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排序方式: 共有661条查询结果,搜索用时 0 毫秒
51.
Chen GJ Kuo CH Chen CI Yu CC Shieh CJ Liu YC 《Journal of Bioscience and Bioengineering》2012,113(2):166-172
In this study, three membranes: regenerated cellulose (RC), glass fiber (GF) and polyvinylidene fluoride (PVDF), were grafted with 1,4-diaminobutane (DA) and activated with glutaraldehyde (GA) for lipase covalent immobilization. The efficiencies of lipases immobilized on these membranes with different hydrophobic/hydrophilic properties were compared. The lipase immobilized on hydrophobic PVDF-DA-GA membrane exhibited more than an 11-fold increase in activity compared to its immobilization on a hydrophilic RC-DA-GA membrane. The relationship between surface hydrophobicity and immobilized efficiencies was investigated using hydrophobic/hydrophilic GF membranes which were prepared by grafting a different ratio of n-butylamine/1,4-diaminobutane (BA/DA). The immobilized lipase activity on the GF membrane increased with the increased BA/DA ratio. This means that lipase activity was exhibited more on the hydrophobic surface. Moreover, the modified PVDF-DA membrane was grafted with GA, epichlorohydrin (EPI) and cyanuric chloride (CC), respectively. The lipase immobilized on the PVDF-DA-EPI membrane displayed the highest specific activity compared to other membranes. This immobilized lipase exhibited more significant stability on pH, thermal, reuse, and storage than did the free enzyme. The results exhibited that the EPI modified PVDF is a promising support for lipase immobilization. 相似文献
52.
A two-dimensional interference model of upwind wind turbine, based on NREL Phase VI, was simulated by an available Navier–Stokes solver under parallel process. The simulation domain was divided into a stationary tower domain and a sliding blade domain with varying geometric factors, including blade chord to tower diameter ratio and tower-blade gap to tower diameter ratio, to figure out the unsteady problem. The turbulence model was treated with SST k–ω turbulence model and the boundary layers around the solid walls were refined by the y+ value. The simulated results of velocity field were compared with the potential cylinder flow, and some phenomena were exhibited, including the movement of stagnation point of tower, the skewed wake of tower and the excess of velocity in the field. The lift force coefficient of blade was different from the ideal angle of attack for the blade passing in front of the potential cylinder flow. 相似文献
53.
Yeung-Nan Shieh 《Papers in Regional Science》1999,78(3):319-321
The purpose of this note is to show that an analogue of the Beckmann-Ingene proposition on price policies of a spatial monopolist applies to a properly formulated profit maximization problem for a spatial monopsonist. The proof of this fact uses the same linear transformation employed in the Beckmann-Ingene argument. Received: 15 October 1998 / Accepted: 9 January 1999 相似文献
54.
Der-Her Lee C. H. Juang Jin-Wen Chen Hung-Ming Lin Wen-Hwang Shieh 《International Journal of Rock Mechanics and Mining Sciences》1999,36(7):315
A series of hollow cylindrical triaxial tests was performed to investigate the potential effect of stress paths on the mechanical behavior of the Pei-Tou sandstone. The tests were carried out with a computer-controlled loading system. The axial loading, outer and inner confining pressures, and torque applied to the specimen were controlled according to a preselected stress path. The stress path moved from the hydrostatic stress axis in principal-stress space and elongated on an octahedral plane, while maintaining a constant angle θ against the projection of the major principal stress axis on the octahedral plane. The proposed hollow cylinder test is shown to be able to follow any designed stress paths in the principal stress space. Thus, it may be used to investigate the effect of stress paths on the mechanical behavior of rock and to construct its failure surface. 相似文献
55.
Ming-Fong Tsai Ce-Kuen Shieh Chih-Heng Ke Der-Jiunn Deng 《Multimedia Tools and Applications》2010,47(1):49-69
Traditional Forward Error Correction (FEC) mechanisms can be divided into Packet level FEC (PFEC) mechanisms and Byte level
FEC (BFEC) mechanisms. The PFEC mechanism of recovering from errors in a source packet requires an entire FEC redundant packet
even though the error involves a few bit errors. The recovery capability of the BFEC mechanism is only half of the FEC redundancy.
