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41.
Noomen Hmidet Hana Maalej Anissa Haddar Moncef Nasri 《Applied biochemistry and biotechnology》2010,162(4):1018-1030
α-Amylase from Bacillus mojavensis A21 (BMA.2) was purified to homogeneity by ultrafiltration, Sephadex G-75 gel filtration and Sepharose mono Q anion exchange chromatography, with a 15.3-fold increase in specific activity and 11% recovery. The molecular weight of the BMA.2 enzyme was estimated to be 58 kDa by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and gel filtration. The optimum temperature and pH were 80?°C and 6.5, respectively. BMA.2 belonged to the EDTA-sensitive α-amylase, but its activity was not stimulated by the presence of Ca2+ ions. The major end-products of starch hydrolysis were maltohexaose, maltopentaose and maltotriose. The N-terminal amino acid sequence of the first ten amino acids of the purified α-amylase was ASVNGTLMQY. Compared to sequences of other amylases, the ten amino acid sequence contains Val at position 3, while amylases from Bacillus licheniformis NH1 and Bacillus sp. SG-1 have Leu and Thr at position 3, respectively. 相似文献
42.
Rym Agrebi Noomen Hmidet Mohamed Hajji Nawrez Ktari Anissa Haddar Nahed Fakhfakh-Zouari Moncef Nasri 《Applied biochemistry and biotechnology》2010,162(1):75-88
In this study, Mirabilis jalapa tuber powder (MJTP) was used as a new complex organic substrate for the growth and production of fibrinolytic enzymes by
a newly isolated Bacillus amyloliquefaciens An6. Maximum protease activity (1,057 U/ml) with casein as a substrate was obtained when the strain was grown in medium containing
(grams per liter) MJTP 30, yeast extract 6, CaCl2 1, K2HPO4 0.1, and K2HPO4 0.1. The strain was also found to grow and produce extracellular proteases in a medium containing only MJTP, indicating that
it can obtain its carbon, nitrogen, and salts requirements directly from MJTP. The B. amyloliquefaciens An6 fibrinase (BAF1) was partially purified, and fibrinolytic activity was assayed in a test tube with an artificial fibrin
clot. The molecular weight of the partially purified BAF1 fibrinolytic protease was estimated to be 30 kDa by sodium dodecyl
sulfate polyacrylamide gel electrophoresis and gel filtration. The optimum temperature and pH for the caseinolytic activity
were 60 °C and 9.0, respectively. The enzyme was highly stable from pH 6.0 to 11.0 and retained 62% of its initial activity
after 1 h incubation at 50 °C. However, the enzyme was inactivated at higher temperatures. The activity of the enzyme was
totally lost in the presence of phenylmethylsulfonyl fluoride, suggesting that BAF1 is a serine protease. 相似文献
43.
Rim Nasri Mourad Jridi Imen Lassoued Ines Jemil Rabeb Ben Slama-Ben Salem Moncef Nasri Maha Karra-Châabouni 《Applied biochemistry and biotechnology》2014,173(5):1121-1134
Antioxidant properties and angiotensin-converting enzyme (ACE) inhibitory activities of protein hydrolysates from goby (Zosterisessor ophiocephalus) muscle, with different degrees of hydrolysis (DH) from 5 to 25 %, prepared by treatment with crude proteases extract from smooth hound intestines, were investigated. Goby protein hydrolysates (GPHs) are rich in Gly and Thr, which accounted for 14.1–15 % and 11.6–13.2 % of the total amino acids, respectively. The antioxidant activities of GPHs were investigated by using several in vitro assay systems. All GPHs exhibited significant metal chelating activity and DPPH free radical-scavenging activity, and inhibited linoleic acid peroxidation. For the ACE-inhibitory activity, as the DH increased, the activity of GPHs increased. The obtained results revealed that antioxidant and ACE-inhibitory activities of GPHs were influenced by the degree of hydrolysis. A medium degree of enzymatic hydrolysis was appropriate to obtain GPHs with good antioxidant activity, while small peptides were essential to obtain high ACE inhibitory activity. 相似文献
44.
A methodology is reported for the regioselective nitration of the phenyl groups of Halterman porphyrin, using NaNO2. These nitro-porphyrins can be reduced to aminoporphyrins and then N-dimethylated to give new optically active porphyrins. Applications to the asymmetric epoxidation of styrene derivatives by H2O2 to give optically active epoxides (ee up to 60%) and hydroxylation of alkanes to give optically active secondary alcohols (ee up to 69%) were carried out in organic solvents (dichloromethane/methanol) using chiral iron and manganese porphyrins as catalysts. 相似文献
45.
