全文获取类型
收费全文 | 838篇 |
免费 | 70篇 |
国内免费 | 7篇 |
专业分类
电工技术 | 10篇 |
综合类 | 4篇 |
化学工业 | 159篇 |
金属工艺 | 26篇 |
机械仪表 | 23篇 |
建筑科学 | 53篇 |
矿业工程 | 2篇 |
能源动力 | 86篇 |
轻工业 | 67篇 |
水利工程 | 5篇 |
石油天然气 | 14篇 |
无线电 | 108篇 |
一般工业技术 | 143篇 |
冶金工业 | 51篇 |
原子能技术 | 4篇 |
自动化技术 | 160篇 |
出版年
2023年 | 25篇 |
2022年 | 32篇 |
2021年 | 37篇 |
2020年 | 22篇 |
2019年 | 37篇 |
2018年 | 41篇 |
2017年 | 32篇 |
2016年 | 34篇 |
2015年 | 21篇 |
2014年 | 54篇 |
2013年 | 76篇 |
2012年 | 37篇 |
2011年 | 55篇 |
2010年 | 28篇 |
2009年 | 56篇 |
2008年 | 36篇 |
2007年 | 31篇 |
2006年 | 35篇 |
2005年 | 21篇 |
2004年 | 18篇 |
2003年 | 14篇 |
2002年 | 25篇 |
2001年 | 12篇 |
2000年 | 15篇 |
1999年 | 6篇 |
1998年 | 9篇 |
1997年 | 12篇 |
1996年 | 15篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 11篇 |
1992年 | 7篇 |
1991年 | 5篇 |
1990年 | 6篇 |
1989年 | 2篇 |
1987年 | 4篇 |
1986年 | 2篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 2篇 |
1982年 | 3篇 |
1981年 | 2篇 |
1979年 | 4篇 |
1976年 | 1篇 |
1973年 | 2篇 |
1971年 | 1篇 |
1970年 | 1篇 |
1969年 | 3篇 |
1968年 | 1篇 |
1961年 | 1篇 |
排序方式: 共有915条查询结果,搜索用时 672 毫秒
51.
52.
Bekir Sami Yilbas 《Numerical Heat Transfer, Part A: Applications》2013,63(3):255-275
High-power-intensity and short-pulse laser heating of metallic surfaces results in thermal separation of electron and lattice subsystems. In this case, energy transport between the subsystems is governed mainly by the collisional process. Moreover, electron and lattice subsystems respond differently for different pulse intensities, despite the fact that the laser pulses have the same energy content. Consequently, in the present study, laser step-input pulse heating of gold substrate is considered and the thermal response of electron and lattice subsystems to four different intensity pulses with the same energy content is examined. The electron kinetic theory approach is introduced to model the nonequilibrium energy transport in the substrate material. It is found that electron temperature rises rapidly in the heating cycle while lattice temperature rise is gradual, which is more pronounced for laser short pulse lengths. In the cooling cycle (time after the laser pulse diminishes), electron temperature decay rate differs from the rate of lattice site temperature rise due to the specific heat ratios of electron and lattice sites. 相似文献
53.
SymbolChat: A flexible picture-based communication platform for users with intellectual disabilities
Tuuli Keskinen Tomi Heimonen Markku Turunen Juha-Pekka Rajaniemi Sami Kauppinen 《Interacting with computers》2012,24(5):374-386
Persons with intellectual disabilities benefit from participating in the modern information society, especially the World Wide Web, social media and Internet-mediated communication services. Although several computer-based prototypes and commercial systems have been introduced for accessible in-person communication, currently few applications and services exist to support synchronous remote communication for this user group. We introduce SymbolChat, a software platform that supports the creation of multimodal communication applications utilizing picture-based instant messaging. End users and their support personnel can customize the input and output features of the application based on their individual needs and abilities. The interaction is based on touchscreen input and speech output using speech synthesis technology. The SymbolChat platform was developed together with the prospective end users and practitioners in the field of special needs care.We evaluated the prototype application in a field study with nine users with varying degrees of intellectual and other disabilities. The results clearly indicate that the participants were able to express themselves in spontaneous communication using a large-scale picture-based vocabulary (around 2000 symbols) even without prior training in the use of symbols. This finding was supported in the constructive feedback gathered from professionals working in the area. We also successfully applied methodology from other settings, such as child-computer interaction to evaluate interaction in this challenging context.Overall, the results show that social inclusion for people with intellectual disabilities can be improved with customizable communication tools. The implemented communication platform forms a solid basis for further improvements and new communication services. In addition, we found that users with motor impairments would greatly benefit from alternative input and output methods for symbol browsing and selection. 相似文献
54.
The objective of this study was to evaluate the effect of Protexin (Probiotics International Ltd., South Petherton, UK) in the prevention of ileocecal infection by Mycobacterium avium ssp. paratuberculosis (MAP) in dairy calves in the field situation. Forty Holstein bull calves whose dams were paratuberculosis negative (confirmed by serum ELISA test and fecal nested PCR) were randomly selected in 2 groups. All calves were fed raw milk collected from the bulk tank in a paratuberculosis-infected dairy farm, which was confirmed by PCR. The treatment group (20 calves) was given 2 g of Protexin from birth until weaning (90 d). The control group (20 calves) did not consume Protexin. The calves were culled at 12 mo of age and the ileocecal lymph nodes were sampled. The lymph nodes were tested by nested PCR to evaluate MAP infection. In the treatment group, 2 out of 20 calf (10%) ileoceca were infected by MAP, whereas in the control group, 8 out of 20 calf (40%) ileoceca were infected by MAP. A significant difference existed between ileocecal infection by MAP in treatment and control groups. Thus, Protexin showed a significant effect in decreasing the ileocecal infection by MAP. 相似文献
55.
