全文获取类型
收费全文 | 502篇 |
免费 | 21篇 |
专业分类
电工技术 | 2篇 |
化学工业 | 133篇 |
金属工艺 | 9篇 |
机械仪表 | 9篇 |
建筑科学 | 42篇 |
矿业工程 | 1篇 |
能源动力 | 6篇 |
轻工业 | 26篇 |
无线电 | 27篇 |
一般工业技术 | 94篇 |
冶金工业 | 16篇 |
原子能技术 | 12篇 |
自动化技术 | 146篇 |
出版年
2023年 | 6篇 |
2022年 | 6篇 |
2021年 | 22篇 |
2020年 | 13篇 |
2019年 | 7篇 |
2018年 | 11篇 |
2017年 | 11篇 |
2016年 | 21篇 |
2015年 | 15篇 |
2014年 | 27篇 |
2013年 | 31篇 |
2012年 | 35篇 |
2011年 | 43篇 |
2010年 | 28篇 |
2009年 | 30篇 |
2008年 | 27篇 |
2007年 | 39篇 |
2006年 | 23篇 |
2005年 | 22篇 |
2004年 | 14篇 |
2003年 | 14篇 |
2002年 | 13篇 |
2001年 | 5篇 |
2000年 | 9篇 |
1999年 | 8篇 |
1998年 | 7篇 |
1997年 | 9篇 |
1996年 | 1篇 |
1995年 | 4篇 |
1994年 | 2篇 |
1993年 | 2篇 |
1992年 | 5篇 |
1988年 | 2篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1985年 | 2篇 |
1984年 | 1篇 |
1981年 | 1篇 |
1980年 | 1篇 |
1975年 | 1篇 |
1974年 | 2篇 |
排序方式: 共有523条查询结果,搜索用时 11 毫秒
91.
92.
93.
Heiko T. Liebel Marie S. Stølen Bjørn S. Frengstad Randi K. Ramstad Bjørge Brattli 《Bulletin of Engineering Geology and the Environment》2012,71(2):235-243
Thermal response tests (TRTs) are used to measure the effective thermal conductivity in boreholes. The results serve as a
basis for the dimensioning of commercial ground-source heat pump installations with closed loop systems. The study evaluated
the reliability of TRTs performed in winter by comparing two TRTs carried out under very different winter weather conditions.
A third TRT elucidated the influence of convection in wells with a higher heat input. Rock cores were analysed for quartz
content and these results and the laboratory-measured thermal conductivity data were compared with the TRT results. This highlighted
the importance of the distribution and orientation of minerals in the rock, and that a high quartz content does not necessarily
give high thermal conductivity values. It is concluded that winter TRTs give useful results if additional temperature loggers
are installed in anticipated fracture zones to detect groundwater flow and to survey the effect of infiltrating water. 相似文献
94.
Anthropogenic tracers, endocrine disrupting chemicals, and endocrine disruption in Minnesota lakes 总被引:1,自引:0,他引:1
Writer JH Barber LB Brown GK Taylor HE Kiesling RL Ferrey ML Jahns ND Bartell SE Schoenfuss HL 《The Science of the total environment》2010,409(1):100-111
Concentrations of endocrine disrupting chemicals and endocrine disruption in fish were determined in 11 lakes across Minnesota that represent a range of trophic conditions and land uses (urban, agricultural, residential, and forested) and in which wastewater treatment plant discharges were absent. Water, sediment, and passive polar organic integrative samplers (POCIS) were analyzed for steroidal hormones, alkylphenols, bisphenol A, and other organic and inorganic molecular tracers to evaluate potential non-point source inputs into the lakes. Resident fish from the lakes were collected, and caged male fathead minnows were deployed to evaluate endocrine disruption, as indicated by the biological endpoints of plasma vitellogenin and gonadal histology. Endocrine disrupting chemicals, including bisphenol A, 17β-estradiol, estrone, and 4-nonylphenol were detected in 90% of the lakes at part per trillion concentrations. Endocrine disruption was observed in caged fathead minnows and resident fish in 90% of the lakes. The widespread but variable occurrence of anthropogenic chemicals in the lakes and endocrine disruption in fish indicates that potential sources are diverse, not limited to wastewater treatment plant discharges, and not entirely predictable based on trophic status and land use. 相似文献
95.
96.
