全文获取类型
收费全文 | 916篇 |
免费 | 22篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 19篇 |
综合类 | 2篇 |
化学工业 | 119篇 |
金属工艺 | 65篇 |
机械仪表 | 28篇 |
建筑科学 | 23篇 |
矿业工程 | 2篇 |
能源动力 | 54篇 |
轻工业 | 39篇 |
水利工程 | 18篇 |
石油天然气 | 5篇 |
无线电 | 127篇 |
一般工业技术 | 253篇 |
冶金工业 | 83篇 |
原子能技术 | 7篇 |
自动化技术 | 96篇 |
出版年
2024年 | 2篇 |
2023年 | 13篇 |
2022年 | 24篇 |
2021年 | 25篇 |
2020年 | 23篇 |
2019年 | 36篇 |
2018年 | 43篇 |
2017年 | 29篇 |
2016年 | 30篇 |
2015年 | 28篇 |
2014年 | 48篇 |
2013年 | 69篇 |
2012年 | 43篇 |
2011年 | 50篇 |
2010年 | 49篇 |
2009年 | 44篇 |
2008年 | 29篇 |
2007年 | 31篇 |
2006年 | 21篇 |
2005年 | 23篇 |
2004年 | 22篇 |
2003年 | 25篇 |
2002年 | 15篇 |
2001年 | 13篇 |
2000年 | 17篇 |
1999年 | 16篇 |
1998年 | 26篇 |
1997年 | 8篇 |
1996年 | 15篇 |
1995年 | 14篇 |
1994年 | 10篇 |
1993年 | 18篇 |
1992年 | 7篇 |
1991年 | 12篇 |
1990年 | 5篇 |
1989年 | 7篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 8篇 |
1985年 | 5篇 |
1984年 | 2篇 |
1983年 | 4篇 |
1981年 | 3篇 |
1980年 | 5篇 |
1977年 | 1篇 |
1976年 | 3篇 |
1970年 | 3篇 |
1968年 | 1篇 |
排序方式: 共有940条查询结果,搜索用时 15 毫秒
11.
Contents A Geodesic Constant Method (GCM) is outlined which provides a common approach to ray tracing on quadric cylinders in general, and yields all the surface ray-geometric parameters required in the UTD mutual coupling analysis of conformal antenna arrays in the closed form. The approach permits the incorporation of a shaping parameter which permits the modeling of quadric cylindrical surfaces of desired sharpness/flatness with a common set of equations. The mutual admittance between the slots on a general parabolic cylinder is obtained as an illustration of the applicability of the GCM.
Eine geodätische Konstanten-Methode zur Berechnung hochfrequenter wechselseitiger Kopplung zwischen Antennen auf allgemeinen Flächen zweiter Ordnung
Übersicht Dargelegt wird eine geodätische Konstanten-Methode (GKM), die einen gemeinsamen Zugang zur Strahlverfolgung auf allgemeinen Zylindern zweiter Ordnung bietet. Sie liefert sämtliche strahlengeometrischen oberflächenbezogenen Parameter, die in der Uniformen Geometrischen Beugungstheorie (UTD) für die wechselseitige Kopplungsanalyse konformer Antennenarrays benötigt werden, in geschlossener Form. Der Zugang gestattet die Einbeziehung eines Formparameters, der die Modellierung von Zylinderflächen zweiter Ordnung mit gewünschter Spitzigkeit/Flachheit durch ein und dasselbe Gleichungssystem zuläßt. Die erhaltene wechselseitige Admittanz zwischen Schlitzen auf einem allgemeinen parabolischen Zylinder dient zur Veranschaulichung der Anwendbarkeit der GKM.相似文献
12.
13.
