全文获取类型
收费全文 | 922篇 |
免费 | 22篇 |
国内免费 | 6篇 |
学科分类
工业技术 | 950篇 |
出版年
2022年 | 2篇 |
2021年 | 10篇 |
2019年 | 9篇 |
2018年 | 16篇 |
2017年 | 10篇 |
2016年 | 17篇 |
2015年 | 15篇 |
2014年 | 14篇 |
2013年 | 49篇 |
2012年 | 40篇 |
2011年 | 63篇 |
2010年 | 30篇 |
2009年 | 36篇 |
2008年 | 43篇 |
2007年 | 36篇 |
2006年 | 43篇 |
2005年 | 43篇 |
2004年 | 28篇 |
2003年 | 30篇 |
2002年 | 25篇 |
2001年 | 20篇 |
2000年 | 18篇 |
1999年 | 29篇 |
1998年 | 21篇 |
1997年 | 24篇 |
1996年 | 18篇 |
1995年 | 17篇 |
1994年 | 17篇 |
1993年 | 17篇 |
1992年 | 7篇 |
1991年 | 19篇 |
1990年 | 9篇 |
1989年 | 10篇 |
1988年 | 4篇 |
1987年 | 14篇 |
1986年 | 17篇 |
1985年 | 13篇 |
1984年 | 18篇 |
1983年 | 11篇 |
1982年 | 12篇 |
1981年 | 11篇 |
1980年 | 7篇 |
1979年 | 15篇 |
1978年 | 14篇 |
1977年 | 8篇 |
1976年 | 8篇 |
1974年 | 2篇 |
1973年 | 2篇 |
1963年 | 1篇 |
1957年 | 1篇 |
排序方式: 共有950条查询结果,搜索用时 15 毫秒
931.
Takao Iijima Satoru Miura Masanori Fujimaki Takasi Taguchi Wakichi Fukuda Masao Tomoi 《应用聚合物科学杂志》1996,61(1):163-175
Aromatic polyesters, prepared by the reaction of aromatic dicarboxylic acids and 1,4-butanediol, were used to improve the toughness of bisphenol-A diglycidyl ether epoxy resin cured with p,p′-diaminodiphenyl sulfone. These polyesters contained poly(butylene phthalate)s (PBP), poly(butylene phthalate-co-butylene isophthalate)s, poly(butylene phthalate-co-butylene terephthalate)s, and poly(butylene phthalate-co-butylene 2,6-naphthalene dicarboxylate)s. All aromatic polyesters used in this study were soluble in the epoxy resin without solvents and were found to be effective as modifiers for toughening the cured epoxy resin. For example, the inclusion of 20 wt % PBP (MW 16,300) led to a 120% increase in the fracture toughness (KIC) of the cured resin with no loss of mechanical and thermal properties. The toughening mechanism was discussed in terms of the morphological and dynamic viscoelastic behaviors of the modified epoxy resin system. © 1996 John Wiley & Sons, Inc. 相似文献
932.
Polysulphones with cross-linkable pendant vinylbenzyl groups (PSF-VB) were prepared via chloromethylation of commercial polysulphones. The curing reactivity of PSF-VB was investigated by differential scanning calori-metry. Interpenetrating polymer networks (IPNs) were prepared based on bisphenol A diglycidyl ether (DGEBA) and PSF-VB, where DGEBA was cured by 4,4′-diaminodiphenyl sulphone and VB groups of PSF-VB were radically polymerized using dicumyl peroxide (DCP). Polysulphones having pendant benzyl groups (PSF-Bz) were also prepared and used as non-reactive modifiers. The fracture toughness (KIC) for the resulting epoxy/PSF-VB IPN increased by 65% with no loss of mechanical properties on 10wt% addition of PSF-VB (7·9mol% VB unit, MW 74000). Non-reactive PSF-Bz was less effective than PSF-VB. Although the PSF-Bz modified resin had a particulate structure, the morphologies of the PSF-VB/epoxy IPNs were not clear from scanning electron micrographs. Furthermore, the epoxy/PSF-VB IPNs had higher solvent resistance than the epoxy/PSF-Bz blends. Morphological behaviour, modification results and high solvent resistance of the cured epoxy/PSF-VB resins indicate that cross-linked PSF-VB and the epoxy network entangled fully in the presence of DCP. © of SCI. 相似文献
933.
934.
Room-temperature continuous-wave operation of GaN-based laser diodes grown by raised-pressure metalorganic chemical vapor deposition 总被引:1,自引:0,他引:1
Katsunori Yanashima Shigeki Hashimoto Tomonori Hino Kenji Funato Toshimasa Kobayashi Kaori Naganuma Tsuyoshi Tojyo Takeharu Asano Tsunenori Asatsuma Takao Miyajima Masao Ikeda 《Journal of Electronic Materials》1999,28(3):287-289
We report our new raised-pressure metalorganic chemical vapor deposition (RP-MOCVD) technique and the room-temperature continuous-wave
(cw) operation of GaN-based laser diodes grown using this technique. We have found that both the defect density as measured
by etch-pit density and optical pumping threshold-powder density decreases as the growth pressure is increased beyond 1 atm.
We fabricated GaN-based laser diodes and achieved lasing under cw conditions at 20°C. The threshold current density was 3.5
kA/cm2 and the operation voltage at threshold was 16.8 V. 相似文献
935.
936.
