全文获取类型
收费全文 | 624篇 |
免费 | 18篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 8篇 |
化学工业 | 168篇 |
金属工艺 | 15篇 |
机械仪表 | 17篇 |
建筑科学 | 27篇 |
矿业工程 | 1篇 |
能源动力 | 9篇 |
轻工业 | 56篇 |
水利工程 | 3篇 |
石油天然气 | 3篇 |
无线电 | 16篇 |
一般工业技术 | 207篇 |
冶金工业 | 19篇 |
原子能技术 | 6篇 |
自动化技术 | 89篇 |
出版年
2022年 | 6篇 |
2021年 | 12篇 |
2020年 | 10篇 |
2019年 | 14篇 |
2018年 | 28篇 |
2017年 | 23篇 |
2016年 | 15篇 |
2015年 | 25篇 |
2014年 | 24篇 |
2013年 | 54篇 |
2012年 | 25篇 |
2011年 | 40篇 |
2010年 | 25篇 |
2009年 | 29篇 |
2008年 | 26篇 |
2007年 | 41篇 |
2006年 | 18篇 |
2005年 | 12篇 |
2004年 | 10篇 |
2003年 | 8篇 |
2002年 | 20篇 |
2001年 | 9篇 |
2000年 | 10篇 |
1998年 | 8篇 |
1996年 | 7篇 |
1995年 | 4篇 |
1994年 | 4篇 |
1993年 | 10篇 |
1992年 | 6篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 3篇 |
1984年 | 4篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 8篇 |
1980年 | 7篇 |
1979年 | 9篇 |
1978年 | 4篇 |
1977年 | 7篇 |
1976年 | 6篇 |
1975年 | 9篇 |
1974年 | 3篇 |
1973年 | 9篇 |
1971年 | 2篇 |
1961年 | 2篇 |
排序方式: 共有644条查询结果,搜索用时 0 毫秒
21.
Vojtech VargaMichal Horá?ek Zdeněk BastlJan Merna Ivana Císa?ováJan Sýkora Ji?í Pinkas 《Catalysis Today》2012,179(1):130-139
The efficient catalytic dehydropolymerization of phenylsilane by homogeneous zirconocene bissilanolates ([{(c-C5H9)7Si8O12O}2Zr(η5-C5H5)2] (1a); [{(c-C5H9)7Si8O12O}2Zr(η5-C5H4Bu)2] (1b) [{(c-C5H9)7Si7O9(OSiMe3)O2}Zr(η5-C5H5)2] (4); [{(Me3CO)3SiO}2Zr(η5-C5H5)2] (5)) and chlorosilanolates ([{(c-C5H9)7Si8O12O}ZrCl(η5-C5H4Bu)2] (2); ([{(c-C5H9)7Si7O9O3}Zr2Cl(η5-C5H5)4] (3a); [{(c-C5H9)7Si7O9O3}Zr2Cl(η5-C5H4Bu)4] (3b)) has been demonstrated. The presence of at least one silanol ligand in the zirconocene moiety was found essential for high catalytic performance. Solid state structure of complex 1a was determined by single crystal X-ray diffraction analysis. A series of nine zirconocene-siliceous catalysts were prepared by grafting of zirconocene moiety onto silica using three general methods: (a) reaction of [(η5-C5H5)2ZrCl2] with silica in the presence of NEt3; (b) reaction of [(η5-C5H5)2ZrMe2] with silica; (c) reaction of solely [(η5-C5H5)2ZrCl2] with silica. Supported catalysts were characterized by ICP-MS, FT-IR, TGA and selected examples by XPS analysis. Those catalysts prepared by method (a) and (b) were found efficient in the phenylsilane polymerization although a higher Zr/monomer ratio had to be used in comparison with homogeneous analogues. The low concentration of residual silanol groups in supported catalysts was found essential for their high catalytic performance. Advantageous reusability of supported catalysts was demonstrated using SiO2(500)/Cp2ZrCl2/NEt3(5.8). The catalytic performance was retained in three consecutive cycles producing polymers with almost identical properties. 相似文献
22.
