全文获取类型
收费全文 | 982篇 |
免费 | 39篇 |
专业分类
电工技术 | 8篇 |
化学工业 | 240篇 |
金属工艺 | 23篇 |
机械仪表 | 19篇 |
建筑科学 | 17篇 |
能源动力 | 49篇 |
轻工业 | 68篇 |
水利工程 | 2篇 |
石油天然气 | 4篇 |
无线电 | 124篇 |
一般工业技术 | 196篇 |
冶金工业 | 152篇 |
原子能技术 | 12篇 |
自动化技术 | 107篇 |
出版年
2023年 | 9篇 |
2022年 | 28篇 |
2021年 | 20篇 |
2020年 | 22篇 |
2019年 | 13篇 |
2018年 | 36篇 |
2017年 | 33篇 |
2016年 | 29篇 |
2015年 | 18篇 |
2014年 | 31篇 |
2013年 | 79篇 |
2012年 | 35篇 |
2011年 | 32篇 |
2010年 | 30篇 |
2009年 | 49篇 |
2008年 | 22篇 |
2007年 | 23篇 |
2006年 | 31篇 |
2005年 | 16篇 |
2004年 | 16篇 |
2003年 | 21篇 |
2002年 | 13篇 |
2001年 | 8篇 |
2000年 | 20篇 |
1999年 | 17篇 |
1998年 | 38篇 |
1997年 | 24篇 |
1996年 | 34篇 |
1995年 | 17篇 |
1994年 | 18篇 |
1993年 | 22篇 |
1992年 | 18篇 |
1991年 | 11篇 |
1990年 | 11篇 |
1989年 | 11篇 |
1988年 | 11篇 |
1987年 | 9篇 |
1986年 | 8篇 |
1985年 | 14篇 |
1984年 | 12篇 |
1983年 | 13篇 |
1982年 | 10篇 |
1981年 | 8篇 |
1980年 | 16篇 |
1979年 | 14篇 |
1978年 | 12篇 |
1977年 | 9篇 |
1976年 | 11篇 |
1975年 | 7篇 |
1974年 | 5篇 |
排序方式: 共有1021条查询结果,搜索用时 0 毫秒
1.
Kumari Asha Neeraj Kumar Biswas Sakshi Saxena Vibha Rani Satsangi Rohit Shrivastav Rama Kant Sahab Dass 《International Journal of Hydrogen Energy》2021,46(40):20858-20870
The present study attempts quantitative determination of changes in the morphological surface features viz. fractal dimension, lower and upper cut off length scale through Power Spectral Density analysis prior to and after irradiation of 100 KeV Ar+ ion beam at incidence angles of 0°, 40° and 60° on ZnO thin films. All the unirradiated and irradiated samples are subjected to photoelectrochemical characterization and a correlation between photoelectrochemical performance and morphological parameters is established. Sample irradiated at 40° angle at the fluence of 5 × 1016 ions/cm2 is found to possess maximum fractal dimension of 2.72, lower and upper cut off length scale of 3.16 nm and 63.00 nm respectively. This sample exhibits maximum photocurrent density of 3.19 mA/cm2 and applied bias photon-to-current efficiency of 1.12% at 1.23 V/RHE. Hydrogen gas collected for duration of 1 h for the same sample was ~4.83 mLcm?2. 相似文献
2.
In a prospective study of layered versus mass closure of abdominal incisions in infants and children, 34 cases underwent wound closure by layered and mass closure technique on an alternate basis. All the patients were assessed for their nutritional status and haemoglobin level pre-operatively, and wound complications were compared with respect to closure technique, nutritional status and normal haemoglobin level. Presence of protein energy malnutrition and anaemia did not increase the risk of wound complications with either of the technique. 相似文献
3.
4.
The present study was aimed at understanding the response of 2014 Al alloy dispersed with graphite particles in various corrosive environments. Marine (sodium chloride) as well as acidic media were selected for the purpose with a view to widen the range of utility of the composite for applications where such environments may be encountered. Studies were also extended to characterize the corrosion resistance of the composite in fresh as well as used lubricating oils to explore the possibilities of using it in bearing, bushing and such other applications. The corrosion behaviour of the base alloy processed under identical conditions was also examined in the above media to see the influence of graphite addition in the alloy. In order to assess the role of the matrix microstructure, the composite as well as the base alloy was subjected to corrosion in heat-treated as well as-cast conditions. It was observed that the specimens suffered from the maximum rate of corrosion in acid, while sodium chloride produced the minimum corrosion rate. Oil in both used and fresh conditions revealed a negligibly small extent of corrosion. The composite was found to show a higher rate of corrosion than the base alloy under identical test conditions. This was attributed to the dispersoid/matrix interfacial corrosion in the case of the graphitic aluminium alloy. Heat treatment of the composite and the base alloy was found to lower the rate of corrosion in the environments tested. Microstructural modifications of the matrix and possible relief of residual stresses were thought to be responsible for the lower rate of corrosion in the heat-treated condition. 相似文献
5.
