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   200篇
  免费   12篇
电工技术   5篇
化学工业   49篇
金属工艺   5篇
机械仪表   13篇
建筑科学   9篇
能源动力   8篇
轻工业   6篇
水利工程   1篇
无线电   14篇
一般工业技术   40篇
冶金工业   28篇
自动化技术   34篇
  2023年   5篇
  2022年   9篇
  2021年   3篇
  2020年   3篇
  2019年   1篇
  2018年   6篇
  2017年   9篇
  2015年   5篇
  2014年   9篇
  2013年   16篇
  2012年   10篇
  2011年   15篇
  2010年   16篇
  2009年   11篇
  2008年   9篇
  2007年   6篇
  2006年   7篇
  2005年   5篇
  2004年   10篇
  2003年   5篇
  2002年   3篇
  2001年   2篇
  2000年   1篇
  1999年   2篇
  1998年   6篇
  1997年   4篇
  1996年   6篇
  1995年   3篇
  1994年   2篇
  1993年   1篇
  1992年   1篇
  1990年   3篇
  1989年   2篇
  1988年   1篇
  1986年   1篇
  1985年   1篇
  1983年   1篇
  1982年   1篇
  1981年   1篇
  1980年   3篇
  1979年   2篇
  1973年   1篇
  1971年   2篇
  1968年   2篇
排序方式: 共有212条查询结果,搜索用时 78 毫秒
191.
Thanks to the massive success of mobile access devices such as netbooks or Apple’s iPhone 3G, Internet on the move has become one of the prominent features of today’s information society. With the emergence of wireless and mobile communication networks, the railroad industry is now catching up on this new technology in their battle with low-cost operators to bring more productivity and entertainment possibilities to its passengers. With millions of daily commuters as potential service users, this transport branch offers high business opportunities. However, while most field trials and research effort have mainly focused on the enabling technology, little research effort has been conducted to forecast the demand-side. This article tries to fill this gap by presenting original results gathered from a large-scale survey amongst 1324 regular train travellers. By means of the Product Specific Adoption Potential method, we predict the potential market penetration of wireless Internet services onboard trains and estimate the size and nature of five adopter segments in terms of socio-demographics, drivers and thresholds, willingness to pay, applications and quality of service. We will discuss the practical implications of these insights in order to develop viable business models, set up introduction strategies and build out user-driven infrastructure networks.  相似文献   
192.
A rapid, sensitive method for evaluating antioxidants is described. The antioxidant comparisons are based on minimizing β-carotene loss in an emulsified, aqueous, coupled oxidation of linoleic acid and β-carotene. The effects of linoleic acid levels were observed. Attempts to replace β-carotene with vitamin A or linoleic acid with ergosterol gave undesired results. The quantitative applications of the method are discussed.  相似文献   
193.
Purpose : In the last few years, serum and joint synovial fluid have been extensively analyzed for the proteomic research of rheumatoid arthritis (RA) biomarkers. Nonetheless, to date, there have been no studies investigating salivary biomarkers in this condition. Therefore, aim of this study is to investigate the presence of potential biomarkers of RA in human whole saliva. Experimental design : We combined 2‐DE and MS to analyze the whole saliva protein profile of 20 RA patients in comparison with 20 sex‐ and age‐matched healthy subjects. Results : Eight salivary proteins resulted differentially expressed, namely calgranulin A, calgranulin B, apolipoprotein A‐1, 6‐phosphogluconate dehydrogenase, peroxiredoxin 5, epidermal fatty acid‐binding protein, 78 kDa glucose‐regulated protein precursor (GRP78/BiP), and 14‐3‐3 proteins. It is particularly interesting that chaperone GRP78/BiP showed the greatest increase in RA patients. This finding was validated by Western Blot analysis and the over‐expression of GRP78/BiP appear to be distinctive of RA and drugs treatment independent. Conclusions and clinical relevance : This study provides a rationale for further studies aimed at evaluating any correlation between GRP78/BiP and different clinical/serological aspects of the disease in order to improve the diagnostic algorithms of RA.  相似文献   
194.
Ultralow noise measurements often require the application of signal processing and correction techniques to go beyond the noise performances of front-end amplifiers. In this paper, a new method for the voltage noise measurement is proposed, which allows, at least in principle, the complete elimination of the noise introduced by the amplifiers used for the measurements. This is obtained by resorting to the conventional cross-correlation technique for the elimination of the contribution of the equivalent input voltage noise of the amplifiers and by using a new three-step-measurement procedure that exploits different amplifier-configuration measurements in order to subtract the contribution of the equivalent input current noise of the amplifiers.  相似文献   
195.
