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31.
The effect of metal exposure on the accumulation and cytosolic speciation of metals in livers of wild populations of European eel with special emphasis on metallothioneins (MT) was studied. Four sampling sites in Flanders showing different degrees of heavy metal contamination were selected for this purpose. An on-line isotope dilution method in combination with size exclusion (SE) high pressure liquid chromatography (HPLC) coupled to Inductively Coupled Plasma time-of-flight Mass Spectrometry (ICP-TOFMS) was used to study the cytosolic speciation of the metals. The distribution of the metals Cd, Cu, Ni, Pb and Zn among cytosolic fractions displayed strong differences. The cytosolic concentration of Cd, Ni and Pb increased proportionally with the total liver levels. However, the cytosolic concentrations of Cu and Zn only increased above a certain liver tissue threshold level. Cd, Cu and Zn, but not Pb and Ni, were largely associated with the MT pool in correspondence with the environmental exposure and liver tissue concentrations. Most of the Pb and Ni and a considerable fraction of Cu and Zn, but not Cd, were associated to High Molecular Weight (HMW) fractions. The relative importance of the Cu and Zn in the HMW fraction decreased with increasing contamination levels while the MT pool became progressively more important. The close relationship between the cytosolic metal load and the total MT levels or the metals bound on the MT pool indicates that the metals, rather than other stress factors, are the major factor determining MT induction.  相似文献   
32.
Cross Magnetron Effect and ITO Film Deposition The large area deposition of TCO films requires a strictly homogeneous lateral distribution of the process parameters at the substrate position. In view of that, Cross Corner Effect (in case of a single magnetron source) and Cross Magnetron Effect (for dual magnetrons) can cause problems. Measurements confirm a distinct influence of these effects on the functional properties of indium tin oxide films. The effect will be discussed in terms of the concentration of the dissociated oxygen in the process gas, which depends on the plasma properties and the oxygen partial pressure.  相似文献   
33.
采用数字分析和相关试验结果研究了无约束钢I截面梁的行为,采用有限元程序拓展了数学模型。在相同弯矩和中跨集中荷载的情况下,对一系列不同的UB和UC截面以及不同跨度,进行了研究。比较了预估的弯矩值与相关试验结果。在此基础上,对无约束梁提出了一种新的更精确和安全防火预报的方法,该方法克服了欧洲规范(EC3:1.2)设计公式中的一些弱点。另外,给设计者提供了一个便捷和简单的设计方法,即该方法易懂又合理,称为兰金方法。可用于预估钢梁在火中的LTB破坏荷载。兰金方法为数值预估提供了一个适宜的下界值。  相似文献   
34.
An Anderson‐type polyoxometalate, [IVIIMo6O24]5–, has been used as a catalyst for the aerobic oxidation at 80 °C of vicinal diols (glycols). This is the first report on the use of such a polyoxometalate as an oxidation catalyst. Reactivity and selectivity were dependent on the substrate. Thus, aryl‐substituted diols yielded mostly the carbon‐carbon bond cleavage products, while 1,2‐cyclohexanediol yielded cyclohexanone‐2‐ol and 1,2‐cyclohexanedione. Aliphatic diols were less reactive but yielded carbon‐carbon bond cleavage products in the presence of additional acid. An abbreviated mechanistic study was carried out indicating that the polyoxometalate oxidizes the diol to the various products even under anaerobic conditions. The reduced polyoxometalates (heteropoly blues and heteropoly browns) formed in the oxidation of the diols are re‐oxidized by the molecular oxygen.  相似文献   
35.
In situ low-voltage aberration corrected transmission electron microscopy (TEM) observations of the dynamic entrapment of a C60 molecule in the saddle of a bent double-walled carbon nanotube is presented. The fullerene interaction is non-covalent, suggesting that enhanced π-π interactions (van der Waals forces) are responsible. Classical molecular dynamics calculations confirm that the increased interaction area associated with a buckle is sufficient to trap a fullerene. Moreover, they show hopping behavior in agreement with our experimental observations. Our findings further our understanding of carbon nanostructure interactions, which are important in the rapidly developing field of low-voltage aberration corrected TEM and nano-carbon device fabrication.   相似文献   
36.
In times of globalisation and international trade, the concept of total quality management (TQM) as a strategy to enhance organisational performance is growing in importance. To exploit the benefits provided by TQM, organisations must manage the complex implementation process successfully. Therefore, organisations need to measure critical success factors (CSFs) when introducing TQM. However, previous research has developed a plethora of measurement instruments and researchers do not agree on certain factors or on one single measurement instrument. A systematic literature review is conducted to structure and clarify the scattered research field. The analysis of 145 studies reveals that CSFs can be classified into 11 distinct dimensions. The article proposes a three-level framework and a holistic set of measurement instruments to help researchers and managers measure each critical dimension in a timely and comprehensive manner. A focus group consisting of six quality managers validated these results. The study concludes with further findings and future research. Deficiencies of current measurements are presented and the article discusses the finding that human related factors are regarded as highly relevant but have remained low on many researchers’ and practitioners’ agendas. Hence, this article is a major contribution to structure the complex research field of measuring CSFs of TQM implementation.  相似文献   
37.
