全文获取类型
收费全文 | 675篇 |
免费 | 27篇 |
专业分类
电工技术 | 5篇 |
化学工业 | 278篇 |
金属工艺 | 9篇 |
机械仪表 | 19篇 |
建筑科学 | 13篇 |
矿业工程 | 1篇 |
能源动力 | 19篇 |
轻工业 | 110篇 |
水利工程 | 1篇 |
石油天然气 | 1篇 |
无线电 | 33篇 |
一般工业技术 | 88篇 |
冶金工业 | 35篇 |
原子能技术 | 10篇 |
自动化技术 | 80篇 |
出版年
2023年 | 10篇 |
2022年 | 58篇 |
2021年 | 59篇 |
2020年 | 18篇 |
2019年 | 19篇 |
2018年 | 17篇 |
2017年 | 17篇 |
2016年 | 21篇 |
2015年 | 16篇 |
2014年 | 20篇 |
2013年 | 54篇 |
2012年 | 36篇 |
2011年 | 41篇 |
2010年 | 39篇 |
2009年 | 38篇 |
2008年 | 49篇 |
2007年 | 28篇 |
2006年 | 20篇 |
2005年 | 23篇 |
2004年 | 15篇 |
2003年 | 4篇 |
2002年 | 8篇 |
2001年 | 9篇 |
2000年 | 10篇 |
1999年 | 7篇 |
1998年 | 9篇 |
1997年 | 8篇 |
1996年 | 3篇 |
1995年 | 5篇 |
1994年 | 6篇 |
1993年 | 2篇 |
1992年 | 3篇 |
1990年 | 5篇 |
1989年 | 1篇 |
1985年 | 2篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 1篇 |
1976年 | 2篇 |
1971年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有702条查询结果,搜索用时 17 毫秒
661.
Daniele Caretti Luigi Angiolini Elisa Cavicchi Laura Mazzocchetti Elisabetta Salatelli Sara Ugolini 《Journal of Inorganic and Organometallic Polymers and Materials》2013,23(4):816-825
An organotin monomer, triphenyltin 3-(4-styryl)-propionate (TPTSPr) has been synthesized and copolymerized in different ratios with styrene and 1,4-divinylbenzene in order to obtain resins with catalytic activity in transesterification reactions. The resins and a low molecular weight model compound, triphenyltin 3-(4-ethylphenyl)-propionate (TPT-C2-Pr), mimicking the catalytic co-unit, have been characterized by FT-IR and NMR spectroscopy, with particular attention paid to the coordination at tin and how it correlates to the catalytic activity. The activity of both the resins and of the model compound have been tested in a transesterification model reaction between ethyl acetate and primary alcohol. All the resins show catalytic activity that decreases with increasing content of the active co-unit in the resins, owing to the interaction of the active sites among themselves. 相似文献
662.
The combined effect of a channel-based approach for dry pressure drop and the Buchanan equation for wet pressure drop in packed beds has been numerically evaluated within the flooding region. The flooding point is an important design parameter since it establishes the maximum hydrodynamic capacity at which a packed column can operate. Upon analyzing the aforementioned approach, it was found that the usual practice of fixing a “reasonable” wet pressure drop at the flooding point (e.g., 1025 Pa/m) may not yield the correct flooding velocity of the gas, particularly at higher liquid loads. In fact, numerical evaluations of the aforementioned model showed a rather “retrograde” non-monotonic behavior of pressure drop with respect to the f factor of the gas near flooding at different liquid loads. A calculation procedure was therefore devised in this work to correctly compute the flooding point for a given liquid load when using the aforementioned modeling approach. Interestingly, it was found that the correct flooding velocity can be directly computed from liquid holdup below the gas loading point. To illustrate the use of the procedure, maximum capacity calculations were performed for a well-known random packing, a conventional structured packing, and a novel catalytic structured packing. 相似文献
663.