In this paper, we present a general mathematical framework for performance analysis of single?carrier (SC) and orthogonal frequency division multiplexing (OFDM) systems employing popular bit?interleaved coded modulation (BICM) and multiple receive antennas. The proposed analysis is applicable to BICM systems impaired by general types of fading (including Rayleigh, Ricean, Nakagami-m, Nakagami-q, and Weibull fading) and general types of noise and interference with finite moments such as additive white Gaussian noise (AWGN), additive correlated Gaussian noise, Gaussian mixture noise, co-channel interference, narrowband interference, and ultra-wideband interference. We present an approximate upper bound for the bit error rate (BER) and an accurate closed-form approximation for the asymptotic BER at high signal-to-noise ratios for Viterbi decoding with the standard Euclidean distance branch metric. For the standard rate-1/2 convolutional code the proposed approximate upper bound and the asymptotic approximation become tight at BERs of 10-6 and 10-12, respectively. However, if the code is punctured to higher rates (e.g. 2/3 or 3/4), the asymptotic approximation also becomes tight at a BER of 10-6. Exploiting the asymptotic BER approximation we show that the diversity gain of BICM systems only depends on the free distance of the code, the type of fading, and the number of receive antennas but not on the type of noise. In contrast their coding gain strongly depends on the noise moments. Our asymptotic analysis shows that as long as the standard Euclidean distance branch metric is used for Viterbi decoding, BICM systems optimized for AWGN are also optimum for any other type of noise and interference with finite moments. 相似文献
46.
Mohsen Nasri Abdelhamid Helali Halim Sghaier Hassen Maaref 《International Journal of Wireless Information Networks》2012,19(3):254-269
It has become necessary in recent years to observe and monitor some physical phenomena. This was made possible by the emergence of wireless sensor networks. The main characteristic of such networks is nodes with scarce resources. Given the stringent resource constraints, nodes are limited in energy, memory and computational power. These resource constraints pose serious difficulties for image processing and transmission to the destination. Therefore, image transfer in wireless sensor networks presents major challenge which raises issues related to its representation, its storage and its transmission. Based on wavelet transform an Adaptive Energy Efficient Wavelet Image Compression Algorithm is proposed in order to be suitable for wireless sensor network. In addition, an identification of the wavelet image compression parameters is investigated to analyze the trade-offs between the energy saving, and the image quality. Performance studies indicate that the proposed scheme enabling significant reductions in computation as well as communication energy needed, with minimal degradation in image quality. 相似文献
47.
This paper proposes the recognition and classification of three dominant patterns of woven fabrics such as twill, satin and plain. The proposed classifier is based on the texture analysis of woven fabric images for the recognition. In the pattern recognition phase, three methods are tested and compared: Gabor wavelet, local binary pattern operators and gray-level co-occurrence matrices (GLCM). Taking advantage of the differences between the woven fabric textures, we adopt a technique which is based on the texture of the images in the pattern recognition phase. For the classification phase we used a support vector machine, which we have proven is a suitable classifier for this type of problem. The experimental results show that some of the studied methods are more compatible with this classification problem than others. Although it is the oldest method, GLCM always remains accurate (97.2%). The fusion of the Gabor wavelet and GLCM gives the best result (98%), but GLCM have the better running time. 相似文献
48.
Over the last decays, the use of conductive biopolymer composites has been growing in areas such as biosensors, soft robotics, and wound dressing applications. They are generally soft hydrophilic materials with good elastic recovery and compatible with biological environments. However, their application and removal from the host are still challenging mainly due to poor mechanical strength. This work displays a technique for the fabrication of complex‐shaped conductive structures with improved mechanical strength by wet three‐dimensional (3‐D) printing, which uses a coagulation bath to quickly solidify an epoxy cross‐linked chitosan/carbon microtube composite ink. The fabricated conductive structure demonstrated higher elongation strength and improved elastic stability upon the introducing of polypropylene glycol diglycidyl ether (PPGDGE) as the epoxy cross‐linker, which can be due to the formation of networks between oxiran groups of PPGDGE and chitosan amino groups. 相似文献
49.
Mouhieddinne Guergueb Frdrique Loiseau Florian Molton Habib Nasri Axel Klein 《Molecules (Basel, Switzerland)》2022,27(5)
The meso-tetrakis(4-(trifluoromethyl)phenyl)porphyrinato cobalt(II) complex [Co(TMFPP)] was synthesised in 93% yield. The compound was studied by 1H NMR, UV-visible absorption, and photoluminescence spectroscopy. The optical band gap Eg was calculated to 2.15 eV using the Tauc plot method and a semiconducting character is suggested. Cyclic voltammetry showed two fully reversible reduction waves at E1/2 = −0.91 V and E1/2 = −2.05 V vs. SCE and reversible oxidations at 0.30 V and 0.98 V representing both metal-centred (Co(0)/Co(I)/Co(II)/Co(III)) and porphyrin-centred (Por2−/Por−) processes. [Co(TMFPP)] is a very active catalyst for the electrochemical formation of H2 from DMF/acetic acid, with a Faradaic Efficiency (FE) of 85%, and also catalysed the reduction of CO2 to CO with a FE of 90%. Moreover, the two triarylmethane dyes crystal violet and malachite green were decomposed using H2O2 and [Co(TMFPP)] as catalyst with an efficiency of more than 85% in one batch. 相似文献
50.