全文获取类型
收费全文 | 3701篇 |
免费 | 7篇 |
国内免费 | 5篇 |
专业分类
航空 | 1510篇 |
航天技术 | 1038篇 |
综合类 | 19篇 |
航天 | 1146篇 |
出版年
2022年 | 15篇 |
2021年 | 37篇 |
2019年 | 16篇 |
2018年 | 205篇 |
2017年 | 163篇 |
2016年 | 129篇 |
2015年 | 48篇 |
2014年 | 112篇 |
2013年 | 134篇 |
2012年 | 132篇 |
2011年 | 217篇 |
2010年 | 190篇 |
2009年 | 250篇 |
2008年 | 236篇 |
2007年 | 188篇 |
2006年 | 74篇 |
2005年 | 124篇 |
2004年 | 98篇 |
2003年 | 106篇 |
2002年 | 83篇 |
2001年 | 115篇 |
2000年 | 36篇 |
1999年 | 53篇 |
1998年 | 61篇 |
1997年 | 42篇 |
1996年 | 43篇 |
1995年 | 80篇 |
1994年 | 61篇 |
1993年 | 38篇 |
1992年 | 47篇 |
1991年 | 10篇 |
1990年 | 19篇 |
1989年 | 41篇 |
1988年 | 11篇 |
1987年 | 17篇 |
1986年 | 16篇 |
1985年 | 70篇 |
1984年 | 56篇 |
1983年 | 48篇 |
1982年 | 42篇 |
1981年 | 82篇 |
1980年 | 25篇 |
1979年 | 16篇 |
1978年 | 14篇 |
1977年 | 17篇 |
1976年 | 13篇 |
1975年 | 13篇 |
1974年 | 11篇 |
1972年 | 13篇 |
1971年 | 11篇 |
排序方式: 共有3713条查询结果,搜索用时 31 毫秒
31.
N. N. Makarov 《Russian Aeronautics (Iz VUZ)》2008,51(1):60-66
The problem is formulated and a technique is revealed for synthesizing the optimal strategy of troubleshooting and constructing an operation algorithm for the information-control system of inspection and diagnostics of the aircraft equipment state. 相似文献
32.
V. A. Ovchinnikov 《Russian Aeronautics (Iz VUZ)》2007,50(2):146-149
We analyze the effect of injection both of uniformly distributed over the entire cylinder surface and of the optimal one on the velocity distribution at the outer border of the boundary layer and, as a result, on friction. 相似文献
33.
The results of studying an incompressible gas flow field in a periodic element of the porous structure made up of the same radius spheres are presented; the studies were based on the solution of the Navier-Stokes equations using FLUENT software. The possibilities to accelerate the solution process with the use of parallel calculations are investigated and the calculation results under changes of pressure differential in the periodic element are given. 相似文献
34.
T. Yu. Gainutdinova 《Russian Aeronautics (Iz VUZ)》2007,50(2):215-217
In this paper, a program package for solving problems in the field of thin-walled three-dimensional FV structure design is described. 相似文献
35.
D.R. Japaridze M.Sh. Gigolashvili V.J. Kukhianidze 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2007,40(12):1912-1916
The differential rotation of the patterns of the large-scale solar magnetic field during solar activity cycles 20 and 21 is investigated. Compact magnetic elements with the polarity of the general solar magnetic field have larger speed of rotation than the elements with the opposite polarity. The surface of the Sun was divided by 10°-zones. In all of them the average rotation rate of the magnetic elements with negative polarity is little higher than that of the magnetic elements with positive polarity, except for 50°-zone of the south hemisphere and at the 10° latitude of the north hemisphere.
The rates of differential rotation for large-scale magnetic elements with negative and positive polarities have similar behavior for both cycles of the solar activity.
The rotation rate varies at polarity reversal of the circumpolar magnetic fields. For the cycle No 20 in 1969–1970 the threefold reversal took place in the northern hemisphere and variations of rotation rate can be noticed for magnetic elements both with positive and negative polarity for each 10°-zone in the same hemisphere. 相似文献
36.
A. I. Belousov S. V. Falaleev A. S. Vinogradov P. V. Bondarchuk 《Russian Aeronautics (Iz VUZ)》2007,50(4):390-394
Problems arising in introduction of gasodynamic seals in aircraft engines are considered. The operation of a face gasodynamic seal as part of a natural gas pump is analyzed and its efficiency in the presence of oil is shown. 相似文献
37.
A system for measuring the altitude-airspeed parameters of rotorcraft and very light flight vehicles
In this paper, a problem on measuring the altitude-airspeed parameters (AAPs) of rotorcraft and very light flight vehicles is considered. Some ways of improving systems used to measure the parameters of FV elements and units have been determined. Also suggested and substantiated are the principles and designs of the basic variants of these measuring systems as well as the algorithms of their operation. 相似文献
38.
Teofilo V.L. Merritt L.V. Hollandsworth R.P. 《Aerospace and Electronic Systems Magazine, IEEE》1997,12(11):30-36
A lithium ion battery charger has been developed for four and eight cell batteries or multiples thereof. This charger has the advantage over those using commercial lithium ion charging chips in that the individual cells are allowed to be taper charged at their upper charging voltage rather than be cutoff when all cells of the string have reached the upper charging voltage limit. Since 30-60% of the capacity of lithium ion cells may be restored during the taper charge, this charger has a distinct benefit of fully charging lithium ion batteries by restoring all of the available capacity to all of its cells 相似文献
39.
A mathematical model of the high-latitude F-region, taking the ionospheric plasma convection into account, is used for modeling a response of the auroral F-region to irradiation by powerful high-frequency (HF) radiowaves. The model enables us to calculate the time variations in the profiles of the electron concentration, the velocity of positive ions, and the ion and electron temperatures in the part of a magnetic-flux tube moving over an artificial ionospheric heater under the action of a convective electric field. The modeling was carried out for a part of the magnetic flux tube intersecting the F-layer irradiated by the Norwegian heater at Tromsö when it is located near the midnight magnetic meridian. The calculations were made for the equinox conditions under the high solar and low geomagnetic activity. The results of our modeling show that substantial variations in the profiles of the electron temperature, the velocity of positive ions, and the electron concentration can be produced in the nighttime high-latitude F-layer due to HF heating. The perturbation caused by a 20 s rectangular pulse should exist for about 20 min at the level of the F-layer maximum. The disturbed plasma volume can leave the region irradiated by the heater and move away for over 500 km within the above-mentioned time period. 相似文献
40.
M V Ivanov 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1995,15(3):215-221
We suggest a new interpretation of the data on so-called SNC meteorites and delta 13C values of the calcium carbonate minerals and organic matter discovered in them. The delta 13C value of calcite (up to 15 ppt) is accounted for by the microbial reaction CO2 + H2 ---> CH4 + H2O. Methane-forming bacteria also synthesize organic carbon (in the form of biomass) from CO2, and this process is accompanied by 12C fractionation. Therefore, the organic carbon of SNC meteorites is enriched with 12C (delta 13C as low as -35 ppt). The environmental conditions under which the calcite of SNC meteorites was formed were favorable for the activity of methanogens. 相似文献