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741.
N.U. Crooker J.T. Gosling V. Bothmer R.J. Forsyth P.R. Gazis A. Hewish T.S. Horbury D.S. Intriligator J.R. Jokipii J. Kóta A.J. Lazarus M.A. Lee E. Lucek E. Marsch A. Posner I.G. Richardson E.C. Roelof J.M. Schmidt G.L. Siscoe B.T. Tsurutani R.F. Wimmer-Schweingruber 《Space Science Reviews》1999,89(1-2):179-220
Corotating interaction regions (CIRs) in the middle heliosphere have distinct morphological features and associated patterns
of turbulence and energetic particles. This report summarizes current understanding of those features and patterns, discusses
how they can vary from case to case and with distance from the Sun and possible causes of those variations, presents an analytical
model of the morphological features found in earlier qualitative models and numerical simulations, and identifies aspects
of the features and patterns that have yet to be resolved.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
742.
Malandraki O.E. Sarris E.T. Lanzerotti L.J. Maclennan C.G. Pick M. Tsiropoula G. 《Space Science Reviews》2001,97(1-4):263-268
In January 2000, the Ulysses spacecraft observed an ICME event at 43° S heliographic latitude and ∼ 4.1 AU. We use electron (E
e>38 keV) observations to trace the topology of the IMF embedded within the ICME. The still controversial issue of whether
ICMEs have been detached from the solar corona or are still magnetically anchored to it when they arrive at the spacecraft
is tackled. An in ecliptic ICME event is also presented.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
743.
Lario D. Haggerty D.K. Roelof E.C. Tappin S.J. Forsyth R.J. Gosling J.T. 《Space Science Reviews》2001,97(1-4):277-280
On day 49 of 1999 a strong interplanetary shock was observed by the ACE spacecraft located at 1 AU from the Sun. This shock
was followed 10 hours later by a magnetic cloud (MC). A large solar energetic particle (SEP) event was observed in association
with the arrival of the shock and the MC at ACE. The Ulysses spacecraft, located at 22° S heliolatitude and nearly the same
ecliptic longitude as ACE, observed a large SEP event beginning on day 54 that peaked with the arrival of a solar wind and
magnetic field disturbance on day 61. A magnetic cloud was observed by Ulysses on days 63–64. We suggest a scenario in which both spacecraft intercepted the same MC, although sampling different regions
of it. We describe the effects that the MC produced on the streaming of energetic particles at both spacecraft.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
744.
O. Moullard R.G. Marsden T.R. Sanderson C. Tranquille R.J. Forsyth B.E. Goldstein 《Space Science Reviews》2001,97(1-4):289-292
We present and compare observations of energetic protons during the two first transits of the Ulysses spacecraft from low to high latitudes in the southern heliosphere. Protons in the energy range 1.8–3.8 MeV from the COSPIN
experiment are studied for global trends and in relation to some ambient structures in the solar wind (corotating interaction
region, forward/reverse shock). The global trends show the large dependence on the heliospheric condition and solar activity,
including indications of a larger ambient particle population during the rising phase of solar activity and more efficient
solar wind particle accelerators during the declining phase. More enhancements in the proton flux intensity are time associated
with forward shocks than reverse contrary to first pass. Recurrent structures are found even during the second transit. Some
latitude dependent periodicities are observed that could relate to the differential solar rotation.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
745.
G. Wibberenz H.V. Cane I.G. Richardson T.T. von Rosenvinge 《Space Science Reviews》2001,97(1-4):343-347
The maximum inclination of the heliospheric current sheet (the tilt angle) and the magnitude B of the heliospheric magnetic field are often used to characterize cosmic ray (CR) modulation. The relevance of B is likely to be the coupling of the interplanetary diffusion coefficients K to the field magnitude in a relation K∝B
−n. In this paper we study the coupled influence of tilt angle and magnetic field variations on the modulation of cosmic rays
at neutron monitor energies for the 1974 mini-cycle and for the onsets of solar cycles 21, 22, and 23. It is suggested that
for A>0 polarity epochs, the sensitivity of the CR response to variations in B is partly controlled by the size of the tilt angle, α. The onsets of cycles 21 and 23 exhibit differences, related to phase
differences in these parameters. A simple model is used to predict the CR response to variations in B.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
746.
We report on our continuing efforts to determine 3He abundances in H II regions and planetary nebulae. Our detections of 3He in some PNe show that some stars produce large amounts of 3He. However the H II region abundances show no evidence for this production. From our sample of > 40 H II regions, the subsample which should yield the most reliable abundances has 3He/H abundances which scatter between 1-2 × 10-5. There is no trend with either galactocentric distance or metallicity. Even if we do not understand the underlying mechanisms, we see empirically that stars neither produce nor destroy 3He in a major way. We thus suggest that the level of the "3He Plateau" (3He/H = 1.5
-0.5
+1.0
× 10-5) is a reasonable estimate for the primordial 3He. 相似文献
747.
On the Slow Solar Wind 总被引:1,自引:0,他引:1
A theory for the origin of the slow solar wind is described. Recent papers have demonstrated that magnetic flux moves across
coronal holes as a result of the interplay between the differential rotation of the photosphere and the non-radial expansion
of the solar wind in more rigidly rotating coronal holes. This flux will be deposited at low latitudes and should reconnect
with closed magnetic loops, thereby releasing material from the loops to form the slow solar wind. It is pointed out that
this mechanism provides a natural explanation for the charge states of elements observed in the slow solar wind, and for the
presence of the First-Ionization Potential, or FIP, effect in the slow wind and its absence in fast wind. Comments are also
provided on the role that the ACE mission should have in understanding the slow solar wind.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
748.
IMMPDAF for radar management and tracking benchmark with ECM 总被引:2,自引:0,他引:2
Kirubarajan T. Bar-Shalom Y. Blair W.D. Watson G.A. 《IEEE transactions on aerospace and electronic systems》1998,34(4):1115-1134
A framework is presented for controlling a phased array radar for tracking highly maneuvering targets in the presence of false alarms (FAs) and electronic countermeasures (ECMs). Algorithms are presented for track formation and maintenance; adaptive selection of target revisit interval, waveform and detection threshold; and neutralizing techniques for ECM, namely, against a standoff jammer (SOJ) and range gate pull off (RGPO). The interacting multiple model (IMM) estimator in combination with the probabilistic data association (PDA) technique is used for tracking. A constant false alarm rate (CFAR) approach is used to adaptively select the detection threshold and radar waveform, countering the effect of jammer-induced false measurements. The revisit interval is selected adaptively, based on the predicted angular innovation standard deviations. This tracker/radar-resource-allocator provides a complete solution to the benchmark problem for target tracking and radar control. Simulation results show an average sampling interval of about 2.5 s while maintaining a track loss less than the maximum allowed 4% 相似文献
749.
Murphy R. T. Rannells David C. 《IEEE transactions on aerospace and electronic systems》1967,(2):236-241
A practical approach for meeting the immediate and future needs of communication systems that require very wideband transmitters capable of operating in the S-, C-, and X-band frequency ranges is described. Included are: 1) a review of the basic studies conducted to determine the most practical transmitter approach for wideband applications; 2) a discussion of a prototype 10-watt frequency-modulated transmitter developed to demonstrate the feasibility of a wideband system; and 3) a review of the preliminary computer analyses and empirical results obtained on the development of a unit capable of wide deviation with reasonable linearity at baseband frequencies up to 10 Megahertz. 相似文献
750.
T. M. Donahue 《Space Science Reviews》1977,20(3):259-263
This paper develops the rationale for a program of Venus exploration by man. 相似文献