全文获取类型
收费全文 | 849篇 |
免费 | 26篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 51篇 |
综合类 | 1篇 |
化学工业 | 215篇 |
金属工艺 | 28篇 |
机械仪表 | 38篇 |
建筑科学 | 13篇 |
能源动力 | 21篇 |
轻工业 | 56篇 |
水利工程 | 5篇 |
石油天然气 | 3篇 |
无线电 | 32篇 |
一般工业技术 | 169篇 |
冶金工业 | 138篇 |
原子能技术 | 33篇 |
自动化技术 | 73篇 |
出版年
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 21篇 |
2020年 | 7篇 |
2019年 | 7篇 |
2018年 | 14篇 |
2017年 | 14篇 |
2016年 | 17篇 |
2015年 | 21篇 |
2014年 | 29篇 |
2013年 | 43篇 |
2012年 | 31篇 |
2011年 | 42篇 |
2010年 | 28篇 |
2009年 | 37篇 |
2008年 | 30篇 |
2007年 | 38篇 |
2006年 | 33篇 |
2005年 | 27篇 |
2004年 | 20篇 |
2003年 | 28篇 |
2002年 | 26篇 |
2001年 | 25篇 |
2000年 | 11篇 |
1999年 | 15篇 |
1998年 | 46篇 |
1997年 | 29篇 |
1996年 | 26篇 |
1995年 | 18篇 |
1994年 | 27篇 |
1993年 | 14篇 |
1992年 | 7篇 |
1991年 | 10篇 |
1990年 | 11篇 |
1989年 | 13篇 |
1988年 | 6篇 |
1987年 | 5篇 |
1986年 | 4篇 |
1985年 | 10篇 |
1984年 | 8篇 |
1983年 | 6篇 |
1982年 | 9篇 |
1981年 | 10篇 |
1980年 | 9篇 |
1979年 | 8篇 |
1978年 | 5篇 |
1977年 | 5篇 |
1976年 | 6篇 |
1975年 | 5篇 |
1974年 | 4篇 |
排序方式: 共有876条查询结果,搜索用时 156 毫秒
11.
Naoki Yuda Miyuki Tanaka Manabu Suzuki Yuzo Asano Hiroshi Ochi Keiji Iwatsuki 《Journal of food science》2012,77(12):H254-H261
Abstract: Polyphenols, retained in black tea wastes following the commercial production of tea beverages, represent an underutilized resource. The purpose of this study was to investigate the potential use of hot‐compressed water (HCW) for the extraction of pancreatic lipase‐inhibiting polyphenols from black tea residues. Black tea residues were treated with HCW at 10 °C intervals, from 100 to 200 °C. The resulting extracts were analyzed using high‐performance liquid chromatography‐mass spectrometry and assayed to determine their inhibitory effect on pancreatic lipase activity in vitro. Four theaflavins (TF), 5 catechins, 2 quercetin glycosides, quinic acid, gallic acid, and caffeine were identified. The total polyphenol content of extracts increased with increasing temperature but lipase inhibitors (TF, theaflavin 3‐O‐gallate, theaflavin 3′‐O‐gallate, theaflavin 3,3′‐O‐gallate, epigallocatechin gallate, and epicatechin gallate) decreased over 150 °C. All extracts inhibited pancreatic lipase but extracts obtained at 100 to 140 °C showed the greatest lipase inhibition (IC50s of 0.9 to 1.3 μg/mL), consistent with the optimal extraction of TFs and catechins except catechin by HCW between 130 and 150 °C. HCW can be used to extract pancreatic lipase‐inhibiting polyphenols from black tea waste. These extracts have potential uses, as dietary supplements and medications, for the prevention and treatment of obesity. Practical Application: Active forms of lipase inhibitors can be recovered from black tea residues. They could be used as dietary supplements or medications. 相似文献
12.
