全文获取类型
收费全文 | 1204篇 |
免费 | 58篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 56篇 |
综合类 | 1篇 |
化学工业 | 318篇 |
金属工艺 | 29篇 |
机械仪表 | 23篇 |
建筑科学 | 28篇 |
能源动力 | 74篇 |
轻工业 | 158篇 |
无线电 | 76篇 |
一般工业技术 | 245篇 |
冶金工业 | 63篇 |
原子能技术 | 60篇 |
自动化技术 | 134篇 |
出版年
2023年 | 7篇 |
2022年 | 7篇 |
2021年 | 30篇 |
2020年 | 18篇 |
2019年 | 22篇 |
2018年 | 37篇 |
2017年 | 26篇 |
2016年 | 57篇 |
2015年 | 33篇 |
2014年 | 56篇 |
2013年 | 95篇 |
2012年 | 71篇 |
2011年 | 104篇 |
2010年 | 81篇 |
2009年 | 82篇 |
2008年 | 80篇 |
2007年 | 61篇 |
2006年 | 37篇 |
2005年 | 43篇 |
2004年 | 57篇 |
2003年 | 41篇 |
2002年 | 23篇 |
2001年 | 12篇 |
2000年 | 16篇 |
1999年 | 11篇 |
1998年 | 28篇 |
1997年 | 9篇 |
1996年 | 12篇 |
1995年 | 17篇 |
1994年 | 15篇 |
1993年 | 15篇 |
1992年 | 3篇 |
1991年 | 8篇 |
1990年 | 5篇 |
1989年 | 6篇 |
1988年 | 4篇 |
1986年 | 4篇 |
1985年 | 5篇 |
1984年 | 6篇 |
1983年 | 2篇 |
1981年 | 5篇 |
1980年 | 6篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1977年 | 5篇 |
1976年 | 1篇 |
排序方式: 共有1265条查询结果,搜索用时 15 毫秒
1.
Increasing the reaction temperature of the living cationic polymerization of isobutylene is crucial for industrial production due to the cost of refrigeration. The reaction temperature increase was achieved with an accelerated reaction rate using a flow reaction system. The polymerization conditions, including the flow reactor design, were based on the results of kinetic studies. Utilizing a milli‐scale flow reactor, polyisobutylene, which has a narrow molecular weight distribution, was obtained within a considerably short residence time at a high temperature. Furthermore, it was confirmed that the value of Mw/Mn correlates with the product of the Reynolds number and the angle of collision. 相似文献
2.
Genki Saito Yuji Kunisada Takumi Watanabe Xuemei Yi Takahiro Nomura Norihito Sakaguchi Tomohiro Akiyama 《Journal of the American Ceramic Society》2019,102(1):524-532
Carbon-and-oxygen-doped AlN specimens were prepared by combustion synthesis using Al, graphite, and AlN. Graphite addition changed the product color from white to blue. By XRD, the lattice constant increased slightly with increasing carbon content. Blue AlN powder was synthesized with a molar ratio of the diluent AlN of 0.2-0.5 with a fixed graphite content of 0.05. At an AlN molar ratio exceeding 0.6, carbon was not successfully incorporated due to the lower reaction temperature. Calcination at 800°C in air removed residual graphite without changing the crystal structure or product color. Oxygen, nitrogen, and carbon analyses revealed that blue AlN powders contained 0.45-0.54 mass% carbon and 1.4-1.6 mass% oxygen, while the undoped AlN contained 0.021 mass% carbon and 0.94 mass% oxygen. The origin of the white-to-blue color change was investigated via reflection measurements. Blue AlN exhibits an absorption peak at 634 nm (1.96 eV). From first-principles electronic structure calculations, the C-doped AlN and carbon-and-oxygen-doped AlN with a 1:1 ratio could be classified as p-type, whereas the O-doped AlN and 1:3 carbon-and-oxygen-doped AlN were n-type. One reason for the absorption peak at 634 nm may be a transition from the conduction band to an upper unoccupied state. These results suggest the possible control of optical and electronic properties of AlN via carbon-and-oxygen doping. 相似文献
3.
