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1.
An overview of quantitative risk measures for loss of life and economic damage   总被引:25,自引:0,他引:25  
A comprehensive overview of methods to quantify and limit risks arising from different sources is still missing in literature. Therefore, a study of risk literature was carried out by the authors. This article summarises about 25 quantitative risk measures. A risk measure is defined as a mathematical function of the probability of an event and the consequences of that event. The article focuses mainly on risk measures for loss of life (individual and societal risk) and economic risk, concentrating on risk measurement experiences in The Netherlands. Other types of consequences and some international practices are also considered. For every risk measure the most important characteristics are given: the mathematical formulation, the field of application and the standard set in this field. Some of the measures have been used in a case study to calculate the flood risks for an area in The Netherlands.  相似文献
2.
Growth mechanisms of modified eutectic silicon   总被引:14,自引:0,他引:14  
Transmission electron microscopy has been used to study the growth mechanism of silicon in modified aluminium-silicon eutectic alloys. In agreement with earlier studies a high density of thin {1 1 1 } faults was observed in silicon modified by relatively large amounts of sodium or strontium. High-resolution microscopy showed that these faults were a mixture of thin twins and stacking faults, the inter-fault spacing being at least ten times the twin width. Because modified silicon is thought to grow by the twin re-entrant edge mechanism, the thin twins were examined in relation to the shape of the modified silicon dendrites and the solidified growth interfaces. It was concluded that the thin faults were not deformation twins resulting from either thermal contraction stresses or mechanical grinding during specimen preparation. No direct evidence was found to support the re-entrant edge mode of growth in modified silicon. Instead it is suggested that the interface may appear macroscopically non-faceted, as in the more general Lateral Microscopic Growth mechanisms.  相似文献
3.
A new matrix-assisted laser desorption/ionization (MALDI) time-of-flight/time-of-flight (TOF/TOF) high-resolution tandem mass spectrometer is described for sequencing peptides. This instrument combines the advantages of high sensitivity for peptide analysis associated with MALDI and comprehensive fragmentation information provided by high-energy collision-induced dissociation (CID). Unlike the postsource decay technique that is widely used with MALDI-TOF instruments and typically combines as many as 10 separate spectra of different mass regions, this instrument allows complete fragment ion spectra to be obtained in a single acquisition at a fixed reflectron voltage. To achieve optimum resolution and focusing over the whole mass range, it may be desirable to acquire and combine three separate sections. Different combinations of MALDI matrix and collision gas determine the amount of internal energy deposited by the MALDI process and the CID process, which provide control over the extent and nature of the fragment ions observed. Examples of peptide sequencing are presented that identify sequence-dependent features and demonstrate the value of modifying the ionization and collision conditions to optimize the spectral information.  相似文献
4.
Transmission electron microscopy has been used to study the growth mechanism of silicon in modified aluminium-silicon eutectic alloys. In agreement with earlier studies a high density of thin {1 1 1 } faults was observed in silicon modified by relatively large amounts of sodium or strontium. High-resolution microscopy showed that these faults were a mixture of thin twins and stacking faults, the inter-fault spacing being at least ten times the twin width. Because modified silicon is thought to grow by the twin re-entrant edge mechanism, the thin twins were examined in relation to the shape of the modified silicon dendrites and the solidified growth interfaces. It was concluded that the thin faults were not deformation twins resulting from either thermal contraction stresses or mechanical grinding during specimen preparation. No direct evidence was found to support the re-entrant edge mode of growth in modified silicon. Instead it is suggested that the interface may appear macroscopically non-faceted, as in the more general Lateral Microscopic Growth mechanisms.  相似文献
5.
Integrated system for rapid PCR-based DNA analysis in microfluidic devices   总被引:13,自引:0,他引:13  
An integrated system for rapid PCR-based analysis on a microchip has been demonstrated. The system couples a compact thermal cycling assembly based on dual Peltier thermoelectric elements with a microchip gel electrophoresis platform. This configuration allows fast (approximately 1 min/ cycle) and efficient DNA amplification on-chip followed by electrophoretic sizing and detection on the same chip. An on-chip DNA concentration technique has been incorporated into the system to further reduce analysis time by decreasing the number of thermal cycles required. The concentration injection scheme enables detection of PCR products after performing as few as 10 thermal cycles, with a total analysis time of less than 20 min. The starting template copy number was less than 15 per injection volume.  相似文献
6.
