全文获取类型
收费全文 | 2343篇 |
免费 | 52篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 85篇 |
综合类 | 2篇 |
化学工业 | 445篇 |
金属工艺 | 90篇 |
机械仪表 | 26篇 |
建筑科学 | 28篇 |
能源动力 | 79篇 |
轻工业 | 136篇 |
水利工程 | 5篇 |
石油天然气 | 1篇 |
无线电 | 228篇 |
一般工业技术 | 357篇 |
冶金工业 | 683篇 |
原子能技术 | 56篇 |
自动化技术 | 180篇 |
出版年
2023年 | 5篇 |
2022年 | 26篇 |
2021年 | 37篇 |
2020年 | 21篇 |
2019年 | 26篇 |
2018年 | 33篇 |
2017年 | 31篇 |
2016年 | 54篇 |
2015年 | 29篇 |
2014年 | 42篇 |
2013年 | 67篇 |
2012年 | 91篇 |
2011年 | 100篇 |
2010年 | 73篇 |
2009年 | 85篇 |
2008年 | 93篇 |
2007年 | 79篇 |
2006年 | 75篇 |
2005年 | 70篇 |
2004年 | 60篇 |
2003年 | 63篇 |
2002年 | 48篇 |
2001年 | 44篇 |
2000年 | 32篇 |
1999年 | 54篇 |
1998年 | 281篇 |
1997年 | 143篇 |
1996年 | 89篇 |
1995年 | 57篇 |
1994年 | 65篇 |
1993年 | 72篇 |
1992年 | 47篇 |
1991年 | 25篇 |
1990年 | 27篇 |
1989年 | 26篇 |
1988年 | 18篇 |
1987年 | 21篇 |
1986年 | 11篇 |
1985年 | 25篇 |
1984年 | 14篇 |
1983年 | 12篇 |
1982年 | 21篇 |
1981年 | 19篇 |
1980年 | 6篇 |
1979年 | 9篇 |
1978年 | 7篇 |
1977年 | 13篇 |
1976年 | 28篇 |
1975年 | 4篇 |
1974年 | 4篇 |
排序方式: 共有2401条查询结果,搜索用时 31 毫秒
21.
C Abe S Hirano K Wakazono T Mase R Yamamoto M Matsufuji N Sakata N Agata H Iguchi M Ishizuka 《Canadian Metallurgical Quarterly》1995,17(5-6):175-180
Cytogenin, 8-hydroxy-3-hydroxymethyl-6-methoxyisocoumarin, has low cytotoxicity on murine and human tumour cells in vitro. It augments or suppresses phagocytosis of macrophages and lymphocyte proliferation. It has been reported that cytogenin has a potent inhibitory effect clinically on adjuvant arthritis in Lewis rats and on type II collagen-induced arthritis in DBA/1J mice. Our experimental findings provide evidence that cytogenin has beneficial effects on spontaneous polyarthritis in MRL/1 mice and pristane-induced arthritis in DBA/1J mice. The results suggest that the mode of the anti-arthritic action of cytogenin is different from those of NSAIDs; although the precise mode of action remains unclear, cytogenin may become an excellent therapeutic agent for rheumatoid arthritis. 相似文献
22.
Highly reliable telecommunication networks require new technologies, such as the reliability specification, design, and evaluation method used at NTT. This paper describes the basic concepts of this method, and the ARDES-NET (Availability Reliability Design and Evaluation System for NETworks) software tool is used to support the reliability design and evaluation. ARDESNET has a user-friendly interface and can be easily put into practice 相似文献
23.
Some work is so complicated and unsteady that it is not possible to use automatic robots, such as FA robots. In such a case, a teleoperated manipulation system is applied. In this research, the authors aim at a reduction in the operator's physical and mental burdens. An artificially intelligent manipulator system has been developed with nonsymmetric and redundant master-slave. This system has five features: (1) a polar coordinates master arm; (2) a highly operational articulated slave arm with 7 degrees of freedom; (3) a nonsymmetric configuration and different degrees of freedom master-slave control; (4) an expert system; and (5) a new master-slave control motion, which makes the operator's task easier with automatic force/position control. The system was experimentally produced and its performance tested and evaluated. A qualitative evaluation was carried out by conducting a comparative test on the conventional master-slave control and the new master-slave control. It was found to be effective in reducing operating time, as well as work-induced fatigue. 相似文献
24.
A numerical evaluation is conducted of electric field distributions, phase constants, and attenuation constants of the lowest eigenmode in the general class of uniformly bent circular hollow waveguides. The analysis is based on a scalar equation, and numerical results are compared with those of existing approximate theories. Normalized forms of attenuation constants are presented for the parallel and perpendicular polarizations to the bending plane by using structural and material parameters. For sharply bent waveguides, useful and simple expressions are derived for the attenuation constants of the TE and TM modes in the corresponding slab geometry with suitable weighting parameters 相似文献
25.
