全文获取类型
收费全文 | 3010篇 |
免费 | 264篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 24篇 |
综合类 | 2篇 |
化学工业 | 636篇 |
金属工艺 | 47篇 |
机械仪表 | 66篇 |
建筑科学 | 101篇 |
矿业工程 | 5篇 |
能源动力 | 67篇 |
轻工业 | 610篇 |
水利工程 | 45篇 |
石油天然气 | 12篇 |
无线电 | 128篇 |
一般工业技术 | 477篇 |
冶金工业 | 720篇 |
原子能技术 | 1篇 |
自动化技术 | 335篇 |
出版年
2024年 | 7篇 |
2023年 | 24篇 |
2022年 | 32篇 |
2021年 | 73篇 |
2020年 | 59篇 |
2019年 | 79篇 |
2018年 | 124篇 |
2017年 | 131篇 |
2016年 | 144篇 |
2015年 | 115篇 |
2014年 | 106篇 |
2013年 | 233篇 |
2012年 | 202篇 |
2011年 | 227篇 |
2010年 | 149篇 |
2009年 | 122篇 |
2008年 | 108篇 |
2007年 | 144篇 |
2006年 | 71篇 |
2005年 | 61篇 |
2004年 | 64篇 |
2003年 | 61篇 |
2002年 | 66篇 |
2001年 | 43篇 |
2000年 | 32篇 |
1999年 | 40篇 |
1998年 | 271篇 |
1997年 | 161篇 |
1996年 | 94篇 |
1995年 | 49篇 |
1994年 | 34篇 |
1993年 | 36篇 |
1992年 | 10篇 |
1991年 | 15篇 |
1990年 | 7篇 |
1989年 | 6篇 |
1988年 | 7篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 7篇 |
1984年 | 4篇 |
1983年 | 2篇 |
1981年 | 5篇 |
1980年 | 5篇 |
1978年 | 5篇 |
1977年 | 7篇 |
1976年 | 23篇 |
1973年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有3276条查询结果,搜索用时 15 毫秒
991.
Flora E Mercader‐Trejo Eduardo Rodríguez de San Miguel Josefina de Gyves 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2009,84(9):1323-1330
BACKGROUND: Regulatory controls to limit mercury emissions in waters have impacted on the development of membrane extraction‐based methodologies for its separation. The specific advantages (effective carrier immobilization, easy preparation, versatility, and good mechanical properties) of polymer inclusion membranes (PIMs) make them suitable for this purpose. In this work a novel procedure using PIMs for mercury separation with a commercial available extractant (Cyanex 471X) is described and evaluated through the determination of the efficiency parameters (permeability, selectivity, stability) and membrane characterization. RESULTS: Using a membrane composed of 30% cellulose triacetate (CTA), 60% 2‐nitrophenyl octyl ether (NPOE), and 10% w/w Cyanex 471X a 0.1 mmol dm?3 Hg(II) solution prepared in 0.01 mol dm?3 HCl was transported to a 0.05 mol dm?3 NaCl solution at pH 12.3 with permeability values in the feed and strip phases of 0.25 and 0.15 cm min?1, respectively. A diffusive Fickian‐type mechanism was inferred from the results. High separation factors ranging between 2 and 5900, less than 11% of competing metal ions transported, active transport of the metal ion and a successful reuse of the PIM were achieved. CONCLUSION: Optimized PIMs using Cyanex 471X represent an interesting alternative for Hg(II) removal from waters showing high efficiency factors and easy implementation. Copyright © 2009 Society of Chemical Industry 相似文献
992.
J. A. Segura V. H. Champac R. Rodríguez-Montañés J. Figueras J. A. Rubio 《Journal of Electronic Testing》1992,3(4):337-348
Physical defects widely encountered in today's CMOS processes (bridges, gate oxide short (gas) and floating gates) are modeled taking into account the topology of the defective circuit and the parameters of the technology. These models are used to simulate at electrical level the behavior of a simple 3-inverter chain with a defective inverter. The results are compared with experimental data of integrated circuits fabricated with intentional defects. The influence of the characteristics of each defect on I
DDQ
has been investigated by electrical simulation and experimentation.J.A. Segura is at the Balearic Islands University (UIB) and is working on his Ph.D. at the Polytechnical University of Catalonia. 相似文献
993.
994.
