全文获取类型
收费全文 | 17716篇 |
免费 | 57篇 |
国内免费 | 127篇 |
专业分类
航空 | 9928篇 |
航天技术 | 5087篇 |
综合类 | 242篇 |
航天 | 2643篇 |
出版年
2021年 | 163篇 |
2018年 | 207篇 |
2016年 | 159篇 |
2014年 | 434篇 |
2013年 | 515篇 |
2012年 | 410篇 |
2011年 | 592篇 |
2010年 | 430篇 |
2009年 | 779篇 |
2008年 | 799篇 |
2007年 | 377篇 |
2006年 | 420篇 |
2005年 | 380篇 |
2004年 | 425篇 |
2003年 | 488篇 |
2002年 | 469篇 |
2001年 | 544篇 |
2000年 | 347篇 |
1999年 | 450篇 |
1998年 | 397篇 |
1997年 | 306篇 |
1996年 | 350篇 |
1995年 | 416篇 |
1994年 | 369篇 |
1993年 | 351篇 |
1992年 | 288篇 |
1991年 | 247篇 |
1990年 | 234篇 |
1989年 | 369篇 |
1988年 | 200篇 |
1987年 | 229篇 |
1986年 | 223篇 |
1985年 | 637篇 |
1984年 | 508篇 |
1983年 | 397篇 |
1982年 | 485篇 |
1981年 | 605篇 |
1980年 | 244篇 |
1979年 | 185篇 |
1978年 | 189篇 |
1977年 | 144篇 |
1976年 | 156篇 |
1975年 | 183篇 |
1974年 | 180篇 |
1973年 | 161篇 |
1972年 | 188篇 |
1971年 | 148篇 |
1970年 | 143篇 |
1969年 | 147篇 |
1967年 | 142篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
L. V. Zasova V. I. Moroz V. M. Linkin I. V. Khatuntsev B. S. Maiorov 《Cosmic Research》2006,44(4):364-383
The goal of this paper is to summarize the experimental data on the atmosphere of Venus obtained after 1985, when the VIRA (Venus International Reference Atmosphere) or COSPAR model was published. Among the most important results that have appeared since then are the following: measurements of the vertical temperature profile by the VEGA spacecraft with high precision and high altitude resolution; measurements made with balloons of the VEGA spacecraft; radio occultation measurements of Magellan, Venera-15, and Venera-16; and temperature profiles derived from the data of infrared spectrometry obtained by Venera-15. The new result as compared to VIRA is the creation of a model of the atmosphere in the altitude range 55 to 100 km dependent on local time. This model is presented in our paper in tabulated form. 相似文献
42.
ected g 《桂林航天工业高等专科学校学报》2006,(2)
with primary goat embryonic fibroblast showed no difference from traditional feederlayer-based culture method used in mouse and human. The putative primary EG colonies were multilayer clumps ofcompact cel 相似文献
43.
De Gaudenzi R. Fanucci L. Giannetti F. Luise M. Rovini M. 《Aerospace and Electronic Systems Magazine, IEEE》2003,18(8):23-30
Since 1999, ESA has conducted a number of system studies and technological developments to support the European and Canadian industry in the definition of a Satellite UMTS (S-UMTS) component development strategy, identifying critical technological areas and promoting S-UMTS demonstrations. In particular, the MUSIC project has successfully demonstrated advanced digital signal processing techniques to mitigate CDMA interference in spread-spectrum receivers, thus increasing the capacity and/or quality of service of a wireless communication network. The low-complexity solution for interference mitigation investigated and developed in the project is particularly suited for being implemented in mobile terminals. 相似文献
44.
M. Mowthorpe 《Space Policy》2002,18(1)
This article uses space power theory to analyse the military space policy of the United States during the Cold War period up to the demise of the Soviet Union. It examines the consensus that emerged during this period which sought to prevent the weaponization of space. This consensus was called into question during the latter period with the announcement of the Strategic Defence Initiative and its subsequent orientation to Global Protection Against Limited Strikes system. 相似文献
45.
Conte E. De Maio A. Ricci G. 《IEEE transactions on aerospace and electronic systems》2002,38(2):415-426
We address the estimation of the structure of the covariance matrix and its application to adaptive radar detection of coherent pulse trains in clutter-dominated disturbance modeled as a compound-Gaussian process. For estimation purposes we resort to range cells in spatial proximity with that under test and assume that these cells, free of signal components, can be clustered into groups of data with one and the same value of the texture. We prove that, plugging the proposed estimator of the structure of the covariance matrix into a previously derived detector, based upon the generalized likelihood ratio test (GLRT), leads to an adaptive detector which ensures the constant false alarm rate (CFAR) property with respect to the clutter covariance matrix as well as the statistics of the texture. Finally, we show that this adaptive receiver has an acceptable loss with respect to its nonadaptive counterpart in cases of relevant interest for radar applications 相似文献
46.
47.
M. I. Becka A. Jurewicz 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1996,17(12)
Currently conducted studies on modelling of scattered solar radiation in the 0.350-1.00 μm range along the Phobos orbit around Mars are presented. Our calculations include various types of grains, various densities and scattering angles. The calculations are performed with the aid of LOWTRAN7 program. These studies are directly related to the photometer coupled to PFS (Planetary Fourier Spectrometer) planned for the Mars-96 mission. 相似文献
48.
49.
Alice K. Harding 《Space Science Reviews》1996,75(1-2):257-268
Young pulsars surrounded by supernova remnants can power synchrotron nebulae through the injection of relativistic particles. Inverse Compton scattering by the high-energy electrons and positrons can produce TeV gamma-ray emission strong enough to be detectable by ground-based telescopes. The Crab nebula is the archetypical example of a gamma-ray plerion and was the first detected TeV source. The observed spectrum is consistent with predictions of synchrotron-self Compton models. This paper will review such models for the Crab and other plerions. Inverse-Compton scattering on other soft photon sources, particularly the 2.7K microwave background, may also be detectable in older remnants. 相似文献
50.
The work studies the application of the morphological (structural) synthesis method of search for the new technical approaches. The method is based on the application of the theory of system, morphological and cluster analysis, methods of mathematics simulation and calculation experiments made by computer. The work shows how this method is used to synthesize the landing spacecrafts, hypersonic spacecrafts and medical equipment and gives the comparison of the present and synthesized technical systems (TS). The conclusion is that this method increases the degree of the validity decision made and broadens the number of possible variants which allows an increase in the quality (technical level) of the TS under development. The work also points out that the method allows the system to search for promising inventions to solve the problems of prognostication and to single out the trends of TS evolution. It also allows the system to single out these systems which are able to respond flexibly to the changing external conditions with the lowest expense, and therefore, increases the compatibility of the chosen TS 相似文献