全文获取类型
| 收费全文 | 5866篇 |
| 免费 | 17篇 |
| 国内免费 | 10篇 |
专业分类
| 航空 | 2625篇 |
| 航天技术 | 2070篇 |
| 综合类 | 22篇 |
| 航天 | 1176篇 |
出版年
| 2021年 | 58篇 |
| 2019年 | 31篇 |
| 2018年 | 148篇 |
| 2017年 | 106篇 |
| 2016年 | 111篇 |
| 2015年 | 53篇 |
| 2014年 | 161篇 |
| 2013年 | 184篇 |
| 2012年 | 182篇 |
| 2011年 | 256篇 |
| 2010年 | 177篇 |
| 2009年 | 296篇 |
| 2008年 | 379篇 |
| 2007年 | 180篇 |
| 2006年 | 140篇 |
| 2005年 | 174篇 |
| 2004年 | 152篇 |
| 2003年 | 202篇 |
| 2002年 | 127篇 |
| 2001年 | 207篇 |
| 2000年 | 100篇 |
| 1999年 | 121篇 |
| 1998年 | 151篇 |
| 1997年 | 108篇 |
| 1996年 | 126篇 |
| 1995年 | 161篇 |
| 1994年 | 142篇 |
| 1993年 | 81篇 |
| 1992年 | 117篇 |
| 1991年 | 60篇 |
| 1990年 | 45篇 |
| 1989年 | 115篇 |
| 1988年 | 50篇 |
| 1987年 | 56篇 |
| 1986年 | 53篇 |
| 1985年 | 143篇 |
| 1984年 | 111篇 |
| 1983年 | 90篇 |
| 1982年 | 110篇 |
| 1981年 | 160篇 |
| 1980年 | 53篇 |
| 1979年 | 41篇 |
| 1978年 | 38篇 |
| 1977年 | 36篇 |
| 1976年 | 34篇 |
| 1975年 | 35篇 |
| 1974年 | 35篇 |
| 1973年 | 29篇 |
| 1972年 | 24篇 |
| 1970年 | 25篇 |
排序方式： 共有5893条查询结果，搜索用时 31 毫秒
81.
David G. Sibeck R. Allen H. Aryan D. Bodewits P. Brandt G. Branduardi-Raymont G. Brown J. A. Carter Y. M. Collado-Vega M. R. Collier H. K. Connor T. E. Cravens Y. Ezoe M.-C. Fok M. Galeazzi O. Gutynska M. Holmström S.-Y. Hsieh K. Ishikawa D. Koutroumpa K. D. Kuntz M. Leutenegger Y. Miyoshi F. S. Porter M. E. Purucker A. M. Read J. Raeder I. P. Robertson A. A. Samsonov S. Sembay S. L. Snowden N. E. Thomas R. von Steiger B. M. Walsh S. Wing 《Space Science Reviews》2018,214(4):79
Both heliophysics and planetary physics seek to understand the complex nature of the solar wind’s interaction with solar system obstacles like Earth’s magnetosphere, the ionospheres of Venus and Mars, and comets. Studies with this objective are frequently conducted with the help of single or multipoint in situ electromagnetic field and particle observations, guided by the predictions of both local and global numerical simulations, and placed in context by observations from far and extreme ultraviolet (FUV, EUV), hard X-ray, and energetic neutral atom imagers (ENA). Each proposed interaction mechanism (e.g., steady or transient magnetic reconnection, local or global magnetic reconnection, ion pick-up, or the Kelvin-Helmholtz instability) generates diagnostic plasma density structures. The significance of each mechanism to the overall interaction (as measured in terms of atmospheric/ionospheric loss at comets, Venus, and Mars or global magnetospheric/ionospheric convection at Earth) remains to be determined but can be evaluated on the basis of how often the density signatures that it generates are observed as a function of solar wind conditions. This paper reviews efforts to image the diagnostic plasma density structures in the soft (low energy, 0.1–2.0 keV) X-rays produced when high charge state solar wind ions exchange electrons with the exospheric neutrals surrounding solar system obstacles.The introduction notes that theory, local, and global simulations predict the characteristics of plasma boundaries such the bow shock and magnetopause (including location, density gradient, and motion) and regions such as the magnetosheath (including density and width) as a function of location, solar wind conditions, and the particular mechanism operating. In situ measurements confirm the existence of time- and spatial-dependent plasma density structures like the bow shock, magnetosheath, and magnetopause/ionopause at Venus, Mars, comets, and the Earth. However, in situ measurements rarely suffice to determine the global extent of these density structures or their global variation as a function of solar wind conditions, except in the form of empirical studies based on observations from many different times and solar wind conditions. Remote sensing observations provide global information about auroral ovals (FUV and hard X-ray), the terrestrial plasmasphere (EUV), and the terrestrial ring current (ENA). ENA instruments with low energy thresholds ((sim1~mbox{keV})) have recently been used to obtain important information concerning the magnetosheaths of Venus, Mars, and the Earth. Recent technological developments make these magnetosheaths valuable potential targets for high-cadence wide-field-of-view soft X-ray imagers.Section 2 describes proposed dayside interaction mechanisms, including reconnection, the Kelvin-Helmholtz instability, and other processes in greater detail with an emphasis on the plasma density structures that they generate. It focuses upon the questions that remain as yet unanswered, such as the