Wirz R  Ferri D  Baiker A 《Analytical chemistry》2008,80(10):3572-3583
A technique is presented which allows studying the enantioselective interactions occurring at the solid-liquid interface of a chiral stationary phase (CSP) and a racemate relevant to high performance liquid chromatography (HPLC). A conventional chiral column (Chiralpak AS) was mounted on an attenuated total reflection-infrared (ATR-IR) cell mimicking an HPLC setup equipped with an ATR-IR detector. Racemic pantolactone (PL) was used as the selectand. This setup in combination with modulation excitation spectroscopy (MES) allows for the identification of inter- and intramolecular hydrogen bonds being crucial for enantioseparation under HPLC operation conditions. The method is based on a two step strategy. In a first step, the enantiomers are separated by the chiral column similar to a standard HPLC experiment and upon adsorption on the identical CSP deposited on the internal reflection element (IRE), they are detected by ATR-IR spectroscopy. This experiment provides a retention time for each enantiomer. From the difference in retention, a suitable frequency is calculated which is used in a second experiment where the racemate concentration is varied alternately (modulation) in a way that the pulses of ( R)-PL and ( S)-PL exhibit a phase lag of 90 degrees after elution through the column. This procedure allows one to gain separate information of the enantioselective selectand-CSP interaction after performing a demodulation similar to a phase sensitive detection (PSD). A further benefit of this method is the strong enhancement of the signal-to-noise ratio. The effectiveness of the method is demonstrated by investigating the observed faster decrease in retention time of the later-eluted ( R)-PL, as compared to ( S)-PL, when separating at higher temperatures (from 12 to 36 degrees C). The origin is attributed to a weakening of a specific hydrogen bond between the C=O of ( R)-PL and the N-H of the CSP.  相似文献   
38.
The oxidation of aqueous sulfide promoted by activated carbon (AC) was investigated. Raman, infrared, X-ray diffraction, ultraviolet–visible spectroscopy and electron paramagnetic resonance analyses show that AC oxidizes aqueous sulfide to form a complex mixture of polysulfides and sulfur oxide species. This oxidation is strongly promoted by the presence of oxygen surface groups introduced by oxidation of the AC as shown by kinetic measurements. These results are discussed in terms of the similarities the AC have with enzymatic systems, i.e. redox surface groups (e.g. quinone) combined with an efficient electron conduction system.  相似文献   
39.
Heat‐stabilized, defatted rice bran (HDRB) serves as a potential source of phenolic compounds which have numerous purported health benefits. An estimated 70% of phenolics present in rice bran are esterified to the arabinoxylan residues of the cell walls. Release of such compounds could provide a value‐added application for HDRB. The objective of this study was to extract and quantify phenolics from HDRB using fermentation technology. Out of 8 organisms selected for rice bran fermentation, Bacillus subtilis subspecies subtilis had the maximum phenolic release of 26.8 mg ferulic acid equivalents (FAE) per gram HDRB. Response surface methodology was used to further optimize the release of rice bran phenolics. An optimum of 28.6 mg FAE/g rice bran was predicted at 168 h, 0.01% inoculation level, and 100 mg HDRB/mL. Fermentation of HDRB for 96 h with B. subtilis subspecies subtilis resulted in a significant increase in phenolic yield, phenolic concentration, and radical scavenging capacity. Fermented rice bran had 4.86 mg gentistic acid, 1.38 mg caffeic acid, 6.03 mg syringic acid, 19.02 mg (‐)‐epicatechin, 4.08 mg p‐courmaric acid, 4.64 mg ferulic acid, 10.04 mg sinapic acid, and 17.59 mg benzoic acid per 100 g fermented extract compared to 0.65 mg p‐courmaric acid and 0.36 mg ferulic acid per 100 g nonfermented extract. The high phenolic content and antioxidant activity of fermented HDRB extract indicates that rice bran fermentation under optimized condition is a potential means of meeting the demand for an effective and affordable antioxidant.  相似文献   
40.
Interferons (IFNs) are a crucial component in the innate immune response. Especially the IFN-β signaling operates in most cell types and plays a key role in the first line of defense upon pathogen intrusion. The induction of IFN-β should be tightly controlled, because its hyperactivation can lead to tissue damage or autoimmune diseases. Activation of the IFN-β promoter needs Interferon Regulatory Factor 3 (IRF3), together with Nuclear Factor kappa-light-chain-enhancer of activated B cells (NF-κB) and Activator Protein 1 (AP-1). Here we report that a human noncoding RNA, nc886, is a novel suppressor for the IFN-β signaling and inflammation. Upon treatment with several pathogen-associated molecular patterns and viruses, nc886 suppresses the activation of IRF3 and also inhibits NF-κB and AP-1 via inhibiting Protein Kinase R (PKR). These events lead to decreased expression of IFN-β and resultantly IFN-stimulated genes. nc886′s role might be to restrict the IFN-β signaling from hyperactivation. Since nc886 expression is regulated by epigenetic and environmental factors, nc886 might explain why innate immune responses to pathogens are variable depending on biological settings.  相似文献   
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