全文获取类型
收费全文 | 643篇 |
免费 | 23篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 52篇 |
综合类 | 3篇 |
化学工业 | 195篇 |
金属工艺 | 14篇 |
机械仪表 | 27篇 |
建筑科学 | 12篇 |
能源动力 | 23篇 |
轻工业 | 43篇 |
水利工程 | 1篇 |
石油天然气 | 3篇 |
无线电 | 53篇 |
一般工业技术 | 89篇 |
冶金工业 | 86篇 |
原子能技术 | 21篇 |
自动化技术 | 46篇 |
出版年
2023年 | 7篇 |
2022年 | 7篇 |
2021年 | 19篇 |
2020年 | 6篇 |
2019年 | 9篇 |
2018年 | 16篇 |
2017年 | 8篇 |
2016年 | 12篇 |
2015年 | 13篇 |
2014年 | 22篇 |
2013年 | 43篇 |
2012年 | 22篇 |
2011年 | 42篇 |
2010年 | 23篇 |
2009年 | 18篇 |
2008年 | 29篇 |
2007年 | 18篇 |
2006年 | 18篇 |
2005年 | 21篇 |
2004年 | 19篇 |
2003年 | 26篇 |
2002年 | 17篇 |
2001年 | 17篇 |
2000年 | 11篇 |
1999年 | 14篇 |
1998年 | 33篇 |
1997年 | 21篇 |
1996年 | 12篇 |
1994年 | 12篇 |
1993年 | 15篇 |
1992年 | 6篇 |
1991年 | 7篇 |
1989年 | 7篇 |
1987年 | 4篇 |
1986年 | 9篇 |
1985年 | 5篇 |
1984年 | 4篇 |
1982年 | 4篇 |
1981年 | 7篇 |
1980年 | 8篇 |
1979年 | 4篇 |
1978年 | 5篇 |
1976年 | 8篇 |
1975年 | 5篇 |
1974年 | 5篇 |
1973年 | 3篇 |
1972年 | 4篇 |
1971年 | 4篇 |
1970年 | 5篇 |
1969年 | 3篇 |
排序方式: 共有668条查询结果,搜索用时 46 毫秒
1.
Multimedia Tools and Applications - 相似文献
2.
Power devices with high capability have been developed. 8‐kV/3.5‐kA‐class light‐triggered thyristors have the highest capability among power devices. These devices are used in the Kii Channel HVDC transmission system in Japan. In this paper, we report the extracted problems of conventional testing methods of 8‐kV/3.5‐kA‐class light‐triggered thyristors among manufacturers, and the proposed unified testing methods on the basis of element characteristics and operating conditions in the Kii Channel HVDC system. Furthermore, we propose a figure of merit for power devices for the practical use, and try to extract elements used at the Kii Channel HVDC system with small margins and low withstand capabilities. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 140(3): 61–70, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10024 相似文献
3.
Solution- and solid-state c.d. spectra, as well as surface energetics values, were collected for a series of peptides derived from human salivary proline-rich glycoprotein (PRG). The acronyms and sequences for these peptides are as follows: PRG9-2 = NH2-G(1)-P(2)-CONH2, PRG9-3 = NH2-G(1)-P(2)-P(3)-CONH2, PRG9-4 = NH2-G(1)-P(2)-P(3)-P(4)-CONH2, PRG9-5 = NH2-G(1)-P(2)-P(3)-P(4)-H(5)-CONH2, PRG9-6 = NH2-G(1)-P(2)-P(3)-P(4)-H(5)-P(6)-CONH2, PRG9-7 = NH2-G(1)-P(2)-P(3)-P(4)-H(5)-P(6)-G(7)-CONH2, PRG9-8 = NH2-G(1)-P(2)-P(3)-P(4)-H(5)-P(6)-G(7)-K(8)-CONH2, and PRG9-9 = NH2-G(1)-P(2)-P(3)-P(4)-H(5)-P(6)-G(7)-K(8)-P(9)-CONH2. The presence of stable poly-L-proline II-like 'mini' helices in the solution state was found to be dependent on peptide chain length, pH, salt, and organic solvent type. Other conformational features such as kinks and beta-/gamma-turns were also found in the larger peptides. Solid-state peptide conformations were not necessarily related to their solution-state counterparts. Poly-L-proline II-like 'mini' helices, kinks, and beta-/gamma-turns were similarly found in the various substrate-bound PRG9 peptides. Surface energetics parameters suggested specific orientations for PRG9 peptides and their constituent acids and homopolymers. 相似文献
4.
Namsin Park Takeyuki Shiraishi Kazuyoshi Kamisugi Yoshitaka Hara Keita Iizuka Takashi Kado Shuzi Hayase 《Journal of Applied Electrochemistry》2008,38(3):371-375
A direct ethanol fuel cell (DEFC), which is less prone to ethanol crossover, is reported. The cell consists of PtRu/C catalyst as the anode, Nafion® 117 membrane, and Ni–Co–Fe (NCF) composite catalyst as the cathode. The NCF catalyst was synthesized by mixing Ni, Co, and Fe complexes into a polymer matrix (melamine-formaldehyde resins), followed by heating the mixture at 800 °C under inert atmosphere. TEM and EDX experiments suggest that the NCF catalyst has alloy structures of Ni, Co and Fe. The catalytic activity of the NCF catalyst for the oxygen reduction reaction (ORR) was compared with that of commercially available Pt/C (CAP) catalyst at different ethanol concentrations. The decrease in open circuit voltage (Voc) of the DEFC equipped with the NCF catalysts was less than that of CAP catalyst at higher ethanol concentrations. The NCF catalyst was less prone to ethanol oxidation at cathode even when ethanol crossover occurred through the Nafion®117 film, which prevents voltage drop at the cathode. However, the CAP catalyst did oxidize ethanol at the cathode and caused a decrease in voltage at higher ethanol concentrations. 相似文献
5.
