全文获取类型
收费全文 | 25511篇 |
免费 | 1553篇 |
国内免费 | 524篇 |
专业分类
电工技术 | 382篇 |
综合类 | 1586篇 |
化学工业 | 8227篇 |
金属工艺 | 707篇 |
机械仪表 | 243篇 |
建筑科学 | 1499篇 |
矿业工程 | 438篇 |
能源动力 | 191篇 |
轻工业 | 9974篇 |
水利工程 | 217篇 |
石油天然气 | 1177篇 |
武器工业 | 76篇 |
无线电 | 301篇 |
一般工业技术 | 1282篇 |
冶金工业 | 623篇 |
原子能技术 | 151篇 |
自动化技术 | 514篇 |
出版年
2024年 | 215篇 |
2023年 | 1014篇 |
2022年 | 1138篇 |
2021年 | 988篇 |
2020年 | 963篇 |
2019年 | 1036篇 |
2018年 | 698篇 |
2017年 | 693篇 |
2016年 | 749篇 |
2015年 | 876篇 |
2014年 | 1525篇 |
2013年 | 1089篇 |
2012年 | 1333篇 |
2011年 | 1308篇 |
2010年 | 1093篇 |
2009年 | 1126篇 |
2008年 | 1837篇 |
2007年 | 1366篇 |
2006年 | 1088篇 |
2005年 | 1097篇 |
2004年 | 956篇 |
2003年 | 853篇 |
2002年 | 669篇 |
2001年 | 629篇 |
2000年 | 503篇 |
1999年 | 394篇 |
1998年 | 328篇 |
1997年 | 313篇 |
1996年 | 316篇 |
1995年 | 280篇 |
1994年 | 227篇 |
1993年 | 155篇 |
1992年 | 193篇 |
1991年 | 166篇 |
1990年 | 151篇 |
1989年 | 153篇 |
1988年 | 15篇 |
1987年 | 12篇 |
1986年 | 7篇 |
1985年 | 5篇 |
1984年 | 12篇 |
1983年 | 8篇 |
1982年 | 2篇 |
1981年 | 2篇 |
1980年 | 6篇 |
1951年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
91.
Mulberry silk is composed of the two major parts of two triangle-like silk fibroin fibers and sericin covering the fibers and a few lipids. After removing the sericin on the raw silk what is left is the silk fibroin fiber. Silk fibroin is the main part of silk accounting for about 75% of the total weight. Silk fibroin contains 18 natural amino acids such as glycine Gly alanine Ala serine Ser serine aspartic acid Asp and tyrosine Tyr . The secondary structure of silk fibroin has three main conformations α-helix β-fold and random coil. Under certain conditions the three conformations can transform into each other and change the mechanical properties of the silk fibroin material. Silk fibroin extracted from silk fiber is a natural polymer with biocompatibility and biodegradability. It can be further processed into different forms of materials nanoparticles films hydrogels sponges etc. It has been applied in many fields such as biomedicine and cosmetics. In order to meet the needs of different fields researchers have conducted further chemical modification treatment based on the original excellent properties of silk fibroin. Meanwhile the active groups on various amino acid residues in silk fibroin also provide chemical reaction sites for the chemical modification of silk fibroin. The chemical modification methods of silk fibroin mainly include amino acid residue modification macromolecular grafting modification and crosslinking reaction modification. Among them amino acid residue modification can modify protein amino acid residues by chemical reagents and some groups can be introduced into the side chains of silk fibroin macromolecules. Grafting modification of silk fibroin macromolecules is one of the main means to bind functional compounds to silk fibroin macromolecular chains. The properties of grafted silk fibroin are affected by the type and grafting rate of the grafts. The chemical crosslinking reaction modification of silk fibroin macromolecules is to make the macromolecular chains connected by covalent bonds and form a network structure by means of crosslinking agents enzymes or ultraviolet irradiation. The cross-linking reaction can not only form covalent bonds within and between the molecular chains of silk fibroin thus changing its structural properties and improving its stability but be used to form covalent bonds with other polymers. At present the chemical modification of silk fibroin is mainly applied in the fields of silk textiles biomedicine and environmental science. In the field of silk textiles graft copolymerization modification of vinyl and other monomers crosslinking agent modification and other methods are used to overcome the shortcomings of silk like being easy to wrinkle. The graft modified monomers mainly include ethylene methacrylate and methylacrylamide. The active groups on crosslinking agents such as polycarboxylic acid / anhydride and epoxide are covalently combined with carboxyl hydroxyl and amino groups on macromolecules of silk fibroin to improve the wrinkle resistance of silk fabrics. In the field of biomedicine silk fibroin materials with appropriate chemical modification have better biological activity drug delivery ability antimicrobial properties and mechanical properties. The optimization of these properties enables silk fibroin materials to show great potential in drug control delivery tissue regeneration and wound repair. The applied research in the field of environmental science mainly focuses on the adsorption separation and catalysis of impurities in water. Therefore the modification of amino acid residues grafting and cross-linking of protein macromolecules can change some important properties of silk fibroin and meet the requirements of various applications and functionalization of silk fibroin. In many fields of chemical modification and application of silk fibroin protein fruitful results have been achieved which has laid a good foundation for the further development of related fields and also shows that the chemical modification of silk fibroin material has great potential and application prospects. However there are still some problems that need to be overcome and further improved in the current chemical modification methods such as mild modification conditions and accurate adjustment of the degree of modification which will be the research direction of related fields in the future. © 2022 Authors. All rights reserved. 相似文献
92.
