全文获取类型
收费全文 | 877篇 |
免费 | 17篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 33篇 |
化学工业 | 222篇 |
金属工艺 | 8篇 |
机械仪表 | 15篇 |
建筑科学 | 55篇 |
矿业工程 | 4篇 |
能源动力 | 33篇 |
轻工业 | 134篇 |
水利工程 | 12篇 |
无线电 | 39篇 |
一般工业技术 | 103篇 |
冶金工业 | 130篇 |
原子能技术 | 5篇 |
自动化技术 | 104篇 |
出版年
2016年 | 16篇 |
2015年 | 14篇 |
2014年 | 16篇 |
2013年 | 25篇 |
2012年 | 35篇 |
2011年 | 31篇 |
2010年 | 21篇 |
2009年 | 22篇 |
2008年 | 30篇 |
2007年 | 37篇 |
2006年 | 25篇 |
2005年 | 26篇 |
2004年 | 27篇 |
2003年 | 20篇 |
2002年 | 16篇 |
2001年 | 13篇 |
2000年 | 16篇 |
1999年 | 19篇 |
1998年 | 22篇 |
1997年 | 22篇 |
1996年 | 15篇 |
1995年 | 16篇 |
1994年 | 8篇 |
1993年 | 10篇 |
1992年 | 11篇 |
1991年 | 19篇 |
1990年 | 16篇 |
1989年 | 8篇 |
1988年 | 8篇 |
1987年 | 7篇 |
1986年 | 10篇 |
1985年 | 9篇 |
1984年 | 15篇 |
1983年 | 10篇 |
1982年 | 9篇 |
1981年 | 11篇 |
1980年 | 7篇 |
1979年 | 10篇 |
1978年 | 12篇 |
1977年 | 14篇 |
1976年 | 8篇 |
1975年 | 14篇 |
1974年 | 11篇 |
1973年 | 18篇 |
1972年 | 12篇 |
1971年 | 10篇 |
1970年 | 16篇 |
1969年 | 9篇 |
1968年 | 7篇 |
1967年 | 7篇 |
排序方式: 共有897条查询结果,搜索用时 0 毫秒
31.
Dierdorff Erich C.; Bell Suzanne T.; Belohlav James A. 《Canadian Metallurgical Quarterly》2011,96(2):247
We examined the influences of different facets of psychological collectivism (Preference, Reliance, Concern, Norm Acceptance, and Goal Priority) on team functioning at 3 different performance depictions: initial team performance, end-state team performance, and team performance change over time. We also tested the extent to which team-member exchange moderated the relationships between facets of psychological collectivism and performance change over time. Results from multilevel growth modeling of 66 teams (N = 264) engaged in a business simulation revealed differential effects across facets of psychological collectivism and across different performance measurements. Whereas facets concerned with affiliation (Preference and Concern) were positively related to initial team performance, reliance was negatively related to initial team performance. Goal Priority was a strong predictor of end-state performance. Team-member exchange moderated the relationship between performance change and 3 of the 5 facets of psychological collectivism (Preference, Reliance, Norm Acceptance). Implications for team composition and team training are discussed. (PsycINFO Database Record (c) 2011 APA, all rights reserved) 相似文献
32.
Marika Vespa Erich Wieland Rainer Dähn Barbara Lothenbach 《Journal of the American Ceramic Society》2015,98(7):2286-2294
Current developments in cement chemistry increasingly rely on predictive thermodynamic modeling of the phase composition in cementitious composites with the aim of linking the performance of the material with the phase composition of the material. This approach requires identification of the cement phases that form in hydrating cementitious materials using standard techniques, such as X‐ray diffraction (XRD) and thermal analysis (DTA, TGA), but also state‐of‐the‐art synchrotron‐based techniques, in particular for those cases in which the signals of solid solutions overlap in XRD and TGA measurements. In this study, two ordinary Portland cements, with different chemical compositions and subject to different hydration times (~10, ~50 yr), were investigated aiming at identifying the most stable Fe‐containing cement phase in the cement pastes. The Fe‐containing cement phases and their solid solutions with the Al analogues in the complex cement matrix were analyzed with X‐ray absorption spectroscopy, indicating the formation of a mixed Fe–Al siliceous hydrogarnet as the major Fe‐containing phase. The presence of this phase after long hydration periods and upon selective dissolution of the pastes further indicates that, independent of the chemical compositions of cements, formation of the mixed Fe–Al siliceous hydrogarnet is thermodynamically favored in aged pastes, which is supported by published thermodynamic calculations. 相似文献
33.