Hiromasa Higasa Ryoichi Takahata Hiroshi Imaizumi Kenzo Miya 《Electrical Engineering in Japan》1996,116(3):96-106
A high-temperature superconductor YBa2Cu3O7-x with strong pinning force has allowed stable magnetic suspension with no control to be developed. Two types of superconducting magnetic bearings (SMB) using YBCO and permanent magnet were assembled. The two types are radial and axial. The dynamic stiffness of each SMB as it was cooled down under a magnetic field by liquid nitrogen was measured both radially and axially. As a result, it was found that the spring constants of these SMBs were almost as large as a practically desirable value; however, their damping coefficients were lower than the practical level. These findings are useful as one of the data bases for development of an optimum SMB design to support the weight of rotors in an axial direction. 相似文献
6.
Shun'ichi Numata Shuuichi Oohara Koji Fujisaki Jun'Ichi Imaizumi Noriyuki Kinjo 《应用聚合物科学杂志》1986,31(1):101-110
The thermal expansion behavior for various aromatic polymides was investigated. Usally polymers, including polyimides, have high thermal expansion coefficients (3–6 × 10?5 K?1), compared with metals and ceramics. However, there are some polyimides which have very low thermal expansion coefficients below 1 × 10?5 K?1. This property was observed for the polymides obtained from pyromellitic dianhydride or 3,3′ 4,4′-biphenyltetracarboxylic dianhydride and aromatic diamines which were constituted of only benzene rings fused at para positions. It was proposed that their low thermal expansion coefficient related to the linearity in their polymer molecular skeltons. 相似文献
7.
A large public service organization was concerned with protection of its customers against hazards associated with furniture tipping in public use concourses. Because no injury experience was available for analysis, hazard patterns for tipping accidents were developed from an observational study of public interaction with the furniture. For each hazard pattern, anthropometric models were used to find the probability of the furniture being safe from tipping, for different age and gender combinations. A safety criterion was developed from this modeling, and used to change the weights of some furniture items to resist tipping. These modifications have now been implemented and are in widespread use. Implications for broader application of these models to the development of valid tipping standards for furniture are discussed. 相似文献
8.
The activities of FexO in CaO + CaF2 + SiO2 + FexO quaternary slags were measured by means of solid-oxide galvanic cell. The FexO activities in the slags are influenced by CaF2 as well as SiO2. At constant FexO mole fractions, e.g., , at low SiO2 mole fractions i.e., , the substitution of CaF2 for CaO has an effect of raising the FexO activity. At higher SiO2 mole fractions, e.g., , however, such an effect becomes insignificant. 相似文献
9.
Hitomi Natomi Toshihito Saitoh Kentaro Sugano Masao Iwamori Masahisa Fukayama Yoshitaka Nagai 《Lipids》1993,28(8):737-742
The composition of the glycosphingolipids of the human gastrointestinal tract was studied. The major neutral glycosphingolipids
were ceramide monohexosides (e.g., GalCer, GlcCer), LacCer, Gb3Cer, Gb4Cer and more polar ones with more than four sugars, whereas neither Gg3Cer nor Gg4Cer were present. The acidic glycosphingolipids consisted of sulfatides and gangliosides such as GM3, GM1, GD3 and GD1a. Also a large amount of sulfatides was found in the gastric mucosa and duodenum. The concentrations of sulfatides in the
fundic mucosa, antral mucosa and duodenum amounted to 416.0, 933.8 and 682.9 nmol/g of dry weight, respectively, exceeding
those in the gastric mucosa and kidney of other mammals. The major molecular species of the sulfatides were identified as
I3SO3-GalCer with hydroxylated longer-chain fatty acids based on the analyses by gas-liquid chromatography and negative ion fast-atom
bombardment mass spectrometry. In contrast, gangliosides in these regions showed a tendency to be lower than sulfatides, and
the molar ratios of sulfatides to gangliosides were about 2.0, whereas those in other parts were less than 0.5. A high content
of sulfatides in the gastric and duodenal mucosa, where mucosa is easily insulted by acid, pepsin and bile salts, may be closely
related to their roles in mucosal protection.
The nomenclature used for gangliosides and other glycosphingolipids follows the system of Svennerholm (Ref. 1) and the recommendation
of the IUPAC-IUB Commission (Ref. 2), respectively. 相似文献
10.
The present study was carried out to examine if the positional distribution of medium-chain fatty acid (MCF) in dietary synthetic
fat influences lymphatic transport of dietary fat and the chemical composition of chylomicrons in rats with permanent cannulation
of thoracic duct. Four types of synthetic triacylglycerol were prepared: (i) sn-1(3) MCF-sn 2 linoleic acid, (ii) interesterified sn-1(3) MCF-sn 2 linoleic acid, (iii) sn-2 MCF-sn-1(3) linoleic acid, and (iv) interesterified sn-2 MCF-sn-1(3) linoleic acid. A purified diet composed of equal amounts of the synthetic fat and cocoa butter was given to rats with
permanent lymph duct cannulation. The positional distribution of MCF in the dietary fat had no significant effect on the lymph
flow, triacylglycerol output, phospholipid output, lipid composition of chylomicrons, or the particle size. The positional
distribution of MCF in the synthetic triacylglycerol was maintained in the chylomicron triacylglycerol. These results showed
that MCF in the dietary triacylglycerol is transported into lymphatics and the positional distribution is well preserved in
chylomicron triacylglycerol. 相似文献