首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2176篇
  免费   4篇
  国内免费   6篇
航空   755篇
航天技术   765篇
综合类   8篇
航天   658篇
  2022年   6篇
  2021年   22篇
  2019年   7篇
  2018年   73篇
  2017年   58篇
  2016年   56篇
  2015年   21篇
  2014年   69篇
  2013年   68篇
  2012年   66篇
  2011年   111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   71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   18篇
  1986年   20篇
  1985年   69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
  1967年   4篇
排序方式: 共有2186条查询结果,搜索用时 31 毫秒
971.
A problem of synthesizing the control laws for nonlinear nonstationary control systems by output being measured under uncertain external actions and nonlinearities that meet the sector constraints is considered.  相似文献   
972.
973.
Results of a detailed analysis of heavy ion fluences measured on the Salyut and MIR orbital stations from 1978 to 1990 are presented. The analysis has made use of new models that describe the cosmic ray fluxes and their transition through the magnetosphere. The penetration of solar cosmic ray particles to the orbit, the increase of the (ScCr)/Fe flux ratio in the orbit, and the occurrences of 200–500 MeV/nucl heavy nuclei in <30° latitudes have been analyzed.  相似文献   
974.
The theory for calculating elastodamping characteristics of multilayer corrugated dampers being used in the rotor supports of aircraft gas turbine engines (GTEs), turbo-pump assemblies of rocket engines as well as in different articles of machine building industry is presented.  相似文献   
975.
Simultaneous GPS observations from about 150 stations of European Permanent Network (EPN) have been used for studying dynamics of latitudinal profiles and structure of mid-latitude ionospheric trough (MIT). For the analyses, the TEC maps over Europe were created with high spatial and temporal resolution. The latitudinal profiles were produced from TEC maps with one-hour interval for geographic latitude range from 35N to 75N. The structure of latitudinal profiles relates to the occurrence of the ionospheric trough. The location of the trough depends on season, local time, and both geophysical and geomagnetic conditions. The trough structure in GPS-TEC demonstrates a smooth shape. The trough occurrence as a distinguished structure is more distinct during winter. The relation of TEC in the trough minimum to the equator and polar walls amounted to a factor of 2–4.  相似文献   
976.
Using long-term (1998--2009) total electron content (TEC) measurements from the GPS global network including dense network of GPS sites in USA and Japan, we have obtained the first data regarding the spatio-temporal structure and the statistics of medium-scale traveling wave packets (MS TWPs) excited by the solar terminator (ST). Total amount of the detected TWPs exceeds 565,000. There is no correlation between TWPs occurrence and geomagnetic and solar activity. We found that the diurnal, seasonal and spectral MS TWPs characteristics are specified by the solar terminator (ST) dynamics. MS TWPs are the chains of narrow-band TEC oscillations with single packet’s duration of about 1–2 h and oscillation periods of 10–20 min. The total duration of chain is about 4–6 h. The MS TWPs spatial structure is characterized by a high degree of anisotropy and coherence at the distance of more than 10 wavelengths. Occurrence rate of daytime MS TWPs is high in winter and during equinoxes. Occurrence rate of nighttime MS TWPs has its peak in summer. These features are consistent with previous MS travelling ionosphere disturbance (TID) statistics obtained from 630-nm airglow imaging observations in Japan. In winter, MS TWPs in the northern hemisphere are observed 3–4 h after the morning ST passage. In summer, MS TWPs are detected 1.5–2 h before the evening ST appearance at the point of observations, but at the moment of the evening ST passage in the magneto-conjugate point. The obtained results are the first experimental evidence for the hypothesis of the ST-generated ion sound waves.  相似文献   
977.
A technique for calculating heat transfer characteristics of heat pipes equipped with isotropic-structure wicks made of the MR material is proposed and the investigation results are presented.  相似文献   
978.
In this paper, a technique for estimating the failure rate for GTE disks, taking into account the random failures, is presented. According to this technique, we analyzed the effect of tolerances for geometrical sizes, rotation frequency and disk material density on the failure rate.  相似文献   
979.
A continual model of humification and mineralization of soil organic matter (SOM) formed under the conditions of a Lunar base from biological waste materials is proposed. The model parameters corresponding to the conditions of several Earths climatic regions are estimated. The time necessary for the formation of organic matter in the soil based on regolith and higher plant residues has been evaluated. Soil formation under tropical conditions are shown to be the most appropriate for Lunar base CELSS due to high matter turnover rate, relatively short formation time, minimum deposited mass, and satisfactory predictability of expected soil parameters.  相似文献   
980.
A process of forming a permanent connection by creasing is considered from the view point of the most important parameters of tooling and equipment setup which influence the connection quality. Making use of the DEFORM 2D software, we produced specimens of such connections and evaluated their quality at different parameters of setup and tools.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号