica》2011,68(7-8):731-738
Astronauts face numerous health challenges during long-duration space missions, including diminished immunity, bone loss and increased risk of radiation-induced carcinogenesis. Changes in the intestinal flora of astronauts may contribute to these problems. Soy-based fermented food products could provide a nutritional strategy to help alleviate these challenges by incorporating beneficial lactic acid bacteria, while reaping the benefits of soy isoflavones. We carried out strain selection for the development of soy ferments, selecting strains of lactic acid bacteria showing the most effective growth and fermentation ability in soy milk (Streptococcus thermophilus ST5, Bifidobacterium longum R0175 and Lactobacillus helveticus R0052). Immunomodulatory bioactivity of selected ferments was assessed using an in vitro challenge system with human intestinal epithelial and macrophage cell lines, and selected ferments show the ability to down-regulate production of the pro-inflammatory cytokine interleukin-8 following challenge with tumour necrosis factor-alpha. The impact of fermentation on vitamin B1 and B6 levels and on isoflavone biotransformation to agluconic forms was also assessed, with strain variation-dependent biotransformation ability detected. Overall this suggests that probiotic bacteria can be successfully utilized to develop soy-based fermented products targeted against health problems associated with long-term space travel. 相似文献
232.
B. I. Rabinovich 《Cosmic Research》2009,47(4):287-298
A mathematical model of the non-steady-state magnetosphere of the ocean of Jupiter’s moon Europa is described. This magnetosphere is induced by the magnetic field of Jupiter, and its interaction with the Europa ocean is considered. Rotation of the ocean and its icy crust with respect to the hard core is described by a system of integro-differential equations with singular kernels, the values of the Reynolds number and magnetic Reynolds number being large for the system. The solution to these equations obtained by the methods of operational calculus is analyzed quantitatively and compared with a model experiment. 相似文献
233.
I. V. Mingalev V. S. Mingalev O. V. Mingalev B. Kazeminejad H. Lammer H. K. Birnat H. I. M. Lihteneger K. Schvingenschu H. O. Ruker 《Cosmic Research》2009,47(2):114-125
The results of numerical simulation of the general circulation in the Titan’s atmosphere at heights from 0 to 250 km are presented, obtained using a new model based on numerical solution of complete equations of motion of viscous compressible gas at the temperature distribution given by an empirical model. The model uses no hydrostatic equation and, as compared with traditional models, has higher resolution in vertical and over horizon. The results presented differ from results of other models and agree with the vertical profile of the zonal component of wind velocity measured by the Huygens spacecraft. Interpretation of this profile is given, including its main peculiarity consisting in a nonmonotonic behavior at heights from 60 to 75 km. 相似文献
234.
Malakhov A. V. Mitrofanov I. G. Litvak M. L. Sanin A. B. Golovin D. V. Djachkova M. V. Nikiforov S. Yu. Anikin A. A. Lisov D. I. Lukyanov N. V. Mokrousov M. I. Shvetsov V. N. Timoshenko G. N. 《Cosmic Research》2022,60(1):23-37
Cosmic Research - The article presents results of ground calibrations of the FREND neutron telescope installed onboard the TGO spacecraft of the Russian-European ExoMars project. The main goal of... 相似文献
235.
This article presents main scientific and practical results obtained in course of scientific and applied research and experiments on Mir space station. Based on Mir experience, processes of research program formation for the Russian Segment of the ISS are briefly described. The major trends of activities planned in the frames of these programs as well as preliminary results of increment research programs implementation in the ISS' first missions are also presented. 相似文献
236.
Based on the results of plasma and magnetic measurements at three different points of the heliosphere and telescopic observations
of the Sun from these points we study simultaneously high-speed streams (HSS) of the solar wind (SW) near the Earths’s orbit
and coronal holes (CH) that have generated them. The data from spacecraft STEREO-A, STEREO-B, ACE, and SOHO are used together with ground-based observations from March 2007 to May 2008. In this period there existed HSS whose sources
represented CH of various polarity, geometry, and location relative to the heliographic and heliomagnetic equators. Dependence
of SW parameters on mutual positions of spacecraft with respect to CH and heliospheric current sheet, and also on heliolatitude
and geometry of the CH is revealed. A difference of more than 5° in locations of spacecraft with respect to the heliospheric
current sheet in November 2007 allowed us to discover a heliolatitude velocity gradient of the SW streams between the STEREO-A and STEREO-B spacecraft. On the average this gradient at that time was equal to 20 km/s per degree. Substantial variations in SW streams
associated with variations of the HSS SW sources during a few hours or days were also observed. This variability makes it
difficult to use the data of spacecraft STEREO-B for sufficiently accurate prediction of SW properties in the near-Earth space by the method of simple advanced ti me shift
due to heliolongitude difference between a spacecraft and the Earth even in solar activity minimum. 相似文献
237.
238.
S. O. Karpenko N. V. Kupriyanova M. Yu. Ovchinnikov V. I. Penkov A. S. Selivanov O. E. Khromov 《Cosmic Research》2010,48(6):517-525
The results of designing the attitude control system of the first Russian nanosatellite TNS-0 no. 1 providing orientation of its longitudinal axis along the local geomagnetic field induction vector are presented. The system consists of a permanent magnet and two sets of hysteresis rods. The magnetic and geometric parameters of the magnet and rods are calculated. The influence of the permanent magnet field on the hysteresis rods and mutual influence of the rods in the case of compact satellite packaging are analyzed. Examples of calculations of transient processes and steady-state angular satellite motion are presented. 相似文献
239.
Dynamics of planets around other stars that demonstrate a variety of possible characteristics is of interest from the point of view of realization of new scenarios of evolution which have not been realized in the Solar System. We consider the rotational evolution of exoplanets under the action of gravitational perturbations and magnetic disturbances using the methods of quality analysis and theory of bifurcation of multiparametric differential equations that describe evolution of non-resonant rotation of a dynamically symmetric planet magnetized along its symmetry axis. We analyze 64 phase portraits describing the evolution of angular momentum vector L for all possible values of planet parameters. The values of parameters are determined for the case when the direct rotation of a planet is changed for its retrograde rotation. 相似文献
240.
A comparison of temporal profiles of low-energy ion intensity and magnetic field magnitude in different periods of solar activity in the outer heliosphere is carried out using the data of the Voyager 1 and Voyager 2 spacecraft. It is shown that temporal, spectral, and statistical characteristics of particle fluxes and magnetic field in the heliospheric regions before and after the terminal shock in 2002–2008 had similar dynamics in different hemispheres. This similarity allowed one to assume that, in the region of the inner heliospheric boundary, a quasistable spatial structure existed moving together with the terminal shock in accordance with the solar wind pressure, as well as, probably, under the action of the interstellar medium. It was revealed that the spatial dimensions of most details of this structure are less on Voyager 2, which, probably, is due to variation of the solar activity level, difference in latitude of spacecraft disposition, and also the influence of the interstellar magnetic field. 相似文献