全文获取类型
收费全文 | 193篇 |
免费 | 19篇 |
国内免费 | 29篇 |
专业分类
化学 | 169篇 |
晶体学 | 1篇 |
力学 | 2篇 |
数学 | 6篇 |
物理学 | 63篇 |
出版年
2024年 | 2篇 |
2023年 | 7篇 |
2022年 | 14篇 |
2021年 | 22篇 |
2020年 | 17篇 |
2019年 | 18篇 |
2018年 | 12篇 |
2017年 | 7篇 |
2016年 | 10篇 |
2015年 | 7篇 |
2014年 | 16篇 |
2013年 | 14篇 |
2012年 | 5篇 |
2011年 | 14篇 |
2010年 | 2篇 |
2009年 | 13篇 |
2008年 | 6篇 |
2007年 | 4篇 |
2006年 | 6篇 |
2005年 | 7篇 |
2004年 | 4篇 |
2003年 | 9篇 |
2002年 | 2篇 |
2001年 | 2篇 |
2000年 | 4篇 |
1999年 | 6篇 |
1997年 | 1篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1993年 | 1篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1988年 | 3篇 |
1984年 | 1篇 |
排序方式: 共有241条查询结果,搜索用时 78 毫秒
1.
Synthesis of Bioactive and Porous Organic-Inorganic Hybrids for Biomedical Applications 总被引:2,自引:0,他引:2
Kanji Tsuru Satoshi Hayakawa Akiyoshi Osaka 《Journal of Sol-Gel Science and Technology》2004,32(1-3):201-205
Bioactivity has been exhibited by a limited range of ceramics since the invention of Bioglass®. Recently, some bioactive polymeric organic-inorganic hybrids were introduced, including not only organically modified silicates (Ormosils) synthesized from polydimethylsiloxane (PDMS) and tetraethoxysilane but also those with gelatin and 3-glycidoxypropyl-tremethoxysilane. Preparation of the bulk and porous hybrids and their polymeric structures analyzed by Si NMR spectroscopy were presented. In vitro bioactivity or apatite deposition in a simulated body fluid of the Kokubo recipe were also described for those hybrids. Freeze-drying techniques introduced porosity (up to 90%) and pores extending in a preferred direction. 相似文献
2.
3.
R. F. Storey J. S. Wiggins A. D. Puckett 《Journal of polymer science. Part A, Polymer chemistry》1994,32(12):2345-2363
Bioabsorbable poly(ester-urethane) networks were synthesized from ethyl 2,6-diisocyanatohexanoate (L -lysine diisocyanate) (LDI) and a series of polyester triols. LDI was synthesized by refluxing L-lysine monohydrochloride with ethanol to form the ester, which was subsequently refluxed with 1,1,1,3,3,3-hexamethyldisilazane to yield a silazane-protected intermediate. This product was then phosgenated using triphosgene. Polyester triols were synthesized from D,L-lactide, ?-caprolactone, or comonomer mixtures thereof, using glycerol as initiator and stannous octoate as catalyst. Polyurethane networks were cured using [NCO]/[OH] = 1.05 and stannous octoate (0.05 wt %) for 24 h at room temperature and pressure and 24 h at 50°C and 0.1 mm Hg. LDI-based polyurethane networks were totally amorphous and possessed very low sol contents. Networks based on poly (D,L-lactide) triols were rigid (Tg ∽ 60°C) with ultimate tensile strengths of ~ 40–70 MPa, tensile moduli of ~ 1.2–2.0 GPa, and ultimate elongations of ~ 4–10%. Networks based on ?-caprolactone triols were low-modulus elastomers with tensile strengths and moduli of ~ 1–4 MPa and ~ 3–6 GPa, respectively, and ultimate elongations of ~ 50–300%. Networks based on copolymers displayed physical properties consistent with monomer composition and were tougher than the networks based on the homopolymers. Tensile strengths for the copolymers were ~ 3–25 MPa with ultimate elongations up to 600%. Hydrolytic degradation under simulated physiological conditions showed that D ,L -lactide homopolymer networks were the most resistant to degradation, undergoing virtually no change in mass or physical properties for 60 days. ?-Caprolactone-based networks were resistant to degradation for 40 days, and high-lactide copolymer-based networks suffered substantial losses in physical properties after only 3 days. © 1994 John Wiley & Sons, Inc. 相似文献
4.
