全文获取类型
收费全文 | 2696篇 |
免费 | 122篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 24篇 |
综合类 | 3篇 |
化学工业 | 705篇 |
金属工艺 | 48篇 |
机械仪表 | 44篇 |
建筑科学 | 77篇 |
矿业工程 | 4篇 |
能源动力 | 45篇 |
轻工业 | 370篇 |
水利工程 | 44篇 |
石油天然气 | 3篇 |
无线电 | 146篇 |
一般工业技术 | 355篇 |
冶金工业 | 671篇 |
原子能技术 | 27篇 |
自动化技术 | 253篇 |
出版年
2023年 | 32篇 |
2022年 | 93篇 |
2021年 | 131篇 |
2020年 | 68篇 |
2019年 | 56篇 |
2018年 | 68篇 |
2017年 | 83篇 |
2016年 | 76篇 |
2015年 | 45篇 |
2014年 | 76篇 |
2013年 | 143篇 |
2012年 | 123篇 |
2011年 | 135篇 |
2010年 | 101篇 |
2009年 | 88篇 |
2008年 | 102篇 |
2007年 | 111篇 |
2006年 | 103篇 |
2005年 | 72篇 |
2004年 | 72篇 |
2003年 | 44篇 |
2002年 | 57篇 |
2001年 | 31篇 |
2000年 | 43篇 |
1999年 | 47篇 |
1998年 | 100篇 |
1997年 | 85篇 |
1996年 | 80篇 |
1995年 | 54篇 |
1994年 | 40篇 |
1993年 | 51篇 |
1992年 | 19篇 |
1991年 | 21篇 |
1990年 | 22篇 |
1989年 | 26篇 |
1988年 | 15篇 |
1987年 | 11篇 |
1986年 | 15篇 |
1985年 | 28篇 |
1984年 | 14篇 |
1983年 | 19篇 |
1982年 | 18篇 |
1981年 | 19篇 |
1980年 | 15篇 |
1979年 | 16篇 |
1978年 | 13篇 |
1977年 | 11篇 |
1976年 | 23篇 |
1975年 | 21篇 |
1974年 | 13篇 |
排序方式: 共有2819条查询结果,搜索用时 15 毫秒
131.
T. Diana L v. A. de Macedo‐Soares Ph.D. Paulo Jacinto Pastor‐Braga B.Sc. 《Information Technology for Development》2013,19(4):453-485
Abstract This article gives an account of the results of a case study undertaken at a pioneer and particularly prominent firm in the Brazilian computer industry: COBRA — Computadores e Sistemas Brasileiros SA. The study is part of a research project1 whose main goal is the identification of viable organizational and technological options that could enhance the performance of firms in the Brazilian electro‐electronics industry. Among the more important findings, it was observed that the firm has the potential to evolve to a more flexible structure, in keeping with the new requirements of the probable future market scenarios within its sector. Everything indicated, however, that the main constraining factors for bringing about such a structure were connected with the firm's culture and beliefs and with the indirect influence of the National Policy of Information Technology upon these. An hypothesis was put forward for an organizational model, and the necessary supportive computerized technology, which could be particularly appropriate in view of the impending deregulation, of the Brazilian computer industry. Also, in the scope of the current discussion on the restructuring of this industry in terms of a greater concentration, an alternative to the prevailing school of thought was proposed, and for whose success the organizational model at issue purports to be particularly relevant. 相似文献
132.
133.
134.
Corneliu Hamciuc Elena Hamciuc Diana Serbezeanu Tachita Vlad‐Bubulac Maria Cazacu 《Polymer International》2011,60(2):312-321
New phosphorus‐containing poly(ester‐imide)‐polydimethylsiloxane copolymers were prepared by solution polycondensation of 1,4‐[2‐(6‐oxido‐6H‐dibenz < c,e > < 1, 2 > oxaphosphorin‐6‐yl)]naphthalene‐bis(trimellitate) dianhydride with a mixture of an aromatic diamine (1,3‐bis(4‐aminophenoxy)benzene) and α,ω‐bis(3‐aminopropyl)oligodimethylsiloxane of controlled molecular weight, in various ratios. Poly(amic acid) intermediates were converted quantitatively to the corresponding polyimide structures using a solution imidization procedure. The polymers are easily soluble in polar organic solvents, such as N‐methyl‐2‐pyrrolidone and N,N‐dimethylformamide, as well as in less polar solvents such as tetrahydrofuran. They show good thermal stability, the decomposition temperature being above 370 °C. The glass transition temperatures are in the range 165–216 °C. Solutions of the polymers in N‐methyl‐2‐pyrrolidone exhibit photoluminescence in the blue region. Copyright © 2010 Society of Chemical Industry 相似文献
135.