Matthias Engleder Dr. Tea Pavkov‐Keller Dr. Anita Emmerstorfer Altijana Hromic Sabine Schrempf Dr. Georg Steinkellner Dr. Tamara Wriessnegger Prof. Erich Leitner Dr. Gernot A. Strohmeier Dr. Iwona Kaluzna Dr. Daniel Mink Dr. Martin Schürmann Dr. Silvia Wallner Prof. Peter Macheroux Prof. Karl Gruber Dr. Harald Pichler 《Chembiochem : a European journal of chemical biology》2015,16(12):1730-1734
Hydratases provide access to secondary and tertiary alcohols by regio‐ and/or stereospecifically adding water to carbon‐carbon double bonds. Thereby, hydroxy groups are introduced without the need for costly cofactor recycling, and that makes this approach highly interesting on an industrial scale. Here we present the first crystal structure of a recombinant oleate hydratase originating from Elizabethkingia meningoseptica in the presence of flavin adenine dinucleotide (FAD). A structure‐based mutagenesis study targeting active site residues identified E122 and Y241 as crucial for the activation of a water molecule and for protonation of the double bond, respectively. Moreover, we also observed that two‐electron reduction of FAD results in a sevenfold increase in the substrate hydration rate. We propose the first reaction mechanism for this enzyme class that explains the requirement for the flavin cofactor and the involvement of conserved amino acid residues in this regio‐ and stereoselective hydration. 相似文献
34.
J. Eversdijk S.J.F. Erich S.P.M. Hermanns O.C.G. Adan M. De Bolle K. de Meyer D. Bylemans M. Bekker A.T. ten Cate 《Progress in Organic Coatings》2012
This paper focuses on the use of modified nano-clay particles as a controlled release system for biocides from building materials. Different (model) biocides were incorporated in a biocide/nano-clay composite and subsequently the release of the biocides was monitored under different environmental conditions. In addition, the biocide/clay material was formulated into a model finishing material (gypsum) to evaluate the antifungal activity. Intercalation of biocides in modified nano-clays was found to significantly prolong the release of the biocide and prevent premature leaching of the biocide from the building material. Release rate of the biocide could be tuned by selection of the type of modification used for the nano-clay platelets. Even after prolonged leaching up to 45 days in artificial rain tests, gypsum samples containing biocide/clay composites did not show any fungal growth, whereas gypsum samples containing pure biocide had lost their antifungal activity after exposure to artificial rain for 7 days or more, demonstrating the potential of this technology for practical applications. The presented approach is very versatile, and may be used for a large variety of biocides and is envisioned to be applicable to different construction and finishing materials, including waterborne paints. To optimize the performance in a specific application area, the leaching or release process of the nano-clays should be known in the different application materials, and consequently requires alternative testing methods, e.g. methods which characterize the fungal growth as a function of release in more detail. Although correlation with practice requires further investigation, the presented method gives a good first indication for prolonged protection of building materials. 相似文献
35.
Karla Čech Barabaszová Sylva Holešová Marianna Hundáková Erich Pazdziora Michal Ritz 《Journal of Inorganic and Organometallic Polymers and Materials》2017,27(4):986-995
Polyethylene (PE) nanocomposites with the zinc oxide-nanoparticles/vermiculite nanofiller were prepared in two-steps. In first step, the ZnO-np/V nanofiller were prepared by the mechanochemical method followed by a heat treatment at 650?°C for 90 min. In second step, this nanofiller was used in concentration 3, 6, 10 and 15 wt% for PE nanocomposites preparation via melt compounding technique, the nanocomposites plates were pressed. The particles morphology of the ZnO-np/V nanofiller, arrangement of the ZnO-np/V nanofiller and surface of the PE plates were studied using scanning electron microscopy, optical light microscopy and atomic force microscopy. The surface roughness of the PE plates was evaluated from AFM measurements. Structural changes of the ZnO-np/V nanofiller in PE nanocomposites were monitored using X-ray diffraction analysis and Fourier transform infrared analysis. The gradual and long-term antibacterial effect of PE nanocomposites was tested on the Gram positive bacteria E. faecalis by counting the colony forming units number. 相似文献
36.