Bekir Sami Yilbas A. F. M. Arif C. Karatas S. Akhtar B. J. Abdul Aleem 《The International Journal of Advanced Manufacturing Technology》2010,48(9-12):1009-1018
In this paper, bees algorithm (BA) has been used for determine the optimal number of material handling equipment (MHE) used on the production centers. The unmet demands become zero at the end of the planning horizon, i.e., the part demands are totally satisfied through the horizon. The newly developed model provides network information, such as unmet demands and number of loaded and empty of MHE at any given time and centers. Consequently, the model provides a tool for helping managers with planning and decision-making in manufacturing systems. Computational tests showed that small-sized instances can be solved by the exact approach in a fair amount of central processing unit time, but it is not feasible for medium and large-sized instances. To tackle this problem, a bees algorithm is proposed to solve the model. The algorithm is a search procedure inspired by the way honeybees forage for food. The results obtained show the robust performance of the bees algorithm. 相似文献
56.
Ayman Ben Mabrouk Hamid Kaddami Albert Magnin Mohamed Naceur Belgacem Alain Dufresne Sami Boufi 《Polymer Engineering and Science》2011,51(1):62-70
A one‐step method was used to prepare stable aqueous nanocomposite dispersions based on cellulose whiskers extracted from the rachis of the date palm tree and a poly(styrene‐co‐2‐ethyl hexylacrylate) copolymer via miniemulsion polymerization. A reactive silane, i.e., methacryloxypropyl triethoxysilane was added to stabilize the dispersion and favor the anchoring of the whiskers on polymer particles. Dynamic light scattering was used to study the effect of the silane and whiskers contents on the average particle size of the polymer. Nanocomposites materials were prepared from these dispersions using a casting/evaporation method. The effect of the silane and whiskers contents on the thermal and mechanical properties were studied using differential scanning calorimetry and dynamic mechanical analysis. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers 相似文献
57.
Experimental work was undertaken to study the thermal performance of three different pond cells under actual climatic conditions of Qatar. The first cell was an open pond. In the second unit, a finned radiator, painted black, was placed over the pond. In the third cell, the water was contained in a polyethylene bag. Experimental results indicated that the exposed pond cell came out best, when considered in terms of how quickly the temperature of the stored water could be reduced, and how low that temperature could be. The water in the exposed pond was cooled directly (by evaporation and radiation to sky) whereas in the case of the finned radiator cell, heat had to be transferred from the stored water to the radiator, and then from the radiator to the surrounding. In the case of water-in-bag cell, evaporation was eliminated and radiative exchange with the sky was reduced due to the partial transparency of the polyethylene bag (in the infrared region). 相似文献
58.
Suzuki K Sami M Kadokura H Nakajima H Kitamoto K 《International journal of food microbiology》2002,76(3):223-230
We isolated a strain from hop-resistant Lactobacillus hrevis ABBC45, which had lost a plasmid (pRH45) harboring a putative hop resistance gene, horA. The hop resistance level of this horA-deficient strain, named ABBC45(C), was initially low but gradually induced by repeated growth in media containing progressively increasing levels of hop compounds. Although the hop resistance level was substantially lower than that of the hop-adapted wild type strain, hop-adapted ABBC45(C) (ABBC45(CR)) was still capable of growing in beer, suggesting ABBC45 possesses at least two hop resistance mechanisms. Hop resistance acquired by ABBC45(CR) gradually diminished to the pre-adapted level, when the strain was grown repeatedly in the absence of hop compounds. ABBC45(CR) was found to be cross-resistant to several structurally unrelated drugs, including ethidium bromide, daunomycin and nisin. In addition, ABBC45(CR) was shown to extrude ethidium in an energy-dependent manner, while ABBC45(C) did not show such activity. This indicates that the efflux pump was induced by adaptation to hop compounds. The efflux activity of ethidium was reduced by the addition of hop compounds, suggesting hop compounds are also the substrate of the efflux pump. It was also shown that the efflux activity was completely dissipated with the abolition of proton motive force (PMF). These results, taken together, suggest the hop resistance mechanism of ABBC45(C) is mediated by PMF-dependent multidrug efflux pump. 相似文献
59.
The catalytic combustion of carbon tetrachloride (CCl4) by metal oxide catalysts coated on the monolith support was investigated. The prepared catalysts were tested at temperatures between 300 and 800 degrees C and at varying gas hourly space velocity (GHSV) values with an excess air ratio of 3100%. The catalyst, whose composition was 18% Cr2O3, 2% Ce2O3 and 80% gamma-Al2O3, was found to almost completely oxidize CCl4. The operating conditions proposed are 5702 h(-1) for GHSV, 3100% excess air and a temperature slightly higher than 800 degrees C. The reaction rate expression was found to be independent of oxygen partial pressure but strongly dependent on CCl4 partial pressure. 相似文献
60.