全文获取类型
收费全文 | 6852篇 |
免费 | 19篇 |
国内免费 | 20篇 |
专业分类
航空 | 3070篇 |
航天技术 | 2407篇 |
综合类 | 21篇 |
航天 | 1393篇 |
出版年
2021年 | 74篇 |
2019年 | 45篇 |
2018年 | 160篇 |
2017年 | 107篇 |
2016年 | 112篇 |
2015年 | 51篇 |
2014年 | 178篇 |
2013年 | 222篇 |
2012年 | 212篇 |
2011年 | 322篇 |
2010年 | 229篇 |
2009年 | 329篇 |
2008年 | 366篇 |
2007年 | 220篇 |
2006年 | 156篇 |
2005年 | 185篇 |
2004年 | 182篇 |
2003年 | 205篇 |
2002年 | 145篇 |
2001年 | 218篇 |
2000年 | 127篇 |
1999年 | 162篇 |
1998年 | 190篇 |
1997年 | 109篇 |
1996年 | 171篇 |
1995年 | 203篇 |
1994年 | 189篇 |
1993年 | 120篇 |
1992年 | 149篇 |
1991年 | 47篇 |
1990年 | 48篇 |
1989年 | 139篇 |
1988年 | 59篇 |
1987年 | 56篇 |
1986年 | 63篇 |
1985年 | 183篇 |
1984年 | 144篇 |
1983年 | 107篇 |
1982年 | 115篇 |
1981年 | 214篇 |
1980年 | 49篇 |
1979年 | 45篇 |
1978年 | 50篇 |
1977年 | 42篇 |
1975年 | 50篇 |
1974年 | 38篇 |
1973年 | 32篇 |
1972年 | 35篇 |
1971年 | 35篇 |
1970年 | 37篇 |
排序方式: 共有6891条查询结果,搜索用时 15 毫秒
71.
The problem of determining the “potential” number of integration steps by explicit difference schemes is solved within the framework of the prediction model for chemically non-equilibrium processes. 相似文献
72.
The paper presents an improved technique and the results of strength analysis for the aircraft structural elements with a structural defect like an arbitrary shape delamination. 相似文献
73.
The paper presents a technique of calculating the life for gas turbine engine parts in a low cycle area based on the influence coefficients taking into account analytical and operational factors. A statistical method is used to determine the influence coefficients. 相似文献
74.
B. Ragent C. A. Privette P. Avrin J. G. Waring C. E. Carlston T. C. D. Knight J. P. Martin 《Space Science Reviews》1992,60(1-4):179-201
The objective of the Nephelometer Experient aboard the Probe of the Galileo mission is to explore the vertical structure and microphysical properties of the clouds and hazes in the atmosphere of Jupiter along the descent trajectory of the Probe (nominally from 0.1 to > 10 bars). The measurements, to be obtained at least every kilometer of the Probe descent, will provide the bases for inferences of mean particle sizes, particle number densities (and hence, opacities, mass densities, and columnar mass loading) and, for non-highly absorbing particles, for distinguishing between solid and liquid particles. These quantities, especially the location of the cloud bases, together with other quantities derived from this and other experiments aboard the Probe, will not only yield strong evidence for the composition of the particles, but, using thermochemical models, for species abundances as well. The measurements in the upper troposphere will provide ground truth data for correlation with remote sensing instruments aboard the Galileo Orbiter vehicle. The instrument is carefully designed and calibrated to measure the light scattering properties of the particulate clouds and hazes at scattering angles of 5.8°, 16°, 40°, 70°, and 178°. The measurement sensitivity and accuracy is such that useful estimates of mean particle radii in the range from about 0.2 to 20 can be inferred. The instrument will detect the presence of typical cloud particles with radii of about 1.0 , or larger, at concentrations of less than 1 cm3.Deceased. 相似文献
75.
