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   109篇
  免费   10篇
电工技术   1篇
化学工业   23篇
金属工艺   2篇
机械仪表   1篇
建筑科学   13篇
能源动力   8篇
轻工业   28篇
无线电   6篇
一般工业技术   15篇
冶金工业   9篇
自动化技术   13篇
  2023年   3篇
  2022年   4篇
  2021年   3篇
  2020年   3篇
  2019年   5篇
  2018年   6篇
  2017年   7篇
  2016年   2篇
  2015年   9篇
  2014年   6篇
  2013年   9篇
  2012年   2篇
  2011年   9篇
  2010年   6篇
  2009年   6篇
  2008年   4篇
  2007年   4篇
  2006年   5篇
  2005年   4篇
  2004年   3篇
  2003年   6篇
  2002年   1篇
  2001年   1篇
  1998年   3篇
  1997年   1篇
  1996年   1篇
  1995年   1篇
  1994年   3篇
  1982年   1篇
  1980年   1篇
排序方式: 共有119条查询结果,搜索用时 2 毫秒
91.
Due to its ferroelectricity, hafnium oxide has attracted a lot of attention for ferroelectric memory devices. Amongst different dopant elements, zirconium is found to be beneficial due to the relatively low crystallization temperature of hafnium-zirconium-oxide (HZO), thus it is back-end-of-line (BEoL) compatible. The thickness of HZO has a significant impact on ferroelectric device reliability. High operation temperatures and high endurance are important criteria depending on the application. Herein, various HZO thicknesses (7, 8, and 10 nm) in MFM (metal-ferroelectric-metal) capacitors are investigated at varying operation temperatures (25 to 175 °C) at varying electric fields (±3 to ±5.4 MV cm−1) with respect to polarization, leakage current, endurance, and retention. 7 nm HZO showed promising results with an endurance of 107 cycles, with a low leakage current density, and almost no retention loss after 10 years. Extrapolated results at operation conditions (±2 MV cm−1 and 10 MHz) showed an endurance of 1010 cycles.  相似文献   
92.
Regarding the aim of a CO2-neutral society by 2050, one target is to use the largest possible amount of the initial feedstock within the bioeconomy. In that context it is necessary to utilize also low-value biomass in biorefineries. For wet streams, hydrothermal processes can make an efficient thermochemical application possible. To be used as transport fuel, strict limitations from national and international standards have to be fulfilled, e.g., regarding oxygen content. To reach these boundaries, commonly multistage approaches have to be applied. Within this framework utilization of hydrogen donors can be beneficial. Basic calculations of costs and greenhouse gas emissions are given for an exemplary case.  相似文献   
93.
The objectives of this study were (1) to analyze the agreement of a standard laboratory ELISA for progesterone (P4) with an automated on-farm ELISA kit operated under commercial conditions in 1,297 milk samples from 50 dairy cows; (2) to study the influence of the method of detection of luteal activity on genetic parameters of fertility traits based on P4 measured with an automated on-farm ELISA once weekly from wk 3 to 9 postpartum in the milk of 1,304 cows; and (3) to study the influence of sampling frequency (once or twice weekly from wk 3 to 9) on the same traits from 296 cows. Luteal activity can be detected when there is an active corpus luteum in the ovary producing P4 and indicating the onset of reproductive cyclicity after calving. The on-farm ELISA overestimated P4 contents by a mean square error of prediction of 2.76 ng/mL and had an intermediate Spearman correlation with the laboratory kit (0.54). For the second objective, the postpartum interval to the commencement of luteal activity (C-LA), proportion of luteal activity between d 15 and 63 postpartum (P-LA), calculated as the number of samples above the threshold for high P4 values divided by the number of all samples, and delay of first ovulation (DOV1), defined as C-LA occurring later than d 45 postpartum, were derived from the P4 profiles. Both C-LA and DOV1 were determined by (a) thorough qualitative visual inspection of the profile, (b) the profile's mean as threshold for the first increase in P4 postpartum, indicating commencement of luteal activity, and (c) 3 ng/mL as threshold for the first increase in P4, a value that has been used by many other studies. Similarly, P-LA was determined by using methods (b) and (c). Estimates of heritability were 0.04 to 0.13 for C-LA, 0.12 to 0.23 for P-LA, and 0.03 to 0.07 for DOV1. Genetic correlation of P-LA with C-LA and with the profile's mean P4 was ?1.00. The profile's mean had a higher estimate of heritability (0.11–0.12) than C-LA or DOV1. It can be calculated as the arithmetic mean of all P4 values of a profile, whereas C-LA, P-LA, and DOV1 need a definition of a threshold for high P4 values. We therefore suggest the profile's mean as a promising candidate for further research. For the third objective, once-weekly sampling was mimicked by neglecting every second sample, and C-LA and DOV1 shifted toward a later onset of cyclicity. Thus, a common standard for sampling regimen and detection algorithm is essential to avoid incompatibility between studies.  相似文献   
94.
Communication deviance (CD), forms of communication that are not bizarrely thought disordered but are hard to follow and that make difficult the consensual sharing of attention and meaning, has been hypothesized as a nonspecific contributor of rearing parents to psychopathology of offspring, including schizophrenia. This hypothesis, or an alternative of genetic transmission, would gain plausibility if CD has long-term stability. CD was evaluated, using tape-recorded and reliably scored Rorschachs in 158 Finnish adoptees, and retested after a median interval of 11 years. Adolescent CD was not stably correlated with follow-up CD. However, initial CD at a mean age of 32 and follow-up CD were significantly correlated. Gender, genetic risk for schizophrenia, and DSM-III-R (American Psychiatric Association, 1987) psychiatric diagnoses had no effect on adult CD stability. CD appears to be a stable, traitlike feature of adult but not adolescent functioning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
95.
