首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   679篇
  免费   92篇
电工技术   3篇
综合类   11篇
化学工业   284篇
金属工艺   5篇
机械仪表   11篇
建筑科学   31篇
矿业工程   10篇
能源动力   32篇
轻工业   77篇
水利工程   4篇
石油天然气   1篇
无线电   41篇
一般工业技术   132篇
冶金工业   22篇
原子能技术   2篇
自动化技术   105篇
  2024年   1篇
  2023年   35篇
  2022年   40篇
  2021年   78篇
  2020年   29篇
  2019年   36篇
  2018年   29篇
  2017年   32篇
  2016年   36篇
  2015年   50篇
  2014年   49篇
  2013年   48篇
  2012年   52篇
  2011年   66篇
  2010年   36篇
  2009年   39篇
  2008年   25篇
  2007年   20篇
  2006年   8篇
  2005年   14篇
  2004年   6篇
  2003年   7篇
  2002年   3篇
  2001年   7篇
  2000年   3篇
  1999年   4篇
  1998年   3篇
  1997年   2篇
  1996年   3篇
  1995年   1篇
  1994年   4篇
  1993年   1篇
  1992年   1篇
  1991年   1篇
  1989年   1篇
  1936年   1篇
排序方式: 共有771条查询结果,搜索用时 15 毫秒
751.
The fungal metabolite Fosfonochlorin features a chloroacetyl moiety that is unusual within known phosphonate natural product biochemistry. Putative biosynthetic genes encoding Fosfonochlorin in Fusarium and Talaromyces spp. were investigated through reactions of encoded enzymes with synthetic substrates and isotope labelling studies. We show that the early biosynthetic steps for Fosfonochlorin involve the reduction of phosphonoacetaldehyde to form 2-hydroxyethylphosphonic acid, followed by oxidative intramolecular cyclization of the resulting alcohol to form (S)-epoxyethylphosphonic acid. The latter reaction is catalyzed by FfnD, a rare example of a non-heme iron/2-(oxo)glutarate dependent oxacyclase. In contrast, FfnD behaves as a more typical oxygenase with ethylphosphonic acid, producing (S)-1-hydroxyethylphosphonic acid. FfnD thus represents a new example of a ferryl generating enzyme that can suppress the typical oxygen rebound reaction that follows abstraction of a substrate hydrogen by a ferryl oxygen, thereby directing the substrate radical towards a fate other than hydroxylation.  相似文献   
752.
Axial temperature profiles of the vapor phase can provide valuable indication of the condensation process along the heat transfer path and highlight the impact of non-condensable gases on a unit's performance. The local measurements at moderate vacuum conditions for condensation of a binary mixture are presented alongside the implementation and assessment of optical sensors in a heat transfer process. The results show a good depiction of the characteristic temperature behavior during the condensation process. The relation between temperature, partial pressure and mole fractions are shown.  相似文献   
753.
The availability of silver as an electrically conductive filler material in printing pastes for solar cell metallization is becoming a more crucial issue for multiterawatt-scale production due to its global constraints. Therefore, the silver consumption for solar cell production needs to be reduced drastically by substituting silver with alternative conductive filler materials or utilizing process-specific phenomena. The phenomenon of filament stretching during microextrusion allows significantly lower paste laydowns. The magnitude of filament stretching is paste-dependent and therefore further knowledge of the pastes’ impact to the filament stretching is required. This study presents nine low-temperature curing pastes differing in the particle system and binder resin. The rheological and thermal behavior of these suspensions are investigated and printing tests onto silicon heterojunction (SHJ) precursors are carried out. Additionally, scanning electron microscopy (SEM)-based microstructure analyses of printed electrodes are performed. Based on these experimental results, the impact of paste compositions regarding the paste behavior during microextrusion and the SHJ solar cell performances are analyzed. The developed paste formulations exhibit a strong filament stretching, leading to a reduced silver laydown of down to ΔmAg = −60%rel. and an absolute efficiency gain of up to Δη = +0.75%abs. due to less shading losses.  相似文献   
754.
Frequent failures of power converters affect the availability of wind turbines and cause considerable maintenance costs. To enhance the reliability of power converters in wind turbines, the prevailing causes and modes of failures have to be identified. This publication contributes to root-cause analysis of the power-converter failures in wind turbines from a statistical point of view. For this purpose, the failure behavior of power-converters is modeled via lifetime models as well as repairable-system models. By means of regression models, covariates are incorporated, including both design-related and site-specific covariates. The analysis is based on a worldwide extensive field-data collection covering more than 9000 turbines, including different turbine designs, sites, and ages. The results obtained by means of the applied regression models indicate that the location of the power converter within the turbine, the cooling system, the converter rated power, the DC-link voltage, the IGBT-module manufacturer, and the commissioning date of the turbine as design-related covariates have a significant effect on the phase-module failure behavior and with that on converter reliability. Among the site-specific covariates, the analysis results confirm humidity as a likely significant driver of failures.  相似文献   
755.
