全文获取类型
收费全文 | 1177篇 |
免费 | 32篇 |
国内免费 | 8篇 |
专业分类
电工技术 | 134篇 |
综合类 | 4篇 |
化学工业 | 356篇 |
金属工艺 | 58篇 |
机械仪表 | 34篇 |
建筑科学 | 23篇 |
矿业工程 | 5篇 |
能源动力 | 20篇 |
轻工业 | 63篇 |
水利工程 | 2篇 |
石油天然气 | 7篇 |
无线电 | 66篇 |
一般工业技术 | 233篇 |
冶金工业 | 46篇 |
原子能技术 | 43篇 |
自动化技术 | 123篇 |
出版年
2022年 | 8篇 |
2021年 | 10篇 |
2020年 | 12篇 |
2019年 | 15篇 |
2018年 | 17篇 |
2017年 | 11篇 |
2016年 | 13篇 |
2015年 | 24篇 |
2014年 | 29篇 |
2013年 | 84篇 |
2012年 | 40篇 |
2011年 | 51篇 |
2010年 | 52篇 |
2009年 | 51篇 |
2008年 | 81篇 |
2007年 | 53篇 |
2006年 | 45篇 |
2005年 | 37篇 |
2004年 | 39篇 |
2003年 | 32篇 |
2002年 | 25篇 |
2001年 | 31篇 |
2000年 | 21篇 |
1999年 | 21篇 |
1998年 | 22篇 |
1997年 | 26篇 |
1996年 | 26篇 |
1995年 | 18篇 |
1994年 | 23篇 |
1993年 | 25篇 |
1992年 | 14篇 |
1991年 | 9篇 |
1990年 | 13篇 |
1989年 | 11篇 |
1988年 | 13篇 |
1987年 | 19篇 |
1986年 | 21篇 |
1985年 | 16篇 |
1984年 | 18篇 |
1983年 | 20篇 |
1982年 | 22篇 |
1981年 | 18篇 |
1980年 | 20篇 |
1979年 | 20篇 |
1978年 | 16篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1974年 | 5篇 |
1971年 | 2篇 |
1969年 | 2篇 |
排序方式: 共有1217条查询结果,搜索用时 15 毫秒
71.
We applied a Mo/B4C multilayer coating to a laminar holographic grating with 2400 grooves/mm and a 1-m radius of curvature. By use of synchrotron soft x rays the multilayer-coated grating was evaluated to have diffraction efficiencies of 3.1% and 0.017% for s- and p-polarized radiation, respectively, at a 6.7-nm wavelength at a 45.35 degrees grazing angle of incidence in the +1 (inside) grating order. Thus the polarizance was estimated to be 98.9% at least. The zero-order peak was suppressed by the destructive interference caused by the groove profile. 相似文献
72.
Tadashi Kitamura Daisuke Nishino 《IEEE transactions on systems, man, and cybernetics. Part B, Cybernetics》2006,36(2):353-365
The design clue for the remote control of a mobile robot is inspired by the Talwar's brain-machine interface technology for remotely training and controlling rats. Our biologically inspired autonomous robot control consciousness-based architecture (CBA) is used for the remote control of a robot as a substitute for a rat. CBA is a developmental hierarchy model of the relationship between consciousness and behavior, including a training algorithm. This training algorithm computes a shortcut path to a goal using a cognitive map created based on behavior obstructions during a single successful trial. However, failures in reaching the goal due to errors of the vision and dead reckoning sensors require human intervention to improve autonomous navigation. A human operator remotely intervenes in autonomous behaviors in two ways: low-level intervention in reflexive actions and high-level ones in the cognitive map. Experiments are conducted to test CBA functions for intervention with a joystick for a Khepera robot navigating from the center of a square obstacle with an open side toward a goal. Their statistical results show that both human interventions, especially high-level ones, are effective in drastically improving the success rate of autonomous detours. 相似文献
73.
Ryosuke Ueyama Masahiro Harada Tamotu Ueyama Takashi Yamamoto Tadashi Shiosaki Kiyoshi Kuribayashi Kunihito Koumoto Won Son Seo 《Journal of Materials Science: Materials in Electronics》2000,11(2):139-143
Ultrafine BaTiO3 particles were prepared by a micro-emulsion charring (MEC) method. The MEC method consisted of two steps. The first step is the preparation of a water/oil micro-emulsion with BaTiO3 elements, and the second is a low temperature firing process in N2 atmosphere, which includes charring of oil in an emulsion and powdering BaTiO3 particles with the char. The char formed around BaTiO3 particles prevents an agglomeration of BaTiO3 particles during firing. In the present experiment, the W/O ratio and the amount of emulsifier greatly influenced the size of droplets of the emulsion. The charring temperature was another important experimental factor in order to obtain the desired BaTiO3 particles. The finally obtained BaTiO3 charring powders were monodispersed spherical particles and the particle size was 0.1 m to 0.5 m. 相似文献
74.
