全文获取类型
收费全文 | 164篇 |
免费 | 16篇 |
专业分类
电工技术 | 4篇 |
化学工业 | 62篇 |
机械仪表 | 15篇 |
建筑科学 | 5篇 |
能源动力 | 7篇 |
轻工业 | 15篇 |
无线电 | 10篇 |
一般工业技术 | 25篇 |
冶金工业 | 13篇 |
原子能技术 | 4篇 |
自动化技术 | 20篇 |
出版年
2023年 | 4篇 |
2022年 | 7篇 |
2021年 | 10篇 |
2020年 | 2篇 |
2019年 | 1篇 |
2018年 | 8篇 |
2017年 | 4篇 |
2016年 | 4篇 |
2015年 | 9篇 |
2014年 | 5篇 |
2013年 | 8篇 |
2012年 | 9篇 |
2011年 | 15篇 |
2010年 | 6篇 |
2009年 | 8篇 |
2008年 | 9篇 |
2007年 | 6篇 |
2006年 | 5篇 |
2005年 | 6篇 |
2004年 | 12篇 |
2003年 | 6篇 |
2002年 | 5篇 |
2001年 | 4篇 |
2000年 | 1篇 |
1999年 | 2篇 |
1998年 | 4篇 |
1997年 | 5篇 |
1996年 | 2篇 |
1995年 | 3篇 |
1994年 | 1篇 |
1991年 | 1篇 |
1989年 | 3篇 |
1988年 | 1篇 |
1987年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1971年 | 1篇 |
排序方式: 共有180条查询结果,搜索用时 31 毫秒
41.
Tubes of ceramic high-temperature proton conductors (CaZr0.9 In0.1 O3− x ,BaZr0.9 Y0.1 O3− x , and Ba3 Ca1.18 Nb1.82 O9− x )were used to introduce hydrogen into a vacuum system. A prerequisite was a leak rate below 10−8 mbar/s for an assembly consisting of the active tube and a 8YSZ support tube. Mass spectrometry showed that the partial pressure of hydrogen in the vacuum system, p H2 , increased linearly with the electric current flowing through the proton conductor. All other important partial pressures remained unaffected by this operation. Calculation of throughput during operation of the hydrogen source essentially revealed that the total current, J , is used to transport protons from the anode to the cathode ( t H ∼ 1). The number of moles of H2 transported per second is given by J /2 F . In essence, the present proton conductor tube constitutes a precise, current-controllable device, with a response time of a few seconds only, that delivers ultrahigh-purity hydrogen to a vacuum system. 相似文献
42.
43.
Model‐based reconstruction for T1 mapping using single‐shot inversion‐recovery radial FLASH 下载免费PDF全文
Volkert Roeloffs Xiaoqing Wang Tilman J. Sumpf Markus Untenberger Dirk Voit Jens Frahm 《International journal of imaging systems and technology》2016,26(4):254-263
Quantitative parameter mapping in MRI is typically performed as a two‐step procedure where serial imaging is followed by pixelwise model fitting. In contrast, model‐based reconstructions directly reconstruct parameter maps from raw data without explicit image reconstruction. Here, we propose a method that determines T1 maps directly from multi‐channel raw data as obtained by a single‐shot inversion‐recovery radial FLASH acquisition with a Golden Angle view order. Joint reconstruction of a T1, spin‐density and flip‐angle map is formulated as a nonlinear inverse problem and solved by the iteratively regularized Gauss‐Newton method. Coil sensitivity profiles are determined from the same data in a preparatory step of the reconstruction. Validations included numerical simulations, in vitro MRI studies of an experimental T1 phantom, and in vivo studies of brain and abdomen of healthy subjects at a field strength of 3 T. The results obtained for a numerical and experimental phantom demonstrated excellent accuracy and precision of model‐based T1 mapping. In vivo studies allowed for high‐resolution T1 mapping of human brain (0.5–0.75 mm in‐plane, 4 mm section thickness) and liver (1.0 mm, 5 mm section) within 3.6–5 s. In conclusion, the proposed method for model‐based T1 mapping may become an alternative to two‐step techniques, which rely on model fitting after serial image reconstruction. More extensive clinical trials now require accelerated computation and online implementation of the algorithm. © 2016 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 26, 254–263, 2016 相似文献
44.