Phosphorus flame retardants in indoor dust and their relation to asthma and allergies of inhabitants
A. Araki I. Saito A. Kanazawa K. Morimoto K. Nakayama E. Shibata M. Tanaka T. Takigawa T. Yoshimura H. Chikara Y. Saijo R. Kishi 《Indoor air》2014,24(1):3-15
Organophosphate esters are used as additives in flame retardants and plasticizers, and they are ubiquitous in the indoor environment. Phosphorus flame retardants (PFRs) are present in residential dust, but few epidemiological studies have assessed their impact on human health. We measured the levels of 11 PFRs in indoor floor dust and multi‐surface dust in 182 single‐family dwellings in Japan. We evaluated their correlations with asthma and allergies of the inhabitants. Tris(2‐butoxyethyl) phosphate was detected in all samples (median value: 580 μg/g in floor dust, 111 μg/g in multi‐surface dust). Tris(2‐chloro‐iso‐propyl) phosphate (TCIPP) was detected at 8.69 μg/g in floor dust and 25.8 μg/g in multi‐surface dust. After adjustment for potential confounders, significant associations were found between the prevalence of atopic dermatitis and the presence of TCIPP and tris(1,3‐dichloro‐2‐propyl) phosphate in floor dust [per log10‐unit, odds ratio (OR): 2.43 and 1.84, respectively]. Tributyl phosphate was significantly associated with the prevalence of asthma (OR: 2.85 in floor dust, 5.34 in multi‐surface dust) and allergic rhinitis (OR: 2.55 in multi‐surface dust). PFR levels in Japan were high compared with values reported previously for Europe, Asia‐Pacific, and the USA. Higher levels of PFRs in house dust were related to the inhabitants' health status. 相似文献
13.
Tadashi C Ozawa Katsutoshi Fukuda Yasuo Ebina Kosuke Kosuda Akira Sato Yuichi Michiue Keiji Kurashima Takayoshi Sasaki 《Science and Technology of Advanced Materials》2011,12(4)
La–Eu solid solution nanosheets La2/3−xEuxTa2O7 have been synthesized, and their photoluminescence properties have been investigated. La2/3−xEuxTa2O7 nanosheets were prepared from layered perovskite compounds Li2La2/3−xEuxTa2O7 as the precursors by soft chemical exfoliation reactions. Both the precursors and the exfoliated nanosheets exhibit a decrease in intralayer lattice parameters as the Eu contents increase. However, there is a discontinuity in this trend between the nominal Eu content ranges x≤ 0.3 and x ≥ 0.4. This discontinuity is attributed to the difference in degree of TaO6 octahedra tilting for the La- and Eu-rich phases. La2/3−xEuxTa2O7 nanosheets exhibit red emission, characteristic of the f–f transitions in Eu3+ photoactivators. The photoluminescence emission can be obtained from both host and direct photoactivator excitation. However, photoluminescence emission through host excitation is much more dominant than that through direct photoactivator excitation, and this behavior is consistent with that of all the other rare-earth photoactivated nanosheets reported previously. The absolute photoluminescence quantum efficiency of the La2/3−xEuxTa2O7 nanosheets increases as the experimentally determined Eu contents increase up to x=0.45 and decrease above it. This result is in good agreement with the optimum photoactivator concentration expected from the percolation theory. These solid solution La2/3−xEuxTa2O7 nanosheets are excellent models for validating the theory of optimum photoactivator concentration in the truly two-dimensional photoactivator matrix. 相似文献
14.
Yoshihiko Moriyama Yuuichi Kamimuta Keiji Ikeda Tsutomu Tezuka 《Solid-state electronics》2011,60(1):89-92
Introduction of tensile strain into Ge substrates was demonstrated by forming embedded SiGe stressors on the recessed regions formed by an anisotropic wet chemical etching process for strained Ge-nMOSFETs having high electron mobility. A damage-free and well controlled anisotropic wet chemical etching process is developed in order to avoid plasma-induced damages in a conventional RIE process. The uni-axial tensile strain over 1% near the Ge recess-edge regions, which is induced by the embedded SiGe stressors, is also demonstrated for the first time. These results suggest that higher electron mobility than the upper-limit for a Si-MOSFET is obtainable in short channel strained Ge-nMOSFETs with the embedded SiGe stressors. 相似文献
15.
