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   528篇
  免费   21篇
  国内免费   1篇
电工技术   1篇
化学工业   123篇
金属工艺   10篇
机械仪表   18篇
建筑科学   28篇
能源动力   14篇
轻工业   34篇
水利工程   2篇
石油天然气   2篇
无线电   28篇
一般工业技术   131篇
冶金工业   76篇
原子能技术   4篇
自动化技术   79篇
  2024年   1篇
  2023年   7篇
  2022年   11篇
  2021年   13篇
  2020年   11篇
  2019年   8篇
  2018年   18篇
  2017年   19篇
  2016年   21篇
  2015年   15篇
  2014年   24篇
  2013年   46篇
  2012年   15篇
  2011年   39篇
  2010年   22篇
  2009年   24篇
  2008年   32篇
  2007年   23篇
  2006年   19篇
  2005年   17篇
  2004年   17篇
  2003年   14篇
  2002年   11篇
  2001年   10篇
  2000年   4篇
  1999年   14篇
  1998年   21篇
  1997年   13篇
  1996年   10篇
  1995年   5篇
  1994年   7篇
  1993年   2篇
  1992年   4篇
  1991年   1篇
  1990年   1篇
  1989年   1篇
  1988年   6篇
  1987年   1篇
  1985年   5篇
  1983年   3篇
  1982年   1篇
  1981年   1篇
  1980年   7篇
  1978年   1篇
  1977年   1篇
  1976年   2篇
  1975年   1篇
  1963年   1篇
排序方式: 共有550条查询结果,搜索用时 10 毫秒
41.
In the modern analogue design, Transistor Level Fault Simulation (TLFS) plays the important part since every fault in the whole circuit has to be simulated at that level. Unfortunately, it is a very CPU intensive task even though it maintains the high accuracy. Therefore, High Level Fault Modeling (HLFM) and High Level Fault Simulation (HLFS) are required in order to alleviate the efforts of simulation. In this paper, different HLFM approaches are reviewed at the device level during last two decades. We clarify their domains of application and evaluate their strengths and current limitations. We also analyze causes of faults and introduce various test approaches.  相似文献   
42.
Negative priming—the slowing of a response to an item that was recently ignored—was investigated in three groups: obsessive-compulsive disorder (OCD) checkers, OCD noncheckers, and nonclinical control participants. All groups performed both a standard negative priming task, selecting targets based on a perceptual feature (i.e., color), and a modified negative priming task, selecting targets based on a semantic feature (i.e., referent size). All three groups demonstrated significant negative priming in both tasks, although the negative priming was much larger in the novel, semantic task than in the common perceptual one. The findings suggest that patients with OCD do not demonstrate impairments in negative priming, contrary to earlier claims (Enright & Beech, 1990, 1993a, 1993b; Enright, Beech, & Claridge, 1995). (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
43.
Simulation of the autoclave manufacturing technique of composites can yield a preliminary estimation of induced residual thermal stresses and deformations that affect component fatigue life, and required tolerances for assembly. In this paper, an approach is proposed to simulate the autoclave manufacturing technique for unidirectional composites. The proposed approach consists of three modules. The first module is a thermo-chemical model to estimate the temperature and the degree of cure distributions in the composite part during the cure cycle. The second and third modules are a sequential stress analysis using FE-implicit and FE-explicit respectively. User-material subroutine is used to model the viscoelastic properties of the material based on theory of micromechanics.  相似文献   
44.
In this study, we investigated a new instrument: the Southampton Test of Empathy for Preschoolers (STEP). The test incorporated 8 video vignettes of children in emotional scenarios, assessing a child's ability to understand (STEP-UND) and share (STEP-SHA) in the emotional experience of a story protagonist. Each vignette included 4 emotions (angry, happy, fearful, sad) that reflected emotion judgments based on the protagonist's facial expression, situation, verbal cues, and desire. The STEP was administered to 39 preschool children, and internal reliability, concurrent validity, and construct validity were addressed. The results showed good internal consistency. They also highlighted moderate concurrent validity with parent-rated empathy, a measure of facial indices, and construct validity with teacher-rated prosocial behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
45.
In this study, polyhydroxybutyrate (PHB) nanoparticles were synthesised following nanoprecipitation method having different solvents and surfactant (Tween 80) concentrations. In this study, PHB nanoparticles were encapsulated with curcumin and subjected for sustained curcumin delivery. Both the curcumin loaded and unloaded PHB nanoparticles were characterised using FTIR, SEM, and AFM. Sizes of the particles were found to be between 60 and 300 nm. The drug encapsulation efficiency and in vitro drug release of the nanoparticles were analysed. Antibacterial activity and anticancer activity were also evaluated. The LC50 values of most of the nanoparticles were found to be between 10 and 20 µg/100 µl, anticancer activity of curcumin loaded PHB nanoparticles were further confirmed by AO/PI staining and mitochondrial depolarisation assay.Inspec keywords: encapsulation, cancer, scanning electron microscopy, nanoparticles, surfactants, drugs, nanofabrication, antibacterial activity, biomedical materials, drug delivery systems, polymers, nanomedicine, Fourier transform infrared spectra, precipitation (physical chemistry), atomic force microscopy, particle sizeOther keywords: surfactant‐mediated synthesis, polyhydroxybutyrate nanoparticles, sustained drug delivery, surfactant concentrations, PHB nanoparticles, sustained curcumin delivery, drug encapsulation efficiency, anticancer activity, in vitro drug release, nanoprecipitation method, Tween 80, FTIR spectra, SEM, AFM, particle sizes, antibacterial activity, AO‐PI staining, mitochondrial depolarisation assay  相似文献   
46.
