全文获取类型
收费全文 | 6854篇 |
免费 | 230篇 |
国内免费 | 87篇 |
专业分类
电工技术 | 86篇 |
综合类 | 131篇 |
化学工业 | 638篇 |
金属工艺 | 258篇 |
机械仪表 | 153篇 |
建筑科学 | 389篇 |
矿业工程 | 27篇 |
能源动力 | 76篇 |
轻工业 | 358篇 |
水利工程 | 41篇 |
石油天然气 | 45篇 |
武器工业 | 24篇 |
无线电 | 441篇 |
一般工业技术 | 818篇 |
冶金工业 | 3189篇 |
原子能技术 | 100篇 |
自动化技术 | 397篇 |
出版年
2023年 | 37篇 |
2022年 | 52篇 |
2021年 | 89篇 |
2020年 | 62篇 |
2019年 | 88篇 |
2018年 | 96篇 |
2017年 | 81篇 |
2016年 | 87篇 |
2015年 | 90篇 |
2014年 | 119篇 |
2013年 | 207篇 |
2012年 | 180篇 |
2011年 | 206篇 |
2010年 | 169篇 |
2009年 | 169篇 |
2008年 | 157篇 |
2007年 | 195篇 |
2006年 | 208篇 |
2005年 | 150篇 |
2004年 | 146篇 |
2003年 | 132篇 |
2002年 | 129篇 |
2001年 | 87篇 |
2000年 | 121篇 |
1999年 | 198篇 |
1998年 | 906篇 |
1997年 | 581篇 |
1996年 | 400篇 |
1995年 | 234篇 |
1994年 | 200篇 |
1993年 | 247篇 |
1992年 | 67篇 |
1991年 | 70篇 |
1990年 | 66篇 |
1989年 | 74篇 |
1988年 | 58篇 |
1987年 | 70篇 |
1986年 | 44篇 |
1985年 | 41篇 |
1984年 | 33篇 |
1983年 | 34篇 |
1982年 | 35篇 |
1981年 | 32篇 |
1980年 | 50篇 |
1979年 | 30篇 |
1978年 | 36篇 |
1977年 | 108篇 |
1976年 | 213篇 |
1975年 | 26篇 |
1974年 | 27篇 |
排序方式: 共有7171条查询结果,搜索用时 93 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.
Thermally conductive polymers offer new possibilities for the heat dissipation in electric and electronic components, for example, by a three‐dimensional shaping of the heat sinks. To face safety regulations, improved fire performance of those components is required. In contrast to unfilled polymers, those materials exhibit an entirely different thermal behavior. To investigate the flammability, a phosphorus flame retardant was incorporated into thermally conductive composites of polyamide 6 and hexagonal boron nitride. The flame retardant decreased the thermal conductivity only slightly. However, the burning behavior changed significantly, due to a different heat propagation, which was investigated using a thermographic camera. An optimum content of hexagonal boron nitride for a sufficient thermal conductivity and fire performance was found between 20 and 30 vol%. The improvement of the fire performance was due to a faster heat release out of the pyrolysis zone and an earlier decomposition of the flame retardant. For higher contents of hexagonal boron nitride, the heat was spread faster within the part, promoting an earlier ignition and increasing the decomposition rate of the flame retardant. 相似文献
3.
Annika Jahn Anton Hoffmann Luisa Blaesing Fabian Kunde Martin Bertau Martina Bremer Steffen Fischer 《化学,工程师,技术》2020,92(11):1733-1740
The enzymatic conversion of lignins, possibly in combination with electrochemical oxidation, makes aromatics such as syringol, guaiacol, vanillin and catechol available in the qualities required by the fragrance industry. The lignins were obtained by soda digestion from wheat straw and Miscanthus, characterized and then converted with laccases. The overall yield amounted up to 9 wt % with a product spectrum confined to four substances. Catechol was the major product, with a fraction of ≈75 %. It can easily be isolated by extraction with acetone. 相似文献
4.
5.
6.
BA Elliott 《Canadian Metallurgical Quarterly》1993,20(2):277-288
Primary care physicians can easily incorporate efforts toward the primary and secondary prevention of family violence into their practices. By designing a preventive effort using the phases of the family life cycle, a developmentally appropriate system of prevention is created. The anticipatory guidance at each (annual) visit acknowledges family transitions and assures the family that abuse is a health issue and that the physician is a resource for issues of violence prevention. Using the FLC, the first phase is Coupling, when there is a risk of partner violence that continues as long as there is a partnership. Pregnancy and childbirth bring concerns of child neglect and battery. Older children are at additional risk for child sexual abuse. As families age, risks develop for elder abuse, too. The regular discussion of these issues raises the awareness that the potential for family violence continues over the life span and allows the physician opportunities to assess the risk of violence in that family and make appropriate preventive referrals. Primary care physicians are optimally positioned to address violence and its prevention in the office: they know and care for family units over time. Physicians are respected and trusted advisors who can become effective in preventing violence. 相似文献
7.
8.
9.
Fischer B. Ghetti A. Selmi L. Bet R. Sangiorgi E. 《Electron Devices, IEEE Transactions on》1997,44(2):288-296
In this paper, new homogeneous hot-electron injection data at 300 K and 77 K is provided covering applied voltages from well below to well above the Si-SiO2 barrier height, and a wide range of oxide fields. We found that, in contrast to the MOSFET case, homogeneous injection shows two different regimes for accelerating voltages below and above the barrier height. A simple interpretation of the data is proposed, and supported by Monte Carlo (MC) simulations of the injection experiment. Essentially, the two regimes are the signature of a marked transition between an electron population mostly heated by the electric field, and a tail population created by additional but less efficient energy gain mechanisms, leading to a sharp transition in the carrier distribution function. The details of the bias and temperature dependence of injection are then interpreted as the combined effect of tunneling and carrier distribution. Furthermore, possible implications on MOSFET gate currents are briefly discussed 相似文献
10.