Yuji Tatemoto Yoshiyuki Bando Koji Oyama Keiji Yasuda Masaaki Nakamura Yasuhiro Sugimura Masahito Shibata 《Drying Technology》2001,19(7):1287-1303
The effects of operational conditions on the drying performance in closed superheated steam drying were examined theoretically and experimentally. The vapor generated from the sample was circulated in the drying chamber. In the theoretical analysis, the replacement of air with vapor in drying chamber and the convective vapor transfer in sample were considered. At the start of drying, the drying chamber was filled with air. As the drying proceeded, the air was replaced with the vapor generated from sample. The calculated results explained the characteristics of experimental data. The pore diameter of sample had little effect on the drying characteristics. During the internal evaporation period, the evaporation occurred in the narrow zone, which moved from the surface to the bottom of sample. The convective vapor transfer in sample had a significant influence on the drying performance. The excess increments in temperature and velocity of drying gas hardly contributed to shortening the drying time. 相似文献
16.
Yuji Tatemoto Yoshiyuki Bando Keiji Yasuda Yoshitaka Senda Masaaki Nakamura 《Drying Technology》2001,19(7):1305-1318
The drying characteristics of porous material in fluidized bed were examined theoretically and experimentally. The brick ball was used as the sample and immersed in the fluidized bed. The glass beads were used as the fluidizing particles and the particle diameters were changed. When the pore diameter of sample was relatively large, the fluidizing particles were adhered on the sample surface. In the theoretical analysis, the heat and mass transfers in adhered particle layer were considered. The fluidizing particles were adhered on the sample surface during the earlier period of drying. The sample temperature largely decreased when the mass of adhered particle decreased. The calculated results are in good agreement with experimental data. The diameter of fluidizing particle had a small effect on the drying time. The excess increments in drying gas temperature hardly contributed to shortening the drying time. 相似文献
17.
18.
There has been continuous progress at the High Energy Accelerator Research Organization (KEK) in R&D on vacuum beam ducts adaptable to future high-current particle storage rings. Here we proposed copper beam ducts with antechambers to deal with the severe issues attributed to the high beam currents. The proposed antechamber scheme can withstand intense synchrotron radiation (SR), provide a beam duct with low beam impedance, and effectively reduce the electron cloud effect (ECE) in positron/proton rings. Several trial models were manufactured by a pressing or cold-drawn method, and assembled with electron beam welding. Special vacuum components, such as connection flanges, distributed pumps, and gate valves, were customized for the beam ducts. TiN coating on the inner surface of the beam duct was also investigated as a mitigating measure for the ECE. Trial models of the copper beam ducts were installed into the KEK B-factory (KEKB), and their performances were evaluated using real positron and electron beams. 相似文献
19.
Meisen Li Yoshiyuki Bando Ryo Tanigawara Toru Kamiya Keiji Yasuda Masaaki Nakamura 《加拿大化工杂志》2001,79(4):602-607
The effects of operation conditions on the flow behaviour in gas–liquid countercurrent trickle bed biofilter were experimentally examined. In order to prevent gas channelling in the biofilter, packings with a relatively large void fraction, which have a role to maintain a high void fraction in the bed, were added. The gas and liquid velocities of the packed structure and the packings were changed, and the residence time distributions (RTDs) of the gas and liquid were measured. It was found that the addition of void supporters was very effective in the suppression of gas channelling. 相似文献
20.
Shinya Yasumoto Andrew P. Jones Tomoki Nakaya Keiji Yano 《Computers, Environment and Urban Systems》2011,35(6):464-473
The development of virtual city models has provided novel possibilities for analyses that require consideration of building heights in urban areas. The study was undertaken to explore these possibilities by using the virtual Kyoto model to examine equity in access to views in the Japanese city. A sample of just over 5000 residences was selected by stratifying for population age and affluence. A series of viewsheds were computed to quantify the visibility of a range of environmental amenities (greenspaces, water bodies, historical buildings, mountains) and disamenities (factories and roads). Evidence of inequity in visual amenity was identified, whereby homes in areas with many old people were much less likely to have views of greenspaces and water bodies, although they were also less likely to see factories and roads and were more likely to view mountains. Homes in more affluent areas had better views of greenspaces, historical buildings, and mountains, and were less likely to see factories and water bodies. We discuss the potential of virtual city models for furthering analyses of the urban environment and raise some caveats regarding their use. 相似文献