全文获取类型
收费全文 | 759篇 |
免费 | 29篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 130篇 |
综合类 | 4篇 |
化学工业 | 160篇 |
金属工艺 | 12篇 |
机械仪表 | 10篇 |
建筑科学 | 12篇 |
能源动力 | 27篇 |
轻工业 | 45篇 |
水利工程 | 1篇 |
石油天然气 | 2篇 |
无线电 | 84篇 |
一般工业技术 | 169篇 |
冶金工业 | 66篇 |
原子能技术 | 11篇 |
自动化技术 | 57篇 |
出版年
2023年 | 1篇 |
2022年 | 6篇 |
2021年 | 15篇 |
2020年 | 4篇 |
2019年 | 10篇 |
2018年 | 7篇 |
2017年 | 13篇 |
2016年 | 13篇 |
2015年 | 14篇 |
2014年 | 26篇 |
2013年 | 37篇 |
2012年 | 33篇 |
2011年 | 41篇 |
2010年 | 34篇 |
2009年 | 41篇 |
2008年 | 48篇 |
2007年 | 37篇 |
2006年 | 43篇 |
2005年 | 45篇 |
2004年 | 29篇 |
2003年 | 21篇 |
2002年 | 27篇 |
2001年 | 13篇 |
2000年 | 14篇 |
1999年 | 19篇 |
1998年 | 38篇 |
1997年 | 18篇 |
1996年 | 17篇 |
1995年 | 14篇 |
1994年 | 9篇 |
1993年 | 12篇 |
1992年 | 12篇 |
1991年 | 9篇 |
1990年 | 16篇 |
1989年 | 3篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 10篇 |
1985年 | 2篇 |
1984年 | 3篇 |
1983年 | 8篇 |
1981年 | 5篇 |
1980年 | 3篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 1篇 |
1974年 | 1篇 |
排序方式: 共有790条查询结果,搜索用时 684 毫秒
231.
Osuke Miura Naotaka Ichiyanagi Hirokazu Misawa Naomi Hashimoto 《Electrical Engineering in Japan》1997,121(3):20-26
A composite insulation system of laminated tape and high vacuum is newly proposed for a superconducting bus-line cable operated at relatively low voltage. Its breakdown characteristics were investigated using model cable specimens with different kinds of laminated tapes such as semisynthetic paper, polypropylene film, and kraft paper of insulation thickness less than 1 mm. First, ±dc, ac, and —Imp breakdown stresses of the semisynthetic papers were investigated. +dc breakdown stress was 21.7 kV/mm for a specimen of insulation thickness 1 mm and −dc breakdown stress was 41.5 kB/mm, so that the remarkable polar effect was observed. ac breakdown stress was 18 kV/mm. Also, the ratio of −Imp breakdown stress was about 3. Furthermore, ac breakdown stresses of other tapes were investigated, but remarkable differences among their stresses were not observed. Most of the specimens were broken from the “butt gap” between tapes. To understand this cause, measurements of the partial discharge were carried out. It was found that the inception stress of partial discharge of butt gap located just on the conductor was about 20 kV/mm, not dependent on the kind of tape. This value is much lower than the breakdown stress of the same length of vacuum gap. Therefore, it is considered that the trigger of the breakdown of this insulation system is the surface discharge along the edge of the butt gap. © 1998 Scripta Technica, Inc. Electr Eng Jpn, 121(3): 20–26, 1997 相似文献
232.
Hirokazu Masai Ryota Shirai Takamichi Miyazaki Kazuki Yoshida Takumi Fujiwara Yomei Tokuda Toshinobu Yoko 《Journal of the American Ceramic Society》2013,96(11):3576-3583
Transparent (Sr0.5Ba0.5)Nb2O6 (SBN50) nanocrystallite‐precipitated phosphate glass‐ceramics were prepared by a conventional glass‐ceramic process. x(SrO–BaO–2Nb2O5) ? (100–4x)P2O5 (xSBNP) glasses with a refractive index of 1.9–2.0 exhibited high water resistance owing to the presence of Q0 and Q1 phosphate units. Both bulk and surface crystallization of the SBN50 phase were observed in 20SBNP and 21SBNP glass‐ceramics. Although the nominal content of SBN50 crystals in the 21SBNP glass was larger than that in the 20SBNP glass, the latter exhibited better crystallinity of SBN50 and a higher number density of precipitated SBN nanocrystallites. By tuning the two‐step heat‐treatment and the chemical composition, transparent SBN50‐precipitated glass‐ceramics were successfully obtained. Given that no remarkable increase of the relative dielectric constants was observed after crystallization of the SBN50 nanocrystallites, it is postulated that the relative dielectric constant of the bulk is mainly governed by the amorphous phosphate region, and that the contribution of precipitation of the SBN50 nanocrystallites to the dielectric constant is not very significant in this system. 相似文献
233.