Gia Quyet Ngo Antony George Robin Tristan Klaus Schock Alessandro Tuniz Emad Najafidehaghani Ziyang Gan Nils C. Geib Tobias Bucher Heiko Knopf Sina Saravi Christof Neumann Tilman Lühder Erik P. Schartner Stephen C. Warren-Smith Heike Ebendorff-Heidepriem Thomas Pertsch Markus A. Schmidt Andrey Turchanin Falk Eilenberger 《Advanced materials (Deerfield Beach, Fla.)》2020,32(47):2003826
Atomically thin transition metal dichalcogenides are highly promising for integrated optoelectronic and photonic systems due to their exciton-driven linear and nonlinear interactions with light. Integrating them into optical fibers yields novel opportunities in optical communication, remote sensing, and all-fiber optoelectronics. However, the scalable and reproducible deposition of high-quality monolayers on optical fibers is a challenge. Here, the chemical vapor deposition of monolayer MoS2 and WS2 crystals on the core of microstructured exposed-core optical fibers and their interaction with the fibers’ guided modes are reported. Two distinct application possibilities of 2D-functionalized waveguides to exemplify their potential are demonstrated. First, the excitonic 2D material photoluminescence is simultaneously excited and collected with the fiber modes, opening a novel route to remote sensing. Then it is shown that third-harmonic generation is modified by the highly localized nonlinear polarization of the monolayers, yielding a new avenue to tailor nonlinear optical processes in fibers. It is anticipated that the results may lead to significant advances in optical-fiber-based technologies. 相似文献
45.
Simulation of the Dynamic Behaviour of Heat Exchangers . Four models for heat exchangers under transient conditions are presented. Three of them describe a single phase heat exchanger, and the forth one is used for the simulation of a condenser. All models are of intermediate complexity and valid for simulation of both single heat exchangers and chemical processes. They use distributed variables and incorporate the calculation of local heat transfer coefficients so that temperature profiles over the apparatus can be determined in addition to the transient behaviour of the outlet variables. 相似文献
46.
Franziska Döhler Tilman Zscheckel Susanne Kasch Thomas Schmidt Christian Patzig Thomas Höche Christian Rüssel 《Journal of Materials Science》2018,53(24):16207-16219
A glass with the composition 61 CaO·30 Al2O3·9 SiO2 was studied with respect to its crystallization behavior and its suitability as a rapidly crystallizing material for laser sealing. The glass was studied by differential scanning calorimetry; from the profiles recorded, Avrami activation energies and Avrami coefficients were calculated. The latter are in the range between 0.99 and 1.55 which is supposedly attributed to sole surface crystallization. During thermal treatment as well as during laser sealing, Ca12Al14O33, CaAl2O4 and Ca3Al2O6 are formed. These phases were also observed in SEM micrographs as evidenced by electron backscatter diffraction from the attributed Kikuchi patterns. Transmission electron microscopy showed a crystallized CaO- and SiO2-enriched interface which strongly adhered to the Al2O3 ceramic. The porosity of the crystallized seal was in the order of few percent. The studied glass proved suitable as crystallizing seal for rapid laser sealing. 相似文献
47.
Tilman J. Schildhauer Sander Tromp Ivo Müller Alexej Schilkin Eugeny Y. Kenig Freek Kapteijn Jacob A. Moulijn 《Catalysis Today》2005,105(3-4):414-2
In this work, (reactive) stripping carried out in film flow monolith reactors developed for counter-current operation is investigated. Usually mass transfer in reactive separation has to be determined experimentally due to the complex flow patterns. However, monoliths have a simple geometry; only laminar flow is present throughout the column. This allows the calculation of the thickness of the liquid layer directly using Navier–Stokes equations. With this thickness known, the mass transfer can be calculated based on the convection in axial direction, diffusion in radial direction and vapour–liquid equilibrium. A model has been developed and implemented in Fortran® based on the concept of a direct solution of convective diffusion equations, using the Thomas algorithm for solving the counter-current operation mode. Experimental data from literature have been used to validate the model for a binary and a multi-component system. The stripping of oxygen from saturated water by nitrogen was modelled assuming Fickian diffusion and vapour–liquid transfer based on the Henry constants. In a second step, multi-component diffusion and complex mass transfer at the interface were taken into account to describe the stripping of water by nitrogen from a mixture of hexyl-octanoate and cumene (solvent) under reactive stripping conditions. 相似文献
48.
49.
50.
Kalyani Pangarkar Tilman J. Schildhauer J. Ruud van Ommen John Nijenhuis Jacob A. Moulijn Freek Kapteijn 《Chemical engineering science》2010,65(1):420-426
Improvements in catalyst activity make the heat transport in fixed bed reactors increasingly important. Structured packings operated in two-phase flow are expected to outperform randomly packed beds, but heat transfer data on structured packings is scarce. In this work structured packings such as OCFS (Open Cross Flow Structures), CCFS (Closed Cross Flow Structures), knitted wire, and foam were characterised with respect to the heat transfer performance. A dedicated set-up was designed and built which enabled us to measure the heat transfer rates in two-phase flow at ambient pressure in the absence of reaction. Benchmarking and set-up validation was carried out using glass beads. The structured packings—especially OCFS and CCFS—show heat transfer coefficients that are superior over those of glass beads, at lower energy dissipation. 相似文献