全文获取类型
收费全文 | 834篇 |
免费 | 42篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 9篇 |
综合类 | 7篇 |
化学工业 | 301篇 |
金属工艺 | 10篇 |
机械仪表 | 12篇 |
建筑科学 | 82篇 |
矿业工程 | 1篇 |
能源动力 | 10篇 |
轻工业 | 37篇 |
无线电 | 53篇 |
一般工业技术 | 211篇 |
冶金工业 | 48篇 |
原子能技术 | 7篇 |
自动化技术 | 90篇 |
出版年
2023年 | 7篇 |
2022年 | 11篇 |
2021年 | 26篇 |
2020年 | 14篇 |
2019年 | 16篇 |
2018年 | 16篇 |
2017年 | 10篇 |
2016年 | 21篇 |
2015年 | 22篇 |
2014年 | 32篇 |
2013年 | 48篇 |
2012年 | 39篇 |
2011年 | 44篇 |
2010年 | 31篇 |
2009年 | 31篇 |
2008年 | 31篇 |
2007年 | 40篇 |
2006年 | 29篇 |
2005年 | 24篇 |
2004年 | 22篇 |
2003年 | 23篇 |
2002年 | 23篇 |
2001年 | 18篇 |
2000年 | 13篇 |
1999年 | 15篇 |
1998年 | 18篇 |
1997年 | 16篇 |
1996年 | 11篇 |
1995年 | 5篇 |
1994年 | 15篇 |
1993年 | 15篇 |
1992年 | 12篇 |
1991年 | 14篇 |
1990年 | 12篇 |
1989年 | 13篇 |
1988年 | 10篇 |
1987年 | 8篇 |
1986年 | 7篇 |
1985年 | 11篇 |
1984年 | 10篇 |
1983年 | 8篇 |
1982年 | 6篇 |
1981年 | 13篇 |
1980年 | 9篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1976年 | 5篇 |
1974年 | 11篇 |
1973年 | 6篇 |
排序方式: 共有878条查询结果,搜索用时 15 毫秒
21.
Florian Meierhofer Lutz Mädler Udo Fritsching 《American Institute of Chemical Engineers》2020,66(2):e16885
In flame spray pyrolysis (FSP), the evolution of metal oxide nanoparticles relies on quite a number of droplet (liquid) and vapor phase related physical mechanism as for instance precursor evaporation, oxidation, nucleation via gas-to-particle conversion mechanism, and subsequent particle (solid) growth mechanisms based on coagulation, sintering/coalescence, and agglomeration. The liquid precursor and dispersion oxygen feed rates are relevant control parameters of the FSP process for tailoring the nanoparticle size (diameter) and structure as well as the atomizer nozzle configuration. Sophisticated nonintrusive, laser-based in situ and ex situ diagnostics with multiscale spatial resolution (micrometer to meter range) are applied for analyzing droplet formation and size, gas velocity, temperature, species concentration, as well as primary and agglomerate diameters along the flow direction. Computational fluid dynamics (CFD) are coupled with population balance modeling (PBM) to elucidate the nanoparticle dynamics within the reactive spray. It is found that the CFD-PBM approach allows estimations of primary and agglomerate nanoparticle diameters within 80 and 75% accuracy compared to experimental data, suggesting that the methods presented could pave the way for designing next-generations of flame reactors. 相似文献
22.
Erkan Aydin Michele De Bastiani Xinbo Yang Muhammad Sajjad Faisal Aljamaan Yury Smirnov Mohamed Nejib Hedhili Wenzhu Liu Thomas G. Allen Lujia Xu Emmanuel Van Kerschaver Monica Morales‐Masis Udo Schwingenschlgl Stefaan De Wolf 《Advanced functional materials》2019,29(25)
Parasitic absorption in transparent electrodes is one of the main roadblocks to enabling power conversion efficiencies (PCEs) for perovskite‐based tandem solar cells beyond 30%. To reduce such losses and maximize light coupling, the broadband transparency of such electrodes should be improved, especially at the front of the device. Here, the excellent properties of Zr‐doped indium oxide (IZRO) transparent electrodes for such applications, with improved near‐infrared (NIR) response, compared to conventional tin‐doped indium oxide (ITO) electrodes, are shown. Optimized IZRO films feature a very high electron mobility (up to ≈77 cm2 V?1 s?1), enabling highly infrared transparent films with a very low sheet resistance (≈18 Ω □?1 for annealed 100 nm films). For devices, this translates in a parasitic absorption of only ≈5% for IZRO within the solar spectrum (250–2500 nm range), to be compared with ≈10% for commercial ITO. Fundamentally, it is found that the high conductivity of annealed IZRO films is directly linked to promoted crystallinity of the indium oxide (In2O3) films due to Zr‐doping. Overall, on a four‐terminal perovskite/silicon tandem device level, an absolute 3.5 mA cm?2 short‐circuit current improvement in silicon bottom cells is obtained by replacing commercial ITO electrodes with IZRO, resulting in improving the PCE from 23.3% to 26.2%. 相似文献
23.
