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排序方式: 共有172条查询结果,搜索用时 15 毫秒
31.
R Sader HF Zeilhofer H Deppe HH Horch B Nuber B Hornung 《Canadian Metallurgical Quarterly》1995,16(6):269-274
AIM: The use of a new 3D ultrasound system should reduce the drawbacks of former 3D workstations (long image generation time, limited use due to the need for special 3D transducers), so that it is now applicable in daily clinical routine. METHOD: An ultrasound 3D workstation was used based on a pentium PC platform, employing a magnetoelectronic position detection system for spatial reconstruction of conventional 2D B-scan image sequences. RESULTS: Better assessment of topographico-anatomical spatial relationships was achieved when presenting pathological findings, especially in assessing lymph nodes and salivary stones. Pathological processes in the maxillofacial area occurring during a period of five months were visualised. CONCLUSION: The method of 3D reconstruction of standard two-dimensional electronic scans, as presented here, is the first method of its kind enabling applicability in daily clinical routine thanks to rapid imaging. The images can be produced with any ultrasound unit or transducer. First clinical results in maxillofacial surgery clearly show improved diagnostic possibilities although there still room for an improvement of the image quality. The possibility of semi-automatic exact volumetry appears meaningful especially in the investigation of lymph nodes. Integration of colour duplex sonography will further enhance the diagnostic value of this method. 相似文献
32.
Schwudke D Hannich JT Surendranath V Grimard V Moehring T Burton L Kurzchalia T Shevchenko A 《Analytical chemistry》2007,79(11):4083-4093
Direct profiling of total lipid extracts on a hybrid LTQ Orbitrap mass spectrometer by high-resolution survey spectra clusters species of 11 major lipid classes into 7 groups, which are distinguished by their sum compositions and could be identified by accurately determined masses. Rapid acquisition of survey spectra was employed as a "top-down" screening tool that, together with the computational method of principal component analysis, revealed pronounced perturbations in the abundance of lipid precursors within the entire series of experiments. Altered lipid precursors were subsequently identified either by accurately determined masses or by in-depth MS/MS characterization that was performed on the same instrument. Hence, the sensitivity, throughput and robustness of lipidomics screens were improved without compromising the accuracy and specificity of molecular species identification. The top-down lipidomics strategy lends itself for high-throughput screens complementing ongoing functional genomics efforts. 相似文献
33.
Ruthenium supported on magnesia was found to be a highly active and selective catalyst for the reduction of NO to N2 with H2. The adsorption of NO on Ru/MgO was studied at room temperature by applying frontal chromatography with a mixture of 2610
ppm NO in He. Subsequently, temperature‐programmed desorption (TPD) and temperature‐programmed surface reaction (TPSR) experiments
in H2 were performed. The adsorption of NO was observed to occur partly dissociatively as indicated by the formation of molecular
nitrogen. The TPD spectrum exhibited a minor NO peak at 340 K indicating additional molecular adsorption of NO during the
exposure to NO at room temperature, and two N2 peaks at 480 K and 625 K, respectively. The latter data are in good agreement with previous results with Ru(0001) single‐crystal
samples, where the interaction with NH3 was found to lead to two N2 thermal desorption states with a maximum coverage of atomic nitrogen of about 0.38. Heating up the catalyst after saturation
with NO at room temperature in a H2 atmosphere revealed the self‐accelerated formation of NH3 after partial desorption of N2, whereby sites for reaction with H2 become available. As a consequence, the observed high selectivity towards N2 under steady‐state reduction conditions is ascribed to the presence of a saturated N+O coadsorbate layer resulting in an
enhanced rate of N2 desorption from this layer and a very low steady‐state coverage of atomic hydrogen. The formation of H2O by reduction of adsorbed atomic oxygen is the slow step of the overall reaction which determines the minimum temperature
required for full conversion of NO.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
34.
35.
Temperature-programmed surface reaction (TPSR) experiments with a ruthenium-based catalyst supported on MgO were conducted in a microreactor flow system. The hydrogenation of preadsorbed atomic nitrogen obtained under various experimental conditions has been studied followed by a detailed microkinetic analysis including an evaluation of the influence of backmixing. The shape of the TPSR profile was found to depend strongly on the initial surface coverage and on the presence of coadsorbates. 相似文献
36.
A Meffre B Mehdaoui V Kelsen PF Fazzini J Carrey S Lachaize M Respaud B Chaudret 《Nano letters》2012,12(9):4722-4728
We report a tunable organometallic synthesis of monodisperse iron carbide and core/shell iron/iron carbide nanoparticles displaying a high magnetization and good air-stability. This process based on the decomposition of Fe(CO)(5) on Fe(0) seeds allows the control of the amount of carbon diffused and therefore the tuning of nanoparticles magnetic anisotropy. This results in unprecedented hyperthermia properties at moderate magnetic fields, in the range of medical treatments. 相似文献
37.
