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排序方式: 共有108条查询结果,搜索用时 78 毫秒
1.
Valderrama Pilar Escabias Manuel Jiménez-Contreras Evaristo Valderrama Mariano J. Baca Pilar 《Scientometrics》2018,116(2):1203-1212
Scientometrics - In order to estimate the impact factor value for a journal in Dentistry, two sets of variables were considered in this study: the first takes in the longitudinal behavior of the... 相似文献
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Hussein Fakhoury Papy Ndungidi Carlos Valderrama 《Analog Integrated Circuits and Signal Processing》2011,67(3):273-284
A low-power, low-pass continuous-time sigma-delta A/D modulator with 1-MHz bandwidth is implemented in a 130-nm CMOS process.
The circuit is targeted for an IEEE 802.15.4 direct conversion receiver operating in the 2.4-GHz band. It has a third-order
feedforward single-loop filter and a 1-bit quantizer to minimize power consumption. Non-return-to-zero DAC pulse shaping is
used to reduce sensitivity to clock jitter. Clocked at 64 MHz, the prototype chip achieves 62-dB peak SNR, −70-dB peak THD,
63-dB dynamic range with an oversampling ratio of 32. The built-in anti-alias filter provides alias attenuation greater than
57 dB, which improves coexistence of the receiver with other devices that operate in the 2.4-GHz band. The circuit dissipates
1.44 mW from the 1.2-V supply and the active die area is 0.1 mm2. 相似文献
4.
Results of copper–gold rougher-flash flotation in a three-product column (3PC) are presented, and separation parameters are compared with results of an existing industrial small mill (rougher–scavenger–cleaner treating 100–120 t/day). This 3PC cell yielded 2%–5% richer Cu and Au concentrate grades at higher recoveries (5% RCu and 15% RAu, respectively) while consuming only 5% of the circuit energy and occupying 10% of the actual footprint. The flotation of the fresh tailings from the same industrial circuit was also successful in recovering more than 40% of the copper losses and 25% of the gold losses with concentrate grades that were high enough to permit recycling of the recovered copper and gold. The cleaning action of the cell is due to the selective separation of the third product (froth drop-back), which corresponded to a low-grade material amenable for discard. This third product is primarily composed of misplaced (entrained) gangue particles, and the mass recoveries were found to be a function of froth height with an optimal value varying from 40 to 60 cm. Results are discussed in terms of the high potential of this 3PC cell and the positive impact on the design of a more simplified and efficient flotation flowsheet. 相似文献
5.
M. Carmen Aguilera-Morillo Ana M. Aguilera Manuel Escabias Mariano J. Valderrama 《TEST》2013,22(2):251-277
The problem of multicollinearity associated with the estimation of a functional logit model can be solved by using as predictor variables a set of functional principal components. The functional parameter estimated by functional principal component logit regression is often nonsmooth and then difficult to interpret. To solve this problem, different penalized spline estimations of the functional logit model are proposed in this paper. All of them are based on smoothed functional PCA and/or a discrete penalty in the log-likelihood criterion in terms of B-spline expansions of the sample curves and the functional parameter. The ability of these smoothing approaches to provide an accurate estimation of the functional parameter and their classification performance with respect to unpenalized functional PCA and LDA-PLS are evaluated via simulation and application to real data. Leave-one-out cross-validation and generalized cross-validation are adapted to select the smoothing parameter and the number of principal components or basis functions associated with the considered approaches. 相似文献
6.
A new balanced scorecard approximation to enhance performance management systems of Chilean wineries
The Chilean wine industry faces a growing challenge in terms of the increasing global competition, along with other difficult challenges such as exchange rate fluctuations, higher labor and energy costs and climate change. In light of this, the present paper proposes a new approach to increase competitiveness of Chilean wineries based on findings of the current performance management systems practice in the industry. The methodology encompasses a thorough survey of the industry's management systems, with special emphasis on the balanced scorecard (BSC) and its derivatives. The study finds, upon examining the results, that the ISO 9001 norm and the national code of sustainability of the Chilean wine industry are the two most commonly used and that only 14% of the companies have designed a BSC of some type, offering a unique opportunity to introduce this novel approach focusing on performance and sustainability, incorporating the spatial and temporal dimensions of the industry today. 相似文献
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César Valderrama Xavier Gamisans Jose L Cortina Adriana Farrán F Xavier de las Heras 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2009,84(2):236-245
BACKGROUND: Sorption of polycyclic aromatic hydrocarbons (PAHs) on activated carbon and the Macronet polymeric sorbent MN200 was investigated to determine the effectiveness of each sorbent for removal of pollutants from aqueous solution and their possible use as sorbent materials for groundwater. Experiments were carried out to determine the loading capacities of a family of PAHs (acenaphthene, anthracene, fluoranthene, fluorene, naphthalene and pyrene). RESULTS: Activated carbon was the more effective sorbent, with maximum loadings of PAHs between 90 and 230 g kg?1, while MN200 resin showed values of 25–160 g kg?1. Loading isotherms based on the Langmuir, Freundlich and Redlich–Peterson models were determined. The hydrophobic character of the pollutants appeared as an important parameter related to the sorption process. Equilibrium and kinetic parameters were used to determine the retardation factors for each PAH. CONCLUSION: The calculated values for the simulation of barrier thickness using both sorbents, taking into account EU requirements for PAHs in groundwater effluent, were perfectly reasonable as a first estimate. The better kinetic properties of MN200 are evident in lower hydraulic residence times and consequently in a lower barrier thickness. Copyright © 2008 Society of Chemical Industry 相似文献
9.
In this study, three semipredictive activity coefficient models: Wilson, non-random-two liquid model (NRTL), and universal quasi-chemical model (UNIQUAC), have been used for modeling vapor-liquid equilibrium properties of ternary mixtures that include substances found in alcoholic distillation processes of wine and musts. In particular, vapor-liquid equilibrium in ternary mixtures containing water + ethanol + congener has been modeled using parameters obtained from binary and ternary mixture data. The congeners are substances that although present in very low concentrations, of the order of part per million, are important enological parameters. The results given by these different models have been compared with literature data and conclusions about the accuracy of the models studied are drawn, recommending the best models for correlating and predicting phase equilibrium properties of this type of mixtures. 相似文献
10.
C. A. Faúndez J. O. Valderrama V. H. Alvarez 《Journal of Phase Equilibria and Diffusion》2004,25(3):230-236
Phase equilibrium in binary mixtures that are found in wine and must distillation processes have been modeled using the predictive
Soave-Redlich-Kwong equation, with original and modified molecular parameters. In wine and must distillation, the presence
of polar substances found in the mixture to be distilled and the many components (i.e., those different from ethanol and water),
called congeners, makes it difficult to model these mixtures. Thus, the prediction and correlation of the concentration of
the distilled product, which is the most interesting variable, become very complex, and some experimental data are needed.
The cases studied considered nine binary water + congener mixtures. The congeners considered are acetic acid, acetaldehyde,
ethyl acetate, furfural, methanol, 3-methylbutanol, 2-methyl-1-propanol, 1-pentanol, and 1-propanol. These are the substances
that are considered to be legal compounds by the Chilean legislation governing the production of a spirit called Pisco. The
work allows evaluation of the advantages, disadvantages, and expected accuracy of this model. Comparison with available literature
data is done. 相似文献