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排序方式: 共有802条查询结果,搜索用时 15 毫秒
781.
782.
Elisabete Matos Tomé S. SilvaTeresa Tiago Manuel AurelianoMaria Teresa Dinis Jorge Dias 《Food chemistry》2011
A trial was undertaken to evaluate Differential Scanning Calorimetry (DSC) as a fast analytical tool to differentiate gilthead seabream subjected to variable conditions of slaughter stress and post-mortem storage. Fish were subjected to different harvesting stress conditions: profound anaesthesia (PA, low stress) and net crowding (NC, high stress). Fish were slaughtered in an ice-salt water slurry, and subsequently stored on ice (7 days). Additional NC fish were frozen (−20 °C) and subjected to a freeze–thaw cycle. Dorsal muscle was assessed for cathepsins activity, liquid loss and DSC analysis. It is demonstrated that DSC analysis is capable of differentiating fresh, frozen and thawed-re-frozen fish, while liquid loss and cathepsin B activity are good markers to distinguish fresh from frozen fish. Harvesting stress had little effect on myosin and actin enthalpy transitions, as observed by DSC at 49 and 74 °C, respectively, but a lower ΔH actin/myosin ratio was found in PA fish, suggesting that intense exercise prior to slaughter promoted partial denaturation of muscle myosin. 相似文献
783.
C. Pires S. CostaA.P. Batista M.C. Nunes A. Raymundo I. Batista 《Journal of food engineering》2012,108(2):268-275
Cape hake protein powder (HPP) was prepared by alkaline extraction, isoelectric precipitation and freeze drying. It contained 90% protein, 0.53% fat, and 1.44% ash. HPP showed high levels of Na, K, Ca and Mg but lower than in hake mince. The protein profile of HPP was similar to the raw material.The surface hydrophobicity and sulfhydryl group content of HPP were identical to those of the proteins before freeze-drying. The HPP had higher fat absorption capacity, lower emulsifying and foaming capacity than soy protein concentrate, pea protein isolate and egg white powder. The gel strength of HPP was medium (44.8 Nxmm) and was increased by addition of transglutaminase.Gels with different HPP concentrations showed a typical pattern of myofibrillar protein networks with a thermo-reversible behavior. The structure of emulsions prepared with HPP showed increasing complexity as the protein level increased. An increase in the magnitude of the viscoelastic functions and an increment in the magnitude of the zero shear rate limiting viscosity with increasing HPP content were observed. 相似文献
784.
785.
Maíra?Maciel?Mattos?de?OliveiraEmail author Danilo?Florisvaldo?Brugnera Josianne?Arantes?do Nascimento Nádia?Nara?Batista Roberta?Hilsdorf?Piccoli 《European Food Research and Technology》2012,234(5):821-832
The antibacterial effects of Cinnamomum cassia essential oil (EO) and cinnamaldehyde were evaluated against single- and mixed-species cultivation of enteropathogenic Escherichia coli (EPEC) and Listeria monocytogenes attached to stainless steel. A central composite rotational design with two variables and eleven assays was used to optimize the concentrations (0.00–1.00% v/v for the EO and 0.00–0.80% v/v for cinnamaldehyde) and contact times (1–21 min). The models generated were validated, and the effectiveness of C. cassia EO and cinnamaldehyde was compared with that of commercially available chemical sanitizers. Cinnamaldehyde and C. cassia EO proved to be efficient alternatives to commercial chemical sanitizers in the reduction or elimination of sessile bacterial cells. The activity of these natural compounds was, in most cases, equivalent or superior to that of the chemical sanitizers tested. However, L. monocytogenes was more resistant than EPEC to C. cassia EO and cinnamaldehyde, and the bacterial association in mixed-species biofilms made them more susceptible to these compounds. 相似文献
786.
Luís Batista Sara Monteiro Virgílio B. Loureiro Artur R. Teixeira Ricardo B. Ferreira 《Food chemistry》2010
The effect on the wine protein haze potential of five organic acids commonly encountered in wines (l(+)-tartaric, l(−)-malic, citric, succinic and gluconic acids) was assessed. All five acids, tested at 20 mM, reduced dramatically the haze potential of proteins, either in wine or dissolved in water, throughout the range of pH values typical of wines (i.e., from 2.8 through 3.8). Subtle differences among the acid effects did not correlate with the number of their carboxyl groups, but were attributed to electrostatic interactions that depend upon the acid pKa values, the protein pI values and the medium pH. These results invalidate or question the validity of all experiments on wine proteins involving wine model solutions containing organic acids. Overall, the results obtained in the present work clearly indicate that organic acids with a common occurrence in wines exhibit a stabilising effect upon the haze potential of the wine proteins. 相似文献
787.