Extremely thin gold layers were sputter deposited on glass and silicon substrates, and their thickness and morphology were studied by Rutherford backscattering (RBS) and atomic force microscopy (AFM) methods. The deposited layers change from discontinuous to continuous ones for longer deposition times. While the deposition rate on the silicon substrate is constant, nearly independent on the layer thickness, the rate on the glass substrate increases with increasing layer thickness. The observed dependence can be explained by a simple kinetic model, taking into account different sticking probabilities of gold atoms on a bare glass substrate and regions with gold coverage. Detailed analysis of the shape of the RBS gold signal shows that in the initial stages of the deposition, the gold layers on the glass substrate consist of gold islands with significantly different thicknesses. These findings were confirmed by AFM measurements, too. Gold coverage of the silicon substrate is rather homogeneous, consisting of tiny gold grains, but a pronounced worm-like structure is formed for the layer thickness at electrical continuity threshold. On the glass substrate, the gold clusters of different sizes are clearly observed. For later deposition stages, a clear tendency of the gold atoms to aggregate into larger clusters of approximately the same size is observed. At later deposition stages, gold clusters of up to 100 nm in diameter are formed. 相似文献
23.
Plastic immersed heat exchangers are used in various applications where chemically neutral and noncorrosive equipment is required. Their potential competitors, namely, polymeric hollow‐fiber bundles, were investigated. Three different fiber bundles were tested as immersed coolers of a hot reservoir. Two types of polypropylene hollow fibers with various outside diameters were employed. Fibers were twisted with different curvature to achieve better distribution and improve natural convection on their outer surface. Calculation by experimental results was compared with the equation for natural convection across the horizontal cylinder, which overestimates heat transfer coefficients and can be applied for only rough estimation. Experimentally achieved pressure drops agreed well with theoretical prediction for laminar flow. 相似文献
24.
A simplified two-dimensional finite elements model was created for a polyvinyl alcohol (PVA) coated Bioglass® strut undergoing tensile stresses (loading mode I). The strengthening contributions due to the infiltration of coating into surface cracks and coating's stiffness were evaluated in terms of stress intensity factor KI and tensile stresses σyy in the proximity of the crack tip. The infiltration of the coating until the crack tip resulted as the most effective criterion for the struts strengthening. Bioglass® based scaffolds were dip coated into PVA and PVA/microfibrillated cellulose (MFC) aqueous solutions and tested in tensile load. Coated samples exhibited remarkably higher tensile strength than non-coated ones, which further raised with the increased amount of MFC. Contact angle θ and linear viscosity η measurements of PVA/MFC solutions showed that MFC caused a reduction in θ and a drastic increase in η, indicating that a balance between these two effects must be achieved. 相似文献
25.
Vandana Srivastava Petr Chýlek R G. Pinnick R. L. Dod T. Novakov 《Aerosol science and technology》2013,47(1):151-160
We collected several samples of fresh snow from the areas of southern New Mexico and western Texas. Samples were analyzed to determine graphitic carbon content of snow in rural and urban areas and to compare these present values with those obtained from deep ice core samples several thousand years old. To model the optical properties of snow grains containing carbon we used several different versions of effective medium approximations. Calculations are compared with microwave analog measurements to determine which of these approximations can reasonably well predict the properties of mixtures such as snow and carbon. Suggestions regarding which of the effective medium approximations that should not be used are presented. 相似文献
26.
27.
Elena Pâslaru Lidija Fras Zemljic Matej Bračič Alenka Vesel Irena Petrinić Cornelia Vasile 《应用聚合物科学杂志》2013,130(4):2444-2457
A two‐step procedure was applied to obtain antimicrobial films; this procedure involved a corona treatment of the polyethylene (PE) surface and its chemical activation with 1‐ethyl‐3‐[3‐dimethylaminopropyl] carbodiimide hydrochloride and N‐hydroxysuccinimide, and this led to the covalent bonding of chitosan on the PE surface. Electrochemical methods were used to investigate the stability of the deposited chitosan layer. The potentiometric and polyelectrolyte titrations showed that some amount of chitosan desorbed faster from the surface until equilibrium was reached and also that the grafted chitosan layer was more stable than the physically adsorbed one. The chitosan immobilized on the PE surface exhibited the expected antibacterial activity when tested against three bacteria, which included two Gram‐negative bacteria, Salmonella enteritidis and Escherichia coli, and one Gram‐positive bacterium, Listeria monocytogenes. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2444–2457, 2013 相似文献
28.