Accordingly, an adaptive Sub-Packet FEC (SPFEC) mechanism is proposed in this paper to improve the quality of video streaming
data over wireless networks, simultaneously enhancing the recovery performance and reducing the end-to-end delay jitter. The
SPFEC mechanism divides a packet into n sub-packets by means of the concept of a virtual packet. The SPFEC mechanism uses a checksum in each sub-packet to identify
the position of the error sub-packet. Simulation experiments show the adaptive SPFEC mechanism achieves high recovery performance
and low end-to-end delay jitter. The SPFEC mechanism outperforms traditional FEC mechanism in terms of packet loss rate and
video Peak Signal-to-Noise Ratio (PSNR). SPFEC offers an alternative for improved efficiency video streaming that will be
of interest to the designers of the next generation environments. 相似文献
56.
The objective of this study was set out to characterize the polycyclic aromatic hydrocarbon (PAH) content in the atmosphere of an oil furnace carbon black manufacturing plant located in southern Taiwan. A standard semi-volatile sampling train, the PS-1 sampler, was used to collect samples from eight areas, including the feedstock oil unloading, furnace, filtering/micro-pulverization, pelletizing, packaging, office/outside, office/inside, and boundary area, respectively. For each area, side-by-side static samples were collected simultaneously and a total of 16 samples were obtained. For each collected sample, the adsorbent-retained PAH content and the filter-retained PAH content were used directly to determine the concentrations of gaseous-phase PAHs and particle-bound PAHs, respectively. The gas chromatograph/mass spectrometer (GC/MS) technique was used for PAH analyses, and a total of 21 PAH species were determined. Results show the gaseous-phase PAHs accounted for only 69.2% of the total PAH content for samples collected from the packaging area, which was significantly lower than those samples collected from the rest of seven areas (ranging from 96.3 to 99.7%). The result is not so surprising since the packaging area had the highest dust concentration due to the releasing of carbon black dusts during the packaging process. In this study, we further examine the contribution of gaseous-phase PAHs to the total benzo[a]pyrene equivalent (BaP(eq)) content from the health-risk assessment view of point. It can be found the contribution of gaseous-phase PAHs to the total BaP(eq) content (63.1%) was quite comparable to the corresponding contribution to the total PAH content for samples collected from the packaging area. However, a different trend can be found for samples collected from the other seven areas, where the contributions of gaseous-phase PAHs to the total BaP(eq) content (ranging from 67.7 to 93.4%) were lower than the corresponding contributions to the total PAH content. The above results can be explained by PAH homologues that contained in both gaseous-phase and particle-bound PAHs. It was found the gaseous-phase PAHs contained higher fractions of less carcinogenic low molecular weight PAH homologues, whereas particle-bound PAHs contained higher fractions of more carcinogenic high molecular weight PAH homologues. Considering the contributions of gaseous-phase PAHs to both total PAH content and total BaP(eq) content were well above 50% for the eight studied areas, it is concluded that both particle-bound and gaseous-phase PAHs should be included for assessing the exposures of carbon black workers. 相似文献
57.
Daily intake of TBT, Cu, Zn, Cd and As for fishermen in Taiwan 总被引:7,自引:0,他引:7
Chien LC Hung TC Choang KY Yeh CY Meng PJ Shieh MJ Ha BC 《The Science of the total environment》2002,285(1-3):177-185
The consumption of contaminated seafood has been reported as an important route of human exposure to metals in Taiwan. We consider the concentrations of TBT, Cu, Zn, Cd, As, and the consumption of oysters of Taiwanese to be the important information related to public health in Taiwan. Therefore, the aim of this study was to evaluate the public health risks associated with TBT, Cu, Zn, Cd and As from shellfish for the general population and fishermen of Taiwan. In general, TBT concentrations in various oysters ranging from 0.32 to 1.51 microg/g dry wt. varied with sampling locations. The highest TBT, Cu, and Zn geometric mean (GM) concentrations in oysters of 1.51, 1180 and 1567 microg/g dry wt. were obtained from the Hsiangshan coastal area. The values of oyster consumption for fishermen were 94.1 and 250 g/day for typically and maximally exposed individuals, respectively. In particular, the highest intake (250 g/day) from fishermen was almost two times greater than that of the general population (139 g/day). The THQ (target hazard quotient) values of Hsiangshan's fishermen are 3.87 and 20.50 for TBT and Cu for maximally exposed individuals are higher than other oyster culture areas. It is interesting that those consuming oysters from Hsiangshan, Lukang, Taishi caused abnormally high THQs of TBT and other metals (100% over 1.0), and TBT was attributed to only 3-21% of the total THQs in different fishermen of Taiwan. Our results suggest that current environmental levels of TBT and other metals are associated with a significant potential threat to human health for fishermen resident in coastal areas of Taiwan. 相似文献
58.
