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41.
By using fiber gratings as pump reflectors with various reflectivities or N pieces of gain fibers with various lengths externally to linear cavity as self-equalizers, a parallel-type, pump-shared linear cavity laser array (LCLA) is proposed and numerically studied. The average output power is increased and the maximum power variation among channels is reduced from 7.2 to less than 0.1 dB when the reflectivity of each pump reflector or the length of each gain fiber is adjusted appropriately 相似文献
42.
Kao-Shang Shih Ching-Chi Hsu Tzu-Pin Hsu Sheng-Mou Hou Chen-Kun Liaw 《Computer methods and programs in biomedicine》2014
Femoral shaft fractures can be treated using retrograde interlocking nailing systems; however, fracture nonunion still occurs. Dynamic fixation techniques, which remove either the proximal or distal locking screws, have been used to solve the problem of nonunion. In addition, a surgical rule for dynamic fixation techniques has been defined based on past clinical reports. However, the biomechanical performance of the retrograde interlocking nailing systems with either the traditional static fixation technique or the dynamic fixation techniques has not been investigated by using nonlinear numerical modeling. Three-dimensional nonlinear finite element models were developed, and the implant strength, fixation stability, and contact area of the fracture surfaces were evaluated. Three types of femoral shaft fractures (a proximal femoral shaft fracture, a middle femoral shaft fracture, and a distal femoral shaft fracture) fixed by three fixation techniques (insertion of all the locking screws, removal of the proximal locking screws, or removal of the distal locking screws) were analyzed. The results showed that the static fixation technique resulted in sufficient fixation stability and that the dynamic fixation techniques decreased the failure risk of the implant and produced a larger contact area of the fracture surfaces. The outcomes of the current study could assist orthopedic surgeons in comprehending the biomechanical performances of both static and dynamic fixation techniques. In addition, the surgeons could also select a fixation technique based on the specific patient situation using the numerical outcomes of this study. 相似文献
43.
P. K. Liaw M. N. Gungor W. A. Logsdon Y. Ijiri B. J. Taszarek S. Frohlich 《Metallurgical and Materials Transactions A》1990,21(2):529-538
Interfaces of two different babbitt-bronze composites were tested ultrasonically and then were fractured using the Chalmers
test method. The primary distinction between the two composites was in the copper content. Use of less copper in the babbitt
resulted in interfaces with higher strength, lower ductility, less cracking, and less unbonded area. The differences appeared
to stem from the structure of the intermetallic compounds found at the interface, namely, the Cu3Sn and the Cu6Sn5 layers. The low-copper composite failed within a thick, dendrite-like Cu6Sn5 layer, while the high-copper one separated at the interface between a smooth Cu6Sn5 layer and the babbitt metal. The rough interface morphology seemed responsible for the low-copper composite’s increased strength.
The correlation between mechanical and ultrasonic properties was poor for the low-copper composite but excellent for the high-copper
one. These results suggest that interface morphology can significantly affect mechanical as well as ultrasonic properties.
Formerly with the Westinghouse Power Systems Operations Division
Formerly with the Westinghouse Science and Technology Center 相似文献
44.
The properties of a novel cationic, naphthalene-labeled cationic poly(dimethyl sulfate quaternized acrylamide/N,N-dimethylaminopropylmaleimide
copolymer), poly-(DSQADMAPM)/NA in aqueous solution are examined in this study, measuring intrinsic viscosity, reduced viscosity,
and ionic strength. This cationic poly(DSQADMAPM)/NA’s intrinsic viscosity is dependent on the type and concentration of salt
added to the aqueous solution. The intrinsic viscosity behavior of the cationic poly(DSQADMAPM)/NA resulting from the electrostatic
repulsive force of the polymer chain is contrasted with polyampholyte. Smaller anions such as F− with a common cation (K+) are found to be the most difficult to be bound to the end group, indicating that a higher intrinsic viscosity of the poly(DSQADMAPM)/NA
would be in KF salt aqueous solution. Smaller cations such as Li+ with a common anion (Cl−) are found to be the most difficult to be bound to the quaternary ammonium group, indicating that a higher intrinsic viscosity
of the poly(DSQADMAPM)/NA would also be in LiCI salt aqueous solution. Models are proposed to account for the poly(DSQADMAPM)/NA
solution viscometrics. 相似文献
45.
