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排序方式: 共有980条查询结果,搜索用时 58 毫秒
91.
Antonio J. López-Martín Alfonso Carlosena Jaime Ramirez-Angulo 《Analog Integrated Circuits and Signal Processing》2004,40(1):71-74
A novel technique for operating MOS Translinear loops at very low supply voltages is described, based on the use of Flipped Voltage Followers for biasing the loops. The resulting topologies, suited to standard CMOS processes, can be successfully applied to a varied repertory of low-voltage analog circuits, such as squarers, multipliers, filters, oscillators, and RMS-DC converters. Measurement results for a geometric-mean and a squarer/divider circuit demonstrate on silicon the usefulness of this technique. 相似文献
92.
Susana Nieto Argelia Garrido Julio Sanhueza Luis A. Loyola Glauco Morales Federico Leighton Alfonso Valenzuela 《Journal of the American Oil Chemists' Society》1993,70(8):773-778
The antioxidant activities against fish oil oxidation of six commercially available flavonoids and of five flavonoids purified
from two Chilean native plants were compared to those ofdl-α-tocopherol and of two synthetic antioxidants, butylated hydroxytoluene and butylated hydroxyanisole. Among the commercial
flavonoids, catechin, morin and quercetin showed a higher activity when fish oil oxidation (either spontaneous or Fe2+-induced) was assessed from the formation of peroxides or thiobarbituric acid-reactive substances. Among the native flavonoids,
the 5,3′,4′-trihydroxy-7-methoxy flavanone (designated as Pt-2) showed the highest antioxidant activity. Mixtures of quercetin
or of Pt-2 withdl-α-tocopherol produced better inhibitory effects when compared to that of each substance assayed by itself. Also, when Pt-2
and quercetin were assayed in combination (0.3 g/kg oil and 0.7 g/kg oil, respectively), a synergistic antioxidant effect
was observed. Results indicate that several flavonoids could be used as natural antioxidants as a means to replace those synthetic
antioxidants, the use of which has been questioned. 相似文献
93.
Validation of the rancimat test for the assessment of the relative stability of fish oils 总被引:2,自引:1,他引:1
Eduardo Méndez Julio Sanhueza Hernán Speisky Alfonso Valenzuela 《Journal of the American Oil Chemists' Society》1996,73(8):1033-1037
The induction periods for the peroxidation of various fish oils at 55–90°C were studied by the Rancimat test. The natural
logarithms of the induction periods varied linearly with respect to temperature, with a mean coefficient of −7.5×10−2°C−1, which was significantly different from that reported for vegetable oils. The activation energy for the formation of volatile
acids had a mean value of 38.9 kJ/mol and was independent of the fish oil source. Peroxide formation under Rancimat test conditions
followed first-order kinetics. The same kinetics were followed under Schaal Oven test conditions (forced-air oven, 60°C).
On the basis of the results obtained, the Rancimat test appears to be useful in determining the relative stabilities of fish
oils without the change in peroxide decomposition kinetics that may occur at elevated temperatures. 相似文献
94.
JM Quintela C Peinador C Veiga L González LM Botana A Alfonso R Riguera 《Canadian Metallurgical Quarterly》1998,6(10):1911-1925
The synthesis of a series of pyridothienopyrimidines and their evaluation as inhibitors or inducers of the release of histamine from rat mast cells is reported. The activity was measured after immunological stimulation with ovoalbumin and chemical stimulation with polymer 48/80 and the drugs adryamicin and vinorelbine. The experiments were carried out with and without preincubation of the stimulus with the cells before addition of the drug. Several pyridothienopyrimidines show inhibitory IC50 values in the range 2-25 microM, indicating they are up to 100 times more potent than cromoglycate (DSCG) and 10 times greater than Ketotifen. Compound 9l is a potent inhibitor in all the conditions tested and shows IC50 = 9-25 microM. Pyridothienopyrimidines 4l and 9e are very strong inducers of histamine release in the immunological (4l, 170-230%) and chemical (9e, 100-150%) assays, respectively. Compounds 4l and 9i are cytotoxic in vitro (IC50 = 0.1-0.2 microgram/mL) against P-388, A-549, HT-29, and MEL-28 tumor cell lines. 相似文献
95.
This article analyses how Internet‐based technologies can help companies to: monitor their business environment online in search of potentially conflictive issues that need to be managed (issues management); to prepare a crisis communications plan that considers the Internet side of today's business landscape (crisis communications planning); to respond adequately to crises should they arise by using all available online tools (crisis response); and to establish appropriate Internet‐based actions once the crisis dies down (post‐crisis). The article also questions whether the traditional one‐way corporate approach and tone is still suitable in the new, more participative, online business environment, or whether companies should use a different tone, language, and attitude when engaging with their audiences on the Internet in a crisis situation. 相似文献
96.
