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91.
J. W. Holmes 《Journal of fluorescence》1993,3(3):179-183
Aerodynamic tests are designed to give information about the performance of a model when subjected to an airflow. The introduction of pressure sensitive paint provides a new method for obtaining the pressure distribution on the surface of wind-tunnel models. A paint, the luminescence of which is dependent on air pressure, is applied to the surface of the model and the pressure distribution is obtained from the image produced. This paper gives an explanation of this technique, a résumé of possible applications and some results from research performed at DRA Bedford. 相似文献
92.
93.
在采用冻结湍流假设和几何光学近似的条件下,得到了经自适应光学系统校正后的剩余波前相位扰动的结构函数,进而根据剩余相位结构函数与系统Strehl比的关系,求出自适应光学系统的补偿效果受系统的时空传递函数,大气湍流,光波传播路径上的横向风,观察目标的旋转角速度以及系统时间延迟影响情况的解析表达式。 相似文献
94.
Predictions, by the Galerkin method, are presented of the stability of three-dimensional disturbances in laminar boundary-layer flow at zero pressure gradient along a concave surface. The analysis confirms Meksyn's finding of more than one critical state; predictions for the first agree with those of Kahawita and Meroney at low Goertler number G and with the vortex amplification predictions of Smith at high G. Both the first and second critical states have G values below those of Meksyn; the amplification field of the second, however, encompasses the range of available measurements, and therein, has dimensionless vortex energy levels only half those of the first. The plausibility of least vortex energy as a determining factor in favour of the second critical field is further strengthened by its limited G range, the upper limit of about 7 corresponding closely to Liepmann's observations4,5 of the onset of transition to turbulence. These findings are almost insensitive to mainstream Mach numbers up to 0.9, stagnation conditions up to 15 bar and 1200 K, and Reynolds numbers from 2000 to 6000 based on boundary layer thickness 相似文献
95.
R.J. Grant C.G. Johnson D.H. Wilkinson 《International Journal of Heat and Fluid Flow》1983,4(4):239-245
A single stage model turbine has been provided with a set of three special inlet sections which include backward facing steps to produce casing separations of varying size upstream of the stator blades. In addition each inlet section is equipped so as tc be able to emit a swirling jet which simulates the tip leakage jet from a preceeding stage. It is demonstrated that there is a substantial efficiency penalty associated with the stepped casing and its attendant separation and that a small mitigation is brought about by the tip leakage jet, by re-energising the fluid in the separation zone 相似文献
96.
有扰流柱的复合倾斜式气膜冷却导向叶片换热特性的研究 总被引:1,自引:0,他引:1
本文采用试验方法研究复合倾斜式涡轮导向叶片的内换热特性。针对有无扰流柱、有无气膜孔以及三种不同直径的节流孔的模型进行了试验研究,获得了扰流柱、气膜孔以及180°弯的节流板孔径的变化对其内换热特性的影响,并得到了一些换热准则方程,从而获得了加强叶片内部换热的方法。 相似文献
97.
Niranjan Das 《Pramana》2004,62(1):135-142
In the present paper, a study of the deep-sea water wave caused by an oscillatory wind stress due to the atmospheric depression,
resulting in spiral cyclonic wind pressure on the surface of the sea is made. It has been observed that the motion of the
water wave in the case of wind stress exhibits a greater elevation on the sea surface asg the acceleration due to gravity decreases and maintains the oscillatory nature with the increase of time. For the case of
spiral cyclonic motion for which the sea surface experiences the elliptical pressure on the surface, the motion diminishes
asg diminishes and oscillates with the variation of time. The motion also diminishes asymptotically as the radius vector of the
elliptical pressure approaches unity. 相似文献
98.
99.
A new incoherent Doppler lidar scheme is proposed using a high resolution Mach-Zehnder interferometer discriminator with sinusoidal transmission functions. A two-channel differential discrimination technique is developed which provides high sensitive velocity measurement. The aerosol and molecular backscatter signals can be separately measured and the backscatter ratio obtained. Principle of the measurement is described and the characteristics of this technique are analyzed and compared. Numerical calculation for a moderate size 1.064 μ lidar shows that an accuracy better than 1 m/s for the velocity measurement and 18% for the backscatter ratio measurement can be obtained up to a height of 10 km by a 500 shot average. 相似文献
100.
From a careful examination of the diurnal variation of cosmic ray intensity at high energies and the interplanetary field
characteristics, the average characteristics of diurnal variation were recently explained by us in terms of a balance between
outward convection and field aligned diffusion, the latter arising out of a positive radial density gradient. In this paper,
we extend this new concept to explain the large variability observed in the diurnal variation on a day-to-day basis and further
demonstrate that the measurement of diurnal anisotropy characteristic of cosmic ray particles on a day-to-day basis can be
used directly to infer the nature and scale sizes of interplanetary field parameters. Comparing with the magnetic field vector,
we show that this simple concept holds good on more than 80% of days. On the rest 20% of days which have a predominant morning
maxima, the diurnal anisotropy characteristics seem to indicate the presence of a significant component of transverse diffusion
current in addition to the normal convection and diffusion flow. Such days are found to be present in the form of trains of
consecutive days and are found to be associated with abrupt changes in the interplanetary field direction having scale sizes
>4 hr. The value ofK
⊥/K
‖ which is normally about ⩽0.05 is found to be ≈1.0 on non-field aligned days. 相似文献