全文获取类型
收费全文 | 7706篇 |
免费 | 154篇 |
国内免费 | 28篇 |
专业分类
电工技术 | 504篇 |
综合类 | 21篇 |
化学工业 | 1862篇 |
金属工艺 | 172篇 |
机械仪表 | 216篇 |
建筑科学 | 226篇 |
矿业工程 | 5篇 |
能源动力 | 310篇 |
轻工业 | 686篇 |
水利工程 | 25篇 |
石油天然气 | 14篇 |
无线电 | 666篇 |
一般工业技术 | 1330篇 |
冶金工业 | 922篇 |
原子能技术 | 260篇 |
自动化技术 | 669篇 |
出版年
2023年 | 38篇 |
2022年 | 79篇 |
2021年 | 134篇 |
2020年 | 65篇 |
2019年 | 91篇 |
2018年 | 102篇 |
2017年 | 98篇 |
2016年 | 141篇 |
2015年 | 99篇 |
2014年 | 191篇 |
2013年 | 408篇 |
2012年 | 253篇 |
2011年 | 373篇 |
2010年 | 326篇 |
2009年 | 339篇 |
2008年 | 396篇 |
2007年 | 330篇 |
2006年 | 270篇 |
2005年 | 282篇 |
2004年 | 237篇 |
2003年 | 237篇 |
2002年 | 224篇 |
2001年 | 163篇 |
2000年 | 136篇 |
1999年 | 168篇 |
1998年 | 401篇 |
1997年 | 246篇 |
1996年 | 190篇 |
1995年 | 156篇 |
1994年 | 150篇 |
1993年 | 135篇 |
1992年 | 101篇 |
1991年 | 104篇 |
1990年 | 83篇 |
1989年 | 109篇 |
1988年 | 98篇 |
1987年 | 66篇 |
1986年 | 103篇 |
1985年 | 78篇 |
1984年 | 72篇 |
1983年 | 83篇 |
1982年 | 78篇 |
1981年 | 69篇 |
1980年 | 57篇 |
1979年 | 54篇 |
1978年 | 50篇 |
1977年 | 52篇 |
1976年 | 65篇 |
1975年 | 26篇 |
1973年 | 20篇 |
排序方式: 共有7888条查询结果,搜索用时 15 毫秒
71.
Kojima Masami Tasaki Takafumi Suzuki Yukihisa Kamijo Toshio Hada Aki Kik Alfred Ikehata Masateru Sasaki Hiroshi 《Journal of Infrared, Millimeter and Terahertz Waves》2022,43(3-4):260-271
Journal of Infrared, Millimeter, and Terahertz Waves - Millimeter waves (MMW) absorbed by skin or cornea may induce damage by heat. We have developed a 60 GHz MMW exposure-induced eye... 相似文献
72.
73.
74.
Chung Loong Yiin Suzana Yusup Armando T. Quitain Yoshimitsu Uemura Mitsuru Sasaki Tetsuya Kida 《Clean Technologies and Environmental Policy》2018,20(9):1987-2000
Recently, the development of efficient and environmentally benign solvents has received great attention to replace current harsh organic solvents. In this context, low-transition-temperature mixtures (LTTMs) have emerged as favorable green solvents for biomass delignification. Palm oil biomass, empty fruit bunch (EFB) was pretreated with commercial l-malic acid and microwave hydrothermally extracted cactus malic acid-derived LTTMs at 60, 80, and 100 °C. The LTTMs applied in this study were derived from malic acid–choline chloride–water and malic acid–monosodium glutamate–water with a molar ratio of 2:4:2 and 3:1:5, respectively. Three first-order reactions were used to express the delignification kinetic model of EFB. The first term was based on the initial stage and assigned as infinite due to the fast rate of delignification which could not be detected. The second and third terms were proportional to bulk and residual delignification stages. A good agreement was obtained between the kinetic model and the experimental data obtained in this study with R2?≥?0.91. The activation energies for the delignification reactions using l-malic acid and cactus malic acid-based LTTMs in the bulk and residual stages were approximated as 36–56 and 19–26 kJ/mol and 34–90 and 47–87 kJ/mol, respectively. 相似文献
75.
Hiroshi Kametani 《Metallurgical and Materials Transactions B》1998,29(6):1261-1267
Data concerning the length of longitudinal cracks on the surface of continuously cast steel slabs were collected from two
plants. The data were analyzed to find the relation between crack length and crack frequency. The analysis revealed the following.