The morphology and growth kinetics of discontinuous precipitation in a Zn-2.5 at % Cu alloy have been studied in the temperature range 383–583 K by optical and scanning electron microscopy. The precipitate phase has a lamellar morphology, and maintains a statistically constant interlamellar spacing under isothermal growth conditions. The interlamellar spacing increases with an increase in temperature. The isothermal growth kinetics in terms of reaction front migration rate is maximum at 523 K. The upper temperature limit for the occurrence of reaction in this alloy has been predicted to be 643 K. A detailed kinetic analysis of the experimental data using several analytical models has confirmed discontinuous precipitation in this system to be a boundary diffusion controlled reaction, and enabled the determination of the grain boundary chemical diffusivity of Cu in a Zn-rich Zn-Cu alloy in the temperature range studied. The corresponding activation energy values determined in this study, range between 65 to 86 kJ/mol–1, which compare well with the relevant data in the literature. 相似文献
14.
First-principles investigation of F-functionalized ZGNR/AGNR for nanoscale interconnect applications
Jatkar Mandar Jha Kamal K. Patra Sarat K. 《Journal of Computational Electronics》2021,20(4):1461-1470
Journal of Computational Electronics - Zigzag and armchair graphene nanoribbons (ZGNR and AGNR) have been investigated using the density functional theory (DFT) and nonequilibrium Green’s... 相似文献
15.
The influence of 3-aminopropyltriethoxysilane, 3-glycidyloxypropyltrimethoxysilane, and neoalkoxytric(dioctyl pyrophosphato)zirconate on thermal expansion behavior, dielectric strength, and arc resistance of mica/epoxy composites has been investigated. The addition of mica up to 30% resulted in the reduction of thermal expansion with respect to neat resin. However, the coefficient of linear thermal expansion of 30% mica treated with aminosilane was the least among the various coupling agent-coated filler/epoxy composites. Mica (30%)/epoxy composites showed the highest dielectric strength values (26 kV/mm), but the highest arc resistance was obtained in zirconate-treated mica (30%)/epoxy composite. © 1995 John Wiley & Sons, Inc. 相似文献
16.
A. Prasad S. K. Sen S. Varadrajan S. Jha 《Journal of Materials Engineering and Performance》1997,6(6):728-731
Localized swelling has been observed in 24Cr-24Ni-Nb steel transportation rollers used in the normalizing furnace of a plate
mill after prolonged service at high temperature. Due to high localized thermal and mechanical stresses, the chromia layer
formed on the roller surface ruptures, exposing the roller substrate to furnace oxygen. Oxidation of second-phase carbides
results in the formation of carbon monoxide at very high partial pressure. This leads to formation of voids, leading in turn
to localized swelling of the roller material. 相似文献
17.
S. Singh A.K. Jha S. Kumar 《International Journal of Machine Tools and Manufacture》2007,47(7-8):1101-1113
The present paper reports an investigation on the dynamic effects during sinter forging of axi-symmetric hollow disc preforms at room temperature. The preforms have been prepared by compacting the copper metal powder within the closed-cavity circular compaction dies and experiments have been conducted on computer-controlled hydraulic press to investigate the effect of die velocity, i.e. dynamic effects on various deformation characteristics, e.g. flow of material, densification during dry and lubricated interfacial friction conditions, bulging and strains at preform-free surfaces and die loads. The theoretical analysis for die pressure distribution, average die load and bulged profile by ‘upper bound’ approach has been presented. The identification of critical sinter-forging characteristics and their interrelationships are the cornerstones of present study. The effect of die velocity along with other deformation characteristics on die load and inertia energy dissipation has been investigated critically using ‘design of experiment’ technique and the important interactions have been displayed graphically using ‘response surface methodology’ technique. The study on dynamic effects revealed that die velocity is the most critical factor during sinter-forging operations, especially at higher die speeds and hence, inertia energy must be considered during its analysis. The experimental and theoretical results have been found in close agreement with each other and it is expected that the work will be highly useful for the assessment of various deformation characteristics during processing of sintered materials. 相似文献
18.
