全文获取类型
收费全文 | 1693篇 |
免费 | 47篇 |
国内免费 | 10篇 |
专业分类
电工技术 | 19篇 |
化学工业 | 286篇 |
金属工艺 | 44篇 |
机械仪表 | 92篇 |
建筑科学 | 49篇 |
矿业工程 | 4篇 |
能源动力 | 61篇 |
轻工业 | 64篇 |
水利工程 | 5篇 |
石油天然气 | 9篇 |
无线电 | 215篇 |
一般工业技术 | 395篇 |
冶金工业 | 236篇 |
原子能技术 | 60篇 |
自动化技术 | 211篇 |
出版年
2023年 | 18篇 |
2022年 | 31篇 |
2021年 | 37篇 |
2020年 | 34篇 |
2019年 | 30篇 |
2018年 | 33篇 |
2017年 | 30篇 |
2016年 | 35篇 |
2015年 | 23篇 |
2014年 | 48篇 |
2013年 | 104篇 |
2012年 | 62篇 |
2011年 | 92篇 |
2010年 | 88篇 |
2009年 | 70篇 |
2008年 | 73篇 |
2007年 | 64篇 |
2006年 | 59篇 |
2005年 | 34篇 |
2004年 | 38篇 |
2003年 | 42篇 |
2002年 | 34篇 |
2001年 | 27篇 |
2000年 | 28篇 |
1999年 | 21篇 |
1998年 | 39篇 |
1997年 | 35篇 |
1996年 | 32篇 |
1995年 | 34篇 |
1994年 | 29篇 |
1993年 | 25篇 |
1992年 | 20篇 |
1991年 | 29篇 |
1990年 | 31篇 |
1989年 | 19篇 |
1988年 | 22篇 |
1987年 | 21篇 |
1986年 | 16篇 |
1985年 | 18篇 |
1984年 | 26篇 |
1983年 | 20篇 |
1982年 | 25篇 |
1981年 | 21篇 |
1980年 | 14篇 |
1979年 | 17篇 |
1978年 | 11篇 |
1977年 | 19篇 |
1976年 | 30篇 |
1975年 | 6篇 |
1973年 | 9篇 |
排序方式: 共有1750条查询结果,搜索用时 0 毫秒
101.
Classification of underground pipe scanned images using featureextraction and neuro-fuzzy algorithm 总被引:1,自引:0,他引:1
Pipeline surface defects such as holes and cracks cause major problems for utility managers, particularly when the pipeline is buried under the ground. Manual inspection for surface defects in the pipeline has a number of drawbacks, including subjectivity, varying standards, and high costs. Automatic inspection system using image processing and artificial intelligence techniques can overcome many of these disadvantages and offer utility managers an opportunity to significantly improve quality and reduce costs. A recognition and classification of pipe cracks using images analysis and neuro-fuzzy algorithm is proposed. In the preprocessing step the scanned images of pipe are analyzed and crack features are extracted. In the classification step the neuro-fuzzy algorithm is developed that employs a fuzzy membership function and error backpropagation algorithm. The idea behind the proposed approach is that the fuzzy membership function will absorb variation of feature values and the backpropagation network, with its learning ability, will show good classification efficiency. 相似文献
102.
Debabrata Rautaray Kaustav Sinha Sudhakar R. Sainkar Renu Pasricha Neela R. Pavaskar Murali Sastry 《Journal of the American Ceramic Society》2005,88(1):24-27
This paper describes the growth of barium chromate (BaCrO4 ) nanocrystallites within thermally evaporated thin films of stearic acid (StA) and sodium bis-2-ethylhexyl-sulfosuccinate by a process of Ba2+ ion entrapment followed by in situ reaction with CrO4 2− ions. Dense spherical assemblies of BaCrO4 nanocrystallites of very uniform size (∼50 nm) were obtained within the two different host matrices. The spherical assemblies were composed of smaller (ca. 5–10 nm size) BaCrO4 crystals indicating that efficient size control over crystal size may be exercised by the matrix. Contact angle measurements of the BaCrO4 –StA and BaCrO4 –sodium bis-2-ethylhexyl-sulfosuccinate films indicated that they were hydrophobic, thus pointing to the possible role of hydrophobic interaction between the StA and sodium bis-2-ethylhexyl-sulfosuccinate monolayer-covered BaCrO4 crystals in the assembly process. 相似文献
103.