Green synthesis of metal nanoparticles (NPs) has now received the attention of researchers due to ease of preparation and its potential to overcome hazards of these chemicals for an eco‐friendly milieu. In this study, copper oxide (CuO) NPs were synthesised via Desmodium gangeticum aqueous root extract and standard chemical method, further characterised by UV–visible spectroscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, Thermogravimetric analysis and scanning electron microscopy. The nephrotoxicity of the NP obtained from two routes were compared and evaluated at subcellular level in Wistar rat, renal proximal epithelial cells (LLC PK1 cell lines) and isolated renal mitochondria. CuO NP synthesised by chemical route showed prominent nephrotoxicity measured via adverse cytotoxicity to LLC PK1 cells, elevated renal oxidative stress and damage to renal tissue (determined by impaired alanine transaminase, aspartate transaminase, urea, uric acid and creatinine in the blood). However, at the level of cell organelle, CuO NP from both routes are non‐toxic to mitochondrial functional activity. The authors’ finding suggests that CuO NP synthesised by chemical route may induce nephrotoxicity, but may be overcome by co‐administration of antioxidants, as it is not mito‐toxic.Inspec keywords: cellular biophysics, scanning electron microscopy, toxicology, nanomedicine, oxidation, nanoparticles, enzymes, blood, visible spectra, X‐ray diffraction, biochemistry, nanofabrication, antibacterial activity, ultraviolet spectra, copper compounds, Fourier transform infrared spectra, molecular biophysics, thermal analysis, biological tissuesOther keywords: green synthesised copper oxide nanoparticles, murine model, metal nanoparticles, chemicals, eco‐friendly milieu, copper oxide NPs, standard chemical method, X‐ray diffraction, scanning electron microscopy, subcellular level, renal proximal epithelial cells, LLC PK1 cell lines, renal mitochondria, renal tissue, cell organelle, mitochondrial functional activity, UV‐visible spectroscopy, Fourier transform infrared spectroscopy, nephrotoxicity, renal oxidative stress, Desmodium gangeticum aqueous root extract, thermogravimetric analysis, Wistar rat, cytotoxicity, impaired alanine transaminase, aspartate transaminase, urea, uric acid, creatinine, blood, CuO  相似文献   
196.
Model based catalyst design is an emerging methodology in the development of new catalytic materials with properties tailored to the needs of specific industrial applications. A Single-Event MicroKinetic model (SEMK) was used to assess the hydrocracking behavior of n-dodecane, 4,4,6-trimethyl nonane and 2,5,8-trimethyl nonane, on a non-selective USY zeolite. The differences in cracking pattern exhibited by the various feed molecules provide guidelines for the control of the cracked product distribution through modifications of the zeolite pore structure. The connection of ZSM-22 type channels to the zeolite Y super cage is considered in this work. The percentage of C6 products obtained by central cracking in the chain can be increased from 25% up to 93% by the design of an appropriate zeolite topology combining USY-like super cages with ZSM-22 like channel segments. This is a promising approach for the development of zeolite catalysts for the selective hydrocracking of Fischer Tropsch waxes into middle distillates.  相似文献   
197.
Due to the lack of experimental data regarding two-phase flow through safety relief valves, a number of different calculation methods are presently available in the literature for their sizing. All these models mainly refer to the flow through an ideal nozzle, so that, in order to match the measured values, a discharge coefficient is to be introduced in the calculation, the coefficient thus depending on the model adopted. Furthermore, most of the available data are referred to a few operating conditions. As a result, none of the available models is presently considered sufficiently accurate to be used in a wide range of operating conditions.In the present paper, new data are produced on a steam/water flashing system through a real valve with different values of the main operating parameters (vapour quality, inlet pressure, mass flow rate, and backpressure). The measurements are compared with the predictions of a commonly used homogeneous equilibrium model (HEM), the so-called ω method, and show that the model markedly underestimates the mass flow rate in the whole range of conditions investigated. This unexpectedly implies the introduction of a two-phase discharge coefficient much higher than the vapour coefficient.Finally, a new correlation for the discharge coefficient as a function of the main operating parameters is proposed.  相似文献   
198.
This work proposes a cross‐correlation‐based trans‐impedance amplifier for current noise measurements in the low‐frequency range. The proposed solution is compared with the classical cross‐correlation trans‐impedance amplifier showing a lower background noise. Furthermore, a three‐step measurement method, based on the new trans‐impedance amplifier, is proposed to cancel the residual background noise. SPICE simulations and noise measurements performed on prototype circuits demonstrate the validity of the proposed approach. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   
199.
Recently, the concept of equal thermodynamic distance (ETD) has been proposed to minimize entropy production in a distillation process using a diabatic column. ETD gives the optimal temperature profile to first-order in N−1, where N is the number of trays. ETD, however, does not generally give the true minimum for distillation columns with few trays. We therefore apply a fully numerical, multidimensional optimization routine to determine minimum entropy production. Since this method does not depend on an underlying theory, we expect a true minimum to be revealed. We then compare the performance of ETD and numerical optimization by varying the number of trays and the purity requirements. Our results show a surprisingly good agreement between the ETD results and those obtained numerically.  相似文献   
200.
The independent cue technique has been developed to test traditional interference theories against inhibition theories of forgetting. In the present study, the authors tested the critical criterion for the independence of independent cues: Studied cues not presented during test (and unrelated to test cues) should not contribute to the retrieval process. Participants first studied a subset of cues (e.g., rope) that were subsequently studied together with a target in a 2nd study phase (e.g., rope–sailing, sunflower–yellow). In the test phase, an extralist category cue (e.g., sports, color) was presented, and participants were instructed to recall an item from the study list that was a member of the category (e.g., sailing, yellow). The experiments showed that previous study of the paired-associate word (e.g., rope) enhanced category cued recall even though this word was not presented at test. This experimental demonstration of covert cuing has important implications for the effectiveness of the independent cue technique. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
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