Production of eicosapentaenoic acid by a recombinant marine cyanobacterium, Synechococcus sp. 总被引:1,自引:0,他引:1
The eicosapentaenoic acid (EPA) synthesis gene cluster from an EPA-producing bacterium, Shewanella sp. SCRC-2738, was cloned into a broad-host range vector, pJRD215, and then introduced into a marine cyanobacterium, Synechococcus sp. NKBG15041c, by conjugation. The transconjugant cyanobacteria produced 3.7±0.2% (2.24±0.13 mg/L) EPA (n-3) and 2.5 ±0.2%
(1.49±0.06 mg/L) eicosatetraenoic acid (n-3) of the total fatty acids when the cells were cultured at 23°C at a light intensity
of 1,000–1,500 Lux. The EPA and eico-satetraenoic acid contents of the cells were increased to 4.6±0.6% (3.86±1.11 mg/L) and
4.7±0.3% (3.86±0.82 mg/L), and 7.5±0.3% (1.76±0.10 mg/L) and 5.1±0.2% (1.19±0.06 mg/L) when they were cultured at low temperature
(18°C) and at lower light intensity (40 Lux), respectively. 相似文献
75.
Takeshi Kuroki Takashi Sawaguchi Kazumasa Suzuki Shoaki Ide Tadashi Ikemura 《Polymer》1983,24(4):428-432
The distribution of double bonds in thermally degraded polyisobutylene was determined quantitatively by using pulsed Fourier transform 1H n.m.r. spectroscopic analysis. The double bonds in the degraded polymer did not exist in the interior but at the terminal positions of the polymer chain. These olefins were of the terminal trisubstituted and terminal vinylidene types. The content of the former was much greater than that of the latter. This shows that radical chain transfer predominantly occurs at the methylene hydrogen rather than at the methyl groups of the polymer chain. The average number of double bonds per molecule, f, was greater than 1 and tended to be near 2. Thereby most of the degraded polyisobutylene was shown to have two terminal unsaturations per molecule. 相似文献
76.
77.
Transparent La0.33NbO3 flakes were fabricated by a rapid quenching technique. The quenched La0.33NbO3 phase takes a simple cubic perovskite structure and cation vacancies are randomly distributed on the A sites. The cubic La0.33NbO3 phase is a new modification which is different from the well-known orthorhombic phase with ordered A-site vacancies. Transparent flakes were found to show the predominant orientation of (110) and (220) planes. 相似文献
78.
Summary The permeation characteristics of polymer blend membranes from poly(vinylidene fluoride) and poly-(ethylene glycol) to aqueous polymer solution were investigated under carefully controlled conditions. The permeation characteristics were influenced significantly by the blend ratio, the temperature and time of heat treatment, which changed the structure of the resulting membranes. 相似文献
79.
In this study, the effect of temperature on the stereoselectivity of phospholipase D (PLD) toward the two primary hydroxyl
groups of glycerol in the transphosphatidylation reaction of phosphatidylcholine to phosphatidylglycerol (PtdGro) was investigated.
For this purpose, PLD from bacteria (Streptomyces septatus TH-2, S. halstedii subsp. scabies K6, and Actinomadura sp.) and cabbage were tested. At the reaction temperatures employed (0–60°C), the proportions of the two PtdGro diastereomers,
namely, 1,2-dioleoyl-sn-glycero-3-phospho-3′-sn-glycerol (R,R configuration) and 1,2-dioleoyl-sn-glycero-3-phosphol-1′-sn-glycerol (R,S configuration), which were produced with PLD from Streptomyces TH-2 and Actinomadura sp., changed gradually from 50% R,R and 50% R,S at 50–60°C to 70% R,R and 30% R,S at O°C. These alterations suggested that the stereoselectivity of the bacterial PLD toward the two primary hydroxyl groups
of prochiral glycerol was significantly influenced by reaction temperature. PLD from Streptomyces K6 showed relatively little effect of temperature on stereoselectivity, giving 65–69% R,R in the temperature range of 60–10°C examined. The plots of In ([R,R]/[R,S]) vs. 1/T gave good linear fits for these three bacterial PLD. No temperature effect was observed for cabbage PLD, which gave an almost
equimolar mixture of the R,R and R,S diastereomers in the range from 0 to 40°C. The temperature-dependent change in enantiomeric selectivity of the bacterial
PLD promises potentially profitable commercial exploitation. 相似文献
80.
The effects of Ni(II) in a synthetic wastewater on the activity of activated sludge microorganisms and sequencing batch reactor (SBR) treatment process were investigated. Two parallel lab-scale SBR systems were operated. One was used as a control unit, while the other received Ni(II) concentrations equal to 5 and 10 mg/l. The SBR systems were operated with FILL, REACT, SETTLE, DRAW and IDLE modes in the time ratio of 0.5:3.5:1.0:0.75:0.25 for a cycle time of 6 h. The addition of Ni(II) into SBR system caused drastically dropped in TOC removal rate (k) and specific oxygen uptake rate (SOUR) by activated sludge microorganisms due to the inhibitory effects of Ni(II) on the bioactivity of microorganisms. The addition of 5 mg/l Ni(II) caused a slight reduction in TOC removal efficiency, whereas 10 mg/l Ni(II) addition significantly affected the SBR performance in terms of suspended solids and TOC removal efficiency. Termination of Ni(II) addition led to almost full recovery of the bioactivity in microorganisms as shown in the increase of specific oxygen uptake rate (SOUR) and SBR treatment performance. 相似文献