全文获取类型
收费全文 | 319篇 |
免费 | 11篇 |
专业分类
电工技术 | 3篇 |
化学工业 | 86篇 |
金属工艺 | 8篇 |
机械仪表 | 8篇 |
建筑科学 | 9篇 |
矿业工程 | 1篇 |
能源动力 | 8篇 |
轻工业 | 56篇 |
水利工程 | 1篇 |
石油天然气 | 1篇 |
无线电 | 9篇 |
一般工业技术 | 44篇 |
冶金工业 | 57篇 |
原子能技术 | 4篇 |
自动化技术 | 35篇 |
出版年
2023年 | 4篇 |
2022年 | 12篇 |
2021年 | 12篇 |
2019年 | 6篇 |
2018年 | 10篇 |
2017年 | 4篇 |
2016年 | 6篇 |
2015年 | 5篇 |
2014年 | 9篇 |
2013年 | 29篇 |
2012年 | 15篇 |
2011年 | 20篇 |
2010年 | 15篇 |
2009年 | 14篇 |
2008年 | 11篇 |
2007年 | 15篇 |
2006年 | 11篇 |
2005年 | 5篇 |
2004年 | 5篇 |
2003年 | 4篇 |
2002年 | 9篇 |
2001年 | 4篇 |
2000年 | 3篇 |
1999年 | 5篇 |
1998年 | 11篇 |
1997年 | 9篇 |
1996年 | 4篇 |
1995年 | 3篇 |
1993年 | 3篇 |
1991年 | 5篇 |
1990年 | 2篇 |
1989年 | 2篇 |
1988年 | 4篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 6篇 |
1983年 | 3篇 |
1982年 | 2篇 |
1980年 | 5篇 |
1979年 | 3篇 |
1978年 | 1篇 |
1977年 | 7篇 |
1976年 | 9篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1972年 | 1篇 |
1971年 | 1篇 |
1970年 | 2篇 |
1966年 | 1篇 |
1956年 | 1篇 |
排序方式: 共有330条查询结果,搜索用时 15 毫秒
11.
Marta K. Schütz Natália F. Lopes Angélica Cenci João Marcelo M. Ketzer Sandra Einloft Jeane Dullius Rosane Ligabue 《化学工程与技术》2018,41(3):573-579
Carbon dioxide (CO2) gas is the main contributor to climate change. CO2 storage in underground brines and oil‐field brines by mineral trapping has been considered as a promising alternative in order to reduce CO2 emissions. However, permanent storage of CO2 in stable carbonate minerals is greatly dependent on brine pH, being favored over an alkaline pH. The effect of alkaline additives (NaOH, KOH, CaO) and buffer solutions (NaHCO3/NaOH, Na2HPO4/NaOH, NH4Cl/NH4OH) on the mineral trapping of CO2 under mild conditions using a synthetic brine is investigated. The results indicate that both NaOH+NH4Cl/NH4OH and KOH+NH4Cl/NH4OH mixtures promote precipitation mainly of calcium carbonate (CaCO3). 相似文献
12.
Ariel Burgos Hernán Svoboda Zhuyao Zhang Estela Surian 《Journal of Materials Engineering and Performance》2018,27(12):6328-6338
Creep-resistant 9Cr steels are extremely important in thermal power generation industry due to their marked resistance to creep and corrosion. The weldability of these alloys is critical since they are used in welded construction equipment. The required mechanical properties are achieved after post-weld heat treatment. This study examined the effect of different post-weld heat treatments on microstructure and mechanical properties of creep strength-enhanced 9Cr steel welding deposits. It was obtained with an experimental flux-cored arc welding wire used under protective gas (Ar-20% CO2). The heat treatments used were: (1) tempering (760 °C?×?2 h), (2) solubilizing (1050 °C?×?1 h)?+?tempering (760 °C?×?2 h) and (3) solubilizing (1150 °C?×?1 h)?+?first tempering (660 °C?×?3 h)?+?second tempering (660 °C?×?3 h). All-weld metal chemical composition was analyzed, and hot tensile tests were carried out at different temperatures. Charpy-V impact tests and Vickers microhardness measurements were also performed. Microstructures were studied using x-ray diffraction and optical and scanning electron microscopy. In all cases, a martensitic matrix with intergranular and intra-granular precipitates was detected. In the as-welded condition, δ-ferrite was also found. Microhardness dropped, and the impact energy increased with post-weld heat treatments. The highest hot tensile strength result was achieved with samples submitted to austenization at 1150 °C and double tempering at 660 °C. 相似文献
13.
Agustín Gualco Hernán G. Svoboda Estela S. Surian Luis A. de Vedia 《Welding International》2013,27(4):258-265
The effect of different post-weld heat treatments on the microstructure and wear resistance of martensitic deposits were studied. The deposit was welded using a metal-cored tubular wire, in the flat welding position, on a 375 × 75 × 19 mm SAE 1010 plate, using 98% Ar–2% CO2 shielding gas mixture and with an average heat input of 2.8 kJ/mm. The samples were heat treated at temperatures between 500 and 680°C for 2 h. Chemical composition, Vicker's microhardness and wear properties with AMSLER tests in a sliding condition were determined. In the as welded condition, the microstructure was principally composed of martensite and retained austenite. Significant variations in wear resistance and hardness were measured for different tempering temperatures. For the different heat-treated conditions, it was observed that the decomposition of retained austenite to martensite and carbide precipitation was associated with the tempering of martensite. A secondary hardness effect was detected with maximum hardness of 710 HV for 550°C heat treatment temperature. The best performance in wear test was obtained for this condition. Wear rates for the different conditions were obtained and mathematical expressions were developed. For each case, wear mechanisms were analyzed. 相似文献
14.
