全文获取类型
收费全文 | 1127篇 |
免费 | 34篇 |
国内免费 | 6篇 |
专业分类
电工技术 | 73篇 |
综合类 | 3篇 |
化学工业 | 298篇 |
金属工艺 | 51篇 |
机械仪表 | 18篇 |
建筑科学 | 22篇 |
能源动力 | 63篇 |
轻工业 | 117篇 |
水利工程 | 3篇 |
无线电 | 78篇 |
一般工业技术 | 196篇 |
冶金工业 | 46篇 |
原子能技术 | 24篇 |
自动化技术 | 175篇 |
出版年
2024年 | 2篇 |
2023年 | 6篇 |
2022年 | 17篇 |
2021年 | 26篇 |
2020年 | 23篇 |
2019年 | 16篇 |
2018年 | 37篇 |
2017年 | 32篇 |
2016年 | 33篇 |
2015年 | 19篇 |
2014年 | 44篇 |
2013年 | 78篇 |
2012年 | 66篇 |
2011年 | 83篇 |
2010年 | 52篇 |
2009年 | 71篇 |
2008年 | 78篇 |
2007年 | 53篇 |
2006年 | 41篇 |
2005年 | 48篇 |
2004年 | 45篇 |
2003年 | 37篇 |
2002年 | 36篇 |
2001年 | 21篇 |
2000年 | 11篇 |
1999年 | 24篇 |
1998年 | 20篇 |
1997年 | 13篇 |
1996年 | 15篇 |
1995年 | 19篇 |
1994年 | 11篇 |
1993年 | 11篇 |
1992年 | 9篇 |
1991年 | 5篇 |
1990年 | 3篇 |
1989年 | 9篇 |
1988年 | 5篇 |
1987年 | 6篇 |
1986年 | 3篇 |
1985年 | 5篇 |
1984年 | 5篇 |
1983年 | 6篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1979年 | 4篇 |
1977年 | 5篇 |
1976年 | 2篇 |
1974年 | 1篇 |
1973年 | 1篇 |
1970年 | 2篇 |
排序方式: 共有1167条查询结果,搜索用时 234 毫秒
991.
992.
A combined cycle power plant which combines a gas turbine and a steam turbine can achieve high energy efficiency. Many combined cycle plants have been installed worldwide. However, a large‐scale blackout due to combined cycle chain trip‐out occurred in Malaysia in 1996. The cause of this chain trip was considered to be a large drop of system frequency. Thus, there is a need to investigate the stability of the combined cycle power plant for the frequency drop. Several dynamic models of a combined cycle plant have been proposed. In our analysis, we use some of them and build a model for a single‐shaft combined cycle plant. We execute numerical simulations to see how the combined cycle plant behaves when the system frequency drops. The cause and the countermeasure of the combined cycle plant trip‐out are explained. © 2003 Wiley Periodicals, Inc. Electr Eng Jpn, 143(3): 9–19, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10117 相似文献
993.
994.
Yasuo Morimoto Hiroto Izumi Yukiko Yoshiura Kei Fujishima Kazuhiro Yatera Kazuhiro Yamamoto 《International journal of molecular sciences》2016,17(2)
Inhalation studies are the gold standard for the estimation of the harmful effects of respirable chemical substances, while there is limited evidence of the harmful effects of chemical substances by intratracheal instillation. We reviewed the effectiveness of intratracheal instillation studies for estimating the hazards of nanoparticles, mainly using papers in which both inhalation and intratracheal instillation studies were performed using the same nanoparticles. Compared to inhalation studies, there is a tendency in intratracheal instillation studies that pulmonary inflammation lasted longer in the lungs. A difference in pulmonary inflammation between high and low toxicity nanoparticles was observed in the intratracheal instillation studies, as in the inhalation studies. Among the endpoints of pulmonary toxicity, the kinetics of neutrophil counts, percentage of neutrophils, and chemokines for neutrophils and macrophages, heme oxygenase-1 (HO-1) in bronchoalveolar lavage fluid (BALF), reflected pulmonary inflammation, suggesting that these markers may be considered the predictive markers of pulmonary toxicity in both types of study. When comparing pulmonary inflammation between intratracheal instillation and inhalation studies under the same initial lung burden, there is a tendency that the inflammatory response following the intratracheal instillation of nanoparticles is greater than or equal to that following the inhalation of nanoparticles. If the difference in clearance in both studies is not large, the estimations of pulmonary toxicity are close. We suggest that intratracheal instillation studies can be useful for ranking the hazard of nanoparticles through pulmonary inflammation. 相似文献
995.
Wang Yuehua Yu Meiqi Luo Hongliang Qiao Qi Xiao Zeze Zhao Yan Zhao Lili Sun Hui Xu Zhefeng Matsugi Kazuhiro Yu Jinku 《Journal of Materials Engineering and Performance》2016,25(10):4402-4407
Journal of Materials Engineering and Performance - NiWP alloy coatings electrodeposited on pure copper substrates with additive saccharin (C7H5NO3S) contents of 0-6 g/L were investigated... 相似文献
996.
Yosuke Yamazaki Yohei Abe Yukio Hioki Mitsuyoshi Nakatani Akikazu Kitagawa Kazuhiro Nakata 《Welding International》2016,30(9):699-707
Laser welding with oscillation laser beams enables control of the heat input distribution. In this study, we attempted to develop a narrow-gap welding process with oscillation laser welding. This process is expected to prevent a lack of fusion because the entire bottom to the groove can be melted by the oscillation laser. As the first step of the study, bead-on-plate welding experiments with an oscillation laser beam were performed to investigate the relationship between the welding conditions and welding results. The experiments revealed that the oscillation conditions strongly affect the welding penetration shape. It was clarified that the wire melting phenomena in oscillation laser welding differed from those of straight (non-oscillation) laser welding. Additionally, narrow-gap laser welding experiments were performed to investigate the relationship between the oscillation conditions and gap width. The results confirmed the effectiveness of oscillation laser welding for narrow-gap welding. 相似文献
997.