An empirical analysis was performed to compare the effectiveness of different approaches to training a set of procedural skills to a sample of novice trainees. Sixty-five participants were randomly assigned to one of the following three training groups: (1) learning-by-doing in a 3D desktop virtual environment, (2) learning-by-observing a video (show-and-tell) explanation of the procedures, and (3) trial-and-error. In each group, participants were trained on two car service procedures. Participants were recalled to perform a procedure either 2 or 4 weeks after the training. The results showed that: (1) participants trained through the virtual approach of learning-by-doing performed both procedures significantly better (i.e. p < .05 in terms of errors and time) than people of non-virtual groups, (2) the virtual training group, after a period of non-use, were more effective than non-virtual training (i.e. p < .05) in their ability to recover their skills, (3) after a (simulated) long period from the training—i.e. up to 12 weeks—people who experienced 3D environments consistently performed better than people who received other kinds of training. The results also suggested that independently from the training group, trainees’ visuospatial abilities were a predictor of performance, at least for the complex service procedure, adj R 2 = .460, and that post-training performances of people trained through virtual learning-by-doing are not affected by learning styles. Finally, a strong relationship (p < .001, R 2 = .441) was identified between usability and trust in the use of the virtual training tool—i.e. the more the system was perceived as usable, the more it was perceived as trustable to acquire the competences. 相似文献
19.
Extranasal Staphylococcus aureus colonization predisposes to bloodstream infections in patients on hemodialysis with noncuffed internal jugular vein catheters 下载免费PDF全文
Anand Devraj Venkata Siva Tez Pinnamaneni Manisha Biswal Raja Ramachandran Vivekanand Jha 《Hemodialysis international. International Symposium on Home Hemodialysis》2017,21(1):35-40
Introduction: Staphylococcal infection of endogenous origin is an important cause of morbidity and mortality in patients who receive hemodialysis (HD). The risk of such infections in nasal carriers of the organism is well defined. Extranasal carriage of the organism at extranasal sites may pose similar risks. Methods: A total of 70 patients about to undergo internal jugular vein catheterization for HD were enrolled in this prospective observational study. Swab cultures were obtained from anterior nares, posterior pharynx, axillae, toe web spaces, and vascular access sites at baseline and 1 week later. A patient was defined as a persistent carrier when the same organism was grown in both samples. Staphylococcus aureus bloodstream infections were assessed by blood and catheter tip cultures over a 90‐day period. Findings: The mean age of the patients was 43.71 ± 16.2 years. Persistent S. aureus carriage at anterior nares, throat, axilla, toe web spaces, vascular access site, and all sites was documented in 27.9%, 11.4%, 40%, 32.9%, 4.3%, and 64.2% of patients, respectively. Fifteen patients developed S. aureus infections. Catheter related S. aureus infections (CRI) were more likely in persistent carriers than nonpersistent carriers with odds ratios (95% CI) of 10.2 (2.8–37.1), 8.6 (1.7–42.2), 17.3 (3.4–86.0), 3.0 (0.9–9.8), and 1.9 (0.2–22.4) for anterior nares, throat, axilla, toe web spaces, and vascular access site carriers, respectively. The probability of developing CRI in persistent S. aureus carriers was 55% compared to none in noncarriers at 90 days (P = 0.04). Discussion: Extranasal S. aureus carriage is as significant a risk factor as nasal carriage for staphylococcal infections in patients on HD through catheters. The study is limited by lack of molecular phenotyping. 相似文献
20.
K. K. Pathak S. Lomash A. K. Jha N. Ramakrishnan 《Structural and Multidisciplinary Optimization》2010,40(1-6):491-496
This study is related to material modeling and die and process design of tube extrusion of γ iron. Strain dependent rate power law is used for material modeling whose coefficients are arrived at through genetic algorithm (GA). Die profile of the tube extrusion process is optimized to produce microstructurally sound product at maximum production speed and minimum left out material in the die. The design problem is formulated as a nonlinear programming problem which is solved using GA. Selection of the processing parameters is carried out using dynamic material modeling (DMM). Using this approach tube extrusion process of γ iron is successfully designed. 相似文献