Ranjana Rai Marwa Tallawi Niccoletta Barbani Caterina Frati Denise Madeddu Stefano Cavalli Gallia Graiani Federico Quaini Judith A. Roether Dirk W. Schubert Elisabetta Rosellini Aldo R. Boccaccini 《Materials science & engineering. C, Materials for biological applications》2013,33(7):3677-3687
In this study biomimetic poly(glycerol sebacate) PGS matrix was developed for cardiac patch application. The rationale was that such matrices would provide conducive environment for the seeded cells at the interphase with PGS. From the microstructural standpoint, PGS was fabricated into dense films and porous PGS scaffolds. From the biological aspect, biomimetic PGS membranes were developed via covalently binding peptides Tyr-Ile-Gly-Ser-Arg (YIGSR) and Gly-Arg-Gly-Asp-Ser-Pro (GRGDSP), corresponding to the epitope sequences of laminin and fibronectin, respectively onto the surface. To improve and enhance homogenous binding of peptides onto the PGS surface, chemical modification of its surface was carried out. A sequential regime of alkaline hydrolysis with 0.01 M NaOH for 5 min and acidification with 0.01 M HCl for 25 s was optimal. More COOH chemical group was exposed without causing deleterious effect on the bulk properties of the polymer as revealed by the physicochemical analysis carried out. HPLC analysis, chemical imaging and ToF-SIMS were able to establish the successful homogenous functionalization of PGS membranes with the peptides. Finally, the developed biomimetic membranes supported the adhesion and growth of rat and human cardiac progenitor cells. 相似文献
664.
Bo Liu Yu Wu Jinggang Qin Feng Long Yi Shi Pierluigi Bruzzone Boris Stepanov 《Fusion Engineering and Design》2013,88(11):2802-2809
The first ITER Main Busbar (MBCN1) and Correction Busbar (CBCN1) conductor samples were manufactured in ASIPP and tested in the SULTAN facility. This paper introduces the sample manufacture, including strand, cabling, jacketing and sample preparation, and discusses the performance of MBCN1 and CBCN1 conductors. The testing results show that both samples have high Tcs, and meet the ITER requirement.Due to the ITER acceptance standard Tcs of MB conductor was changed to 6.7 K at 45.5 kA/3.9 T. The performance of MBCN1 conductor after cyclic load fits the ITER requirement, but the sample was only tested at 57 kA/2.75 T before cycling test. Using some hypothesis and equation to extrapolate the Tcs performance of MBCN1 conductor before cycling test, the result also fits the ITER requirement.For CBCN1 conductor, the central line of the central cooling spiral shifted about 1.3 mm during the cabling. The deviation causes an increase of the max self-field by about 0.005 T, which could not influence the CBCN1 conductor real Tcs performance at peak field. 相似文献
665.
In this work, a study concerning the composition of Italian papers from the seventeenth to the twentieth centuries was carried out using energy dispersive X-ray fluorescence spectrometry (EDXRF), X-ray diffraction (XRD), and scanning electron microscopy coupled to energy dispersive spectrometry (SEM-EDS). The analyzed samples consisted of papers employed for drawing, writing, printing, and absorbance. Observations carried out by SEM magnified the typical paper morphology. EDXRF in combination with XRD and SEM-EDS allowed the determination of calcite, gypsum, kaolin, talc, magnesite, and dolomite, used as fillers in the production of the papers studied herein. The inks present in the handwritten and printed papers, investigated by SEM-EDS and μ-EDXRF, were synthetic, Fe based, and iron gall inks. 相似文献
666.
667.
Linda Monaci Elisabetta De Angelis Simona L. Bavaro Rosa Pilolli 《Food additives & contaminants. Part A, Chemistry, analysis, control, exposure & risk assessment》2015,32(10):1607-1616
Peanut represents one of the most harmful allergenic foods capable of triggering severe and sometimes lethal reactions in allergic consumers upon ingestion of even small amounts. Several proteins capable of inducing allergic reactions that have been recognised by patients’ IgE antibodies have been identified from this nut source. Methods mainly based on ELISA assays have been developed in order to detect peanuts in several food commodities. In addition LC-MS/MS methods based on different mass analysers have also been devised for tracing peanut contamination in different foods achieving low limits of detection. The applicability of a benchtop high-resolution Exactive? mass spectrometer has never been investigated for the rapid screening of peanut contamination in complex food matrices like mixtures of nuts. We report in this paper the design of suitable peanut markers and the development of an high-resolution Orbitrap? mass spectrometer-based method for peanut detection in a mixture of nuts species. With this aim, different types of samples were prepared: (1) nuts-based powder made up of a mixture of hazelnuts, pistachios, almonds and walnuts; and (2) nuts powder fortified with peanuts. Different levels of fortifications were produced and the applicability of the method was tested. Finally, a subset of six peptides fulfilling specific analytical requirements was chosen to check the suitability of the method tailored to the detection of peanuts in nuts-based products, and two of them, peptides VYD and WLG, were selected as quantitative markers. The method proved to be a suitable screening tool to assess the presence of traces of peanuts in other tree nuts with a limit of detection as low as 4 µg of peanuts proteins or 26 µg of peanuts in 1 g of matrix. 相似文献
668.