Paulo Eduardo Batista de Mello 《Journal of Wind Engineering & Industrial Aerodynamics》2010,98(2):113-119
The objective of the present work is to propose a numerical and statistical approach, using computational fluid dynamics, for the study of the atmospheric pollutant dispersion. Modifications in the standard k-ε turbulence model and additional equations for the calculation of the variance of concentration are introduced to enhance the prediction of the flow field and scalar quantities. The flow field, the mean concentration and the variance of a flow over a two-dimensional triangular hill, with a finite-size point pollutant source, are calculated by a finite volume code and compared with published experimental results. A modified low Reynolds k-ε turbulence model was employed in this work, using the constant of the k-ε model Cμ=0.03 to take into account the inactive atmospheric turbulence. The numerical results for the velocity profiles and the position of the reattachment point are in good agreement with the experimental results. The results for the mean and the variance of the concentration are also in good agreement with experimental results from the literature. 相似文献
788.
Kuga MC Só MV De Campos EA Faria G Keine KC Dantas AA Faria- NB 《Microscopy research and technique》2012,75(10):1432-1436
The aim of this study was to evaluate the persistence of methacrylate‐based cement residues on the dentin, after dentin surface cleaning with ethanol or acetone, with or without previous application of a dentin adhesive. Forty bovine crown fragments were obtained and the dentin surface was washed with 1.0 mL of 2.5% sodium hypochlorite (NaOCl), followed by 0.1 mL of 17% ethylenediaminetetraacetic acid application for 3 min, and final irrigation with 2.5% NaOCl. The specimens were air dried and resin‐based cement was rubbed onto the dentine surface with a microbrush applicator. In 20 specimens, previously to cement, a dentin adhesive was applied in all surfaces. After 15 min, the surface was scrubbed with a cotton pellet and moistened with ethanol or acetone, compounding the following groups: G1—99.5% ethanol and G2—acetone, without previous use of dentin adhesive; G3—99.5% ethanol and G4—acetone, with previous use of dentin adhesive. The dentin surface was scrubbed until the cement residues could not be visually detected. Sections were then processed for scanning electron microscopy and evaluated at 500× magnification and scores were attributed to each image according to the area covered by residual sealer, and data were subjected to Kruskal–Wallis at 5% significance. The lower residue presence was observed in G3 (P = 0.005). All surface presented cement residues when acetone was used as cleaning solution (P = 0.0005). The cleaning solutions were unable to completely remove the cement residues from both surfaces. The ethanol used after previous application of the dentin adhesive promoted the lower presence of residues. Microsc. Res. Tech. 2012. © 2012 Wiley Periodicals, Inc. 相似文献
789.
Pesticides in Portuguese surface and ground waters 总被引:14,自引:0,他引:14
Cerejeira MJ Viana P Batista S Pereira T Silva E Valério MJ Silva A Ferreira M Silva-Fernandes AM 《Water research》2003,37(5):1055-1063
Pesticides used in Portuguese agricultural areas have been found in surface and ground waters. In the surface water collected in three river basins from 1983 to 1999, insecticides and herbicides were detected from the monitored pesticides, particularly atrazine, chlorfenvinphos (Z+E), alpha- and beta-endosulfan, lindane, molinate and simazine, reaching the maximum values, respectively, of 0.63, 31.6, 0.18 microg/L (alpha-endosulfan), 0.18 microg/L (beta-endosulfan), 0.24, 48 and 0.3 microg/L. In the ground water collected from the wells of seven agricultural areas from 1991 to 1998, several monitored herbicides were detected: alachlor, atrazine, metolachlor, metribuzine and simazine, reaching the maximum concentration values of 13, 30, 56, 1.4 and 0.4 microg/L, respectively. The herbicides more frequently detected were atrazine (64%), simazine (45%) and alachlor (25%). Other than these, the monitored pesticides can be present in Portuguese surface and ground waters. Therefore, to improve the analytical conditions, the use of multiresidue methods and automated techniques are desirable in future work. 相似文献
790.
Fl��via Regina de Amorim Milton Batista Franco Cl��sia Cristina Nascentes Jos�� Bento Borba da Silva 《Food Analytical Methods》2011,4(1):41-48
A fast and efficient method to determine molybdenum, Mo, in milk and other infant food by atomic absorption spectrometry with
electrothermal atomization employing slurry sampling was developed. Slurries were prepared in ultrapure water with 5 to 20 min
of sonication in concentrations of 10% w/v. The injection of 5.0 μL of a 0.1% (v/v) cetyl trimethyl ammonium chloride solution before the temperature program reduced the effect of build-up of carbonaceous
residues within the atomizer. Europium (chemical modifier) and niobium (permanent modifier) were chosen for use from several
potential modifiers. The parameters of merit were obtained in the optimized conditions T
a
= 2,700 oC, T
p
= 2,000 oC, tp = 20 s, and Eu 5.0 μg + permanent Nb 500.0 μg. These parameters were linear working range up to 100.0 μg/L, limit of detection
(1.1 ± 0.1) μg/L, aqueous calibration, and standard addition curves with r
2 > 0.9900 and relative standard deviation of 0.6% to 8.7%. The accuracy was evaluated by recovery tests and by certified material
analysis; the agreement among these numbers validated the method. The powdered sample concentrations were between 39 and 1,570 μg/kg. 相似文献