全文获取类型
收费全文 | 4082篇 |
免费 | 24篇 |
国内免费 | 8篇 |
专业分类
航空 | 1634篇 |
航天技术 | 1400篇 |
综合类 | 31篇 |
航天 | 1049篇 |
出版年
2022年 | 20篇 |
2021年 | 47篇 |
2019年 | 22篇 |
2018年 | 134篇 |
2017年 | 105篇 |
2016年 | 119篇 |
2015年 | 46篇 |
2014年 | 126篇 |
2013年 | 152篇 |
2012年 | 142篇 |
2011年 | 190篇 |
2010年 | 151篇 |
2009年 | 233篇 |
2008年 | 273篇 |
2007年 | 143篇 |
2006年 | 100篇 |
2005年 | 139篇 |
2004年 | 127篇 |
2003年 | 133篇 |
2002年 | 106篇 |
2001年 | 154篇 |
2000年 | 52篇 |
1999年 | 86篇 |
1998年 | 91篇 |
1997年 | 52篇 |
1996年 | 71篇 |
1995年 | 98篇 |
1994年 | 85篇 |
1993年 | 52篇 |
1992年 | 70篇 |
1991年 | 20篇 |
1990年 | 31篇 |
1989年 | 65篇 |
1988年 | 23篇 |
1987年 | 23篇 |
1986年 | 25篇 |
1985年 | 81篇 |
1984年 | 75篇 |
1983年 | 68篇 |
1982年 | 60篇 |
1981年 | 102篇 |
1980年 | 31篇 |
1979年 | 22篇 |
1978年 | 20篇 |
1977年 | 24篇 |
1976年 | 17篇 |
1975年 | 18篇 |
1974年 | 14篇 |
1972年 | 14篇 |
1971年 | 12篇 |
排序方式: 共有4114条查询结果,搜索用时 62 毫秒
801.
Y. Yamamoto T. Okada H. Shiraishi K. Shirai T. Arai K. Ogawa K. Hosono M. Arakawa M. Kato 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
The X-ray spectrometer (XRS) on the SELENE (SELenological and ENgineering Explorer) spacecraft, XRS, will observe fluorescent X-rays from the lunar surface. The energy of the fluorescent X-ray depends on the elements of which the lunar soil consists, therefore we can determine elemental composition of the upper most lunar surface. The XRS consists of three components: XRF-A, SOL-B, and SOL-C. XRF-A is the main sensor to observe X-rays from the lunar surface. SOL-B is direct monitor of Solar X-ray using Si-PIN photodiode. SOL-C is another Solar X-ray monitor but observes the X-rays from the standard sample attached on the base plate. This enables us to analyze by a comparative method similar to typical laboratory XRF methods. XRF-A and SOL-C adopt charge coupled device as an X-ray detector which depletion layer is deep enough to detect X-rays. The X-ray spectra were obtained by the flight model of XRS components, and all components has been worked well to analyze fluorescent X-rays. Currently, development of the hardware and software of the XRS has been finished and we are preparing for system integration test for the launch. 相似文献
802.
T.A. Borisova N.V. Krisanova 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
High-affinity Na+-dependent glutamate transporters of the plasma membrane mediate the glutamate uptake into neurons, and thus maintain low levels of extracellular glutamate in the synaptic cleft. The study focused on the release of glutamate by reversal of Na+-dependent glutamate transporters from rat brain nerve terminals (synaptosomes) under conditions of centrifuge-induced hypergravity. Flow cytometric analysis revealed similarity in the size and cytoplasmic granularity between synaptosomal preparations obtained from control and G-loaded animals (10 G, 1 h). The release of cytosolic l-[14C]glutamate from synaptosomes was evaluated using the protonophore FCCP, which dissipated synaptic vesicle proton gradient, thus synaptic vesicles were not able to keep glutamate inside and the latter enriched cytosol. FCCP per se induced the greater release of l-[14C]glutamate in hypergravity as compared to control (4.8 ± 1.0% and 8.0 ± 1.0% of total label). Exocytotic release of l-[14C]glutamate evoked by depolarization was reduced down to zero after FCCP application under both conditions studied. Depolarization stimulated release of cytosolic l-[14C]glutamate from synaptosomes preliminary treated with FCCP was considerably increased from 27.0 ± 2.2% of total label in control to 35.0 ± 2.3% in hypergravity. Non-transportable inhibitor of glutamate transporter dl-threo-β-benzyloxyaspartate was found to significantly inhibit high-KCl and FCCP-stimulated release of l-[14C]glutamate, confirming the release by reversal of glutamate transporters. The enhancement of transporter-mediated release of glutamate in hypergravity was found to result at least partially from the inhibition of the activity of Na/K-ATPase in the plasma membrane of synaptosomes. We suggested that hypergravity-induced alteration in transporter-mediated release of glutamate indicated hypoxic injury of neurons. 相似文献
803.
M. Poje B. Vuković M. Varga V. Radolić I. Miklavčić D. Faj J. Planinić 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
Cosmic radiation bombards us at high altitude with ionizing particles; the radiation has a galactic component, which is normally dominant, and a component of solar origin. Cosmic ray particles are the primary source of ionization in the atmosphere above 1 km; below 1 km radon is a dominant source of ionization in many areas. 相似文献
804.