Water is a basic necessity of man. Economical and efficient production or recycling of water is very much needed in today's world. Solar still has emerged as a life-saving technology to distil brackish water and produce drinkable water using solar energy. The aim of this project was to improve the performance of solar still by adding an air blower which creates a bubbling effect in the still due to which the evaporation rate increases. The bubbling effect using the blower makes the raw water to circulate and to distribute heat energy equally. The evaporated raw water was collected in the glass plate as drop particles. The drop condenses due to ambient air and finally distillate output is collected in the jar, which is placed outside the still. The solar still with air blower arrangement gave higher difference in efficiency and higher distilled output when compared with solar still without an air blower.  相似文献   
47.
The one-step PCR-mediated technique used for modification of chromosomal loci is a powerful tool for functional analysis in yeast. Both Saccharomyces cerevisiae and Schizosaccharomyces pombe are amenable to this technique. However, the scarce availability of selectable markers for Sz. pombe hampers the easy use of this technique in this species. Here, we describe the construction of new vectors deriving from the pFA6a family, which are suitable for tagging in both yeasts owing to the presence of a nourseothricin-resistance cassette. These plasmids allow various gene manipulations at chromosomal loci, viz. N- and C-terminal tagging with 3HA (haemagglutinin) or 13Myc epitopes, GST (glutathione S-transferase), 4TAP (tandem affinity purification) and several GFP (green fluorescent protein) isoforms. For N-terminal modifications, the use of different promoters allows constitutive (PADH1) or regulatable (PGAL1) promoters for S. cerevisiae and derivatives of Pnmt1 for Sz. pombe expression.  相似文献   
48.
Soda-ash roasting of the chromite mineral is commonly used worldwide for the production of watersoluble sodium chromate. The formation of sodium chromate during the soda-ash roasting reaction depends on the oxygen partial pressure and availability of oxygen at the reaction front. The effects of temperature, oxygen partial pressure, charge composition, and their roles on the overall roasting reaction were studied in order to analyze the reaction mechanism. The influence of process parameters such as the addition of alkali and process residue as the filler material on the overall reaction rate is discussed. The rate-determining steps for the soda-ash roasting reaction are analyzed. The importance of the binary Na2CO3-Na2CrO4 liquid phase during the reaction in determining its speed is also examined. It is shown that the experimental results for the roasting reaction can be best described by the Ginstling and Brounshtein (GB) equation for diffusion-controlled kinetics. From the measured kinetics data, the apparent activation energy for the roasting reaction was calculated to be between 180 and 190 kJ · mol−1 in the temperature range from 1023 to 1210 K and between 35 and 40 kJ · mol−1 above 1210 K.  相似文献   
49.
Developing Pt-free catalysts for hydrogen oxidation reaction (HOR) in alkaline solution is becoming a key challenge in the development of anion exchange membrane fuel cells and electrochemical reactors. Herein, we present the preparation, HOR activity, and stability of Pd-decorated tungsten (Pd-d-W) catalysts. The Pd-d-W catalysts were prepared by the chemically activated surface of tungsten nanoparticles by Pd ions. The resultant bimetallic catalysts consisted of crystalline phases of both Pd and W nanoparticles. The CO stripping voltammograms and H-desorption (Hdes) peak potential of hydrogen desorption in Pd suggests that the enhancement of HOR catalytic activity observed in Pd-d-W catalyst can be ascribed to the modification of electronic property of Pd and availability of OHad near-surface Pd atoms.  相似文献   
50.
Drug molecules must cross multiple cell membrane barriers to reach their site of action. We present evidence that one of the largest classes of pharmaceutical drug molecules, the cationic amphiphilic drugs (CADs), does so via a catalytic reaction that degrades the phospholipid fabric of the membrane. We find that CADs partition rapidly to the polar-apolar region of the membrane. At physiological pH, the protonated groups on the CAD catalyse the acid hydrolysis of the ester linkage present in the phospholipid chains, producing a fatty acid and a single-chain lipid. The single-chain lipids rapidly destabilize the membrane, causing membranous fragments to separate and diffuse away from the host. These membrane fragments carry the drug molecules with them. The entire process, from drug adsorption to drug release within micelles, occurs on a time-scale of seconds, compatible with in vivo drug diffusion rates. Given the rate at which the reaction occurs, it is probable that this process is a significant mechanism for drug transport.  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