全文获取类型
收费全文 | 10004篇 |
免费 | 330篇 |
国内免费 | 108篇 |
专业分类
电工技术 | 231篇 |
综合类 | 193篇 |
化学工业 | 1873篇 |
金属工艺 | 353篇 |
机械仪表 | 354篇 |
建筑科学 | 346篇 |
矿业工程 | 103篇 |
能源动力 | 325篇 |
轻工业 | 593篇 |
水利工程 | 107篇 |
石油天然气 | 156篇 |
武器工业 | 16篇 |
无线电 | 1094篇 |
一般工业技术 | 2164篇 |
冶金工业 | 1503篇 |
原子能技术 | 107篇 |
自动化技术 | 924篇 |
出版年
2023年 | 91篇 |
2022年 | 170篇 |
2021年 | 221篇 |
2020年 | 187篇 |
2019年 | 147篇 |
2018年 | 248篇 |
2017年 | 198篇 |
2016年 | 215篇 |
2015年 | 202篇 |
2014年 | 263篇 |
2013年 | 569篇 |
2012年 | 377篇 |
2011年 | 446篇 |
2010年 | 383篇 |
2009年 | 365篇 |
2008年 | 359篇 |
2007年 | 328篇 |
2006年 | 307篇 |
2005年 | 260篇 |
2004年 | 235篇 |
2003年 | 215篇 |
2002年 | 201篇 |
2001年 | 171篇 |
2000年 | 217篇 |
1999年 | 238篇 |
1998年 | 390篇 |
1997年 | 332篇 |
1996年 | 272篇 |
1995年 | 226篇 |
1994年 | 203篇 |
1993年 | 194篇 |
1992年 | 151篇 |
1991年 | 158篇 |
1990年 | 110篇 |
1989年 | 114篇 |
1988年 | 117篇 |
1987年 | 116篇 |
1986年 | 96篇 |
1985年 | 132篇 |
1984年 | 121篇 |
1983年 | 135篇 |
1982年 | 98篇 |
1981年 | 98篇 |
1980年 | 90篇 |
1979年 | 89篇 |
1978年 | 75篇 |
1977年 | 81篇 |
1976年 | 97篇 |
1975年 | 58篇 |
1974年 | 54篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
31.
32.
33.
视频在无线传感器网络传输,由于网络的不稳定,可能使视频质量受到一定的影响。在人类视觉模型的基础上,提出一个改进的无参考质量评估算法,直接通过收到的图像,判断视频质量的好坏。较之当前广泛使用的视频评估算法一媒体延迟指标而言,大大提高在网络丢包时,对于视频质量评估的准确性。评估结果接近人眼观察的效果,并且可以大规模投入使用,具有较强现实意义和商业使用价值。 相似文献
34.
35.
Journal of Electronic Testing - Error-Tolerant applications regularly accomplish more data adaption. Approximate computing is one of the optimum strategies for data manipulation in several... 相似文献
36.
Y. Narendra Babu M. Venkateswara Rao A. Gopala Krishna 《Materialwissenschaft und Werkstofftechnik》2023,54(1):81-89
Developing light weight polymer based composites dispersed with novel reinforcements which can function well in the presence of aggressive environments is an active research field in the materials engineering. Hence, in the current work, halloysite nanotubes (1 %, 2 %, 4 %, 6 %, 8 % and 10 % by weight) were reinforced into acrylonitrile butadiene styrene/polycarbonate blend and the role of reinforcing phases on the mechanical performance under aggressive environmental conditions has been evaluated. Hardness was measured as gradually increased in the composites with the increased content of the reinforcements. Impact strength of the composites was observed as increased in the composites up to 4 % reinforcement and further decreased. Increased strength was measured for the composite up to 2 % reinforcement. Ductility of the composites was decreased as reflected form the decreased % of elongation with the higher fraction of reinforcements due to induced brittleness. The composites were exposed to diluted sulfuric acid for 3 h and 6 h at 60 °C and then subjected to tensile loading. With the increased time of exposure, composites with 1 % and 2 % reinforcement exhibited relatively better performance. 相似文献
37.
Defense frontier analysis of quantum cryptographic systems 总被引:1,自引:0,他引:1
When a quantum cryptographic system operates in the presence of background noise, security of the key can be recovered by a procedure called key distillation. A key-distillation scheme effective against so-called individual (bitwise-independent) eavesdropping attacks involves sacrifice of some of the data through privacy amplification. We derive the amount of data sacrifice sufficient to defend against individual eavesdropping attacks in both BB84 and B92 protocols and show in what sense the communication becomes secure as a result. We also compare the secrecy capacity of various quantum cryptosystems, taking into account data sacrifice during key distillation, and conclude that the BB84 protocol may offer better performance characteristics than the B92. 相似文献
38.
S. K. Mishra L. C. Pathak V. Rao D. Bhattacharya K. L. Chopra 《Journal of Superconductivity》1996,9(2):211-216
Critical current densities of the superconducting Y-Ba-Cu-O (YBCO) films have been observed to decrease with the increase of power of microwave radiation. Presence of Josephson type of junctions in the microbridges has been established from the microwave irradiation and magnetic field studies. BCS energy gap parameter (2/kT
c
) has been calculated from thedI/dV characteristics and found to be 3.7 at 13 K. 相似文献
39.
40.
D. T. Williams S. K. El-Rahaiby Y. K. Rao 《Metallurgical and Materials Transactions B》1981,12(1):161-166
The kinetics of reduction of nickel chloride with hydrogen were investigated in the temperature range of 533 (260 °) to 788 K (515 °). Most experiments were done with porous NiCl2 granules having ?8+10 mesh (Tyler) size. The effects of temperature, sample size, granule size and hydrogen partial pressure on the reduction kinetics were investigated. In the temperature range 533 (260 °) to 651 K (378 °) the reduction is dominated by chemical kinetic factors. At higher temperatures diffusional effects appear to become quite significant. The temperature-dependence of the chemical kinetic rate constantK is given by $$\log K = 6.744 - \frac{{22,240}}{{2.303RT}};K\,\,is\,\,in\,\,\min ^{ - 1} $$ The activation energy for the reduction was found to be 22,240 cal /mol (or 93,050 J/mol) in the chemical kinetic regime. 相似文献