Raphael Rodrigues Corrêa Estela Mancheo Juncosa Rosalinde Masereeuw Rafael Soares Lindoso 《International journal of molecular sciences》2021,22(11)
Extracellular vesicles (EVs) have been described as important mediators of cell communication, regulating several physiological processes, including tissue recovery and regeneration. In the kidneys, EVs derived from stem cells have been shown to support tissue recovery in diverse disease models and have been considered an interesting alternative to cell therapy. For this purpose, however, several challenges remain to be overcome, such as the requirement of a high number of EVs for human therapy and the need for optimization of techniques for their isolation and characterization. Moreover, the kidney’s complexity and the pathological process to be treated require that EVs present a heterogeneous group of molecules to be delivered. In this review, we discuss the recent advances in the use of EVs as a therapeutic tool for kidney diseases. Moreover, we give an overview of the new technologies applied to improve EVs’ efficacy, such as novel methods of EV production and isolation by means of bioreactors and microfluidics, bioengineering the EV content and the use of alternative cell sources, including kidney organoids, to support their transfer to clinical applications. 相似文献
15.
Marta Gmez-Ferrer Estela Villanueva-Badenas Rafael Snchez-Snchez Christian M. Snchez-Lpez Maria Carmen Baquero Pilar Sepúlveda Akaitz Dorronsoro 《International journal of molecular sciences》2021,22(7)
Despite the strong evidence for the immunomodulatory activity of mesenchymal stromal cells (MSCs), clinical trials have so far failed to clearly show benefit, likely reflecting methodological shortcomings and lack of standardization. MSC-mediated tissue repair is commonly believed to occur in a paracrine manner, and it has been stated that extracellular vesicles (EVs) secreted by MSCs (EVMSC) are able to recapitulate the immunosuppressive properties of parental cells. As a next step, clinical trials to corroborate preclinical studies should be performed. However, effective dose in large mammals, including humans, is quite high and EVs industrial production is hindered by the proliferative senescence that affects MSCs during massive cell expansion. We generated a genetically modified MSC cell line overexpressing hypoxia-inducible factor 1-alpha and telomerase to increase the therapeutic potency of EVMSC and facilitate their large-scale production. We also developed a cytokine-based preconditioning culture medium to prime the immunomodulatory response of secreted EVs (EVMSC-T-HIFc). We tested the efficacy of this system in vitro and in a delayed-type hypersensitivity mouse model. MSC-T with an HIF-1α-GFP lentiviral vector (MSC-T-HIF) can be effectively expanded to obtain large amounts of EVs without major changes in cell phenotype and EVs composition. EVMSC-T-HIFc suppressed the proliferation of activated T-cells more effectively than did EVs from unmodified MSC in vitro, and significantly blunted the ear-swelling response in vivo by inhibiting cell infiltration and improving tissue integrity. We have developed a long-lived EV source that secretes high quantities of immunosuppressive EVs, facilitating a more standard and cost-effective therapeutic product. 相似文献
16.
17.
In this work, dipole defects are investigated applying the thermally stimulated depolarisation currents (TSDC) technique. The TSDC spectra of Al2O3 doped with Mg and Cr show two bands centred at 230 K and 250 K, respectively. The maximum intensity of the bands increases linearly with the polarisation field, a typical behaviour of defects with dipole origin. An increase of the band at 250 K with gamma irradiation has been observed and a thermal decrease of the bands for heat treatments between 1000 K and 1400 K. Above this temperature the bands are partially recovered. Impurity neutron activation analysis shows that magnesium. chromium and iron content varies from 15 to 60 ppm. Optical absorption (AO) measurements show a broad band centred in 2.6 eV (21000 cm(-1)) associated with trapped holes localised on an O- ion adjacent to a cation site which is deficient in positive charge. It has been assumed that a substitutional Mg2+ ion occupies the cation site near a trapped hole on one of the six oxygen ions surrounding the magnesium impurity giving rise to the dipole responsible for the observed TSDC bands. Calculations carried out through defect simulation methods confirm that the probability of Al3+ being replaced by Mg2+ is higher than Mn2+, Co2+, Fe2+ and Cr2+. 相似文献
18.
S Riskin-Mashiah KJ Moise I Wilkins NA Ayres CD Fraser 《Canadian Metallurgical Quarterly》1998,18(12):1328-1330
We present a case of intrapericardial teratoma diagnosed by ultrasound at 26 weeks of gestation presenting as a large tumour mass and rapid development of hydrops fetalis. The fetus died in utero one day before scheduled open fetal surgery. 相似文献
19.
D.J. Ayres 《Nuclear Engineering and Design》1980,59(1)
The need for a new design basis for pipe break criteria is demonstrated by noting the potential deleterious effect of present criteria in piping during normal operation. Recent advances in fracture mechanics and stress analysis permit development of rational, realistic and conservative criteria that will make possible significant improvements in piping system design. Research needed to form the basis for new criteria is suggested and the nuclear industry is encouraged to work towards this goal. 相似文献
20.