全文获取类型
收费全文 | 4659篇 |
免费 | 280篇 |
国内免费 | 38篇 |
专业分类
电工技术 | 57篇 |
综合类 | 18篇 |
化学工业 | 1002篇 |
金属工艺 | 106篇 |
机械仪表 | 120篇 |
建筑科学 | 159篇 |
矿业工程 | 12篇 |
能源动力 | 193篇 |
轻工业 | 484篇 |
水利工程 | 33篇 |
石油天然气 | 47篇 |
无线电 | 523篇 |
一般工业技术 | 989篇 |
冶金工业 | 246篇 |
原子能技术 | 26篇 |
自动化技术 | 962篇 |
出版年
2024年 | 6篇 |
2023年 | 73篇 |
2022年 | 118篇 |
2021年 | 186篇 |
2020年 | 137篇 |
2019年 | 101篇 |
2018年 | 206篇 |
2017年 | 211篇 |
2016年 | 241篇 |
2015年 | 159篇 |
2014年 | 217篇 |
2013年 | 379篇 |
2012年 | 321篇 |
2011年 | 293篇 |
2010年 | 252篇 |
2009年 | 251篇 |
2008年 | 252篇 |
2007年 | 233篇 |
2006年 | 198篇 |
2005年 | 133篇 |
2004年 | 125篇 |
2003年 | 113篇 |
2002年 | 95篇 |
2001年 | 46篇 |
2000年 | 40篇 |
1999年 | 51篇 |
1998年 | 59篇 |
1997年 | 54篇 |
1996年 | 36篇 |
1995年 | 43篇 |
1994年 | 30篇 |
1993年 | 29篇 |
1992年 | 19篇 |
1991年 | 21篇 |
1990年 | 18篇 |
1989年 | 15篇 |
1988年 | 13篇 |
1987年 | 12篇 |
1986年 | 16篇 |
1985年 | 13篇 |
1984年 | 19篇 |
1983年 | 16篇 |
1982年 | 13篇 |
1981年 | 26篇 |
1980年 | 16篇 |
1978年 | 8篇 |
1977年 | 13篇 |
1976年 | 10篇 |
1975年 | 8篇 |
1973年 | 7篇 |
排序方式: 共有4977条查询结果,搜索用时 15 毫秒
1.
Virginija Sacevičienė Milda Jucienė Vaida Dobilaitė Valentina Krylova Skirma Žalenkienė Nijolė Dukštienė Raimondas Bliūdžius 《应用聚合物科学杂志》2019,136(21):47523
The aim of this work was to investigate the physical and mechanical performance of architectural polyester (PES)–poly(vinyl chloride) (PVC) membranes exposed to different artificial aging conditions. Two commercially available architectural membranes were chosen as research objects. The durability of the PES/PVC fabrics was evaluated by the loss in mechanical performance, scanning electron microscopy, and X-ray diffraction analysis in order to understand the effect of the degradation agents on the surface of the membranes. The mechanical performance of the PES/PVC membranes was unchanged. Scanning electron microscopy images of the tested materials showed initial cracks after aging. The X-ray fluorescence analysis showed that at the time of aging, the amount of Cl and Si decreased slightly, while Ti decreased by half, and Ca by volume increased twice. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47523. 相似文献
2.
3.
4.
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
5.
6.
Evaluation of the effect of processing on cocoa polyphenols: antiradical activity,anthocyanins and procyanidins profiling from raw beans to chocolate
下载免费PDF全文
![点击此处可从《International Journal of Food Science & Technology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Matteo Bordiga Monica Locatelli Fabiano Travaglia Jean Daniel Coïsson Giuseppe Mazza Marco Arlorio 《International Journal of Food Science & Technology》2015,50(3):840-848
The content and composition of anthocyanins and procyanidins in fermented cocoa beans (from different geographic origins: Ecuador, Cameroon, Ivory Coast, Ghana and Nigeria), roasted nibs, cocoa mass and chocolate were determined, beside the determination of the total antiradical capacity. Concerning geographic origin, cocoa beans and processed products from Ecuador showed the highest levels of anthocyanins, followed by Nigeria and Cameroon. Generally, as cocoa beans were further processed, the levels of anthocyanins and flavan‐3‐ols decreased. The largest observed losses of phenolics occurred during roasting. A progressive decreasing trend in polyphenol concentration was observed in the other processed samples as well. Despite the original content of polyphenols in raw cocoa beans, technological processes imply a significant impact on cocoa quality, confirming the need of specific optimisation to obtain high value chocolate. 相似文献
7.