Iva Blazkova Hoai Viet Nguyen Simona Dostalova Pavel Kopel Maja Stanisavljevic Marketa Vaculovicova Marie Stiborova Tomas Eckschlager Rene Kizek Vojtech Adam 《International journal of molecular sciences》2013,14(7):13391-13402
Magnetic particle mediated transport in combination with nanomaterial based drug carrier has a great potential for targeted cancer therapy. In this study, doxorubicin encapsulation into the apoferritin and its conjugation with magnetic particles was investigated by capillary electrophoresis with laser-induced fluorescence detection (CE-LIF). The quantification of encapsulated doxorubicin was performed by fluorescence spectroscopy and compared to CE-LIF. Moreover, the significant enhancement of the doxorubicin signal was observed by addition of methanol into the sample solution. 相似文献
29.
Dagmar Chudobova Lukas Nejdl Jaromir Gumulec Olga Krystofova Miguel Angel Merlos Rodrigo Jindrich Kynicky Branislav Ruttkay-Nedecky Pavel Kopel Petr Babula Vojtech Adam Rene Kizek 《International journal of molecular sciences》2013,14(7):13592-13614
Polymers are currently widely used to replace a variety of natural materials with respect to their favourable physical and chemical properties, and due to their economic advantage. One of the most important branches of application of polymers is the production of different products for medical use. In this case, it is necessary to face a significant disadvantage of polymer products due to possible and very common colonization of the surface by various microorganisms that can pose a potential danger to the patient. One of the possible solutions is to prepare polymer with antibacterial/antimicrobial properties that is resistant to bacterial colonization. The aim of this study was to contribute to the development of antimicrobial polymeric material ideal for covering vascular implants with subsequent use in transplant surgery. Therefore, the complexes of polymeric substances (hyaluronic acid and chitosan) with silver nitrate or silver phosphate nanoparticles were created, and their effects on gram-positive bacterial culture of Staphylococcus aureus were monitored. Stages of formation of complexes of silver nitrate and silver phosphate nanoparticles with polymeric compounds were characterized using electrochemical and spectrophotometric methods. Furthermore, the antimicrobial activity of complexes was determined using the methods of determination of growth curves and zones of inhibition. The results of this study revealed that the complex of chitosan, with silver phosphate nanoparticles, was the most suitable in order to have an antibacterial effect on bacterial culture of Staphylococcus aureus. Formation of this complex was under way at low concentrations of chitosan. The results of electrochemical determination corresponded with the results of spectrophotometric methods and verified good interaction and formation of the complex. The complex has an outstanding antibacterial effect and this effect was of several orders higher compared to other investigated complexes. 相似文献
30.
Zbynek Heger Natalia Cernei Jiri Kudr Jaromir Gumulec Iva Blazkova Ondrej Zitka Tomas Eckschlager Marie Stiborova Vojtech Adam Rene Kizek 《International journal of molecular sciences》2013,14(11):21629-21646
Doxorubicin is a commonly used antineoplastic agent in the treatment of many types of cancer. Little is known about the interactions of doxorubicin with cardiac biomolecules. Serious cardiotoxicity including dilated cardiomyopathy often resulting in a fatal congestive heart failure may occur as a consequence of chemotherapy with doxorubicin. The purpose of this study was to determine the effect of exposure to doxorubicin on the changes in major amino acids in tissue of cardiac muscle (proline, taurine, glutamic acid, arginine, aspartic acid, leucine, glycine, valine, alanine, isoleucine, threonine, lysine and serine). An in vitro interaction study was performed as a comparison of amino acid profiles in heart tissue before and after application of doxorubicin. We found that doxorubicin directly influences myocardial amino acid representation even at low concentrations. In addition, we performed an interaction study that resulted in the determination of breaking points for each of analyzed amino acids. Lysine, arginine, β-alanine, valine and serine were determined as the most sensitive amino acids. Additionally we compared amino acid profiles of myocardium before and after exposure to doxorubicin. The amount of amino acids after interaction with doxorubicin was significantly reduced (p = 0.05). This fact points at an ability of doxorubicin to induce changes in quantitative composition of amino acids in myocardium. Moreover, this confirms that the interactions between doxorubicin and amino acids may act as another factor most likely responsible for adverse effects of doxorubicin on myocardium. 相似文献