全文获取类型
收费全文 | 73533篇 |
免费 | 17193篇 |
国内免费 | 56篇 |
专业分类
电工技术 | 2345篇 |
综合类 | 431篇 |
化学工业 | 27932篇 |
金属工艺 | 1087篇 |
机械仪表 | 1554篇 |
建筑科学 | 3355篇 |
矿业工程 | 287篇 |
能源动力 | 1588篇 |
轻工业 | 10586篇 |
水利工程 | 580篇 |
石油天然气 | 188篇 |
无线电 | 8870篇 |
一般工业技术 | 17439篇 |
冶金工业 | 4651篇 |
原子能技术 | 188篇 |
自动化技术 | 9701篇 |
出版年
2023年 | 747篇 |
2022年 | 489篇 |
2021年 | 1209篇 |
2020年 | 2296篇 |
2019年 | 3960篇 |
2018年 | 3870篇 |
2017年 | 4110篇 |
2016年 | 4698篇 |
2015年 | 4837篇 |
2014年 | 4983篇 |
2013年 | 7410篇 |
2012年 | 4006篇 |
2011年 | 3882篇 |
2010年 | 4000篇 |
2009年 | 4027篇 |
2008年 | 3388篇 |
2007年 | 3081篇 |
2006年 | 2780篇 |
2005年 | 2449篇 |
2004年 | 2235篇 |
2003年 | 2132篇 |
2002年 | 1961篇 |
2001年 | 1589篇 |
2000年 | 1485篇 |
1999年 | 921篇 |
1998年 | 660篇 |
1997年 | 534篇 |
1996年 | 611篇 |
1995年 | 549篇 |
1994年 | 532篇 |
1993年 | 548篇 |
1992年 | 475篇 |
1991年 | 329篇 |
1990年 | 439篇 |
1989年 | 424篇 |
1988年 | 340篇 |
1987年 | 366篇 |
1986年 | 377篇 |
1985年 | 395篇 |
1984年 | 410篇 |
1983年 | 382篇 |
1982年 | 365篇 |
1981年 | 405篇 |
1980年 | 340篇 |
1979年 | 372篇 |
1977年 | 308篇 |
1976年 | 338篇 |
1975年 | 349篇 |
1974年 | 315篇 |
1973年 | 497篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
61.
62.
Jincy Joy Jessica Pereira Rachida Aid‐Launais Graciela Pavon‐Djavid Alok R Ray Didier Letourneur Anne Meddahi‐Pell Bhuvanesh Gupta 《Polymer International》2019,68(7):1367-1377
The work reported involved the fabrication of an electrospun tubular conduit of a gelatin and polycaprolactone (PCL) blend as an adventitia‐equivalent construct. Gelatin was included as the matrix for increased biocompatibility with the addition of PCL for durability. This is contrary to most of the literature available for biomaterials based on blends of gelatin and PCL where PCL is the major matrix. The work includes the assiduous selection of key electrospinning parameters to obtain smooth bead‐free fibres with a narrow distribution of pore size and fibre diameter. Few reports elucidate the optimization of all electrospinning parameters to fabricate tubular conduits with a focus on obtaining homogeneous pores and fibres. This stepwise investigation would be unique for the fabrication of gelatin–PCL electrospun tubular constructs. The fabricated microfibrous gelatin–PCL constructs had pores of size ca 50–100 μm reportedly conducive for cell infiltration. The measured value of surface roughness of 57.99 ± 17.4 nm is reported to be favourable for protein adhesion and cell adhesion. The elastic modulus was observed to be similar to that of the tunica adventitia of the native artery. Preliminary in vitro and in vivo biocompatibility tests suggest safe applicability as a biomaterial. Minimal cytotoxicity was observed using MTT assay. Subcutaneous implantation of the scaffold demonstrated acute inflammation which decreased by day 15. The findings of this study could enable the fabrication of smooth bead‐free microfibrous gelatin–PCL tubular construct as viable biomaterial which can be included in a bilayer or a trilayer scaffold for vascular tissue engineering. © 2019 Society of Chemical Industry 相似文献
63.
64.