Christian Gentzsch Dr. Matthias Hoffmann Dr. Yasuhiro Ohshima Naoko Nose Dr. Xinyu Chen Prof. Dr. Takahiro Higuchi Prof. Dr. Michael Decker 《ChemMedChem》2021,16(9):1427-1437
The enzyme butyrylcholinesterase (BChE) represents a promising target for imaging probes to potentially enable early diagnosis of neurodegenerative diseases like Alzheimer's disease (AD) and to monitor disease progression in some forms of cancer. In this study, we present the design, facile synthesis, in vitro and preliminary ex vivo and in vivo evaluation of a morpholine-based, selective inhibitor of human BChE as a positron emission tomography (PET) tracer with a pseudo-irreversible binding mode. We demonstrate a novel protecting group strategy for 18F radiolabeling of carbamate precursors and show that the inhibitory potency as well as kinetic properties of our unlabeled reference compound were retained in comparison to the parent compound. In particular, the prolonged duration of enzyme inhibition of such a morpholinocarbamate motivated us to design a PET tracer, possibly enabling a precise mapping of BChE distribution. 相似文献
4.
Meng Guo Masakoto Kanezashi Hiroki Nagasawa Liang Yu Kazuki Yamamoto Takahiro Gunji Toshinori Tsuru 《American Institute of Chemical Engineers》2020,66(4):e16850
Fine-tuned, molecular-composite, organosilica membranes were fabricated via the co-condensation of organosilica precursors bis(triethoxysilyl)acetylene (BTESA) and bis(triethoxysilyl)benzene (BTESB). Fourier transform infrared and UV–vis spectra confirmed the co-condensation behaviors of BTESA and BTESB. The evolution of the network structure indicated that the incorporated BTESB decreased the membrane pore size, which was determined by a modified gas translation model according to the steric effect of the phenyl groups. The incorporation of BTESB to BTESA finely tuned the membrane structure and endowed the resultant composite membrane with improved separation properties. The BTESAB 9:1 membrane (molar ratio of BTESA/BTESB was 9:1) exhibited high C3H6 permeance at 4.5 × 10−8 mol m−2 s−1 Pa−1 and a C3H6/C3H8 permeance ratio of 33 at 50°C. One of the most important developments of this study involved clearly defining the relationship between membrane pore size and C3H6/C3H8 separation performance for organosilica membranes in single and binary separation systems. 相似文献
5.
Akira Kaieda Dr. Masashi Takahashi Hiromi Fukuda Dr. Rei Okamoto Dr. Shinji Morimoto Masayuki Gotoh Takahiro Miyazaki Yuri Hori Satoko Unno Dr. Tomohiro Kawamoto Dr. Toshimasa Tanaka Dr. Sachiko Itono Terufumi Takagi Dr. Hiroshi Sugimoto Dr. Kengo Okada Dr. Weston Lane Dr. Bi-Ching Sang Dr. Kumar Saikatendu Dr. Shinichiro Matsunaga Dr. Seiji Miwatashi 《ChemMedChem》2019,14(24):2093-2101
We identified novel potent inhibitors of p38 mitogen-activated protein (MAP) kinase using a structure-based design strategy, beginning with lead compound, 3-(butan-2-yl)-6-(2,4-difluoroanilino)-1,3-dihydro-2H-imidazo[4,5-b]pyridin-2-one ( 1 ). To enhance the inhibitory activity of 1 against production of tumor necrosis factor-α (TNF-α) in human whole blood (hWB) cell assays, we designed and synthesized hybrid compounds in which the imidazo[4,5-b]pyridin-2-one core was successfully linked with the p-methylbenzamide fragment. Among the compounds evaluated, 3-(3-tert-butyl-2-oxo-2,3-dihydro-1H-imidazo[4,5-b]pyridin-6-yl)-4-methyl-N-(1-methyl-1H-pyrazol-3-yl)benzamide ( 25 ) exhibited potent p38 inhibition, superior suppression of TNF-α production in hWB cells, and also significant in vivo efficacy in a rat model of collagen-induced arthritis (CIA). In this paper, we report the discovery of potent, selective, and orally bioavailable imidazo[4,5-b]pyridin-2-one-based p38 MAP kinase inhibitors. 相似文献
6.