SiC (core) and SiO2 (shell) powders were synthesized via rotary chemical vapor deposition (RCVD). The SiC particles (3C, <1 μm in diameter) were coated with a layer of SiO2 (10–15 nm in thickness). Using spark plasma sintering, the SiC/SiO2 nanopowders were then synthesized into SiC/SiO2 composite bodies. Although a phase transformation from 3C to 6H was observed at above 2123 K in the sintered monolithic SiC bodies, sintered SiC/SiO2 bodies did not display such phase transformation. In addition, SiC/SiO2 bodies did not exhibited grain growth until the sintering temperature reached 2223 K. The density and Vickers hardness of the sintered SiC/SiO2 bodies increased with increasing sintering temperature. The highest density and hardness of SiC/SiO2 composite bodies were 98.1% and 24.4 GPa at 2223 K, respectively, which were higher than the corresponding values of 90% and 14 GPa for monolithic SiC bodies. 相似文献
234.
Summary Novel vinyl polymers bearing monoazacrown ether-type side chains with a number average molecular weigh of over 5000 were radically synthesized from the 16-membered α-methylenemacrolide monomers. The obtained polymers possessed a Na+ or K+ selective extraction ability, whereas K+ was preferentially extracted by the monomers. The polymer having the N-(2-naphthoyl)azacrown ether pendant groups showed a selective UV-responsive complexation with Li+ in 1,2-dichloroethane-CH3CN. 相似文献
235.
Development of a ligation-based impedimetric DNA sensor for single-nucleotide polymorphism associated with metabolic syndrome 总被引:1,自引:0,他引:1
Yoshinori Akagi Megumi Makimura Yoshiyuki Yokoyama Masaki Fukazawa Satoshi Fujiki Masahiro Kadosaki Katsumi Tanino 《Electrochimica acta》2006,51(28):6367-6372
Single-nucleotide polymorphism (SNP) detection is becoming important in molecular diagnostics, clinical assay, and novel drug development. Electrochemical methods are well suited for the DNA diagnostics system. Since electrochemical reactions directly emit an electronic signal, expensive signal transduction equipment is not required. We describe the development of a novel DNA sensor that utilizes impedance spectroscopy and DNA ligation reaction on a gold electrode. Impedance spectroscopy enables label-free detection and is nondestructive and useful in equivalent circuit models for interpretation on an electrode surface, whereas from the ligation reaction, the specificity is derived by the allele-specific oligonucleotide of the capture probe on immobilized gold electrode. In other words, DNA diagnostics system using the combination of impedance spectroscopy and ligation reaction is simple, rapid, and allele specific. In this report, we have described a ligation-based impedimetric DNA sensor and the analysis of Trp64Arg polymorphism in the beta3-adrenergic receptor gene (ADRβ3). 相似文献
236.
Isokinetic sampling is required when evaluating the aerodynamic sizes of particles released from dry powder inhalers (DPI) under simulated breathing condition since anisokinetic sampling may lead to significant sampling error for coarse particles. We propose an isokinetic measuring system for aerosol particles from a stream in a narrow conduit of variable flow rates (variable flow rate aerosol sampler, VFAS) combined with Aerodynamic Particle sizer® APSTM spectrometer (model 3321, TSI Inc.). The VFAS was capable of generating variable sampling flow rates by adjusting the flow resistance of makeup air to produce constant flow rate of aerosol to the APS. The penetrations through the VFAS-APS system were measured using monodisperse particles with a size range of 0.7–15 μm by applying a rectangular flow rate–time pattern of sampling air, and we found that the VFAS-APS system can measure the number concentration of particles with the particle detection efficiency (particle penetration through the system) of almost unity. The VFAS-APS system may be a powerful tool to measure the size and concentration of powder released by the DPI in the size range of 0.5–15 μm. Copyright 2012 American Association for Aerosol Research 相似文献
237.
Synergistic extraction of Rh(III) from relatively concentrated HCl solution was studied using two mixed solvents (di-n-hexyl sulfide (DHS)–tri-n-octylamine (TOA) and N,N′-dimethyl-N,N′-di-n-octyl-thiodiglycolamide (TDGA)–TOA) in chloroform. The Rh(III) extraction efficiency is poor when 0.5 M TOA, DHS, or TDGA is used independently. In contrast, the 0.5 M TDGA–0.5 M TOA and 0.5 M DHS–0.5 M TOA mixed solvents extract ?90% and ?70% of Rh(III), respectively, at maximum. Slope analyses and Job’s plots for the distribution ratios of Rh(III) at 2 M HCl show that the apparent stoichiometry of Rh(III):TOA:(DHS or TDGA) in the extracted complex is 1:2:1. 相似文献
238.