136.
An investigation is reported into the mode of action of two commercial flame-resist treatments for wool containing inorganic tin salts. For stannic chloride–ammonium bifluoride formulations, it is shown by 119mSn Mössbauer spectroscopy that the tin species initially exhausted onto the fabric (SnF5OH2?) is chemically different from that observed after washing (SnO2). A similar study of the potassium hexafluorozirconate–stannous chloride–hydrochloric acid system indicated that SnO2 was formed, even before washing, and that no tin (II) species remained. The flame-resist properties of several other tin (IV) salts on wool are also reported. Stannic oxide itself appears to be ineffective as a flame-retardant for wool. 相似文献
137.
Gump Brooks B.; Reihman Jacki; Stewart Paul; Lonky Ed; Granger Douglas A.; Matthews Karen A. 《Canadian Metallurgical Quarterly》2009,28(5):614
Objective: The authors recently reported that blood lead (Pb) was a significant mediator for the positive association between socioeconomic status (SES) and peripheral vascular responses to acute stress in children (B. B. Gump et al., 2007). The present study considers the possibility that Pb may also mediate an association between SES and cortisol responses to acute stress. Design: Early childhood Pb exposure was tested as a mediator for cross-sectional associations between SES and cortisol responses. Main Outcome Measures: The primary outcome was cortisol responses to acute stress in 9.5-year-old children (N = 108). Results: Lower family income was associated with significantly greater cortisol levels following an acute stress task. A mediational analysis confirmed that Pb was a significant mediator for this association. Conclusion: These results reaffirm the importance of considering the chemical environment as well as social and psychological environment when evaluating psychophysiological effects of low SES. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
138.
M.J. Anderson K. McGuire R.C. Zante W.J. Ion A. Rosochowski J.W. Brooks 《Journal of Materials Processing Technology》2013,213(1):111-119
The dies used in the extrusion of nickel based super alloys are subject to severe mechanical and thermal stresses, resulting in shortened life and high manufacturing costs. It is necessary to understand the dominant damage mode in order to guide improvements for increased tool life. The operation under examination consists of the hot extrusion of a nickel based superalloy using nitrided hot work tool steel, glassed workpieces and graphite lubrication. The investigation was conducted through a combination of metallurgical analysis, metrology and finite element analysis. Out of the damage modes observed under these conditions, the plastic deformation of the substrate was found to be the cause for tool failure. This paper discusses the relationship between plastic deformation of the substrate and the formation of scoring marks, which fail the die. 相似文献
139.
Diana Brumini Camilla Bø Furlund Irene Comi Tove Gulbrandsen Devold Donata Marletta Gerd E. Vegarud Christine Monceyron Jonassen 《International Dairy Journal》2013,28(2):109-111
Antiviral activity of Ragusano donkeys' milk proteins was investigated for the effect on echovirus type 5, known to infect the gastrointestinal tract of humans. Three protein fractions were tested; casein (CN), whey protein (WP) and a low molecular whey protein fraction (LWP; <30,000 Da). The antiviral activity of WP and LWP was tested on echovirus type 5 at three concentrations (1, 5 and 10 mg mL?1); CN was assessed only at the lower concentration. All donkey milk protein fractions showed significant inhibition on virus replication at the concentration of 1 mg mL?1, and both WP and LWP fractions showed significant inhibition on the virus replication at all concentrations tested. The strongest antiviral effect was observed for the WP fraction. These findings show that the different whey proteins in donkey milk, probably acting in synergy, exert antiviral activity on echovirus 5 and might contribute to prevent gastrointestinal virus infections in humans. 相似文献
140.
Monique Hoogwijk Stephane de la Rue du Can Aleksandra Novikova Diana Urge-Vorsatz Eliane Blomen Kornelis Blok 《Energy Policy》2010
The greenhouse gas mitigation potential of different economic sectors in three world regions are estimated using a bottom-up approach. These estimates provide updates of the numbers reported in the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR4). This study is part of a larger project aimed at comparing greenhouse gas mitigation potentials from bottom-up and top-down approaches. The sectors included in the analysis are energy supply, transport, industry and the residential and service sector. The mitigation potentials range from 11 to 15 GtCO2eq. This is 26–38% of the baseline in 2030 and 47–68% relative to the year 2000. Potential savings are estimated for different cost levels. The total potential at negative costs is estimated at 5–8% relative to the baseline, with the largest share in the residential and service sector and the highest reduction percentage for the transport and industry sectors. These (negative) costs include investment, operation and maintenance and fuel costs and revenues at moderate discount rates of 3–10%. At costs below 100 US$/tCO2, the largest potential reductions in absolute terms are estimated in the energy supply sector, while the transport sector has the lowest reduction potential. 相似文献