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21.
Equal numbers of barrows (64) and gilts (64) were randomly allocated to two separate diets containing 17·6 and 19·6% crude protein. Subsequently within each gender/diet treatment group, pigs were equally and randomly assigned to two ractopamine treatment groups (i.e. 0 or 20 ppm ractopamine), resulting in 16 pigs per gender/diet/ractopamine subgroup. The feeding trial lasted an average of 41 days, and the pigs went on trial at an average weight of 64·5 kg and were slaughtered at an average weight of 98·2 kg. Five barrows and five gilts were subsampled at random from each gender/diet/ractopamine subgroup for palatability evaluations. Comprehensive palatability evaluations were conducted on both cured and uncured pork cuts. Results revealed no meaningful differences in flavour, texture, or cooking properties attributable to dietary protein level (17·6 vs 19·6% crude protein) or to ractopamine. Thus, within the context of conditions employed in the present study, ractopamine can be administered with different dietary crude protein levels to improve production efficiency and carcass composition, without influencing palatability and cooking properties or consumer acceptance. Gender effects have been reported elsewhere (Jeremiah et al., 1994).  相似文献   
22.
A total of 128 barrows and 128 gilts were equally and randomly allocated to two separate barley-based diets containing two distinct protein sources (soybean meal and canola meal). Subsequently, the pigs within each gender/ diet treatment subgroup were equally and randomly assigned to two ractopamine treatment groups (0 or 20 ppm). The feeding trial lasted an average of 42 days. The pigs went on trial at an average weight of 67·9 kg and were slaughtered at an average weight of 101·9 kg. Ten pigs selected at random from each gender/diet/ractopamine subgroup were utilized for detailed palatability evaluation. These comprehensive palatability evaluations were conducted on both cured and uncured pork cuts. Results revealed no differences of practical importance in flavour, texture, or cooking properties attributable to dietary protein source or to administration of ractopamine, despite the fact a few statistically significant differences were observed. Thus, ractopamine can be administered with different dietary protein sources to improve production efficiency and improve carcass composition, without influencing palatability and cooking properties, or consumer acceptance. Gender effects have been reported elsewhere (Jeremiah et al., 1994b).  相似文献   
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An environmental cell was used in the high voltage electron microscope to observe the formation of radiation damage in aluminium and dilute aluminium alloys in the presence of gas atmospheres of hydrogen, helium and air. The types of defect produced under such conditions are classified and it is shown that the characteristic of electron irradiation in the presence of a gas is the promotion of void nucleation. The implication of this observation with regard to the design of reactor materials is discussed.  相似文献   
25.
The weak beam technique is now used widely for the determination of stacking fault energies, in particular for intermetallic alloys, and the accuracy of the approach is critically dependent upon the reliability of the relationship between the image and the actual position of the dissociated dislocations. Examining as a model case a dislocation dissociated into two Shockley partial dislocations in Cu at 100 kV for orientations ranging through the g(3g) weak beam condition, image simulations are used to explore the accuracy to which the true spacing between the partial dislocations can be determined from the spacing measured on the image as a function of the dislocation character, the foil thickness, the dislocation depth in the foil, the diffraction condition and the beam convergence. It appears that for image simulations and for the given conditions a beam convergence of about 5 mrad allows to greatly improve the accuracy, and that beam convergence must be taken into account quantitatively when deducing the true partial dislocation spacing as it is the principal parameter controlling the precision in this type of measurement.  相似文献   
26.
The scale existent at the initiation of breakaway oxidation kinetics for an Fe-9Cr-1Mo alloy, as oxidized in 1% CO-CO2 at 600°C, is chemically and microstructurally characterized by the transmission electron microscopy of cross-sectional specimens. The relative importance of chemical and mechanical instabilities in the history of the scale development is thus deduced and the importance of changes in the CO/CO2 ratio at the inward growing interfaces of the scale emphasised.  相似文献   
27.
A method is presented of improving the visibility of transmission electron microscope images in any situation in which a high resolution in only one chosen direction is of interest. The technique is based on the use of slot shaped objective apertures. Such apertures are of reduced area relative to a circular aperture giving the same all round resolution. The background intensity due to inelastically scattered electrons is thus reduced. The aperture device developed is described, while the value of the method is demonstrated by its application to the observation of dislocations. Further possible applications are indicated.  相似文献   
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The relative influences of crystal tilt and beam alignment on high-resolution electron-microscopic imaging have been investigated. With the use of contrast transfer theory in generalised dimensionless form, the major effect of slight beam misalignment has been shown to be the introduction of an antisymmetric phase shift in the diffracted beams so that the presence of any such misalignment cannot be detected by the standard diagnostic tool of high-resolution electron microscopy, namely the optical diffractogram. Specific image simulations, at 100 and 500 keV, for materials of both small and large unit cells (SnO2 and Ti2Nb10O29 respectively) show, however, that even slight beam tilt can have a marked effect on the images of crystalline materials, causing considerable spurious detail and a loss of expected symmetry. The various options for ensuring accurate beam and crystal alignment are briefly reviewed, and some aspects of the alignment problems are demonstrated using some recent experimental images recorded at 500 kV.  相似文献   
30.
The martensitic transformation temperature in shape memory alloys can be affected differently by aging above and below the transformation temperature. Under such circumstances the normally reversible transformation can be prevented and the martensite structure “stabilized”. This effect has been studied using electron microscopy, differential scanning calorimetry, and mechanical testing. Evidence is given of an apparently martensitic high temperature transformation, and a careful comparison is made of the stabilized and unstabilized states of the alloy. Three possible models for stabilization are considered in the light of the results obtained, and it is concluded that no single mechanism can be responsible for all the phenomena observed. Formerly with the Department of Metallurgy and Materials Science, University of Cambridge, England  相似文献   
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