全文获取类型
收费全文 | 3213篇 |
免费 | 98篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 65篇 |
综合类 | 5篇 |
化学工业 | 1031篇 |
金属工艺 | 56篇 |
机械仪表 | 40篇 |
建筑科学 | 199篇 |
矿业工程 | 30篇 |
能源动力 | 37篇 |
轻工业 | 377篇 |
水利工程 | 12篇 |
石油天然气 | 13篇 |
无线电 | 178篇 |
一般工业技术 | 458篇 |
冶金工业 | 358篇 |
原子能技术 | 32篇 |
自动化技术 | 421篇 |
出版年
2022年 | 33篇 |
2021年 | 39篇 |
2020年 | 30篇 |
2019年 | 31篇 |
2018年 | 45篇 |
2017年 | 41篇 |
2016年 | 66篇 |
2015年 | 89篇 |
2014年 | 76篇 |
2013年 | 120篇 |
2012年 | 122篇 |
2011年 | 159篇 |
2010年 | 118篇 |
2009年 | 117篇 |
2008年 | 117篇 |
2007年 | 139篇 |
2006年 | 122篇 |
2005年 | 111篇 |
2004年 | 108篇 |
2003年 | 81篇 |
2002年 | 72篇 |
2001年 | 52篇 |
2000年 | 53篇 |
1999年 | 60篇 |
1998年 | 105篇 |
1997年 | 78篇 |
1996年 | 77篇 |
1995年 | 69篇 |
1994年 | 73篇 |
1993年 | 46篇 |
1992年 | 48篇 |
1991年 | 46篇 |
1990年 | 28篇 |
1989年 | 37篇 |
1987年 | 30篇 |
1986年 | 32篇 |
1985年 | 43篇 |
1984年 | 39篇 |
1983年 | 36篇 |
1982年 | 33篇 |
1981年 | 31篇 |
1980年 | 32篇 |
1979年 | 23篇 |
1978年 | 29篇 |
1977年 | 35篇 |
1976年 | 35篇 |
1975年 | 38篇 |
1974年 | 24篇 |
1973年 | 28篇 |
1970年 | 34篇 |
排序方式: 共有3312条查询结果,搜索用时 31 毫秒
1.
Daniela Fogli Antonio Piccinno Stefan Carmien Gerhard Fischer 《Behaviour & Information Technology》2020,39(1):27-46
ABSTRACTThe digital age of the future is ‘not out there to be discovered’, but it needs to be ‘designed’. The design challenge has to address questions about how we want to live, work, and learn (as individuals and as communities) and what we value and appreciate, e.g.: reflecting on quality of life and creating inclusive societies. An overriding design trade-off for the digital age is whether new developments will increase the digital divide or will create more inclusive societies. Sustaining inclusive societies means allowing people of all ages and all abilities to exploit information technologies for personally meaningful activities. Meta-design fosters the design of socio-technical environments that end-user developers can modify and evolve at use time to improve their quality of life and favour their inclusion in the society. This paper describes three case studies in the domain of assistive technologies in which end users themselves cannot act as end-user developers, but someone else (e.g.: a caregiver or a clinician) must accept this role requiring multi-tiered architectures. The design trade-offs and requirements for meta-design identified in the context of the case studies and other researchers’ projects are described to inform the development of future socio-technical environments focused on social inclusion. 相似文献
2.
3.
Semi‐Markovian processes (SMP) serve as a versatile means to model various traffic types generated by sources or superposed
from links in ATM networks. An efficient discrete time analysis method is proposed for SMP/G/1 queueing systems to evaluate
ATM switches with non‐renewal input. Some basic results are derived for the autocorrelation function of semi‐Markovian processes
and for the effect of state space reduction on autocorrelation, which show how to represent correlated traffic with given
characteristic by an adequate SMP model of limited size.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
4.
5.
6.
7.
The traditional approach to severe subglottic stenosis (SGS) in the pediatric age group is laryngotracheal reconstruction (LTR). This approach may be complex and multistaged, with variable and unpredictable success rates in the individual patient. Excellent results have been reported in adults who had severe SGS and underwent partial resection of the cricoid and primary thyrotracheal anastomosis. This procedure has not been widely reported in infants and children. We report our experience with this procedure in 16 pediatric patients with grade III or IV SGS. Eleven patients had multiple previous LTR operations. The preoperative evaluation, surgical techniques, postoperative care, complications, and final results are described and discussed. Fourteen patients were decannulated after the procedure, 1 patient needed a second open procedure prior to decannulation, and 1 patient with concomitant bronchopulmonary dysplasia remains cannulated, for an overall 94% decannulation rate. Fourteen patients have no limitation of respiration, and 1 patient has moderate exercise intolerance. The results of this series suggest that partial cricotracheal resection with primary anastomosis is a relatively safe and effective procedure for pediatric patients with severe SGS. 相似文献
8.
9.
Heinrich Heydt Philipp Eisenbarth Karin Feith Klaus Urgast Gerhard Maas Manfred Regitz 《Israel journal of chemistry》1986,27(1):96-104
Amino-substituted cyclopropenylium salts ( 11a,b ) react with diazomethyl compounds ( 12a-i ) in dichloromethane or acetonitrile in the presence of a base (ethyldiisopropylamine, 1,5-diazabicyclo[4.3.0] non-5-ene) to form 4-aminopyridazines ( 13a-i ) specifically. The reaction is interpreted in terms of an initial electrophilic diazoalkane substitution to give diazomethylcyclopropenes ( 11 + 12 → 14 ) which undergo a [1.5]-cyclisation to form the betaines 16 which, in turn, isomerise with opening of the bridging bond to give the aminopyridazines 13 . In a similar manner, the tris[amino] cyclopropenylium salts 8a,b and 10a-c are converted to the 3,4,5-tris[amino]-pyridazines ( 21a-k ) by treatment with diazomethyl compounds ( 12a, c-f ). 相似文献
10.
Near saturation steam undergoing rapid expansion, with homogeneous nucleation of water droplets, is numerically studied in a series of converging/diverging nozzles with and without shocks. To understand loss mechanisms in such flows a numerical model is presented to calculate thermodynamic losses, which is further used to quantify associated total aerodynamic losses. For the converging/diverging nozzle configuration, the model shows that the overall thermodynamic loss is only mildly influenced by increasing shock strength, while the aerodynamic losses follow that of the single phase flow, and are of the same magnitude as the thermodynamic loss only in the case of very weak shocks. The thermodynamic losses can be attributed to two influences, the homogeneous nucleation event, and the post-shock thermal oscillations in the two-phase system. The calculations rely on a new two-phase CFD model, previously reported, for non-equilibrium phase change with droplet nucleation applicable to general 3D flow configurations. 相似文献