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排序方式: 共有1038条查询结果,搜索用时 20 毫秒
71.
Fast headspace-enantioselective GC-mass spectrometric-multivariate statistical method for routine authentication of flavoured fruit foods 总被引:1,自引:0,他引:1
Cecilia CaglieroCarlo Bicchi Chiara CorderoPatrizia Rubiolo Barbara SgorbiniErica Liberto 《Food chemistry》2012,132(2):1071-1079
This study describes a rapid total analysis system (TAS) to detect the authenticity of fruit-flavoured foods and beverages by on-line combining headspace solid phase microextraction (HS-SPME) with enantioselective GC-MS (Es-GC-MS) and statistical multivariate methods (PCA, HCA). Peach, coconut, apricot, raspberry, as fruits mainly characterised by γ- and δ-lactones as chiral markers, strawberry (α-ionone, linalool, nerolidol, ethyl 2-methylbutyrate, 2-methylbutyric acid and γ-lactones) and melon (ethyl 2-methylbutyrate and 2-methylbutanol) were investigated. The system was developed by (a) optimising non-equilibrium HS-SPME sample preparation, (b) speeding-up ES-GC using cyclodextrin derivatives as chiral selectors with conventional and narrow-bore columns and (c) elaborating data by multivariate methods. The resulting TAS affords a reduction of the time needed for the whole analytical process from about 150 min to 20-50 min (67-87% of the current routine method) depending on matrix, sampling and analysis conditions and Es-GC columns. 相似文献
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Olivieri AC Arancibia JA Muñoz de la Peña A Durán-Merás I Espinosa Mansilla A 《Analytical chemistry》2004,76(19):5657-5666
Four-way fluorescence data recorded by following the kinetic evolution of excitation-emission fluorescence matrices (EEMs) have been analyzed by parallel factor analysis and trilinear least-squares algorithms. These methodologies exploit the second-order advantage of the studied data, allowing analyte concentrations to be estimated even in the presence of an uncalibrated fluorescent background. They were applied to the simultaneous determination of the components of the anticancer combination of methotrexate and leucovorin in human urine samples. Both analytes were converted into highly fluorescent compounds by oxidation with potassium permanganate, and the kinetics of the reaction was continuously monitored by recording full EEM of the samples at different reaction times. A commercial fast scanning spectrofluorometer has been used for the first time to measure the four-way EEM kinetic data. The rapid scanning instrument allows the acquisition of a complete EEM in 12 s at a wavelength scanning speed of 24 000 nm/min. The emission spectra were recorded from 335 to 490 nm at 5-nm intervals, exciting from 255 to 315 nm at 6-nm intervals. Ten successive EEMs were measured at 72-s intervals, to follow the fluorescence kinetic evolution of the mixture components. Good recoveries were obtained in synthetic binary samples and also in spiked urine samples. The excitation, emission, and kinetic time profiles recovered by both chemometric techniques are in good agreement with experimental observations. 相似文献
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Guido H. Jajamovich Wei Huang Cecilia Besa Xin Li Aneela Afzal Hadrien A. Dyvorne Bachir Taouli 《Magma (New York, N.Y.)》2016,29(1):49-58
Objective
To quantify hepatocellular carcinoma (HCC) perfusion and flow with the fast exchange regime-allowed Shutter-Speed model (SSM) compared to the Tofts model (TM).Materials and methods
In this prospective study, 25 patients with HCC underwent DCE-MRI. ROIs were placed in liver parenchyma, portal vein, aorta and HCC lesions. Signal intensities were analyzed employing dual-input TM and SSM models. ART (arterial fraction), K trans (contrast agent transfer rate constant from plasma to extravascular extracellular space), v e (extravascular extracellular volume fraction), k ep (contrast agent intravasation rate constant), and τ i (mean intracellular water molecule lifetime) were compared between liver parenchyma and HCC, and ART, K trans, v e and k ep were compared between models using Wilcoxon tests and limits of agreement. Test–retest reproducibility was assessed in 10 patients.Results
ART and v e obtained with TM; ART, v e , k e and τ i obtained with SSM were significantly different between liver parenchyma and HCC (p < 0.04). Parameters showed variable reproducibility (CV range 14.7–66.5 % for both models). Liver K trans and v e ; HCC v e and k ep were significantly different when estimated with the two models (p < 0.03).Conclusion
Our results show differences when computed between the TM and the SSM. However, these differences are smaller than parameter reproducibilities and may be of limited clinical significance.77.
Zia Abbas Mauro Olivieri 《International Journal of Circuit Theory and Applications》2016,44(7):1400-1424
Process variability, in addition to wide temperature and supply voltage variation ranges, severely degrades the fabrication outcome (yield) of digital cells as for the fulfillment of performance specification bounds. This paper presents the application of mathematical optimization to the design of standard cells that are robust to process variations even in worst‐case operating conditions. The method attains the optimal sizing of individual transistors in the cell for maximizing the statistical yield referring to leakage power and propagation delay bounds, with local and global process variations specified by industrial process development kits (PDKs). The approach is demonstrated for a 40 nm low‐power standard threshold voltage Complementary Metal Oxide Semiconductor (CMOS) technology, for an intended operating temperature range [?40 °C, 125 °C] and supply voltage range [0.95 V, 1.05 V]. The reported optimization results show a yield improvement from an initial 50% to 99.9%, and Simulation Program with Integrated Circuit Emphasis (SPICE)‐level Monte Carlo analysis confirmed the estimated yield of the obtained circuits. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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Luis Uriel Gonzalez-Avila Miguel Angel Loyola-Cruz Cecilia Hernndez-Cortez Juan Manuel Bello-Lpez Graciela Castro-Escarpulli 《International journal of molecular sciences》2021,22(11)
The increase in the use of antimicrobials such as colistin for the treatment of infectious diseases has led to the appearance of Aeromonas strains resistant to this drug. However, resistance to colistin not only occurs in the clinical area but has also been determined in Aeromonas isolates from the environment or animals, which has been determined by the detection of mcr genes that confer a resistance mechanism to colistin. The variants mcr-1, mcr-3, and mcr-5 have been detected in the genus Aeromonas in animal, environmental, and human fluids samples. In this article, an overview of the resistance to colistin in Aeromonas is shown, as well as the generalities of this molecule and the recommended methods to determine colistin resistance to be used in some of the genus Aeromonas. 相似文献