A model is proposed to predict the ability of a filler to reinforce a polymer. The model combines the effects of filler particle size, filler surface chemistry and filler volume fraction into one parameter called the bond energy density. Bond energy density is defined as the total interfacial bond energy per unit volume of a polymer composite. Bond energy density is determined by Fowkes's equation. The critical bond energy density, which is equivalent to the bond energy density of the composite when its tensile strength equals that of its matrix, determines whether a filler will reinforce or weaken a polymer. To get a filler reinforcing effect, the bond energy density of the composite must be greater than its critical bond energy density.  相似文献
7.
Data processing in the split Hopkinson pressure bar tests   总被引:10,自引:0,他引:10  
The effect on dynamic stress—strain curves of dispersion and shifting of elastic strain pulses travelling in a split Hopkinson pressure bar is reported. The dispersion correction is done in the frequency domain after employing FFT algorithm by adjusting the phase of each Fourier component. The three pulses (incident, reflected and transmitted) are analyzed inside three identical windows that propagate along the time axis with a reference velocity . The oscillations in the dynamic stress—strain curves are shown to be very sensitive to small variations in the value of co. A calibration procedure for determining the value of co for each SHPB setup is suggested. The predictions are compared to experimental measurements.  相似文献
8.
Propulsive performance and vortex shedding of a foil in flapping flight   总被引:10,自引:0,他引:10  
X.-Y. Lu  J.-M. Yang  X.-Z. Yin 《Acta Mechanica》2003,165(3-4):189-206
Summary. The propulsive performance and vortex shedding of an oscillating foil, which mimics biological locomotion, are investigated based on a computational fluid dynamics analysis. The objectives of this study are to investigate unsteady forces, in particular a thrust force, for the foil in pitching and plunging motion, and to deal with the relations of the propulsive performance with leading-edge vortex structure and vortex shedding in the near wake. The two-dimensional incompressible Navier–Stokes equations in the vorticity and stream-function formulation are solved by fourth-order essentially compact finite difference schemes for the space derivatives and a fourth-order Runge-Kutta scheme for the time advancement. To reveal the mechanism of the propulsive performance, the unsteady forces and the shedding of the leading- and trailing- edge vortices of the foil in the pitching and plunging motion are analyzed. Based on our calculated results, three types of the leading-edge vortex shedding, which have an effective influence on the vortex structures in the wake of the oscillating foil, are identified. The effects of some typical factors, such as the frequency and amplitude of the oscillation, the phase difference between the pitching and plunging motions, and the thickness ratio of the foil, on the vortex shedding and the unsteady forces are discussed.  相似文献
9.
Ownership costs of operational aircraft have increased steadily over the years. One of the major cost drivers is structural deterioration due to corrosion. Beyond the economics, finding and characterizing corrosion is essential for the continued airworthiness of aircraft fleets. To this end, the pulsed eddy current technique holds the potential of becoming the primary means of detecting corrosion in multilayered structures. Its wide-band frequency spectrum allows the determination of a large number of parameters, such as defect size and location. Pulsed eddy current is still considered an experimental nondestructive technique because of realistic inspection problems (e.g., probe tilting, protrusion of rivets, and thickness variations in adhesive and paint) have not been addressed in the past. Recent advances change this situation and allow pulsed eddy current to be a credible field technique.  相似文献
10.
A steady state computer simulation model has been developed for refrigeration circuits of automobile air conditioning systems. The simulation model includes a variable capacity compressor and a thermostatic expansion valve in addition to the evaporator and micro channel parallel flow condenser. An experimental bench made up of original components from the air conditioning system of a compact passenger vehicle has been developed in order to check results from the model. The refrigeration circuit was equipped with a variable capacity compressor run by an electric motor controlled by a frequency converter. Effects on system performance of such operational parameters as compressor speed, return air in the evaporator and condensing air temperatures have been experimentally evaluated and simulated by means of developed model. Model results deviate from the experimentally obtained within a 20% range though most of them are within a 10% range. Effects of the refrigerant inventory have also been experimentally evaluated with results showing no effects on system performance over a wide range of refrigerant charges.  相似文献
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