A series of fully-acylated dextrin esters (DS = 3) with varying side-chain lengths (C2–12) were synthesized by heterogeneous esterification using trifluoroacetic anhydride/carboxylic acid. The influence of side-chain lengths on structure and properties of dextrin esters were investigated by structural, thermal, mechanical and hydrophobic analysis. The thermal stability of dextrin was enhanced by esterification, presenting ca. 40–60 °C higher decomposition temperatures than that of neat-dextrin. The transition temperatures of melting and crystallization were not observed for all dextrin esters because they were amorphous polymers. The glass transition temperature (Tg) was not observed in dextrin but was observed in dextrin esters. As increasing side-chain length, Tgs of dextrin esters decreased ranged from 162.2 °C (C2) to 49.2 °C (C12). Colorless and transparent dextrin ester films were prepared to measure the film properties. Tensile strength of dextrin ester films tended to decrease with increasing side-chain lengths, whereas the elongation at break increased. And, dextrin ester films showed significantly increased hydrophobicity with a contact angle of up to 102° (C12). 相似文献
7.
Hainan Bai Jiulin Hu Xiaoguang Li Yusen Duan Feng Shao Takahiro Kozawa Makio Naito Jingxian Zhang 《Ceramics International》2018,44(6):6558-6563
Concerning the safety problems of conventional Li-ion batteries with liquid electrolytes, it is crucial to develop reliable solid-state electrolytes with high ionic conductivity. Li1+xAlxTi2?x(PO4)3 (LATP, x = 0.3) is regarded as one of the most promising solid electrolytes due to its high ionic conductivity and excellent chemical stability to humidity.Herein, a new strategy is proposed for improving the sintering behavior and enhancing the ionic conductivity of LATP by using LiBO2 as the sintering aid via liquid phase sintering. The as-prepared sample LATP with homogeneous microstructure and high relative density of 97.1% was successfully synthesized, yielding high total ionic conductivity of 3.5 × 10?4 S cm?1 and low activation energy of 0.39 eV at room temperature. It was found that the addition of LiBO2 could effectively enhance the densification and increase the ionic conductivity of LATP electrolyte, proving an effective way to synthesis LATP ceramics by a simple and reliable route. 相似文献
8.
Applicability of vacuum‐microwave drying for tomato fruit based on evaluations of energy cost,color, functional components,and sensory qualities 下载免费PDF全文
9.
10.
Decomposing regional income inequality in China and Indonesia using two-stage nested Theil decomposition method 总被引:9,自引:0,他引:9
Takahiro Akita 《The Annals of Regional Science》2003,37(1):55-77
The objective of this paper is to present an inequality decomposition method, the two-stage nested Theil decomposition method,
which is an extension of the ordinary one-stage Theil decomposition method. The method is analogous to a two-stage nested
design in the analysis of variance (ANOVA). It considers the three-level hierarchical structure of a country: region-province-district,
and decomposes overall regional inequality, as measured by Theil indices based on district-level mean incomes, into three
components: the between-region, between-province, and within-province inequality components. The within-province component
is a weighted-average of within-province income inequalities for each province, while the between-province component is a
weighted-average of between-province income inequalities within each region. The method uses a district as the underlying
regional unit to measure regional income inequality, rather than a province, and thus can analyze the contribution of within-province
inequalities as well as between-province and between-region inequalities to the overall regional income inequality in a coherent
framework. This paper applies the two-stage nested Theil decomposition method to district-level income and population data
in China and Indonesia and explores factors determining regional income inequality in China and Indonesia.
Received: October 2000/Accepted: June 2002
The author is grateful to the Foundation of International Education (Kokusai Kyoiku Zaidan) and Japan Society for the Promotion
of Science (Grant-in-Aid for Scientific Research No. 12630073) for their financial support, and to anonymous referees for
helpful comments. 相似文献