In this paper, we present a fast codebook generation algorithm called CGAUCD (Codebook Generation Algorithm Using Codeword Displacement) by making use of the codeword displacement between successive partition processes. By implementing a fast search algorithm named MFAUPI (Modified Fast Algorithm Using Projection and Inequality) for VQ encoding in the partition step of CGAUCD, the codebook generation time can be further reduced significantly. Using MFAUPI, the computing time of CGAUCD can be reduced by a factor of 4.7–7.6. Compared to Generalized Lloyd Algorithm (GLA), our proposed method can reduce the codebook generation time by a factor of 35.9–121.2. Compared to the best codebook generation algorithm to our knowledge, our approach can further reduce the corresponding computing time by 26.0–32.8%. It is noted that our proposed algorithm can generate the same codebook as that produced by the GLA. The superiority of our method is more remarkable when a larger codebook is generated. 相似文献
46.
47.
Adaptive array has been used for canceling the interference in communication. When the array cannot suppress all the interference,
an equalizer following the array can add to further enhance the capability of canceling the inter-symbol interference (ISI).
The adaptive array and equalizer (AE) will suffer the problems of insufficient degrees of freedom and main-beam multi-path
ISI. The hybrid of adaptive array and equalizer (HAE) uses a modified training sequence to adjust the weights of adaptive
array that leads the array to cancel only the co-channel interference (CCI). The ISI are removed by the equalizer following
the array. Thus, the HAE can combat the above problems successfully. Though the HAE improves the performance of AE, a transversal
filter is added to generate the modified training sequence. Besides, the weights of equalizer in the HAE, which adjust after
the weights of adaptive array, will make the convergent rate slowly. A simple hybrid of adaptive array and equalizer (SHAE)
utilizes the output signal of system to adjust the weights of both the adaptive array and equalizer simultaneously. Therefore,
the convergent rate of the HAE can improve by the SHAE. Moreover, the ISI can be suppressed by the equalizer instead of the
adaptive array in the SHAE that will improve the performance of AE without using the transversal filter. As the mutual coupling
present, the convergent rate of the SHAE will slow down. In this paper, a least mean square error algorithm with mutual coupling
present is proposed to improve the convergent rate of SHAE, also. 相似文献
48.
S. G. Ma S. F. Zhang M. C. Gao P. K. Liaw Y. Zhang 《JOM Journal of the Minerals, Metals and Materials Society》2013,65(12):1751-1758
For the first time, a face-centered-cubic, single-crystal CoCrFeNiAl0.3 (designated as Al0.3), high-entropy alloy (HEA) was successfully synthesized by the Bridgman solidification (BS) method, at an extremely low withdrawal velocity through a constant temperature gradient, for which it underwent two BS steps. Specially, at the first BS step, the alloy sample underwent several morphological transitions accompanying the crystal growth from the melt. This microstructure evolves from as-cast dendrites, to equiaxed grains, and then to columnar crystals, and last to the single crystal. In particular, at the equiaxed-grain region, some visible annealing twins were observed, which indicates a low stacking fault energy of the Al0.3 alloy. Although a body-centered-cubic CoCrFeNiAl (Al1) HEA was also prepared under the same conditions, only a single columnar-crystal structure with instinctively preferential crystallographic orientations was obtained by the same procedure. A similar morphological transition from dendrites to equiaxed grains occurred at the equiaxed-grain region in Al1 alloy, but the annealing twins were not observed probably because a higher Al addition leads to a higher stacking fault energy for this alloy. 相似文献
49.
Monophasic Sr2(Ce1?xSnx)O4 phosphors (x = 0–0.07) were prepared via the sol–gel process. A broad excitation band ascribed to the Ce4+–O2? transition was observed in the range of 200–450 nm. With doping Sn4+ ions into the host, the intensity of the low-energy peak enhanced remarkably due to a decrease in crystal field. The intensity ratio of the low-energy peak to the high-energy peak increased with the amount of Sn4+ ions doped. Moreover, the red shift of the excitation peaks was observed due to an increase in the bond length of Ce–O. Upon excitation at around 346 nm, the intensity of the blue emission peak peaking at 483 nm was enhanced with doping Sn4+ ions. The doping of tin ions was found to significantly improve the luminescence characteristics of the prepared phosphors when they were excited under UV light. 相似文献
50.