Wei Fan François Stoffelbach Jutta Rieger Laure Regnaud Angélique Vichot Bruno Bresson Nicolas Lequeux 《Cement and Concrete Research》2012,42(1):166-172
It is well-established that a competitive adsorption exists between polycarboxylate superplasticizers (SP) and sulfate ions solubilized in the interstitial solution of cement paste, which may cause a loss of the dispersing properties. This has been explained by competitive weak ionic interactions between functional carboxyl groups and sulfate ions with cement grains. In this study, SPs including trialkoxysilane functional groups have been synthesized. Adsorption and dispersing properties of these SPs were evaluated in the presence of different concentrations of Na2SO4 added in aqueous solution. It appeared that a partial substitution of carboxyl groups by trialkoxysilane in the polymer makes them more resistant to sulfate ions. We suggested that the high adsorption capacity of these SPs results from the formation of strong bonds between hydroxysilane groups and calcium silicate hydrate phases. The improved compatibility of these new silylated SPs has been demonstrated through the formulation of two different concrete equivalent mortars. 相似文献
38.
Steady-state and transient kinetic experiments were performed in a versatile microreactor flow set-up with magnesia- and alumina-supported
ruthenium catalysts in order to elucidate the mechanism of the selective catalytic reduction (SCR) of nitric oxide with hydrogen.
Both Ru/MgO and Ru/γ-Al2O3 were found to be highly active catalysts converting NO and H2 into N2 and H2O with selectivities close to 100% at full conversion, although Ru-based catalysts are known to be active in the synthesis
of NH3 from N2 and H2. Frontal chromatography experiments with NO at room temperature revealed that NO and its dissociation products displace adsorbed
atomic hydrogen (H−*) almost completely from hydrogen-precovered Ru surfaces. Obviously, NO and H2 compete for the same adsorption sites, H−* being the weaker bound adsorbate. Temperature-programmed surface reaction (TPSR)
experiments in H2 subsequent to NO exposure demonstrated that higher heating rates and lower partial pressures of H2 shift the selectivity from NH3 to N2. Therefore, the coverage of H−* is concluded to govern the branching ratio between the rate of associative desorption of
N2 (2N−*→N2 + 2*) and the rate of hydrogenation of N−* (N−* + 3H–* →NH3 + 4*). Finally, the steady-state coverages of N- and O-containing adsorbates were derived by interrupting the SCR reaction
and hydrogenating the adsorbates off as NH3 and H2O. By solving the site balance, the Ru surfaces were found to be essentially N2 is attributed to the very low coverage of H−* due to site blocking by a N + O coadsorbate layer, favouring the recombination
of N−* instead of its hydrogenation to NH3.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
39.
Armin Hornung Kai M. Wurm Maren Bennewitz Cyrill Stachniss Wolfram Burgard 《Autonomous Robots》2013,34(3):189-206
Three-dimensional models provide a volumetric representation of space which is important for a variety of robotic applications including flying robots and robots that are equipped with manipulators. In this paper, we present an open-source framework to generate volumetric 3D environment models. Our mapping approach is based on octrees and uses probabilistic occupancy estimation. It explicitly represents not only occupied space, but also free and unknown areas. Furthermore, we propose an octree map compression method that keeps the 3D models compact. Our framework is available as an open-source C++ library and has already been successfully applied in several robotics projects. We present a series of experimental results carried out with real robots and on publicly available real-world datasets. The results demonstrate that our approach is able to update the representation efficiently and models the data consistently while keeping the memory requirement at a minimum. 相似文献
40.
The Blown Fiber Cable 总被引:1,自引:0,他引:1
Hornung S. Cassidy S. Yennadhiou P. Reeve M. 《Selected Areas in Communications, IEEE Journal on》1986,4(5):679-685
A radically new approach to optical fiber cable design and installation is described. Packages containing a number of optical fibers were drawn into preinstalled empty bores (tubes) using the viscous drag of air. The drag force acting on the fiber package is distributed along its length, which makes it possible to introduce fibers into complicated routes, with low strain. In this paper, we will concentrate mainly on the design of the fiber package, first from the point of view of the hydrodynamic forces acting on it during installation. This leads to a theoretical model for the installation process. Second, we shall consider the package as a subminiature optical fiber cable, and examine its optical performance during manufacture and temperature cycling, which leads to a theoretical model of the temperature performance of the package. Finally, we will describe a trial field installation using this cabling technique. 相似文献