Faezeh Ebrahimzadeh Ying Ting Liao Min-Ching Chung Leang-San Shieh 《International journal of systems science》2017,48(2):376-396
This paper presents a generalised optimal linear quadratic analog tracker (LQAT) with universal applications for the continuous-time (CT) systems. This includes: (1) a generalised optimal LQAT design for the system with the pre-specified trajectories of the output and the control input and additionally with both the input-to-output direct-feedthrough term and known/estimated system disturbances or extra input/output signals; (2) a new optimal filter-shaped proportional plus integral state-feedback LQAT design for non-square non-minimum phase CT systems to achieve a minimum phase-like tracking performance; (3) a new approach for computing the control zeros of the given non-square CT system; and (4) a one-learning-epoch input-constrained iterative learning LQAT design for the repetitive CT system. 相似文献
59.
Faa-Jeng Lin Hsin-Jang Shieh Li-Tao Teng Po-Huang Shieh 《IEEE transactions on magnetics》2005,41(7):2260-2269
We propose a hybrid controller using a recurrent neural network (RNN) to control a levitated object in a magnetic levitation system. We describe a nonlinear dynamic model of the system and propose a computed force controller, based on feedback linearization, to control the position of the levitated object. To relax the requirement of the lumped uncertainty in the design of the computed force controller, an RNN functions as an uncertainty observer to adapt the lumped uncertainty on line. The computed force controller, the RNN uncertainty observer, and a compensated controller are embodied in a hybrid controller, which is based on Lyapunov stability. The computed force controller, with the RNN uncertainty observer, is the main tracking controller, and the compensated controller compensates the minimum approximation error of the RNN uncertainty observer. To ensure the convergence of the RNN, the adaptation law of the RNN is modified by using a projection algorithm. Experimental results illustrate the validity of the proposed control design for the magnetic levitation system. 相似文献
60.
An adaptive recurrent radial basis function network tracking controller for a two-dimensional piezo-positioning stage 总被引:1,自引:0,他引:1
Lin FJ Shieh HJ Huang PK Shieh PH 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2008,55(1):183-198
An adaptive recurrent radial basis function network (ARRBFN) tracking controller for a two-dimensional piezo-positioning stage is proposed in this study. First, a mathematical model that represents the dynamics of the two-dimensional piezo-positioning stage is proposed. In this model, a hysteresis friction force that describes the hysteresis behavior of one-dimensional motion is used; and a nonconstant stiffness with the cross-coupling dynamic due to the effect of bending of a lever mechanism in x and y axes also is included. Then, according to the proposed mathematical model, an ARRBFN tracking controller is proposed. In the proposed ARRBFN control system, a recurrent radial basis function network (RRBFN) with accurate approximation capability is used to approximate an unknown dynamic function. The adaptive learning algorithms that can learn the parameters of the RRBFN on line are derived using Lyapunov stability theorem. Moreover, a robust compensator is proposed to confront the uncertainties, including approximation error, optimal parameter vectors, higher-order terms in Taylor series. To relax the requirement of the value of the lumped uncertainty in the robust compensator, an adaptive law is investigated to estimate the lumped uncertainty. Using the proposed control scheme, the position tracking performance is substantially improved and the robustness to uncertainties, including hysteresis friction force and cross-coupling stiffness, can be obtained as well. The tracking performance and the robustness to external load of the proposed ARRBFN control system are illustrated by some experimental results. 相似文献