Hazardous wastes such as fly ash and asbestos can be melted by plasma treatment to convert them into blocks of vitrified slag resulting in a volume reduction by 49 to 65%. Vitrified slag of fly ash containing such heavy metals as Zn, Cu, and Fe has an extremely high resistance to water. Electric conductivity of the elution of 18.8 g of slag in 700 ml of distilled water is nearly the same as that of pure distilled water, being only about 0.1% of the electric conductivity of the solution of fly ash in distilled water. The surface of the molten asbestos becomes a hard shell without needlelike fibers, thus rendering asbestos safe for human health. As a result, plasma waste treatment can become a powerful tool for environmental protection. © 1999 Scripta Technica, Electr Eng Jpn, 126(3): 73–82, 1999 相似文献
937.
The N‐phenylmaleimide–styrene copolymer (PMS) was prepared and used to improve the brittleness of the cyanate ester resin. PMS was an effective modifier for improving the brittleness of the resin. The morphologies of the modified resins depended on PMS molecular weight and content. The most effective modification of the cyanate ester resin was attained because of the cocontinuous phase structure of the modified resin. Inclusion of 10 wt % PMS (Mw 133,000) led to an 160% increase in the fracture toughness (KIC) for the modified resin with a slight loss of flexural strength and retention of flexural modulus and the glass transition temperature, compared to the values for the unmodified resin. Low water absorptivity of the parent‐cured resin was not deteriorated by modification. The toughening mechanism was discussed in terms of the morphological and dynamic viscoelastic behaviors of the modified cyanate ester resin system. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2931–2939, 1999 相似文献
938.
Poly(ether ketone ketone)s were prepared and used to improve the brittleness of the bismaleimide resin. The bismaleimide resin was composed of 4,4′-bismaleimidediphenyl methane (BMI) and o,o′-diallyl bisphenol A (DBA). Poly(ether ketone ketone)s include poly(phthaloyl diphenyl ether) (PPDE), poly(phthaloyl diphenyl ether-co-isophthaloyl diphenyl ether) (PPIDE), and poly(phthaloyl diphenyl ether-co-terephthaloyl diphenyl ether) (PPTDE). PPIDE (50 mol % isophthaloyl unit) was more effective as a modifier for the bismaleimide resin than were PPDE and PPTDE (50 mol % terephthaloyl unit). Morphologies of the modified resins changed from particulate to cocontinuous and to phase-inverted structures, depending on the modifier structure and content. The most effective modification for the cured resins could be attained because of the cocontinuous phase or phase-inverted structure of the modified resins. For example, when using 10 wt % of PPIDE (50 mol % IP unit, MW 349,000), the modified resin had a phase-inverted morphology and the fracture toughness (KIC) for the modified resins increased 75% with retention in flexural properties and the glass transition temperature, compared to those of the unmodified cured bismaleimide resin. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 67:769–780, 1998 相似文献
939.
Morphology and electrical properties of short carbon fiber-filled high-density polyethylene (HDPE)/poly(methyl methacrylate)(PMMA) polymer blends have been studied. The percolation threshold of HDPE50/PMMA50 blends filled with vapor-grown carbon fiber (VGCF), 1.25 phr VGCF content, is much lower than those of the individual polymers. The SEM micrographs verified that the enhancement of conductivity could be attributed to the selective location of VGCF in the HDPE phase. A double percolation is the basic requirement for the conductivity of the composites, i.e., the percolation of carbon fibers in the HDPE phase and the continuity of this phase in the blends, which hereby are defined as the first percolation and the second percolation, respectively. The SEM micrographs also showed that the short carbon fibers could affect the morphology of the blends. With the increase of VGCF content, the HDPE domains are elongated from spherical into strip shape, finally develop to a continuous structure. As a result, the second percolation threshold of the blends filled with 2.5 phr VGCF, 20 wt % HDPE, is lower than that of the blends filled with 1.5 phr VGCF, 30 wt % HDPE. The influence of molding temperature and time on the second percolation threshold has also been investigated. For the composites molded at a lower temperature, the second percolation threshold is shifted to a higher VGCF content, but there is little influence of molding time on the second percolation threshold. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 1813–1819, 1998 相似文献
940.
Masao Tokunaga Shinya Kato Akiko Kawamura-Watabe Ryoichi Tanaka Hiroko Tokunaga 《Yeast (Chichester, England)》1998,14(14):1285-1295
Hsp70 is structurally composed of three domains, an amino-terminal ATPase domain, a proximal 18 kDa peptide-binding domain and a distal 10 kDa carboxy-terminal (C-terminal) domain. To dissect the functional significance of the distal 10 kDa domain, and the boundary region between the proximal and distal C-terminal domains of Kar2p in vivo in Saccharomyces cerevisiae, we constructed a series of plasmids which were truncated or had internal deletion mutations in this region. We found that all these mutations are recessive, and that the distal 10 kDa C-terminal domain, including the HDEL ER-retention sequence, is not essential for cell growth, although the major role of this 10 kDa C-terminal domain is due to the function of the HDEL ER-retention signal. We also found that the Kar2p region (Thr492–Thr512), corresponding to the β8-sheet in the peptide-binding domain, which constitutes the bottom plate of the binding pocket in E. coli DnaK, is essential for cell viability, and that the following Kar2p region (Glu513–Lys542), corresponding to α-helices A and B of E. coli DnaK, which was proposed to compose the lid of the binding pocket, is critical but not essential for yeast cell growth. This was further supported by the fact that the latter deletion showed a fully reversible ts phenotype in its growth and only a slight inhibitory effect on the secretion of α-amylase at non-permissive temperature. © 1998 John Wiley & Sons, Ltd. 相似文献