A.K. Sharma O.B. Gurav Anindya Bose H.P. Gaikwad G.A. Chavan Atanu Santra S.S. Kamble R.S. Vhatkar 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2019,63(10):3131-3138
Indian Space Research Organization (ISRO) has developed an indigenous system named Indian Regional Navigation Satellite System (IRNSS) or NavIC (Navigation with Indian Constellation), that consists of 7 satellites and transmits navigation signal in L and S bands. ISRO, for validation of the system, has installed many IGS (IRNSS/GPS/SBAS) receivers scattered over the Indian region. Using preliminary data from two geographically widely separated stations over India, this paper presents the results on studies on parameters of IRNSS signal quality and discusses how these parameters may be used to study the ionospheric behavior over the Indian region. The results show the importance and advantages of using IRNSS data for such studies. 相似文献
76.
M.I. Tyasto O.A. Danilova N.G. Ptitsyna V.E. Sdobnov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2013
A very strong interplanetary and magnetospheric disturbance observed on 7–13 November 2004 can be regarded as one of the strongest events during the entire period of space observations. In this paper we report on the studies of cosmic ray cutoff rigidity variations during 7–13 November 2004 showing how storm conditions can affect the direct cosmic ray access to the inner magnetosphere. Effective cutoff rigidities have been calculated for selected points on the ground by tracing trajectories of cosmic ray particles through the magnetospheric magnetic field of the “storm-oriented” Tsyganenko 2003 model. Cutoff rigidity variations have also been determined by the spectrographic global survey method on the basis of experimental data of the neutron monitor network. Relations between the calculated and experimental cutoff rigidities and the geomagnetic Dst-index and interplanetary parameters have been investigated. Correlation coefficients between the cutoff rigidities obtained by the trajectory tracing method and the spectrographic global survey method have been found to be in the limits 0.76–0.89 for all stations except the low-latitude station Tokyo (0.35). The most pronounced correlation has been revealed between the cutoff rigidities that exhibited a very large variation of ∼1–1.5 GV during the magnetic storm and the Dst index. 相似文献
77.
A. Ehmert 《Space Science Reviews》1964,3(1):2-4
78.
This is an analysis of the experimental results to study the metastable phase formation while crystallization of binary metal melts in microgravity and quasi-isostatic (uniform) compression takes place. The alloy system PbSn serves as an illustration 相似文献
79.
In the framework of the general theory for unsteady weakly disturbed fluid flows with free boundaries, a problem is solved to calculate a jet flow around the cascade of plates executing the harmonic oscillations. We developed a program that enables us for the first time to carry out systematic calculations of flow characteristics depending on arbitrary values of determining parameters. 相似文献
80.
E.S. Seo T. Anderson D. Angelaszek S.J. Baek J. Baylon M. Buénerd M. Copley S. Coutu L. Derome B. Fields M. Gupta J.H. Han I.J. Howley H.G. Huh Y.S. Hwang H.J. Hyun I.S. Jeong D.H. Kah K.H. Kang D.Y. Kim H.J. Kim K.C. Kim M.H. Kim K. Kwashnak J. Lee M.H. Lee J.T. Link L. Lutz A. Malinin A. Menchaca-Rocha J.W. Mitchell S. Nutter O. Ofoha H. Park I.H. Park J.M. Park P. Patterson J.R. Smith J. Wu Y.S. Yoon 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
The Cosmic Ray Energetics And Mass (CREAM) instrument is configured with a suite of particle detectors to measure TeV cosmic-ray elemental spectra from protons to iron nuclei over a wide energy range. The goal is to extend direct measurements of cosmic-ray composition to the highest energies practical, and thereby have enough overlap with ground based indirect measurements to answer questions on cosmic-ray origin, acceleration and propagation. The balloon-borne CREAM was flown successfully for about 161 days in six flights over Antarctica to measure elemental spectra of Z = 1–26 nuclei over the energy range 1010 to >1014 eV. Transforming the balloon instrument into ISS-CREAM involves identification and replacement of components that would be at risk in the International Space Station (ISS) environment, in addition to assessing safety and mission assurance concerns. The transformation process includes rigorous testing of components to reduce risks and increase survivability on the launch vehicle and operations on the ISS without negatively impacting the heritage of the successful CREAM design. The project status, including results from the ongoing analysis of existing data and, particularly, plans to increase the exposure factor by another order of magnitude utilizing the International Space Station are presented. 相似文献