significance of each proposed interaction mode, which can be determined from its occurrence pattern as a function of location and solar wind conditions. Section 3 outlines the physics underlying the charge exchange generation of soft X-rays. Section 4 lists the background sources (helium focusing cone, planetary, and cosmic) of soft X-rays from which the charge exchange emissions generated by solar wind exchange must be distinguished. With the help of simulations employing state-of-the-art magnetohydrodynamic models for the solar wind-magnetosphere interaction, models for Earth’s exosphere, and knowledge concerning these background emissions, Sect. 5 demonstrates that boundaries and regions such as the bow shock, magnetosheath, magnetopause, and cusps can readily be identified in images of charge exchange emissions. Section 6 reviews observations by (generally narrow) field of view (FOV) astrophysical telescopes that confirm the presence of these emissions at the intensities predicted by the simulations. Section 7 describes the design of a notional wide FOV “lobster-eye” telescope capable of imaging the global interactions and shows how it might be used to extract information concerning the global interaction of the solar wind with solar system obstacles. The conclusion outlines prospects for missions employing such wide FOV imagers. 相似文献
82.
López-Valverde Miguel A. Gerard Jean-Claude González-Galindo Francisco Vandaele Ann-Carine Thomas Ian Korablev Oleg Ignatiev Nikolai Fedorova Anna Montmessin Franck Määttänen Anni Guilbon Sabrina Lefevre Franck Patel Manish R. Jiménez-Monferrer Sergio García-Comas Maya Cardesin Alejandro Wilson Colin F. Clancy R. T. Kleinböhl Armin McCleese Daniel J. Kass David M. Schneider Nick M. Chaffin Michael S. López-Moreno José Juan Rodríguez Julio 《Space Science Reviews》2018,214(1):1-31
Space Science Reviews - Time measured by an ideal clock crucially depends on the gravitational potential and velocity of the clock according to general relativity. Technological advances in... 相似文献
83.
H. M. Cuppen C. Walsh T. Lamberts D. Semenov R. T. Garrod E. M. Penteado S. Ioppolo 《Space Science Reviews》2017,212(1-2):1-58
The cross-disciplinary field of astrochemistry exists to understand the formation, destruction, and survival of molecules in astrophysical environments. Molecules in space are synthesized via a large variety of gas-phase reactions, and reactions on dust-grain surfaces, where the surface acts as a catalyst. A broad consensus has been reached in the astrochemistry community on how to suitably treat gas-phase processes in models, and also on how to present the necessary reaction data in databases; however, no such consensus has yet been reached for grain-surface processes. A team of ({sim}25) experts covering observational, laboratory and theoretical (astro)chemistry met in summer of 2014 at the Lorentz Center in Leiden with the aim to provide solutions for this problem and to review the current state-of-the-art of grain surface models, both in terms of technical implementation into models as well as the most up-to-date information available from experiments and chemical computations. This review builds on the results of this workshop and gives an outlook for future directions. 相似文献
84.
The results of flow field numerical simulation on the typical wing-body prototype of the modern DLR-F4 airliner under sub- and transonic compressible air flow are presented. Using the DLR-F4 CAD model, the effect of the wingtip end plate area and of the cant angle of a typical Whitcomb winglet is studied. The dependencies of the model lift-to-drag ratio increment on the flat wingtip end plate relative area and on the cant angle of an airfoil Whitcomb winglet are obtained. The concept of an elliptic winglet with a variable cant angle that similar to the winglet used on Airbus A350 is studied. A technique is developed for solving the multi-parameter design optimization task for the Whitcomb winglet, taking the maximum lift-to-drag ratio of the wing as a criterion for optimization. 相似文献
85.
V.?A.?Afanas’ev G.?L.?Degtyarev A.?S.?Meshchanov "mailto:mas@list.ru " title= "mas@list.ru " itemprop= "email " data-track= "click " data-track-action= "Email author " data-track-label= " ">Email author 《Russian Aeronautics (Iz VUZ)》2018,61(1):23-31
Real values of parameters for a space vehicle and its steering devices are specified by using the motion parameters measured in flight based on solving the differential equations of motion. 相似文献
86.