Hydraulic drive train technology is widely used in both mobile and stationary systems, when high forces or torques are applied. In hydraulic components, high load levels must be supported due to increasing pressure levels of the fluid. Conventionally, leaded brass is used right against steel, where the lead not only aids the manufacturing process but also provides good tribological properties, such as low friction over a wide range of speeds and pressures. Currently promising lead-free coatings using high-speed laser material deposition (EHLA) will be implemented in a state-of-the-art axial piston pump.  相似文献   
756.
Oxide-based ceramics offer promising thermoelectric (TE) materials for recycling high-temperature waste heat, generated extensively from industrial sources. To further improve the functional performance of TE materials, their power factor should be increased. This can be achieved by nanostructuring and texturing the oxide-based ceramics creating multiple interphases and nanopores, which simultaneously increase the electrical conductivity and the Seebeck coefficient. The aim of this work is to achieve this goal by compacting electrospun nanofibers of calcium cobaltite Ca3Co4−xO9+δ, known to be a promising p-type TE material with good functional properties and thermal stability up to 1200 K in air. For this purpose, polycrystalline Ca3Co4−xO9+δ nanofibers and nanoribbons were fabricated by sol–gel electrospinning and calcination at intermediate temperatures to obtain small primary particle sizes. Bulk ceramics were formed by sintering pressed compacts of calcined nanofibers during TE measurements. The bulk nanofiber sample pre-calcined at 973 K exhibited an improved Seebeck coefficient of 176.5 S cm−1 and a power factor of 2.47 μW cm−1 K−2 similar to an electrospun nanofiber-derived ceramic compacted by spark plasma sintering.  相似文献   
757.
Creativity and Innovation Management has grown substantially over the last couple of years, both quantitatively and qualitatively. From 2016 to 2021, the number of submissions has grown from 287 to 395. Most of the growth was realized in Asia: The number of submissions from that continent increased from 72 in 2016 to 193 in 2021. The rest of the world remained (close to) stable: 215 in 2016 and 203 in 2021. Equally important, the Thomson ISI Impact Factor increased from 1.423 in 2015 to 3.051 in 2021 and further to 3.644 in 2022. This is not where our ambitions end, though. We want to be the ever-better outlet for authors researching, and practitioners working in, the fields we cover. Editing a journal with the ambition to continuously increase its quality while dealing with a substantial growth requires teamwork—teamwork among the editors and the editorial office, teamwork between the editors and their reviewers and, as surprising as this may sound, teamwork between the authors and their reviewers in a top-quality reviewing process. The purpose of this piece is to present and discuss some reviewing standards. In particular, we aim to share with our reviewers what we think is an excellent reviewing process. Furthermore, we formulate our ideas about what it is that makes a review an excellent one. The title of this piece is deliberately ambiguous. It denotes that Creativity and Innovation Management strives for reviewing excellence—as in an excellent reviewing process. It also denotes that we reach for the stars and hope to one day receive and, hence, review only excellent submissions.  相似文献   
758.
Prioritizing molecules for synthesis is a key role of computational methods within medicinal chemistry. Multiple tools exist for ranking molecules, from the cheap and popular molecular docking methods to more computationally expensive molecular-dynamics (MD)-based methods. It is often questioned whether the accuracy of the more rigorous methods justifies the higher computational cost and associated calculation time. Here, we compared the performance on ranking the binding of small molecules for seven scoring functions from five docking programs, one end-point method (MM/GBSA), and two MD-based free energy methods (PMX, FEP+). We investigated 16 pharmaceutically relevant targets with a total of 423 known binders. The performance of docking methods for ligand ranking was strongly system dependent. We observed that MD-based methods predominantly outperformed docking algorithms and MM/GBSA calculations. Based on our results, we recommend the application of MD-based free energy methods for prioritization of molecules for synthesis in lead optimization, whenever feasible.  相似文献   
759.
Despite the known health benefits and the potential for substituting less environmentally sustainable consumed foods such as meat, the current intake of pulses in developed countries remains less than recommended. Barriers are related to sensory characteristics and lack of knowledge about preparation, while drivers of environmental benefits are intangible. The aim of this study was to investigate the effect of additional information about health or environmental benefits of pulses on the acceptance of novel pulse-based products from chickpeas, black beans, and faba beans. Perceptions of these pulse-based spreads in a blind and informed stage were assessed with 202 consumers in urban and suburban areas of Denmark. In general, the familiar chickpea spread followed by the relatively most unfamiliar black bean spread was liked the most. Only for these two products, additional information increased hedonic perception, regardless of the context (health or environmental benefits). If consumers did not like the spread, as found for the faba bean spread, providing additional information did not significantly alter this perception. Participants’ preferences and willingness to pay (WTP) in a discrete choice experiment corresponded to hedonic scores, whereas providing additional information increased the WTP. These findings suggest that extrinsic cues such as health or environmental benefits may only be useful in products with an acceptable baseline taste profile. Moreover, black beans might be investigated as a promising source for further product development due to their acceptance by consumers besides being the comparably most unfamiliar pulse type.  相似文献   
760.
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号