相似文献
(1) |
After normalization to eliminate the effect of different casting conditions, the fractal relation characterizing the normalized
cumulative frequency distribution (N (m−2)) and the crack length (L (mm)) of the primary surface cracks could be represented by the equation |
|
(2) | The values for γ varied over a wide range, but remained constant throughout a heat and were the same for both the upper and lower faces of the slab. | |
(3) | It was found that in some instances, when L exceeded a critical value (L c), the value of L became δ times longer than the length predicted by the previous distribution. This increase in L was ascribed to secondary growth of the cracks. This occurred more frequently on the lower, rather than on the upper, face of the slab. The product of L c and δ was approximately constant. The formation of the surface cracks is discussed in view of the fractal phenomena. |
76.
Buried channel optical waveguides were fabricated from fluorinated polyimides. They operated in single mode and showed an optical loss of less than 0.3 and 0.7 dB/cm for TE and TM polarizations, respectively, at a wavelength of 1.3 mum. Moreover, these waveguides had high heat and moisture resistance; the optical loss did not significantly change after heating at 380 degrees C for 1 h or after exposure to 85% relative humidity at 85 degrees C for over 200 h. 相似文献
77.
C. Bäuerle N. Mori G. Kurata Hiroshi Fukuyama 《Journal of Low Temperature Physics》1998,113(5-6):927-932
Scanning tunneling microscopy (STM) studies of two-dimensional (2D) cryocrystals
4
He, Kr, Xe) physisorbed on graphite surfaces are presented. Individual helium atoms, usually thought to be invisible with STM, were recently observed on graphite surfaces at a density corresponding to the
commensurate solid. Here we show that a local elastic deformation seems to be the principal mechanism responsible to render the atoms visible. Recent tight-binding calculations of the local density of states (LDOS) of graphite which predict the appearance of an energy gap support this picture. I-z curve measurements for the case of
4
He show a sharp drop (increase) of the tunneling current I at a certain tip-surface distance z during retraction (approach) of the tip. This drop (increase) may be associated with the tunneling of a single He adatom, opening new possibilities to study the quantum tunneling of atoms via STM. 相似文献
78.
The 360° profilometry of a three-dimensional (3-D) diffuse object by use of the light intersection and its image reconstruction by surface shading are presented. The lack of data in one direction, which was due to occlusion, was compensated by the projection of two lines of light from different directions. Some experiments to profile objects and their reconstruction by computer are shown. The entire surface model was constructed, and a real shading image was obtained by means of computer graphics. 相似文献
79.
Neural network modules based on page-oriented dynamic digital photorefractive memory are described. The modules can implement two different interconnection organizations, fan-out and fan-in, depending on their target network applications. Neural network learning is realized by the real-time memory update of dynamic digital photorefractive memory. Physical separation of subvolumes in the page-oriented photorefractive memory architecture contributes to the low cross talk and high diffraction efficiency of the stored interconnection weights. Digitally encoded interconnection weights ensure high accuracy, providing superior neural network system scalability. Module scalability and feedforward throughput have been investigated based on photorefractive memory geometry and the photodetector power requirements. The following four approaches to extend module scalability are discussed: partial optical summation, semiparallel feedforward operation, time partitioning, and interconnection matrix partitioning. Learning capabilities of the system are investigated in terms of required interconnection primitives for implementing learning processes and three memory-update schemes. The experimental results of Perceptron learning network implementation with 900 input neurons with digital 6-bit accuracy are reported. 相似文献
80.
Kim HB Hayashi M Nakatani K Kitamura N Sasaki K Hotta J Masuhara H 《Analytical chemistry》1996,68(3):409-414
Ion-exchange processes of a cationic dye (Rhodamine B; RhB) were studied for individual polymer particles (diameter of 16-20 μm) by laser trapping microspectroscopy and confocal fluorescence laser microspectroscopy. The absorbance of RhB at 565 nm adsorbed on a cation-exchange particle increased linearly with the concentration of RhB in the aqueous phase, while it was independent of the particle diameter. Fluorescence intensity profile measurements of RhB along the particle diameter by confocal fluorescence microspectroscopy directly proved that ion exchange took place in the surface layer (~2-μm thickness) of the particle in the initial stage (1 h). Diffusion of RhB in the particle was very slow, and ion exchange proceeded gradually to the inner volume in the order of days. The ion-exchange processes were analyzed on the basis of simulation of the time course of the concentration profile of RhB in the particle, and the diffusion coefficient of RhB was determined to be (2-4) × 10(-11) cm(2)·s(-1). 相似文献