Mónica Andrea Vargas Eric M. Rivera-Muñoz Jesús E. Diosa Edgar E. Mosquera Jorge E. Rodríguez-Páez 《Ceramics International》2021,47(11):15668-15681
Nanoparticles of zinc oxide and of ZnO doped with MgO in different concentrations (1, 2 and 4 mol%) were synthesized in a controlled and reproducible way, using the Pechini polymer precursor method. To determine the physicochemical and structural characteristics of the synthesized nanoparticles, Fourier transform IR (FTIR), X-ray diffraction (XRD), UV–Vis spectroscopy and transmission and scanning electron microscopy (TEM and SEM) were used. Characterization revealed the particles obtained to be nanometric in size (<50 nm) and with a deformed hexagonal morphology. Taking into account the doping percentage, the energy gap value varied between 3.3 eV for pure ZnO and 3.45 eV for ZnO with 4 mol% of Mg, which indicates that the optical properties of these nanoparticles were affected by dopant concentration. The effect of doping with Mg2+ on the capacity for removal of pollutant molecules by ZnO, for different working conditions, was evaluated by studying the removal of methyl orange (MO) in aqueous solution. Irradiation of the compounds led to a greater removal of MO from the solution such that all ZnO samples doped with MgO showed higher photoactivity than ZnO. The ZnO nanoparticles doped with 2% Mg were the most efficient in removing MO, achieving a removal percentage of ~73% after 2 h of testing and a totally transparent solution after 3 h of treatment. The kinetics of removal of MO promoted by this sample was best represented by pseudo-first-order kinetics. The results of this work showed that on combining a photosensitive semiconductor, ZnO, with a wide band gap insulator, MgO, Zn–Mg solid solutions are obtained that showed adequate capacity to remove contaminating organic molecules, specifically MO. 相似文献
995.
E Velázquez E Cervantes JM Igual A Peix PF Mateos S Benamar A Moiroud CT Wheeler J Dawson D Labeda C Rodríguez-Barrueco E Martínez-Molina 《Canadian Metallurgical Quarterly》1998,21(4):539-545
The modulation of the Cl- current activated by gamma-aminobutyric acid (GABA) by changes in extracellular pH in freshly isolated rat dorsal root ganglia (DRG) neurons was studied using the whole-cell patch-clamp technique. In the pH range of 5.0-9.0, increased extracellular pH enhanced, and decreased extracellular pH suppressed, current activated by 10 microM GABA in a reversible and concentration-dependent manner with an IC50 of pH 7.1 in these neurons. Acidification to pH 6.5 inhibited currents activated by the GABAA-selective agonist muscimol in all neurons tested. The antagonism of GABA-activated current by lowering the pH was equivalent at holding potentials between -80 and +40 mV and did not involve a significant alteration in reversal potential. Acidification shifted the GABA concentration/response curve to the right, significantly increasing the EC50 for GABA without appreciably changing the slope or maximal value of the curve. Inhibition of the GABA-activated current by protons was not significantly different when the patch-pipette solution was buffered at pH 7.4 or pH 6.5. These results suggest that extracellular protons inhibit GABAA receptor channels in primary sensory neurons by decreasing the apparent affinity of the receptor for GABA. This represents a novel mechanism of inhibition by protons of a neurotransmitter-gated ion channel. Proton inhibition of GABAA receptor channels may account in part for the modulation by protons of sensory information transmission under certain pathophysiological conditions. 相似文献
996.
997.
L Llanes González E Martín Osés I Fernández González JM Rodríguez Barbero JL Ruiz Rubio C Llorente Abarca A Berenguer Sánchez 《Canadian Metallurgical Quarterly》1998,51(9):923-925
OBJECTIVE: To report an additional case of nephrogenic adenoma of the bladder. METHODS/RESULTS: A case of nephrogenic adenoma of the urinary bladder in a 28-year-old female is described. Patient clinical history and diagnostic imaging findings are presented. CONCLUSIONS: Nephrogenic adenoma of the bladder is a rare benign tumor with specific histological features that has been associated with previous surgery, trauma, infections and lithiasis. Although it is currently not considered to be a premalignant lesion, its rate of recurrence is high (37%-49%). The treatment of choice is by transurethral resection and yearly cytological, ultrasound and cystoscopic follow-up evaluation to detect recurrence. 相似文献
998.
999.
B. Saruhan Dr.‐Ing. habil. M. Stranzenbach G. C. Mondragón Rodríguez 《Materialwissenschaft und Werkstofftechnik》2007,38(9):725-733
Upcoming emission regulations order highly effective NOx‐reduction systems in lean‐burn engines requiring new catalytic materials and integrated control of the reduction process. Thus, new approaches for NOx‐reduction and its monitoring over an On‐Board‐Diagnostic (OBD) system are suggested throughout the globe. A promising attempt is the development of a catalytic system having an integrated NOx‐sensor, based on selective catalytic reduction process and impedance sensors. The study displays the results achieved both with a perovskite type of self‐regenerative catalyst functioning by H2‐reductant and with impedance NOx‐sensors. The catalysts were tested at the temperature range of 150 °C to 360 °C yielding NOx conversion rates of 92 % with high selectivity to N2. Impedance sensors having NiCr2O4‐ and NiO‐SE and PYSZ‐ and FYSZ‐electrolytes are developed and tested at 600 °C under lean atmosphere (5 vol. % O2). Better sensing behaviour towards NO and lower cross‐selectivity towards O2, CO, CO2 and CH4 have been observed with sensors having NiO‐SE. 相似文献
1000.