Joon‐Young Jun Sosuke Nakajima Koji Yamazaki Yuji Kawai Hajime Yasui Yasuyuki Konishi 《International Journal of Food Science & Technology》2015,50(4):871-877
Cystoseira hakodatensis is an unutilised brown algae belonging to family Sargassaceae. A crude methanol extract from the algae showed inhibitory effects on the growths of Bacillus cereus and Bacillus licheniformis. To isolate the major antimicrobial agent, a sequential active‐guided isolation procedure was applied: liquid–liquid extraction, column chromatography and bio‐autography. A marked antimicrobial agent (active α) was isolated in hydrophobic fraction and was determined to phenolics without carbohydrates and proteins by phytochemical test. Regarding the antimicrobial potential, the isolated active α showed better inhibitory effects against B. cereus and B. licheniformis at 2 and 4 times of lower concentrations (62.5 and 31.3 μg mL?1) in comparison with epigallocatechin gallate. These results showed that C. hakodatensis is a potential source of antimicrobial agent capable of preventing the growth of the two bacteria. 相似文献
65.
66.
67.
Prof. Dr. Britto S. Sandanaraj Pavankumar Janardhan Bhandari Mullapudi Mohan Reddy Akshay Bhagwan Lohote Dr. Bankanidhi Sahoo 《Chembiochem : a European journal of chemical biology》2020,21(3):408-416
The custom design of protein–dendron amphiphilic macromolecules is at the forefront of macromolecular engineering. Macromolecules with this architecture are very interesting because of their ability to self-assemble into various biomimetic nanoscopic structures. However, to date, there are no reports on this concept due to technical challenges associated with the chemical synthesis. Towards that end, herein, a new chemical methodology for the modular synthesis of a suite of monodisperse, facially amphiphilic, protein–dendron bioconjugates is reported. Benzyl ether dendrons of different generations (G1–G4) are coupled to monodisperse cetyl ethylene glycol to form macromolecular amphiphilic activity-based probes (AABPs) with a single protein reactive functionality. Micelle-assisted protein labeling technology is utilized for site-specific conjugation of macromolecular AABPs to globular proteins to make monodisperse, facially amphiphilic, protein–dendron bioconjugates. These biohybrid conjugates have the ability to self-assemble into supramolecular protein nanoassemblies. Self-assembly is primarily mediated by strong hydrophobic interactions of the benzyl ether dendron domain. The size, surface charge, and oligomeric state of protein nanoassemblies could be systematically tuned by choosing an appropriate dendron or protein of interest. This chemical method discloses a new way to custom-make monodisperse, facially amphiphilic, protein–dendron bioconjugates. 相似文献
68.
69.
Pierre Santucci Christina Dedaki Alexandros Athanasoulis Laura Gallorini Anaïs Munoz Dr. Stéphane Canaan Dr. Jean-François Cavalier Dr. Victoria Magrioti 《ChemMedChem》2019,14(3):349-358
In the quest for new antibacterial agents, a series of novel long- and medium-chain mono- and disubstituted β-lactones was developed. Their activity against three pathogenic mycobacteria—M. abscessus, M. marinum, and M. tuberculosis—was assessed by the resazurin microtiter assay (REMA). Among the 16 β-lactones synthesized, only 3-hexadecyloxetan-2-one (VM005) exhibited promising activity against M. abscessus, whereas most of the β-lactones showed interesting activities against M. marinum, similar to that of the classical antibiotic, isoniazid. Regarding M. tuberculosis, six compounds were found to be active against this mycobacterium, with β-lactone VM008 [trans-(Z)-3-(hexadec-7-en-1-yl)-4-propyloxetan-2-one] being the best growth inhibitor. The promising antibacterial activities of the best compounds in this series suggest that these molecules may serve as leads for the development of much more efficient antimycobacterial agents. 相似文献
70.
Chinh Ngo Radhika Mehta Kanchan Aggarwal Audrey G. Fikes Dr. Ines C. Santos Dr. Sylvester M. Greer Prof. Dr. Emily L. Que 《Chembiochem : a European journal of chemical biology》2019,20(8):1003-1007
One-third of all proteins are estimated to require metals for structural stability and/or catalytic activity. Desthiobiotin probes containing metal binding groups can be used to capture metalloproteins with exposed active-site metals under mild conditions so as to prevent changes in metallation state. The proof-of-concept was demonstrated with carbonic anhydrase (CA), an open active site, Zn2+-containing protein. CA was targeted by using sulfonamide derivatives. Linkers of various lengths and structures were screened to determine the optimal structure for capture of the native protein. The optimized probes could selectively pull down CA from red blood cell lysate and other protein mixtures. Pull-down of differently metallated CAs was also investigated. 相似文献