Total mercury and methylmercury levels in fish from hydroelectric reservoirs in Tanzania 总被引:4,自引:0,他引:4
Total mercury (THg) and methylmercury (MeHg) levels have been determined in fish species representing various tropic levels in four major hydroelectric reservoirs (Mtera, Kidatu, Hale-Pangani, Nyumba ya Mungu) located in two distinct geographical areas in Tanzania. The Mtera and Kidatu reservoirs are located along the Great Ruaha River drainage basin in the southern central part of the country while the other reservoirs are located within the Pangani River basin in the north eastern part of Tanzania. Fish mercury levels ranged from 5 to 143 microg/kg (mean 40 microg/kg wet weight) in the Mtera Reservoir, and from 7 to 119 microg/kg (mean 21 microg/kg) in the Kidatu Reservoir downstream of the Great Ruaha River. The lowest THg levels, in the range 1-10 microg/kg (mean 5 microg/kg), were found in fish from the Nyumba ya Mungu (NyM) Reservoir, which is one of the oldest reservoirs in the country. Fish mercury levels in the Pangani and Hale mini-reservoirs, downstream of the NyM Reservoir, were in the order of 3-263 microg/kg, with an average level of 21 microg/kg. These THg levels are among the lowest to be reported in freshwater fish from hydroelectric reservoirs. Approximately 56-100% of the total mercury in the fish was methylmercury. Herbivorous fish species contained lower THg levels than the piscivorous species; this was consistent with similar findings in other fish studies. In general the fish from the Tanzanian reservoirs contained very low mercury concentrations, and differed markedly from fish in hydroelectric reservoirs of similar age in temperate and other regions, which are reported to contain elevated mercury concentrations. The low levels of mercury in the fish correlated with low background concentrations of THg in sediment and flooded soil (mean 2-8 microg/kg dry weight) in the reservoir surroundings. This suggested a relatively clean reservoir environment that has not been significantly impacted by mercury contamination from natural or anthropogenic sources. 相似文献
239.
Kazufumi Nakamura Toru Miyoshi Masashi Yoshida Satoshi Akagi Yukihiro Saito Kentaro Ejiri Naoaki Matsuo Keishi Ichikawa Keiichiro Iwasaki Takanori Naito Yusuke Namba Masatoki Yoshida Hiroki Sugiyama Hiroshi Ito 《International journal of molecular sciences》2022,23(7)
There is a close relationship between diabetes mellitus and heart failure, and diabetes is an independent risk factor for heart failure. Diabetes and heart failure are linked by not only the complication of ischemic heart disease, but also by metabolic disorders such as glucose toxicity and lipotoxicity based on insulin resistance. Cardiac dysfunction in the absence of coronary artery disease, hypertension, and valvular disease is called diabetic cardiomyopathy. Diabetes-induced hyperglycemia and hyperinsulinemia lead to capillary damage, myocardial fibrosis, and myocardial hypertrophy with mitochondrial dysfunction. Lipotoxicity with extensive fat deposits or lipid droplets is observed on cardiomyocytes. Furthermore, increased oxidative stress and inflammation cause cardiac fibrosis and hypertrophy. Treatment with a sodium glucose cotransporter 2 (SGLT2) inhibitor is currently one of the most effective treatments for heart failure associated with diabetes. However, an effective treatment for lipotoxicity of the myocardium has not yet been established, and the establishment of an effective treatment is needed in the future. This review provides an overview of heart failure in diabetic patients for the clinical practice of clinicians. 相似文献
240.
Masashi Kotobuki Hirokazu Munakata Yosuke Sato Toshihiro Yoshida 《Journal of power sources》2010,195(17):5784-9819
In order to improve performance of all-solid-state lithium ion battery with honeycomb structure, a compatibility of two commonly used cathode materials, LiCoO2 and LiMn2O4, to Li0.55La0.35TiO3 (LLT) solid electrolyte was studied. LiCoO2/honeycomb LLT and LiMn2O4/honeycomb LLT half cells were fabricated by the impregnation of mixture of the cathode material with its precursor sol into honeycomb holes followed by the calcination. Impurity phases were observed at interface between LiCoO2 and honeycomb LLT, while no impurity phase was confirmed in the case of LiMn2O4. In half cell test, the LiMn2O4/honeycomb LLT cell showed about 6 times larger discharge capacity than the LiCoO2/honeycomb LLT cell, because of high internal resistance of the LiCoO2/honeycomb LLT cell caused by the impurity phases. It can be said that the formation of low resistance interface at active material/electrolyte is one of the most important key to improve performance of the all-solid-state battery. Using LiMn2O4 instead of LiCoO2, better interface between cathode material and LLT was obtained. 相似文献