鲍鱼是一种单壳软体动物,属于海洋贝类的一种。鲍鱼的营养价值很高,是人类所需蛋白质、微量元素、矿物质、脂类和碳水化合物的良好来源。鲍鱼所含有的活性物质具有抗癌、抗氧化、抗炎、抗凝血、调节糖脂代谢等保健作用。然而,对鲍鱼所含的活性物质的研究仅停留在理论阶段,在药用和保健食品上的应用仍未被完全开发。此外,由于鲜活鲍鱼的不易贮藏和运输,深加工包括干燥、冷冻等成为开发鲍鱼加工产品以及延长货架期的主要手段。而不同加工方式对鲍鱼的营养活性成分以及肌肉结构等具有不同的影响,这又会反向影响着鲍鱼加工技术的创新与突破。本文主要阐述了鲍鱼的营养价值、功能活性及其功效的作用机制以及鲍鱼的加工现状,以期为鲍鱼的深入开发提供理论依据,并对鲍鱼在食品工业上的创新应用进行了全面展望。 相似文献
93.
搅拌磨机械活化硬锌渣浸铟的动力学研究 总被引:2,自引:1,他引:2
以硬锌渣为浸出对象,用盐酸作为浸出剂,研究了硬锌渣经搅拌磨活化后浸铟的动力学.与未活化硬锌渣相比较,经机械活化30 min、60 min后,硬锌渣中铟与盐酸的化学反应活性提高、反应速度加快、表观活化能和反应级数降低.其中表观活化能由未活化时的24.5 kJ/moL分别降至13.9 kJ/moL、11.4 kJ/moL,反应级数由原来的0.39分别降至0.36和0.22. 相似文献
94.
95.
96.
97.
含有石英、磁铁矿和其它杂质的硅镁镍矿在一台行星齿轮式球磨机中研磨,磨后的矿石在浓度为0.5mol/dm^3的HCl溶液中于297K温度下浸出。矿石进行干磨使硅镁镍矿结构从晶质变为非晶质,而二氧化硅和磁铁矿保持晶质不变。这种动力活化的硅镁矿导致在HCl溶液中镁和镍的高浸取率。约80%的Mg和Ni被提取出来,而只有约20%的Si被提取。短时间磨矿可以有效地从矿石中提取Mg和Ni,而抑制了Si的提取。 相似文献
98.
微生物絮凝剂产生菌的筛选及其絮凝性能影响因素的研究 总被引:1,自引:0,他引:1
从土壤中筛选分离得到一株絮凝剂产生菌并将其编号为M1。该菌产生的絮凝剂对高岭土悬浊液具有良好的絮凝能力。进一步实验表明,M1菌产生的絮凝剂是在稳定期后期絮凝活性达到最大;对培养基的研究表明,脲是M1产生絮凝剂的最佳氮源,淀粉、麦芽糖和木糖作为碳源能够促进M1合成和分泌絮凝剂。M1分泌的絮凝剂在pH=8~11范围内絮凝效果最好;多种阳离子对M1产生的絮凝剂都有助凝作用,并且三价阳离子Fe3+、Al3+对M1产生的絮凝剂助凝效果显著。 相似文献
99.
100.