Sohrin Y Urushihara S Nakatsuka S Kono T Higo E Minami T Norisuye K Umetani S 《Analytical chemistry》2008,80(16):6267-6273
GEOTRACES is an international research project on marine biogeochemical cycles of trace elements and their isotopes. GEOTRACES key trace metals in seawater are Al (8-1000 ng/kg), Mn (4-300 ng/kg), Fe (1-100 ng/kg), Cu (30-300 ng/kg), Zn (3-600 ng/kg), and Cd (0.1-100 ng/kg), of which global oceanic distribution will be determined on a number of research cruises. This work introduces a novel method of solid-phase extraction to determine Al, Mn, Fe, Co, Ni, Cu, Zn, Cd, and Pb in seawater by adjusting the pH of the sample to 6 and carrying out a single preconcentration step. The trace metals were collected from approximately 120 mL of seawater using a column of a chelating resin containing the ethylenediaminetriacetic acid functional group and eluted with approximately 15 mL of 1 M HNO3. Mn and Fe in the eluate were measured by inductively coupled plasma mass spectrometry (ICPMS) using the dynamic reaction cell mode, and the other metals were measured using the standard mode. Using this procedure, the trace metals were collected quantitatively, while >99.9% of alkali and alkaline earth metals in seawater were removed. The procedural blank was <7% of the mean concentration in deep ocean waters, except 16% for Pb. The overall detection limit was <14% of the mean concentration in deep ocean waters. The RSD was <9%. Our values for the trace metals in the certified reference materials of seawater NASS-5 and nearshore seawater CASS-4 agreed with the certified values (except that there is no certified value for Al). This method was also successfully applied to the reference materials of open-ocean seawater produced by the SAFe program. Our Fe concentrations were 5.9 +/- 0.7 ng/kg for surface water (S1) and 50.4 +/- 2.9 ng/kg for deep water (D2), which are in agreement with the interlaboratory averages of 5.4 +/- 2.4 and 50.8 +/- 9.5 ng/L, respectively. The data for other metals were oceanographically consistent. 相似文献
998.
A shaft kiln is considered to be a promising pyrolysis device for the efficient decomposition of municipal wastes. In this device, the temperature distributions of the gas and solid phases can be separately controlled, thereby leading to considerably different profiles for both the phases. The temperature controllability in a shaft kiln helps us to obtain a suitable profile of the gas-phase temperature for the decomposition of tar that evolves from the solid phase. By leveraging this advantage of the shaft kiln, we performed further pyrolysis and steam reforming of the volatiles formed from the pyrolysis of biomass and several polymers using a two-stage reactor that was maintained at different temperatures. The amount of tar decreased with an increase in the temperature in the upper reactor in the absence of a catalyst. By using the experimental results, we developed a lumped kinetic model for secondary gas-phase reactions and performed a kinetic analysis of the reactions that proceeded in the upper reactor. It is confirmed that the simulation model is successful in reproducing the product distribution of the gas-phase reactions of volatiles from biomass and polymers. 相似文献
999.
In view of the high potential of trimethylsilylated chitin as a reaction precursor, the influence
of trimethylsilylation and detrimethylsilylation on the molecular weight characteristics has been studied.
Chitin was trimethylsilylated, and the product was detrimethylsilylated to regenerate chitin. The molecular
weights of the original and regenerated chitins were determined by viscometry and GPC. The viscosity measurements,
with either an Ubbelohde or a rotational viscometer, gave highly reproducible values, which were quite similar
to each other. The molecular weight of the regenerated chitin was found to be a little over a half that
of the original chitin despite after the silylation-desilylation reactions. GPC also supported a similarly
low extent of main chain scission. These results indicate that the silylation-desilylation reactions are
reproducible without a significant damage to the chitin main chain, and both viscometry and GPC have proved
reliable in elucidating the molecular weight characteristics. Trimethylsilylation of chitin can thus be
conveniently used as a key intermediate for further controlled modification reactions to prepare well-defined
derivatives. 相似文献
1000.
The efficacy of pulmonary administration of liposomal ciprofloxacin (CPFX) in pneumonia was evaluated. In brief, the pharmacokinetics following pulmonary administration of liposomal CPFX (particle size, 1,000 nm; dose, 200 microg/kg) were examined in rats with lipopolysaccharide-induced pneumonia as an experimental pneumonia model. Furthermore, the antibacterial effects of liposomal CPFX against the pneumonic causative organisms were estimated by pharmacokinetic/pharmacodynamic (PK/PD) analysis. The time-courses of the concentration of CPFX in alveolar macrophages (AMs) and lung epithelial lining fluid (ELF) following pulmonary administration of liposomal CPFX to rats with pneumonia were markedly higher than that following the administration of free CPFX (200 microg/kg). The time course of the concentrations of CPFX in plasma following pulmonary administration of liposomal CPFX was markedly lower than that in AMs and ELF. These results indicate that pulmonary administration of liposomal CPFX was more effective in delivering CPFX to AMs and ELF compared with free CPFX, and it avoids distribution of CPFX to the blood. According to PK/PD analysis, the liposomal CPFX exhibited potent antibacterial effects against the causative organisms of pneumonia. This study indicates that pulmonary administration of CPFX could be an effective technique for the treatment of pneumonia. 相似文献