M. F. Sorokïna O. M. Kanunnikova F. Z. Gil'mutdinov V. I. Kozhevnikov 《Glass and Ceramics》1996,53(1-2):11-13
The method of x-ray electron spectroscopy is used to investigate lead silicatexPbO(1 -x) · SiO2 (x - 0.3, 0.4, 0.5, 0.55, 0.667) glasses. The concentration dependences of the spectra of inner Pb4f, Si2p, and Ols levels led to the conclusion that for low contents of PbO, lead is present in the glass in the form of modifying ions, whereas in high concentrations, it plays the role of glass former. Restructuring in the glass occurs for about 50% molar concentration of PbO. The Pb - O bond in the glass is more ionic than in PbO. With an increase in the PbO content in the glass, the Pb - O bond becomes closer to that of lead monoxide, i.e., is more covalent. 相似文献
8.
Frédéric Gaschet 《Papers in Regional Science》2002,81(1):63-81
This article examines the relationships between the employment suburbanisation from central cities towards their suburbs,
and the process of intra-urban specialisation that occurred simultaneously in the fifty largest French metropolitan areas.
A methodology is proposed to identify urban subcentres and to analyse the effects of the intra-urban specialisations on suburbanisation
patterns. We conclude that the specialisation of both subcentres and central cities has a significant effect on suburbanisation
rates. Lastly, an intra-metropolitan shift/share analysis provides additional insights into the employment dynamics of central
cities and suburbs during the last twenty years.
Received: 25 July 2000 / Accepted: 29 May 2001 相似文献
9.
Recently, there has been a growing interest in using cylindrical transmission lines that contain magnetized ferrite material in a variety of applications. In this paper, the finite-difference time-domain (FDTD) method (in cylindrical coordinates) and the spectral-domain analysis (SDA) are used to calculate the propagation characteristics of cylindrical transmission lines that contain magnetized ferrite material. The magnetization can be either in the longitudinal or azimuthal directions. Specifically, the cylindrical microstrip line, and the cylindrical coplanar waveguide printed on magnetized ferrite substrate are analyzed. Both the FDTD and SDA results are in very good agreement. In addition, the results are compared to those of planar structures by taking the radius of the substrate to be large enough such that the curvature effect is negligible 相似文献
10.
Omar Snchez Estrella Asp María C Martí Marlene Roeckel 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2005,80(11):1261-1267
Most of the kinetic studies on nitrification have been performed in diluted salts medium. In this work, the ammonia oxidation rate (AOR) was determined by respirometry at different ammonia (0.01 and 33.5 mg N‐NH3 L?1), nitrite (0–450 mg N‐NO2? L?1) and nitrate (0 and 275 mg N‐NO3? L?1) concentrations in a saline medium at 30 °C and pH 7.5. Sodium azide was used to uncouple the ammonia and nitrite oxidation, so as to measure independently the AOR. It was determined that ammonia causes substrate inhibition and that nitrite and nitrate exhibit product inhibition upon the AOR. The effects of ammonia, nitrite and nitrate were represented by the Andrews equation (maximal ammonia oxidation rate, rAOMAX, = 43.2 [mg N‐NH3 (g VSSAO h)?1]; half saturation constant, KSAO, = 0.11 mg N‐NH3 L?1; inhibition constant KIAO, = 7.65 mg N‐NH3 L?1), by the non‐competitive inhibition model (inhibition constant, KINI, = 176 mg N‐NO2? L?1) and by the partially competitive inhibition model (inhibition constant, KINA, = 3.3 mg N‐NO3? L?1; α factor = 0.24), respectively. The rAOMAX value is smaller, and the KSAO value larger, than the values reported in diluted salts medium; the KIAO value is comparable to those reported. Process simulations with the kinetic model in batch nitrifying reactors showed that the inhibitory effects of nitrite and nitrate are significant for initial ammonia concentrations larger than 100 mg N‐NH4+ L?1. Copyright © 2005 Society of Chemical Industry 相似文献