P.A.J. Donkers H.P. Huinink S.J.F. Erich N.J.W. Reuvers O.C.G. Adan 《Progress in Organic Coatings》2013
Coatings are used in a variety of applications. Last decades more and more coating systems are transforming from solvent to waterborne coating systems. In this study the influence of pigments on the water permeability of a waterborne coating system is studied, with special interest in the possible interfacial layer of additives around the pigments. In our study an acrylate based binder is mixed with different glass sphere concentrations and sizes. Subsequently, the coating permeability is studied through wet-cup experiments and water uptake in the coating, either on a glass substrate or on wood, is monitored with NMR. These experiments show that water is absorbed more quickly by coatings containing glass spheres. From the experimental results it can be concluded that an interface layer around the pigment particles facilitates water migration and increases the effective diffusion. A modification of the effective medium theory is used to describe the observation and good agreement between experiments and theory is obtained. Both theory and experiment show that in a coating a layer around the pigments facilitates water transport and increases the effective diffusion constant. 相似文献
37.
Yusuf Tanrikulu Ewgenij Proschak Dr. Tim Werner Tim Geppert Nickolay Todoroff Alexander Klenner Tim Kottke Kerstin Sander Erich Schneider Dr. Roland Seifert Prof. Dr. Holger Stark Prof. Dr. Timothy Clark Prof. Dr. Gisbert Schneider Prof. Dr. 《ChemMedChem》2009,4(5):820-827
A new pseudoreceptor modeling method (PRPS) was applied to the refinement of a homology model of the human histamine H4 receptor (H4R), the prediction of a ligand binding site, and virtual screening. Retrieval of two new H4R ligands demonstrates the biological relevance of the pseudoreceptor model and provides a means for finding new hits and leads in the early phases of drug discovery.
38.
Sorantin E Halmai C Erdöhelyi B Palágyi K Nyúl LG Ollé K Geiger B Lindbichler F Friedrich G Kiesler K 《IEEE transactions on medical imaging》2002,21(3):263-273
PURPOSE: Demonstration of a technique for three-dimensional (3-D) assessment of tracheal-stenoses, regarding site, length and degree, based on spiral computed tomography (S-CT). PATIENTS AND METHODS: S-CT scanning and automated segmentation of the laryngo-tracheal tract (LTT) was followed by the extraction of the LTT medial axis using a skeletonization algorithm. Orthogonal to the medial axis the LTT 3-D cross-sectional profile was computed and presented as line charts, where degree and length was obtained. Values for both parameters were compared between 36 patients and 18 normal controls separately. Accuracy and precision was derived from 17 phantom studies. RESULTS: Average degree and length of tracheal stenoses was found to be 60.5% and 4.32 cm in patients compared with minor caliber changes of 8.8% and 2.31 cm in normal controls (p < 0.0001). For the phantoms an excellent correlation between the true and computed 3-D cross-sectional profile was found (p < 0.005) and an accuracy for length and degree measurements of 2.14 mm and 2.53% respectively could be determined. The corresponding figures for the precision were found to be 0.92 mm and 2.56%. CONCLUSION: LTT 3-D cross-sectional profiles permit objective, accurate and precise assessment of LTT caliber changes. Minor LTT caliber changes can be observed even in normals and, in case of an otherwise normal S-CT study, can be regarded as artifacts. 相似文献
39.
Steinle ED Mitchell DT Wirtz M Lee SB Young VY Martin CR 《Analytical chemistry》2002,74(10):2416-2422
This paper describes synthetic micropore and nanotube membranes that mimic the function of a ligand-gated ion channel; that is, these membranes can be switched from an "off" state (no or low ion current through the membrane) to an "on" state (higher ion current) in response to the presence of a chemical stimulus. Ion channel mimics based on both microporous alumina and Au nanotube membranes were investigated. The off state was obtained by making the membranes hydrophobic by chemisorbing either a C18 silane (alumina membrane) or a C18 thiol (Au nanotube membrane). Water and electrolyte are forbidden from entering these very hydrophobic pores/nanotubes. The transition to the on state was induced by the partitioning of a hydrophobic ionic species (e.g., a drug or a surfactant) into the membrane. The membrane switches to the on state because at a sufficiently high concentration of this ionic analyte species, the pores/nanotubes flood with water and electrolyte. A pH-responsive membrane was also prepared by attaching a hydrophobic alkyl carboxylic acid silane to the alumina membrane. 相似文献
40.