Abstract A biocompatible zinc (II) complex based on a tetradentate N,N,O,O-type salen ligand was synthesized, characterized and used for the solvent-free ring-opening polymerization (ROP) of L-lactide in bulk at 180?°C to prepare high molecular weight poly(L-lactide) (Mn : 82,600?Da; Mw : 140,000?Da; PDI: 1.70). Poly(L-lactide) (PLLA) was characterized using FTIR, 1H NMR, 13C NMR, GPC, TGA, DSC, WAXD, and MALDI-ToF. Kinetic measurement was carried out and first-order behavior to monomer was observed. The k app was found as 6?±?0.001?×?10?4?s?1. The biocompatibility of the PLLA was confirmed by in vitro cytotoxicity against NIH/3T3 fibroblast cell line and can be used in biomedical applications. 相似文献
5.
6.
Jesús Emmanuel Solís‐Prez Jos Francisco Gmez‐Aguilar Lizeth Torres Ricardo Fabricio Escobar‐Jimnez Juan Reyes‐Reyes 《Mathematical Methods in the Applied Sciences》2019,42(18):7335-7348
In this work, the design of spectral observers for signal reconstruction based on Kalman filters is performed and evaluated. The conformable derivative and the beta‐derivative were used to design the Kalman filters. Both derivatives satisfy the same formulas of the classical derivation, eg, the chain rule. The derivative order, the Ricatti equation parameters, and the observers tuning parameters were optimized using an optimization algorithm based on the bat's echolocation behavior (Bat algorithm). The simulation results showed the advantages of using the proposed observers for the signal reconstruction. 相似文献
7.
《先进技术聚合物》2018,29(1):30-40
Our daily life needs depend on plastics, as they are cheap and durable, so they become the most commonly used synthetic chemical products. But from an environmentalist's point of view, a major concern related to these plastics is their non‐biodegradable nature. Driven by growing demand to search for sustainable solutions to dispose off generating huge volume of synthetic plastic wastes, shifted the mind of researcher towards the use of biodegradable plastics which can be completely disposed‐off by microbial enzymatic degradation. These biodegradable plastics or “bioplastics” are also synthesized by microbes under certain stressed environmental conditions out of which poly(R‐3‐hydroxybutyrate) (PHB) is the most ubiquitous and best known representatives of polyhydroxyalkanoate family. The PHB is most intensively used for the innovative biomedical applications owing to suitable combination of biocompatibility, transport characteristics, and mechanical properties. These challenging aspects of PHB can be used for designing of novel medical devices, in tissue engineering, and for systematic sustained drug delivery. Lots of research reports on PHB degrading enzymes and their producing microorganisms including biochemical aspects are available but in scattered form. So this review highlighted all the relevant information of PHB and PHB‐degrading enzymes starting with basic classification, synthesis, mechanism, and applications that are environment friendly and are of public interest. 相似文献
8.
免疫胶体金技术的应用与展望 总被引:1,自引:0,他引:1
免疫胶体金技术是一种新型固相标记免疫检测技术,因其独特的性质在许多领域得到广泛应用和快速发展。简述了免疫胶体金技术在电镜、光镜快速检测诊断中的发展以及在生物医学、免疫组织化学和细胞生物学等领域的研究和应用。未来免疫胶体金技术在提高胶体金制备质量的同时将实现定量和多元化检测。 相似文献
9.
Advanced organic-inorganic materials-composites, nanocomposites, and hybrids with various compositions offer unique properties required for biomedical applications. One of the most promising inorganic (nano)additives are polyhedral oligomeric silsesquioxanes (POSS); their biocompatibility, non-toxicity, and phase separation ability that modifies the material porosity are fundamental properties required in modern biomedical applications. When incorporated, chemically or physically, into polyurethane matrices, they substantially change polymer properties, including mechanical properties, surface characteristics, and bioactivity. Hence, this review is dedicated to POSS-PU composites that have recently been developed for applications in the biomedical field. First, different modes of POSS incorporation into PU structure have been presented, then recent developments of PU/POSS hybrids as bio-active composites for scaffolds, cardiovascular stents, valves, and membranes, as well as in bio-imaging and cancer treatment, have been described. Finally, characterization and methods of modification routes of polyurethane-based materials with silsesquioxanes were presented. 相似文献
10.