Guillermo Niño-Medina Elizabeth Carvajal-Millán Jaime Lizardi Agustín Rascon-Chu Jorge A. Marquez-Escalante Alfonso Gardea Ana L. Martinez-Lopez Victor Guerrero 《Food chemistry》2009
Water-soluble feruloylated arabinoxylans were extracted from maize processing waste water (nejayote) generated from tortilla-making industries. Nejayote arabinoxylans (NAX) presented a ferulic acid content of 0.23 μg/mg, an arabinose to xylose ratio (A/X) of 0.65, an intrinsic viscosity, [η], of 183 ml/g and a molecular weight (Mw) of 60 kDa. Laccase-induced gels were obtained from 4% (w/v) NAX solution while, at lower concentrations, no gelation was observed. Laccase covalent cross-linking of NAX led to the formation of diferulic (di-FA) and triferulic (tri-FA) acid structures. 4% (w/v) NAX gel presented di-FA and tri-FA contents of 0.02 and 0.01 μg/mg NAX, respectively, and a G′ value of 2 Pa. Recuperation of this gum from a low-value maize by-product could represent a commercial advantage over other gums commonly used in the food industry. 相似文献
97.
Maria Rosaria Corbo Barbara Speranza Alfonso Filippone Amalia Conte Milena Sinigaglia & Matteo Alessandro Del Nobile 《International Journal of Food Science & Technology》2009,44(10):2021-2027
Natural antimicrobial compounds to control the quality decay of a fresh fish burger were studied. In particular, thymol, lemon extract and grape fruit seed extract (GFSE), at 20, 40 and 80 ppm, have been tested against the main spoilage microorganisms inoculated in fish burgers stored at 5 °C. The evolution of mesophilic and psychrotrophic bacteria was also monitored. The sensorial quality decay was determined by means of a panel test, which assessed odour, colour, texture, drip loss and general appearance during the storage period. Results show that all the active substances efficiently slowed down the growth of the spoilage microorganisms. In particular, GFSE was the most efficient against Photobacterium phosphoreum , Shewanella putrefaciens and mesophilic bacteria, whereas thymol was the most efficient against both psychrotrophic bacteria and Pseudomonas fluorescens . Microbial growth was the factor limiting fresh fish burger acceptability. 相似文献
98.
Alfonso Pompella Emilia Maellaro Alessandro F. Casini Marco Ferrali Lucia Ciccoli Mario Comporti 《Lipids》1987,22(3):206-211
A study was undertaken to investigate whether some of the methods commonly used to detect lipid peroxidation of cellular membranes
in vivo correlate with each other. The study was performed with the livers of bromobenzene-intoxicated mice, in which lipid
peroxidation develops when the depletion of glutathione (GSH) reaches a threshold value. The methods tested and compared were
the following: i) measurement of the malondialdehyde (MDA) content of the liver; ii) detection of diene conjugation absorption
in liver phospholipids; iii) measurement of the loss of polyunsaturated fatty acids in liver phospholipids; and iv) determination
of carbonyl functions formed in acyl residues of membrane phospholipids as a result of the peroxidative breakdown of phospholipid
fatty acids. Correlations among the values obtained with these methods showed high statistical significances, indicating that
the procedures measure lipid peroxidation in vivo with comparable reliability. Analogously, the four methods appeared also
to correlate when applied to in vitro microsomal lipid peroxidation. 相似文献
99.
Iñigo Navarro Antonio J. López-Martín Carlos A. de la Cruz Alfonso Carlosena 《Analog Integrated Circuits and Signal Processing》2004,41(2-3):159-166
A compact, four-quadrant analog CMOS multiplier featuring wide dynamic range is presented. The capacitive voltage division obtained by the use of Floating-Gate MOS (FGMOS) transistors, and an accurate wide-swing current mirror based on active bootstrapping, allow a wide input range, low harmonic distortion, and high linearity. Simulation and measurement results for a 0.8 μm CMOS prototype demonstrate the validity of the proposed approach. 相似文献
100.
The study of monthly mean half hourly values of global radiation received at 315 (u.v.) and 545 nm (green) on a horizontal surface at Uccle (Belgium) in 1980 for clear (half hourly sunshine fraction σ = 1) and overcast (σ = 0) skies shows that for any solar altitude, global radiation received at 315 nm is less absorbed by clouds than radiation received at 545 nm. An explanation is given of the dependence on solar altitude for clear skies of the ratio between monthly mean half hourly values of global radiation received at both wavelengths, based on considerations concerning the direct and diffuse components. 相似文献