Pilar Vila Donat Giovanni Caprioli Paolo Conti Filippo Maggi Massimo Ricciutelli Elisabetta Torregiani Sauro Vittori Gianni Sagratini 《Food Analytical Methods》2014,7(5):1024-1031
In this work, an innovative and fast analytical method for the quantification of soyasaponins I and βg in lentils has been developed. Samples were extracted using 70 % aqueous ethanol at room temperature and then injected into a high-performance liquid chromatography–tandem mass spectrometry system. The correlation coefficients of calibration curves of the analyzed compounds were ≥0.9997. The recoveries obtained by spiking the lentil samples with a standard mixture of soyasaponins I and βg at 50 and 100 mg l?1 were in the range of 96–101 and 98–103 %, respectively. The validated method was applied to the analysis of 30 lentil samples from central Italy. Soyasaponins I and βg were present in these lentils in concentrations that ranged from 54 to 226 mg kg?1 and from 436 to 1,272 mg kg?1, respectively. Our data indicated that lentils cultivated in fields at intermediate altitudes (1,142–1,387 m) showed the highest levels of soyasaponins, a finding confirmed by principal component analysis. 相似文献
669.
Daniele Pala Laura Scalvini Alessio Lodola Marco Mor Lisa Flammini Elisabetta Barocelli Valeria Lucini Francesco Scaglione Silvia Bartolucci Annalida Bedini Silvia Rivara Gilberto Spadoni 《International journal of molecular sciences》2014,15(9):16114-16133
Melatonin is an endogenous molecule involved in many pathophysiological processes. In addition to the control of circadian rhythms, its antioxidant and neuroprotective properties have been widely described. Thus far, different bivalent compounds composed by a melatonin molecule linked to another neuroprotective agent were synthesized and tested for their ability to block neurodegenerative processes in vitro and in vivo. To identify a novel class of potential neuroprotective compounds, we prepared a series of bivalent ligands, in which a prototypic melatonergic ligand is connected to an imidazole-based H3 receptor antagonist through a flexible linker. Four imidazolyl-alkyloxy-anilinoethylamide derivatives, characterized by linkers of different length, were synthesized and their binding affinity for human MT1, MT2 and H3 receptor subtypes was evaluated. Among the tested compounds, 14c and 14d, bearing a pentyl and a hexyl linker, respectively, were able to bind to all receptor subtypes at micromolar concentrations and represent the first bivalent melatonergic/histaminergic ligands reported so far. These preliminary results, based on binding affinity evaluation, pave the way for the future development of new dual-acting compounds targeting both melatonin and histamine receptors, which could represent promising therapeutic agents for the treatment of neurodegenerative pathologies. 相似文献
670.
Investigation of Binding‐Site Homology between Mushroom and Bacterial Tyrosinases by Using Aurones as Effectors 下载免费PDF全文
Dr. Romain Haudecoeur Aurélie Gouron Dr. Carole Dubois Dr. Hélène Jamet Mark Lightbody Dr. Renaud Hardré Prof. Anne Milet Dr. Elisabetta Bergantino Prof. Luigi Bubacco Dr. Catherine Belle Prof. Ahcène Boumendjel 《Chembiochem : a European journal of chemical biology》2014,15(9):1325-1333
Tyrosinase is a copper‐containing enzyme found in plants and bacteria, as well as in humans, where it is involved in the biosynthesis of melanin‐type pigments. Tyrosinase inhibitors have attracted remarkable research interest as whitening agents in cosmetology, antibrowning agents in food chemistry, and as therapeutics. In this context, commercially available tyrosinase from mushroom (TyM) is frequently used for the identification of inhibitors. This and bacterial tyrosinase (TyB) have been the subjects of intense biochemical and structural studies, including X‐ray diffraction analysis, and this has led to the identification of structural homology and divergence among enzymes from different sources. To better understand the behavior of potential inhibitors of TyM and TyB, we selected the aurone family—previously identified as potential inhibitors of melanin biosynthesis in human melanocytes. In this study, a series of 24 aurones with different hydroxylation patterns at the A‐ and B‐rings were evaluated on TyM and TyB. The results show that, depending on the hydroxylation pattern of A‐ and B‐rings, aurones can behave as inhibitors, substrates, and activators of both enzymes. Computational analysis was performed to identify residues surrounding the aurones in the active sites of both enzymes and to rationalize the interactions. Our results highlight similarities and divergence in the behavior of TyM and TyB toward the same set of molecules. 相似文献