The real toughness response of RPV material can only be determined after the final shut down of the NPP. Such a chance is given now by investigating material from the former Greifswald NPP (VVER-440/230).In the first part the paper deals with fast neutron fluence calculations and retrospective dosimetry based on Niobium. Unfortunately, a second neutron reaction besides 93Nb(n,n’) leading to 93mNb-activity is the reaction 92Mo(n,γ)93Mo. Based on the found Nb and Mo contents in the RPV material, it turned out that the 93mNb generation on the Mo path mostly dominates over the fast neutron induced generation from Nb.The comparison between the calculated and the measured 93mNb activities typically resulted in deviations of 50%. Possible reasons for the observed differences are discussed.In the second part first results of fracture mechanic investigations are reported. SE(B) specimens from three thickness positions were tested and evaluated according to the test standard ASTM E1921-05. Cleavage fracture toughness values, KJc, were determined and Master Curve based reference temperatures (T0) were evaluated. The T0 measured at the inner surface of the RPV did not represent the conservative condition. The T0 of disc 1-1.3 located between the surface and 1/4 thickness is about 40K higher compared with those of the surface.The measured KJc values are not enveloped by the 5% fractile indexed with T0 according to the Master Curve concept. However, the 5% fractile indexed with the VERLIFE reference temperature RTTo that includes an additional margin envelops the measured KJc values. Therefore the VERLIFE lower bound curve conservatively describes the fracture toughness of the investigated weld metal. 相似文献
24.
Production, processing and properties of higher‐strength steel plates for application in wind energy plants. The mechanical and technological demands on steels for offshore wind energy plants are high. Advanced technologies in steel production make normalized or thermomechanically rolled plates with minimum yield strengths up to 460 MPa as well as quenched and tempered steels with minimum yield strengths from 520 up to 1100 MPa available for construction. Plates with up to 460 MPa are well established for building wind energy plants. Material properties and processing of these steel grades are well known. High‐strength steels offer further possibilities for construction. These steels are characterised by high yield strength and at the same time high toughness and excellent processing behaviour. By modern fracture mechanical safety concepts, it could be shown, that even under critical service conditions there can be guaranteed a high level of safety against brittle failure. 相似文献
25.
26.
In this paper we report on a newly developed multi-gate nanowire-field-effect device (NWFET) in which the transistor type (i.e. PMOS and NMOS) is freely selectable by the application of a control-voltage. This significantly adds to flexibility in design of integrated circuits and their fabrication, respectively. We will show, that the use of midgap Schottky-barrier source and drain contacts are the key enabler for this device concept to be functional. A fully functional freely configurable CMOS-NWFET inverter circuit is presented, demonstrating the capability of this SOI technology platform. All this makes the presented NWFET-technology suitable for the fabrication multi-purpose devices for many applications. 相似文献
27.
Gayatri Koyar Rane Udo Welzel Sai Ramudu Meka Eric Jan Mittemeijer 《Acta Materialia》2013,61(12):4524-4533
An anomalous dependence of the lattice parameter on the crystallite size of nanocrystalline ball-milled powders of metals was observed: lattice contraction followed by lattice expansion with decreasing crystallite size. These data were determined by application of detailed X-ray diffraction measurements. To this end the lattice parameters of the metals investigated – nickel, copper, iron and tungsten – were precisely determined by correcting for influences of stacking faults, in the face-centred cubic metals, as well as by correcting for instrument-related aberrations. The non-monotonic variation of the lattice constant was interpreted as the result of two competing mechanisms: interface-stress-induced contraction vs. expansion as a result of the stress field generated at the crystallite boundary due to the increased excess free volume in the crystallite boundary upon decreasing crystallite size. 相似文献
28.
A surface of epoxy-impregnated hardened cement paste was investigated using a novel atomic force microscopy (AFM) imaging mode that allows for the quantitative mapping of the local elastic modulus. The analyzed surface was previously prepared using focussed ion beam milling. The same surface was also characterized by electron microscopy and energy-dispersive X-ray spectroscopy.We demonstrate the capability of this quantitative nanomechanical mapping to provide information on the local distribution of the elastic modulus (from about 1 to about 100 GPa) with a spatial resolution in the range of decananometers, that corresponds to that of low-keV back-scattered electron imaging. Despite some surface roughness which affects the measured nanomechanical properties it is shown that topography, adhesion and Young's modulus can be clearly distinguished.The quantitative mapping of the local elastic modulus is able to discriminate between phases in the cement paste microstructure that cannot be distinguished from the corresponding back-scattered electron images. 相似文献
29.
30.
Hans-Juergen Odenthal Uwe Thiedemann Udo Falkenreck Jochen Schlueter 《Metallurgical and Materials Transactions B》2010,41(2):396-413
The oscillation of argon oxygen decarburization (AOD) converters is flow related and depends on the process parameters (e.g., vessel geometry, melt fill height, process gas type and blowing rate, vessel tilting angle, as well as geometry, number,
and arrangement of the side-wall nozzles). For a 120-ton AOD converter with seven submerged side-wall nozzles, plant tests,
physical simulations on a 1:4 scale water model, and computational fluid dynamics simulations have been done. The investigations
show that the penetration depth of an inert gas jet into the melt does not exceed approximately 0.4 m. The plumes are located
close to the nozzle-side converter wall and induce a large-scale primary vortex as well as intensive surface movements; both
are responsible for the oscillation. Several process mechanisms were investigated. The oscillation is highest in the last
stage of the dynamic blow and is still high during the reduction stage. As the amount of inert gas increases, the vibration
level also increases. Inert gas has a greater influence on the oscillation than oxygen. Tilting the converter around 8 deg
clearly leads to more intensive oscillations. Increasing the blowing rate increases the forces and torques acting on the vessel,
whereas the oscillation frequency remains nearly constant. A varying fill level does not influence the vibration level the
same way as the blowing rate. The operational test shows, for example, that the maximum torque does not depend on the heat
size when the latter varies between –8 pct and +21 pct of the nominal heat size. The water model test shows decreasing forces
and torques with a rising fill level. 相似文献