全文获取类型
收费全文 | 4670篇 |
免费 | 378篇 |
国内免费 | 2篇 |
专业分类
电工技术 | 94篇 |
综合类 | 8篇 |
化学工业 | 1474篇 |
金属工艺 | 77篇 |
机械仪表 | 133篇 |
建筑科学 | 146篇 |
矿业工程 | 12篇 |
能源动力 | 158篇 |
轻工业 | 839篇 |
水利工程 | 26篇 |
石油天然气 | 22篇 |
无线电 | 267篇 |
一般工业技术 | 1023篇 |
冶金工业 | 73篇 |
原子能技术 | 12篇 |
自动化技术 | 686篇 |
出版年
2024年 | 13篇 |
2023年 | 40篇 |
2022年 | 135篇 |
2021年 | 258篇 |
2020年 | 115篇 |
2019年 | 142篇 |
2018年 | 179篇 |
2017年 | 187篇 |
2016年 | 238篇 |
2015年 | 184篇 |
2014年 | 238篇 |
2013年 | 464篇 |
2012年 | 331篇 |
2011年 | 348篇 |
2010年 | 274篇 |
2009年 | 227篇 |
2008年 | 237篇 |
2007年 | 182篇 |
2006年 | 157篇 |
2005年 | 107篇 |
2004年 | 65篇 |
2003年 | 76篇 |
2002年 | 58篇 |
2001年 | 48篇 |
2000年 | 43篇 |
1999年 | 36篇 |
1998年 | 28篇 |
1997年 | 20篇 |
1996年 | 32篇 |
1995年 | 24篇 |
1994年 | 31篇 |
1993年 | 26篇 |
1992年 | 24篇 |
1991年 | 20篇 |
1990年 | 21篇 |
1989年 | 23篇 |
1988年 | 17篇 |
1985年 | 36篇 |
1984年 | 40篇 |
1983年 | 29篇 |
1982年 | 26篇 |
1981年 | 36篇 |
1980年 | 32篇 |
1979年 | 25篇 |
1978年 | 24篇 |
1977年 | 18篇 |
1976年 | 20篇 |
1975年 | 13篇 |
1973年 | 14篇 |
1972年 | 14篇 |
排序方式: 共有5050条查询结果,搜索用时 15 毫秒
1.
2.
3.
Aleksandar Miletić Peter Panjan Miha Čekada Lazar Kovačević Pal Terek Janez Kovač Goran Dražič Branko Škorić 《Ceramics International》2021,47(2):2022-2033
With the goal to produce a hard and tough coating intended for tribological applications, CrAlN/TiSiN nanolayer coating was prepared by alternative deposition of CrAlN and TiSiN layers. In the first part of the article, a detailed study of phase composition, microstructure, and layer structure of CrAlN/TiSiN coating is presented. In the second part, its mechanical properties, fracture and tribological behavior are compared to the nanocomposite TiSiN coating. An industrial magnetron sputtering unit was used for coating deposition. X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy were used for compositional and microstructural analysis. Mechanical properties and fracture behavior were studied by instrumented indentation and focused ion beam techniques. Tribological properties were evaluated by ball-on-disk test in a linear reciprocal mode. A complex layer structure was found in the nanolayer coating. The TiSiN layers were epitaxially stabilized inside the coating which led to formation of dislocations at interfaces, to introduction of disturbances in the coating growth, and as a result, to development of fine-grained columnar microstructure. Indentation load required for the onset of fracture was twice lower for the nanolayer CrAlN/TiSiN, compared to the nanocomposite TiSiN coating. This agrees very well with their mechanical properties, with H3/E2 being twice higher for the TiSiN coating. However, the nanolayer coating experienced less severe damage, which had a strong impact on tribological behavior. A magnitude of order lower wear rate and four times lower steady state friction coefficient were found for the nanolayer coating. 相似文献
4.
Hydrophilic polymer networks (hydrogels) based on sodium carboxymethylcellulose (NaCMC) and polycarboxylic acids (oxalic, succinic, citric and adipic) as cross-linking agents are synthesized by esterification reaction; one series of NaCMC hydrogels cross-linked with citric acid is prepared with acrylamide and acrylic acid (Aam/Aac) copolymers using the design of semi-interpenetrating polymer networks (semi-IPN), in order to increase their potential application for flocculation purposes. The Infrared spectroscopy (FTIR) of hydrogels confirms the esterification reaction between NaCMC and cross-linking agents. Results of swelling measurements show that citric acid in the amount of 15 wt% gives the hydrogels with the best absorption capacity. The results of Differential scanning calorimetry (DSC) and Thermal gravimetric analysis (TGA) show no significant difference in thermal properties of neat and semi-interpenetrating NaCMC hydrogels. The amorphous nature of hydrogels is confirmed by X-ray diffraction analysis (XRD). The results of flocculation study show that combination of NaCMC network and Aam/Aac copolymer with initial mass ratio of 10/90 creates a theoretical platform for the production of flocculant which could show high efficacy in purifying of water dominated by positively charged particles. 相似文献
5.
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
6.
The present study was conducted to develop subcritical water extraction (SWE) of Echinacea purpurea flowers. The influence of temperature and extraction time on quality of extracts considering total phenols content, total flavonoids content, antioxidant capacity and extraction yield, was determined. Optimized extraction parameters for maximised investigated responses were as follows: 147.56 °C and 8.43 min. The experimental values agreed with the values predicted, thus indicating the adequacy of central composite experimental design for modelling the SWE of bioactive compounds from E. purpurea. Results of the study also highlighted the potential application of E. purpurea subcritical water extracts as a source of valuable bioactive compounds. 相似文献
7.
8.
9.
10.
Daniela Frasca Maria Romero Alain Diaz Denisse Garcia Seth Thaller Bonnie B. Blomberg 《International journal of molecular sciences》2021,22(4)
Senescent cells accumulate in the adipose tissue (AT) of individuals with obesity and secrete multiple factors that constitute the senescence-associated secretory phenotype (SASP). This paper aimed at the identification of B cells with a SASP phenotype in the AT, as compared to the peripheral blood, of individuals with obesity. Our results show increased expression of SASP markers in AT versus blood B cells, a phenotype associated with a hyper-metabolic profile necessary to support the increased immune activation of AT-derived B cells as compared to blood-derived B cells. This hyper-metabolic profile is needed for the secretion of the pro-inflammatory mediators (cytokines, chemokines, micro-RNAs) that fuel local and systemic inflammation. 相似文献