The current status of high electron mobility transistor (HEMT) technology at Fujitsu for high-performance VLSI is presented, focusing on device performance in the submicrometer dimensional range and the HEMT LSIs implemented in supercomputer systems. The HEMT is a very promising device for ultrahigh-speed LSI/VLSI applications because of the high-mobility GaAs/AlGaAs heterojunction structure. A 1.1 K-gate bus-driver logic LSI has been developed to demonstrate the high-speed data transfer in a high-speed parallel processing system at room temperature, operating at 10.92 GFLOPS. A cryogenic 3.3 K-gate random number generator logic LSI with maximum clock frequency of 1.6 GHz has also been developed to demonstrate the high-clock-rate system operations at liquid-nitrogen temperature. For VLSI level complexity, a HEMT 64-kb static RAM with 1.2-ns access operation and a 45 K-gate gate array with 35-ps logic delay have been developed operating at room temperature, demonstrating the high performance required for future high-speed computer systems 相似文献
26.
Namsin Park Takeyuki Shiraishi Kazuyoshi Kamisugi Yoshitaka Hara Keita Iizuka Takashi Kado Shuzi Hayase 《Journal of Applied Electrochemistry》2008,38(3):371-375
A direct ethanol fuel cell (DEFC), which is less prone to ethanol crossover, is reported. The cell consists of PtRu/C catalyst as the anode, Nafion® 117 membrane, and Ni–Co–Fe (NCF) composite catalyst as the cathode. The NCF catalyst was synthesized by mixing Ni, Co, and Fe complexes into a polymer matrix (melamine-formaldehyde resins), followed by heating the mixture at 800 °C under inert atmosphere. TEM and EDX experiments suggest that the NCF catalyst has alloy structures of Ni, Co and Fe. The catalytic activity of the NCF catalyst for the oxygen reduction reaction (ORR) was compared with that of commercially available Pt/C (CAP) catalyst at different ethanol concentrations. The decrease in open circuit voltage (Voc) of the DEFC equipped with the NCF catalysts was less than that of CAP catalyst at higher ethanol concentrations. The NCF catalyst was less prone to ethanol oxidation at cathode even when ethanol crossover occurred through the Nafion®117 film, which prevents voltage drop at the cathode. However, the CAP catalyst did oxidize ethanol at the cathode and caused a decrease in voltage at higher ethanol concentrations. 相似文献
27.
Keita Yagi Junji Murata Yasuhisa Sano Hidekazu Goto 《Science and Technology of Advanced Materials》2007,8(3):166-169
The copper damascene process is one of the most promising technologies for fabricating Cu wirings for electronic devices such as LSIs. In this research, the fabrication of damascene Cu wirings was conducted using solid acidic catalyst. When a Cu-plated wafer, whose oxide is a basic oxide is dipped into a mixture of oxidizing solution and acidic solution, surface atoms are ionized and etched off into the solution. However, because conventional nonelectrolytic etching does not have a reference surface, it is difficult to utilize for planarization. Therefore, a new nonelectrolytic machining method using a cation-exchange fabric instead of an acidic solution was developed. To be more precise, the planarization of a Cu-plated wafer was carried out by rubbing with the cation-exchange fabric in ozone water. Basically, this method exploits chemical reactions so that the physical properties of the workpiece surface are not deteriorated. Furthermore, this method uses no chemicals except for ozone water, which easily dissociates into water and oxygen molecules; thus, this method is a low-cost, environmentally friendly process. In this paper, as a preliminary experiment, the nonelectrolytic etching of a Cu sample using solutions of O3 and CO2 was carried out to inspect the dependence of the etching rate on [O3] and [H+]. The results indicate that the etching rate increased as [O3] and [H+] increased. When [H+] was high relative to [O3], a smooth etch-pit-free surface was achieved. Next, nonelectrolytic etching using a cation-exchange fabric was carried out, and properties similar to those in the case of etching using solutions were obtained. Finally, damascene Cu wirings were fabricated using ozone water and a cation-exchange catalyst. 相似文献
28.
29.
Hamada H. Hirano K. Goda N. Abe H. Hasegawa I. Okita Y. Arioka S. Niina T. 《Electronics letters》1994,30(20):1719-1720
The off state current for polysilicon thin-film transistors for pixels in LCDs has been successfully reduced by introducing a polysilicon buffer layer between a polysilicon active layer fabricated by solid-phase-crystallisation (SPC) and a fused quartz substrate. Off-slate current of less than 1 pA under Vgs=-25 V at Vds=3 V was obtained for n-channel single-gate coplanar transistors using the buffer layer (400 Å) 相似文献
30.