We analyze and numerically study the code-matching logic module that is the central element in a proposed soliton-based ring network system running at peak rates of 100 Gb/s. The proposed network is packet-switched, and fast logic is required to route each packet. That is the function of the code-matching logic module, and four soliton logic gates that can perform fast logic are the key devices in its design. The behavior of the code-matching logic module is governed by a large set of parameters, and we simulate it by varying many of these parameters. The physical effects that occur in these devices and their significance are analyzed. The results indicate that the logic module will work but within a restricted parameter range 相似文献
6.
7.
8.
To define the clinical course of ventricular septal defect, 410 consecutive patients with isolated ventricular septal defect were evaluated over a period of 13 years. Their age ranged from 12 days to 24 years at the time of first visit to the hospital. Patients with less than 2 years follow-up period were excluded. One hundred and fifty seven patients were one year of age or less. The left to right shunt size remained the same in 52.4% of cases. In 34.4% the shunt size decreased, with complete closure of ventricular septal defect in 8.8%. Closure of ventricular septal defect was observed even in patients who had initially presented with large left to right flow, and congestive heart failure in infancy. Right ventricular outflow tract obstruction developed in 8.5% of patients usually between 2 and 10 years of age. Murmur of aortic regurgitation appeared in 8.9% on follow-up. Infective endocarditis developed in 6 cases. The unfortunate complication of Eisemenger's complex was seen in 3 patients; they had not returned for follow up for a long period of time. Hence, our data show that the left to right shunt across the ventricular septal defect decreases in about one-third of patients. However, a regular follow up is essential to prevent development of Eisenmenger's complex and for early detection of other complications like aortic regurgitation and right ventricular outflow tract obstruction. 相似文献
9.
N Majumdar P Bhattacharya DC Biswas RK Choudhury DM Nadkarni A Saxena 《Canadian Metallurgical Quarterly》1995,51(6):3109-3115
10.
The behavior of small cracks growing out of the roots of blunt notches in compact type specimens of an austenitic steel was characterized under fatigue loading in wet H
2 plus air environment. The growth rates of cracks in the size range of 0.125 mm to 0.75 mm were up to two orders of magnitude higher than the rates expected for conventional cracks at equal stress intensity range, K. It was also observed that the small cracks grew at these fast rates only in corrosive environments when the loading frequency was 0.02 Hz or less. At a frequency of 10 Hz, the behavior was in agreement with the trend predicted for conventional size cracks.The above observations are rationalized in terms of the breakdown of the concept of a single parameter representation of the crack tip stress and strain field by K or in terms of differences in crack tip environments between small and long cracks for the same bulk environment. A simple engineering model is proposed which adequately represents the observed small crack growth behavior.
Metallurgy Department 相似文献
Résumé On a procédé à la caractérisation, sous charges de fatigue en atmosphère humide de H 2 et d'air, de petites fissures se développant à partir des racines d'entailles arrondies dans des éprouvettes compactes.Les vitesses de croissance des fissures d'une taille allant de 0,125 à 0,750 mm se sont révélé être de deux ordres de grandeur plus grandes que les vitesses prévues dans le cas de fissures conventionnelle, soumises aux mêmes variations de l'intensité de contrainte K. On a également observé que de petites fissures croissaient à ces grandes vitesses seulement dans des atmosphères corrosives, lorsque la fréquence de sollicitation était de 0,02 Hz ou moins. A la fréquence de 10 Hz, le comportement observé s'est trouvé en accord avec les tendances prévues pour des fissures de taille conventionnelle.Les observations ci-dessus sont rationnalisées en un élargissement du concept de représentation monoparamétrique par le facteur K du champ de contraintes et de dilatation à l'extrémité de la fissure, ou en termes des différences rencontrées dans l'environnement local de l'extrémité d'une fissure, selon que celle-ci est longue ou courte, et ce dans un même environnement global.On propose un modèle simple utilisable en pratique, pour représenter de manière adéquate le comportement à la croissance observé pour des petites fissures.
Metallurgy Department 相似文献