    
In this study, the effects of process parameters for joining of AISI 1010 low carbon steel and copper alloys by friction welded were investigated. Low carbon steel and commercial copper each of 12 mm diameter was used to fabricate the joints. The friction welding tests were carried out using a direct-drive type friction welding machine which was designed and manufactured for this purpose by us. After friction welding, in order to determine the microstructural changes that occurred, the interface regions of the welded specimens were examined by means of OM, SEM, EDS and X-Ray analysis. Microhardness and tensile tests were conducted to determine the mechanical properties of the welded specimens. The experimental results indicated that AISI 1010 low carbon steel could be joined to copper using the friction welding technique and for achieving a welding with a sufficient strength, the friction time has to be held as short as possible, while the rotational speed, friction and forging pressure has to be as high as possible. Tensile strength values also confirmed this result and at the interface did not occurred intermetallic phases. The maximum tensile strength of 294,67 MPa could be obtained for the joints welded under the welding conditions of rotation speed of 2300 rpm, friction pressure of 40 MPa, forging pressure of 80 MPa, friction time of 6 s and forging time of 3 s.  相似文献   
96.
The aim of this study is to present an overall view of friction stir processing (FSP), including the method, the state‐of‐the‐art regarding current studies, and possible applications. FSP is a solid‐state thermo‐mechanical processing method. It can be used to produce defect‐free, recrystallized, homogeneous, fine grained microstructures. Structures can be processed at specific locations, through‐section or to a desired depth, or entirely. The benefits obtained with FSP include elimination of casting defects and refinement of microstructures resulting in improved strength, ductility, resistance to corrosion and fatigue, and formability (including high strain rate superplasticity). Alsosurface composites can be produced by FSP.  相似文献   
97.
Mass spectrometry-based analysis of whole-grain phytochemicals   总被引:1,自引:0,他引:1  
Whole grains are a rich source of several classes of phytochemicals, such as alkylresorcinols, benzoxazinoids, flavonoids, lignans, and phytosterols. A high intake of whole grains has been linked to a reduced risk of some major noncommunicable diseases, and it has been postulated that a complex mixture of phytochemicals works in synergy to generate beneficial health effects. Mass spectrometry, especially when coupled with liquid chromatography, is a widely used method for the analysis of phytochemicals owing to its high sensitivity and dynamic range. In this review, the current knowledge of the mass spectral properties of the most important classes of phytochemicals found in cereals of common wheat, barley, oats, and rye is discussed.  相似文献   
98.
Abstract

Event tourism has become an important economic component of modern tourism, given the growing numbers of visitors and the development of local communities that it entails. This study examines whether the distances traveled by foreign visitors to events differ from those traveled by non-event (i.e., regular) visitors, and which factors influence such distances. We use passive mobile positioning data obtained from visitors to 145 events in Estonia (119,288 visits) and from a comparison group of regular visitors (199,859 visits) between 2006 and 2009. The results show that events visitors come from nearer locations than regular visitors; similarly to regular visitors, the distance decay principle applies in case of events visitors; and that events bring more visitors from more distant countries in the off-season (winter).  相似文献   
99.
The valine at position 82 (Val 82) in the active site of the human immunodeficiency virus (HIV) protease mutates in response to therapy with the protease inhibitor ritonavir. By using the X-ray crystal structure of the complex of HIV protease and ritonavir, the potent protease inhibitor ABT-378, which has a diminished interaction with Val 82, was designed. ABT-378 potently inhibited wild-type and mutant HIV protease (Ki = 1.3 to 3.6 pM), blocked the replication of laboratory and clinical strains of HIV type 1 (50% effective concentration [EC50], 0.006 to 0.017 microM), and maintained high potency against mutant HIV selected by ritonavir in vivo (EC50, 50-fold after 8 h. In healthy human volunteers, coadministration of a single 400-mg dose of ABT-378 with 50 mg of ritonavir enhanced the area under the concentration curve of ABT-378 in plasma by 77-fold over that observed after dosing with ABT-378 alone, and mean concentrations of ABT-378 exceeded the EC50 for >24 h. These results demonstrate the potential utility of ABT-378 as a therapeutic intervention against AIDS.  相似文献   
100.
Design of new materials for nanostructured dye solar cells (DSC) requires understanding the link between the material properties and cell efficiency. This paper gives an overview of the fundamental and practical aspects of the modeling and characterization of DSCs, and integrates the knowledge into a user‐friendly DSC device model. Starting from basic physical and electrochemical concepts, mathematical expressions for the IV curve and differential resistance of all resistive cell components are derived and their relation to electrochemical impedance spectroscopy (EIS) is explained. The current understanding of the associated physics is discussed in detail and clarified. It is shown how the model parameters can be determined from complete DSCs by current dependent EIS and incident‐photon‐to‐collected‐electron (IPCE) measurements, supplemented by optical characterization, and used to quantify performance losses in DSCs. The paper aims to give a necessary theoretical background and practical guidelines for establishing an effective feedback‐loop for DSC testing and development.  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