Litvak ML Mitrofanov IG Barmakov YN Behar A Bitulev A Bobrovnitsky Y Bogolubov EP Boynton WV Bragin SI Churin S Grebennikov AS Konovalov A Kozyrev AS Kurdumov IG Krylov A Kuznetsov YP Malakhov AV Mokrousov MI Ryzhkov VI Sanin AB Shvetsov VN Smirnov GA Sholeninov S Timoshenko GN Tomilina TM Tuvakin DV Tretyakov VI Troshin VS Uvarov VN Varenikov A Vostrukhin A 《Astrobiology》2008,8(3):605-612
We present a summary of the physical principles and design of the Dynamic Albedo of Neutrons (DAN) instrument onboard NASA's 2009 Mars Science Laboratory (MSL) mission. The DAN instrument will use the method of neutron-neutron activation analysis in a space application to study the abundance and depth distribution of water in the martian subsurface along the path of the MSL rover. 相似文献
805.
The results of a numerical simulation of such parameters of the topside ionosphere as concentration N e and temperature T e of electrons, and concentration n(H+) and fluxes along the magnetic field lines Φ(H+) of H+ ions at an altitude of ~2000 km for the conditions of the August 11, 1999 solar eclipse are presented. The calculations were performed using the Global Self-consistent Model of the Thermosphere, Ionosphere, and Protonosphere of the Earth (GSM TIP). It is shown that during the eclipse, in addition to a region of decreased values of T e in the Northern Hemisphere and in the magnetically conjugate region in the Southern Hemisphere, regions of electron heating emerge in both hemispheres. Simultaneously, an extended region of decreased values of N e comes into existence and moves behind the Moon’s shadow. Regions with decreased (down to ~30%) and enhanced (up to ~50%) concentrations of H+ ions are detected in the global distribution of these ions. 相似文献
806.
V. P. Varin 《Cosmic Research》2007,45(1):78-84
We study degeneracies in families of periodic solutions to the Beletsky equation which correspond to intersections of three manifolds of these solutions: the symmetric, the asymmetric, and the manifold belonging to one of the integrable cases, i.e., e = 0 or μ = 0. We obtain equations for these isolated solutions, which allow us to compute them with an arbitrary precision. It is shown that additional degeneracies take place at some of these solutions. The method we use is applicable to a wide class of nonlinear ordinary differential equations (ODEs) depending on parameters. 相似文献
807.
V. V. Andreyanov 《Cosmic Research》2007,45(6):486-492
At present, space radio astronomers and engineers study the prospects of design of the second-generation ground-space interferometers for astrophysical research with the microsecond angular resolution of sources. The implemented Japanese VSOP project (1998–2003) and the Russian Radioastron project (under preparation for space flight) are related to the first generation. In this paper, the ideology and configuration of the Space-Space interferometer are considered. It would allow one to obtain principally new capabilities: to exclude the Earth’s atmosphere influence, to realize a quasi-phase-stable interferometer, and to remove the problems of electromagnetic compatibility with other services. Moreover, a capability will appear to carry out preliminary correlation processing onboard the spacecraft due to achievement of small residual uncertainties in signal delay and frequency and, owing to this, to realize onboard data compression in order to transmit data to the Earth by usual space communication channel. 相似文献
808.
The five main types of antisunward propagating energetic fluxes (particles and emission) may be thought of as well established to date, the effects of which lead to a particilar character of disturbance in the near-terrestrial environment (the Earth's magnetosphere, ionosphere and atmosphere). The strongest global restructuring of the magnetosphere and ionosphere is caused by fluxes of relatively dense n of 1-70 cm-3 at the Earth's orbit) Solar Wind (SW) quasi-neutral, low-energy (E < 10 keV) plasma which cause magnetospheric and ionospheric storms lasting 24 hours or longer. For that reason, main attention is given to their study at the initial stage of research. The physical essence of the method of predicting disturbances in the near-terrestrial space environment, the amplitude of which can be expressed in, for example, the Kp index units, involves:(1) identifying all the most geo-effective SW streams of type, (2) determing their sources on the solar disk,and (3) quantifying the correlations between the characteristics of their solar sources with a maximum value of the Kp-index that is caused by the concerned type of SW stream. Semi-phenomenological relations have been obtained, which relate parameters of type SW stream sources to characteristics of geomagnetic storms:storm commencement, the time at which the storm intensity reaches its maximum values, the storm duration,as well as to the storm amplitude expressed in terms of geomagnetic indeces. 相似文献
809.
Development of a plant growth unit for growing plants over a long-term life cycle under microgravity conditions. 总被引:4,自引:0,他引:4
Y Kitaya A Tani E Goto T Saito H Takahashi 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2000,26(2):281-288
To study the effect of the space environment on plant growth including the reproductive growth and genetic aberration for a long-term plant life cycle, we have initiated development of a new type of facility for growing plants under microgravity conditions. The facility is constructed with subsystems for controlling environmental elements. In this paper, the concept of the facility design is outlined. Subsystems controlling air temperature, humidity, CO2 concentration, light and air circulation around plants and delivering recycled water and nutrients to roots are the major concerns. Plant experiments for developing the facility and future plant experiments with the completed facility are also overviewed. We intend to install this facility in the Japan Experiment Facility (JEM) boarded on the International Space Station. 相似文献
810.