全文获取类型
收费全文 | 994篇 |
免费 | 30篇 |
国内免费 | 26篇 |
专业分类
电工技术 | 39篇 |
综合类 | 62篇 |
化学工业 | 54篇 |
金属工艺 | 185篇 |
机械仪表 | 53篇 |
建筑科学 | 26篇 |
矿业工程 | 1篇 |
能源动力 | 12篇 |
轻工业 | 285篇 |
水利工程 | 6篇 |
石油天然气 | 1篇 |
无线电 | 50篇 |
一般工业技术 | 171篇 |
冶金工业 | 23篇 |
原子能技术 | 19篇 |
自动化技术 | 63篇 |
出版年
2023年 | 3篇 |
2022年 | 9篇 |
2021年 | 6篇 |
2020年 | 3篇 |
2019年 | 11篇 |
2018年 | 7篇 |
2017年 | 10篇 |
2016年 | 7篇 |
2015年 | 11篇 |
2014年 | 37篇 |
2013年 | 145篇 |
2012年 | 77篇 |
2011年 | 102篇 |
2010年 | 58篇 |
2009年 | 82篇 |
2008年 | 47篇 |
2007年 | 35篇 |
2006年 | 51篇 |
2005年 | 21篇 |
2004年 | 30篇 |
2003年 | 17篇 |
2002年 | 13篇 |
2001年 | 6篇 |
2000年 | 9篇 |
1999年 | 6篇 |
1998年 | 20篇 |
1997年 | 58篇 |
1996年 | 20篇 |
1995年 | 10篇 |
1994年 | 17篇 |
1993年 | 13篇 |
1992年 | 10篇 |
1991年 | 10篇 |
1990年 | 4篇 |
1989年 | 14篇 |
1988年 | 7篇 |
1987年 | 15篇 |
1986年 | 9篇 |
1985年 | 4篇 |
1984年 | 4篇 |
1983年 | 5篇 |
1978年 | 6篇 |
1976年 | 4篇 |
1975年 | 5篇 |
1973年 | 1篇 |
1970年 | 1篇 |
1967年 | 2篇 |
1962年 | 1篇 |
1960年 | 2篇 |
1959年 | 1篇 |
排序方式: 共有1050条查询结果,搜索用时 31 毫秒
101.
102.
103.
104.
This study is a fundamental work performed to obtain basic information about designing two-phase closed thermosyphons with a working fluid of FC-72 (C6F14). FC-72 is a kind of alternative refrigerant designed to be chemically safe and more environmentally friendly than any other conventional CFC refrigerants. To obtain experimental data on operational performances of a FC-72 two-phase closed thermosyphon, an experimental model was designed and manufactured with a micro fin groove copper tube with an outside diameter of 22.2 mm for its container, on which a series of operational performance tests were conducted. Its maximum capacity of heat transport rate was designed to be about 300–400 W. The focus was given to investigate the effects of such parameters as micro fin grooves and fill charge ratios on operational performances of the FC-72 two-phase closed thermosyphon. The experimental data on phase change heat transfer coefficients and heat transport limitations were compared with some corresponding correlations, and a couple of measures that would help to predict operational performances were suggested with some physical explanations. 相似文献
105.
This paper is a study on modal model method in estimating system inputs from vibration responses, which is one of the indirect input identification methods in frequency domain. The method has advantages over the direct inverse method especially when points of operational inputs are inaccessible for artificial excitation but accessible for response measurement. Systematic procedures of an extended modal model method are proposed and checked by numerical experiments. Mechanisms of error propagation, i.e. how errors in modal parameters such as poles and mode shape vectors affect estimation of the input forces, are illustrated. Then, in order to counteract the error propagation, discrete modal filter approach is used in this paper to compute the inversion of modal matrix in which most serious errors seem to be generated. Further, a reduced form of modified reciprocal modal vector (MRMV) is proposed to estimate multiple inputs, which is shown to have orthogonality errors smaller than by the MRMV filter. 相似文献
106.
Abstracts are not published in this journal
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
107.
Effect of chromium on the phase evolution and microstructure of ZnO doped with bismuth and antimony 总被引:2,自引:0,他引:2
Crystalline phase formation and microstructure of ZnO varistors with a basic composition ZnO–Bi2O3–Sb2O3 were examined. Addition of chromium oxide to this basic varistor resulted in an α-spinel (α-Zn7Sb2O12) phase dissolving a significant amount of Cr, while the β-spinel did not. β-spinel transformed to pyrochlore during cooling,
whereas α-spinel hardly transformed to pyrochlore irrespective of the cooling conditions. When Sb2O3 was completely replaced by Cr2O3, ZnCr2O4 was formed instead of spinel. α-spinel particles were 1–2 μm in size and intra- as well as intergranular. ZnCr2O4 particles, smaller than 1 μm in size, however, were present as aggregates in the bismuth-rich matrix phase at the grain boundaries.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
108.
Detection of damage to structures has recently received considerable attention from the viewpoint of maintenance and safety assessment. In this respect, the vibration characteristics of buildings have been applied consistently to obtain a damage index of the whole building, but it has not been established as a practical method until now. It is reasoned that this is perhaps due to restrictions on the experiment, use of improper method, and lack of inspection opportunity for the structures. In addition, in the case of large‐scale structures such as buildings, many variables to be considered for the analysis contribute to a large number of degrees of freedom, and this can also be a considerable problem for the analysis. A practical method for the detection of structural damage using the first natural frequency and mode shape of building is proposed in this paper. The effectiveness of the proposed method is verified by numerical analysis and experimental tests. From the results, it is observed that the severity and location of the damage can be estimated with a relatively small error by using modal properties of building. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
109.
CHANG JUNG KIM DAE SUNG YOON ZHONG-TAO JIANG KWANGSOO NO 《Journal of Materials Science》1997,32(5):1213-1219
The crystal orientations of lead zirconate titanate (PZT) thin films have been investigated by using various drying temperatures
in the sol–gel process. The films were dried at different temperatures between 310 and 350°C for pyrolysis and then were heat
treated at 650°C using rapid thermal annealing (RTA). TG/DTA and FTIR spectroscopy were used to detect the remnants of organic
materials in the thin films prior to the final heat treatment. In order to examine the relationship between the film orientation
and the remaining organic materials for the prior and final heat treatment, the films were fabricated with different coating
cycles and dried for different holding times and then annealed at 650°C. The preferred orientations were investigated using
X-ray diffraction.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
110.
To solve information asymmetry problem on online auction, this study suggests and validates a forecasting model of winning bid prices. Especially, it explores the usability of data mining approaches, such as neural network and Bayesian network in building a forecasting model. This research empirically shows that, in forecasting winning bid prices on online auction, data mining techniques have showed better performance than traditional statistical analysis, such as logistic regression and multivariate regression. 相似文献