全文获取类型
收费全文 | 18417篇 |
免费 | 40篇 |
国内免费 | 126篇 |
专业分类
航空 | 9957篇 |
航天技术 | 5539篇 |
综合类 | 247篇 |
航天 | 2840篇 |
出版年
2021年 | 159篇 |
2018年 | 228篇 |
2016年 | 158篇 |
2014年 | 433篇 |
2013年 | 517篇 |
2012年 | 421篇 |
2011年 | 606篇 |
2010年 | 425篇 |
2009年 | 777篇 |
2008年 | 810篇 |
2007年 | 403篇 |
2006年 | 429篇 |
2005年 | 401篇 |
2004年 | 457篇 |
2003年 | 535篇 |
2002年 | 478篇 |
2001年 | 577篇 |
2000年 | 370篇 |
1999年 | 459篇 |
1998年 | 441篇 |
1997年 | 331篇 |
1996年 | 397篇 |
1995年 | 460篇 |
1994年 | 446篇 |
1993年 | 357篇 |
1992年 | 342篇 |
1991年 | 250篇 |
1990年 | 238篇 |
1989年 | 405篇 |
1988年 | 207篇 |
1987年 | 240篇 |
1986年 | 238篇 |
1985年 | 645篇 |
1984年 | 521篇 |
1983年 | 408篇 |
1982年 | 488篇 |
1981年 | 614篇 |
1980年 | 245篇 |
1979年 | 184篇 |
1978年 | 189篇 |
1977年 | 146篇 |
1976年 | 156篇 |
1975年 | 185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 15 毫秒
151.
E. J. Smith 《Space Science Reviews》1983,34(1):101-110
Interplanetary shock observations since the prior Solar Terrestrial Physics Symposium in 1978 are reviewed. Since the interval coincides with the recent solar maximum, emphasis is placed on shocks associated with transient solar phenomena, including coronal transients and eruptive prominences as well as flares. A good correlation between shocks and Storm Sudden Commencements has persisted into the recent maximum. Shocks have been identified that are associated with disappearing filaments and coronal transients rather than with flares. Significant progress has been made in the indirect observation of shocks near the Sun as a result of radio wave measurements in interplanetary space and measurement of the scintillation and spectral broadening of spacecraft radio transmissions. Preliminary results regarding the thickness of interplanetary shocks have appeared. Several quasi-parallel shocks propagating more nearly along, rather than across, the magnetic field have been identified. The plasma drivers accompanying interplanetary shocks have received increased attention and distinctive features have been found in electron, ion and magnetic field data. 相似文献
152.
An adaptive array architecture is described which has improved convergence speed over the conventional Applebaum array when the eigenvalue spread of the input signal covariance matrix is large. The architecture uses N+1 Applebaum adaptive arrays in a two-layer cascaded configuration. The gain constants in the first layer are set so that large interfering sources are quickly nulled, but small interfering sources are suppressed more slowly. Since the first layer removes the large interfering signals, the gain constant for the second layer can be set to a large value to quickly null the smaller interferers. The adaptation time is examined for several combinations of signal levels and array sizes. It is shown that, in many signal environments, the computational requirements for the cascaded array compare favorably with those of conventional sample matrix inversion (SMI) methods for large arrays 相似文献
153.
The problem of Earth-pointing attitude control for a spacecraft with magnetic actuators is addressed and a novel approach to the problem is proposed, which guarantees almost global closed loop stability of the desired relative attitude equilibrium for the spacecraft. Precisely, a proportional derivative (PD)-like state feedback control law is employed together with a suitable adaptation mechanism for the controller gain. Simulation results are presented, which illustrate the performance of the proposed control law 相似文献
154.
E. G. Dem’yanenko 《Russian Aeronautics (Iz VUZ)》2014,57(2):204-211
In this paper, a new technique for shaping the thin-walled barrel-type parts is presented. 相似文献
155.
N. I. Akishev I. I. Zakirov V. A. Ivanov V. N. Paimushin M. A. Shishov 《Russian Aeronautics (Iz VUZ)》2011,54(2):115-124
The known analytical solutions of the linearized stability problems for rectangular hinged plates under the combined loading
are generalized to the similar problems for skew plates, the deformation mechanics of which is described by the equations
of the classical theory formed in the oblique Cartesian coordinates. 相似文献
156.
In this paper, we examine experimentally some devices the principle of action of which is based on using the dynamic pressure
of air extracted to engine cooling and which are meant for reducing the radial temperature gradient in GTE rotor disks. We
established that the devices equipped with the ejector channels make it possible to accelerate the process of the disk hub
heating by hot air suction from the cavity periphery towards the rotor axis of rotation. Using the data of visualization studies,
we show the possibility for efficient operation of ejector devices in the conditions of real GTE rotor circumferential velocities. 相似文献
157.
A technique of optimizing the electrode system of the differential recorder for the aircraft time-of-flight ion-marking airspeed
and aircraft angle of attack sensor by the criterion of ion-marking recording error variance minimum is considered. The technique
is based on analyzing the function of spatial distribution for the ion-marking and recorder electrode interaction field potential
and determining a point for which this function reaches the maximum slope. The relations making it possible to synthesize
the sensor electrode system by the complex criterion as a ratio of error variance to transformation channel response are obtained. 相似文献
158.
M. V. Usanin A. A. Siner A. M. Sipatov L. Yu. Gomzikov V. G. Avgustinovich 《Russian Aeronautics (Iz VUZ)》2011,54(1):34-42
The application of the low dissipative high-order accurate scheme for numerical solution of the Euler and Navier-Stokes equations
in the two-dimensional statement is considered. The scheme of calculating space derivatives is the seven-point central-difference
approximation of the fourth order with the coefficients optimized to reduce the dispersion errors. The optimized six-step
Runge-Kutta method is used for evaluating the time derivatives. By means of filtration, spurious pulsations are suppressed
and shocks are processed. The results of verifying the calculation scheme realized on the stationary problem of flow around
the model turbine blades are presented. 相似文献
159.
N. M. Bodunov 《Russian Aeronautics (Iz VUZ)》2011,54(1):89-94
A mathematical model of the process of bending and rolling the thin-walled components is presented taking into account the
geometrical nonlinearity. Also presented is the technique for calculating the setup variables of bending equipment, which
is based on reduction of the initial differential boundary-value problem to the discrete one with the use of the finite difference
method. 相似文献
160.