Martin Schaper Jan Schmidt Heiko Plagwitz Rolf Brendel 《Progress in Photovoltaics: Research and Applications》2005,13(5):381-386
We have developed a crystalline silicon solar cell with amorphous silicon (a‐Si:H) rear‐surface passivation based on a simple process. The a‐Si:H layer is deposited at 225°C by plasma‐enhanced chemical vapor deposition. An aluminum grid is evaporated onto the a‐Si:H‐passivated rear. The base contacts are formed by COSIMA (contact formation to a‐Si:H passivated wafers by means of annealing) when subsequently depositing the front silicon nitride layer at 325°C. The a‐Si:H underneath the aluminum fingers dissolves completely within the aluminum and an ohmic contact to the base is formed. This contacting scheme results in a very low contact resistance of 3.5 ±0.2 mΩ cm2 on low‐resistivity (0.5 Ω cm) p‐type silicon, which is below that obtained for conventional Al/Si contacts. We achieve an independently confirmed energy conversion efficiency of 20.1% under one‐sun standard testing conditions for a 4 cm2 large cell. Measurements of the internal quantum efficiency show an improved rear surface passivation compared with reference cells with a silicon nitride rear passivation. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
97.
Localized Collection of Airborne Analytes: A Transport Driven Approach to Improve the Response Time of Existing Gas Sensor Designs 下载免费PDF全文
Jun Fang Se‐Chul Park Leslie Schlag Thomas Stauden Jörg Pezoldt Heiko O. Jacobs 《Advanced functional materials》2014,24(24):3706-3714
The detection of single binding has been a recent trend in sensor research introducing various sensor designs where the active sensing elements are nanoscopic in size. Currently, transport and collection of airborne analytes for gas sensors is either diffusion based or non‐localized and it becomes increasingly unlikely for analytes to interact with sensing structures where the active area is shrunk, trading an increased sensitivity with a slow response time. This report introduces a corona discharge based analyte charging method and an electrodynamic nanolens based analyte concentration concept to effectively transport airborne analytes to sensing points to improve the response time of existing gas sensor designs. Localized collection of analytes over a wide range, including microscopic particles, nanoparticles, and small molecules, is demonstrated. In all cases, the collection rate is several orders of magnitudes higher than in the case where the collection is driven by diffusion. The collection scheme is integrated on an existing SERS (surface‐enhanced Raman spectroscopy) based sensor. In terms of response time, the process is able to detect analytes at 9 ppm (parts per million) within 1 s. As a comparison, 1 h is required to reach the same signal level when diffusion‐only‐transport is used. 相似文献
98.
Andrzej Dziedzic Leszek J. Golonka Jaroslaw Kita Heiko Thust Karl-Heinz Drue Reinhard Bauer Lars Rebenklau Klaus-Jurgen Wolter 《Microelectronics Reliability》2001,41(5)
This paper presents systematic investigations of electrical and stability properties of various low temperature co-fired ceramics (LTCC) resistors. One of the goals of this work was to check the compatibility of LTCC materials (tapes, resistive and conductive inks) from various manufacturers. Three commercially available green tapes and three LTCC resistor/conductor systems were examined. The resistive inks with 1 kΩ/sq. nominal sheet resistance were used. Buried (inside) and surface resistors were laminated and fired according to the tape manufacturers’ recommendations. The influence of dimensional effect on sheet resistance and hot temperature coefficient of resistance, the temperature dependence of resistance in a wide temperature range (from −180°C to +130°C), long-term stability of thermally aged as-fired resistors (150°C, 500 h) and durability to high-voltage micro- or nanosecond pulses (50 ns pulses with 4000 V/mm maximum electric field or 10 μs ones with 700–1000 V/mm electrical field) were carried out for electrical and stability characterisation of LTCC resistors. Non-destructive scanning acoustic microscope diagnostics was applied for structure investigation and estimation of lamination and cofiring process quality of buried LTCC resistors. 相似文献
99.
100.
Proffitt Dennis R.; Rock Irvin; Hecht Heiko; Schubert Jim 《Canadian Metallurgical Quarterly》1992,18(1):3
The stereokinetic effect (SKE) has been defined and studied by nested circular patterns rotating on a turntable. Circles must appear not to rotate as they revolve, which in turn results in their appearing to translate relative to one another. A powerful illusion of object depth results even though the individual circles do not undergo an appropriate foreshortening consistent with their apparent changes in slant. It is suggested and tested that the SKE is based on the changing positions between the nested contours despite the absence of any change within each contour, whereas the kinetic depth effect (KDE) entails both kinds of change. It follows that a turntable method of presentation is not necessary, and between-contour transformations can be stimulated by computer animation. Displays consisting of simple translations were shown to evoke robust depth impressions as were patterns consisting of contours of varying shapes. Comparisons of the depth, compellingness, and rigidity of matched SKE and KDE displays are reported. The SKE is taken to be paradigmatic for how the visual system perceives depth when observing small object rotations that occur in everyday situations. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献