The higher-order-mode cut-off frequencies in symmetric transverse electromagnetic cells are computed with the finite-element method. Transverse electric and transverse magnetic modes are considered. For symmetry, only one-quarter of the cross section is analyzed. Electric and magnetic walls are introduced in the cross section, which includes the effect of the gap between the center conductor and the sidewalls. This arrangement enhances the accuracy of the solution. The results obtained by this method are compared with those of other methods. Discrepancies observed in the results of other methods are explained. The present method is the more powerful one; with this method, mode identification can easily be made using an eigenvector solution 相似文献
104.
V. J. Rao Madhuri V. Salvi V. Samuel A. P. B. Sinha 《Journal of Materials Science》1985,20(9):3277-3282
Conditions have been developed for the deposition of a stoichiometric thin film of zinc phosphide (Zn3P2) using electron beam evaporation. Structural properties of as-deposited and annealed thin films of zinc phosphide have been
studied using electron and X-ray diffraction. The as-deposited film is non-crystalline, structural ordering starts on annealing
at 200° C and the film becomes crystalline at 300° C with the structure matching that of the bulk material. Optical absorption
has been investigated over the range 1 to 3 eV with emphasis on the region of interband absorption. The thin film absorption
edge is found to be exponential for lower values of absorption coefficient. Analysis of thin film data showed that Zn3P2 is a direct-band-gap material. On annealing there is a shift in the band edge towards higher energy.
NCL Communication No. 3571. 相似文献
105.
A failure-time distribution made up of two exponential distributions having two distinct failure rates and a specific mixture proportion is considered. The associated experiment is terminated after a predetermined time has elapsed and the numbers of failures in each time interval are recorded. As soon as an item fails it can be attributed to the appropriate subpopulation. An empirical procedure is proposed to estimate the 3 parameters of the model. The maximum likelihood estimators and our estimators are compared using both real and simulated data. The procedure can be extended to a mixed model of three or more exponential distributions, and can be applied to ungrouped and/or uncensored samples. 相似文献
106.
Studies were made on the longitudinal ultrasonic velocity and its attenuation characteristics in medium carbon steel forging subjected to 0–60% hot upsetting followed by heat treatment. The fineness of ferrite and pearlite increased with increasing deformation and cooling rate during heat treatment. The area fraction of pearlite increased from 21% to 45% as well as the mean interlamellar spacing in pearlite decreased from 8.79 μm to 0.689 μm in the 40% deformed (upsetted) normalized sample It was observed that the ultrasonic velocity decreased with increasing degree of deformation. The velocity was found to be highest in the normalized steel acquiring a value of 5920 m/s and lowest in hardened steel acquiring a value of 4979 m/s. The attenuation decreased with increasing deformation resulting in increased back wall echo heights. The residual stresses on the surface of typical 60% deformed and annealed steel samples using x-ray diffractometry were measured to be — 39.7 MPa (compressive) and — 188.0 MPa (compressive) respectively. 相似文献
107.
Use of the singular value decomposition is suggested for problems of linear least-squares system identification rather than the usual method involving the normal equations. 相似文献
108.
R. K. Gupta M. K. Karthikeyan D. N. Bhalia B. R. Ghosh P. P. Sinha 《Metal Science and Heat Treatment》2008,50(3-4):175-179
A cobalt-base refractory alloy containing W, Ni, and Cr, which is widely used for making spacecraft components operating at high temperatures, is studied. Changes in the microstructure of the alloy are studied depending on the heat treatment, and the effect of these changes on mechanical properties at room and high temperatures is determined. 相似文献
109.
Ron Adams B.S. Uday Sinha Ph.D. 《JOM Journal of the Minerals, Metals and Materials Society》1990,42(5):31-34
Southwire continuous rod technology has been used for approximately a quarter of a century to produce high-quality copper rod, and ongoing modifications to the process have improved not only the copper product, but the actual efficiency of the production system. Some of these developments have been achieved through automatic quality monitoring and the application of sophisticated control devices. 相似文献
110.
This paper presents the theory and performance of a differential induction machine, which is a special type of induction machine
having two shafts projected from the two ends of a single stator. Application of a differential load on the two shafts cause
them to run at different speed as a motor, which permits true differential movement and thus can meet the requirements of
a differential drive in an electric vehicle. The machine is also capable of regeneration in the differential mode. This paper
presents the construction of the above machine and performance of the same based on experimental results from a laboratory
prototype. The equivalent circuit of the motor has been presented and verified experimentally. 相似文献