Lauretta D. S. Balram-Knutson S. S. Beshore E. Boynton W. V. Drouet d’Aubigny C. DellaGiustina D. N. Enos H. L. Golish D. R. Hergenrother C. W. Howell E. S. Bennett C. A. Morton E. T. Nolan M. C. Rizk B. Roper H. L. Bartels A. E. Bos B. J. Dworkin J. P. Highsmith D. E. Lorenz D. A. Lim L. F. Mink R. Moreau M. C. Nuth J. A. Reuter D. C. Simon A. A. Bierhaus E. B. Bryan B. H. Ballouz R. Barnouin O. S. Binzel R. P. Bottke W. F. Hamilton V. E. Walsh K. J. Chesley S. R. Christensen P. R. Clark B. E. Connolly H. C. Crombie M. K. Daly M. G. Emery J. P. McCoy T. J. McMahon J. W. Scheeres D. J. Messenger S. Nakamura-Messenger K. Righter K. Sandford S. A. 《Space Science Reviews》2017,212(1-2):925-984
In May of 2011, NASA selected the Origins, Spectral Interpretation, Resource Identification, and Security–Regolith Explorer (OSIRIS-REx) asteroid sample return mission as the third mission in the New Frontiers program. The other two New Frontiers missions are New Horizons, which explored Pluto during a flyby in July 2015 and is on its way for a flyby of Kuiper Belt object 2014 MU69 on January 1, 2019, and Juno, an orbiting mission that is studying the origin, evolution, and internal structure of Jupiter. The spacecraft departed for near-Earth asteroid (101955) Bennu aboard an United Launch Alliance Atlas V 411 evolved expendable launch vehicle at 7:05 p.m. EDT on September 8, 2016, on a seven-year journey to return samples from Bennu. The spacecraft is on an outbound-cruise trajectory that will result in a rendezvous with Bennu in November 2018. The science instruments on the spacecraft will survey Bennu to measure its physical, geological, and chemical properties, and the team will use these data to select a site on the surface to collect at least 60 g of asteroid regolith. The team will also analyze the remote-sensing data to perform a detailed study of the sample site for context, assess Bennu’s resource potential, refine estimates of its impact probability with Earth, and provide ground-truth data for the extensive astronomical data set collected on this asteroid. The spacecraft will leave Bennu in 2021 and return the sample to the Utah Test and Training Range (UTTR) on September 24, 2023.
相似文献87.
Yu. A. Gravchenko B. K. Grankin V. V. Kozlov S. V. Chirva 《Russian Aeronautics (Iz VUZ)》2017,60(3):327-334
The paper adduces the relators for algebraic operations on graphs using the numeric codes of the graphs. The special algebra of codes has been devised with consideration of the principles of graph transformation. This paper demonstrates the relevance of numeric coding of graphs for solving the problems of enumeration, systematization, and compact representation of the information about the structural and functional characteristics of the systems of flow distribution and conversion of rocket and space technology and for conducting the modeling transformations of given systems in the course of the structural and functional studies as well. 相似文献
88.
89.
通过研究产品(零件)制造过程、方法、参数等工艺因素,给零件表面及表层带来(留下)特有的微观特征性,首次在高精度惯性仪表和高可靠电磁继电器(机电类)产品制造体系中引入了零件表面微观工艺特征性概念,提出了制造阶段的产品工艺可靠性设计和微观工艺特征(性)分析方法,提出了该类产品制造中的工艺设计更应该关注零件与产品设计原理匹配性和性能特性符合性观点,提出零件制造要从单纯的控制几何精度向控制性能特性转变,从宏观、单一采标的几何参数评价向微观、综合采标的非几何(非尺寸)参数评价模式为主转变的建议.零件表面存在的这种微观特征现象与零件几何精度一样,将对产品制造的合格率、稳定性、可靠性的实现起到至关重要的作用,尤其对产品的合格率影响极大,有必要开展更深入、更系统的研究,以建立起我国自主的高端产品(或零件)制造基准工艺平台. 相似文献
90.
A. S. Meshchanov 《Russian Aeronautics (Iz VUZ)》2010,53(4):382-393
The results obtained for the systems with a linear stationary object and scalar control of sliding and switching modes [1] are further developed. The methods of forming five modes of system operation with discontinuous and linear vector control at nominal and uncertain limited disturbances are suggested. The necessary quality of transient processes with regard to the speed of response and zero stationary error at all five modes and also controlled oscillation frequency and amplitude of control signals at the sliding modes are provided. The effective sequence of switching the modes mentioned during the finite and unlimited time intervals is proposed. The results are useful for qualitative tracking of programmed motion for flight vehicles, robot manipulators, and other technical and production systems. 相似文献