全文获取类型
收费全文 | 669篇 |
免费 | 13篇 |
国内免费 | 1篇 |
专业分类
电工技术 | 10篇 |
化学工业 | 113篇 |
金属工艺 | 7篇 |
机械仪表 | 4篇 |
建筑科学 | 30篇 |
矿业工程 | 2篇 |
能源动力 | 27篇 |
轻工业 | 59篇 |
水利工程 | 4篇 |
石油天然气 | 1篇 |
无线电 | 60篇 |
一般工业技术 | 98篇 |
冶金工业 | 180篇 |
原子能技术 | 5篇 |
自动化技术 | 83篇 |
出版年
2023年 | 4篇 |
2022年 | 4篇 |
2021年 | 8篇 |
2020年 | 6篇 |
2019年 | 11篇 |
2018年 | 11篇 |
2017年 | 9篇 |
2016年 | 9篇 |
2015年 | 5篇 |
2014年 | 11篇 |
2013年 | 33篇 |
2012年 | 23篇 |
2011年 | 33篇 |
2010年 | 20篇 |
2009年 | 40篇 |
2008年 | 52篇 |
2007年 | 34篇 |
2006年 | 27篇 |
2005年 | 26篇 |
2004年 | 23篇 |
2003年 | 17篇 |
2002年 | 17篇 |
2001年 | 14篇 |
2000年 | 16篇 |
1999年 | 17篇 |
1998年 | 35篇 |
1997年 | 18篇 |
1996年 | 17篇 |
1995年 | 17篇 |
1994年 | 16篇 |
1993年 | 15篇 |
1992年 | 11篇 |
1991年 | 5篇 |
1990年 | 9篇 |
1989年 | 17篇 |
1988年 | 5篇 |
1987年 | 2篇 |
1986年 | 2篇 |
1985年 | 4篇 |
1984年 | 6篇 |
1983年 | 3篇 |
1982年 | 5篇 |
1981年 | 6篇 |
1980年 | 4篇 |
1979年 | 3篇 |
1978年 | 3篇 |
1977年 | 3篇 |
1976年 | 6篇 |
1958年 | 1篇 |
排序方式: 共有683条查询结果,搜索用时 187 毫秒
91.
Properties of polymeric microgels are influenced by the internal polymer cross-linked structure, but tools to quantitatively analyze this internal structure are limited. With the finding that polymer networks alter the diffusivity and subsequent excimer formation of pyrene, this study used the ratio between pyrene excimer and monomer emission to determine the number of cross-links (N) and average pore size (ξ) in poly(ethylene glycol) diacrylate (PEGDA) microgels. A calibration curve to relate pyrene emission to N and ξ in PEGDA hydrogels was prepared and used to calculate N and ξ in PEGDA microgels. The pyrene emission indicated that PEGDA microgels had a higher cross-linking density and a smaller average pore size when compared with bulk cross-linked hydrogels of the same PEGDA concentration. The analytical method demonstrated in this study may be useful for fine-tuning polymeric microgel properties for a broad array of applications. 相似文献
92.
Indicators of Small Town Tourism Development Potential: The Case of Fouriesburg, South Africa 总被引:1,自引:0,他引:1
As small towns experience economic and social restructuring, many are pursuing tourism opportunities as one component of a
more diversified local economic strategy. This paper is interested in the small town of Fouriesburg in South Africa's Free
State. While the town was once a thriving service center for a surrounding rural agricultural region, this traditional economy
has faded. Given that the nearby town of Clarens has developed a substantial tourism economy, we pose the question of whether
there already exist indicators that Fouriesburg may be poised for a similar change. These indicators include location within
the urban field, timing within the tourist area life cycle model, differentials/opportunities in property values, and the
role of real estate agents as “gatekeepers” in directing investments. The findings suggest that, while Fouriesburg has potential
for developing a tourism-oriented economy, many of the important policy and planning supports needed to assist with diversification
are not yet in place.
相似文献
Cathy MeiklejohnEmail: |
93.
A novel design of personal cooling clothing incorporating additional insulation sandwiched between phase change materials (PCMs) and clothing outer layer is proposed. Performance of four personal cooling systems including clothing with only PCMs, clothing with PCMs and insulation (PCM?+?INS), clothing with PCMs and ventilation fans (HYB), and clothing with PCMs, ventilation fans and insulation (HYB?+?INS) was investigated. Effect of additional insulation on clothing cooling performance in terms of human physiological and perceptual responses was also examined. Human trials were carried out in a hot environment (i.e. 36?°C, RH = 59%). Results showed that significantly lower mean skin/torso temperatures were registered in HYB?+?INS as compared to HYB. In contrast, no significant effect of the use of insulation on both skin and body temperatures between PCM and PCM?+?INS was observed. Also, no significant difference in thermal sensations, thermal comfort, and skin wetness sensation was registered between cooling systems with and without additional insulation.
Practitioner Summary: Hybrid personal cooling clothing has shown the ability to provide a relatively cool microclimate around the wearer’ body while working in hot environments. The present work addresses the importance of cooling energy saving for PCMs in a hot environment. This work contributes to optimising cooling performance of hybrid personal cooling systems. 相似文献
94.
Clíona Rooney Karim Hadjri Keith Mcallister Máirín Rooney Verity Faith Cathy Craig 《Journal of Housing and the Built Environment》2018,33(1):45-67
Lifetime home standards (LTHS) are a set of standards aimed at making homes more accessible. Previous research, however, indicates that LTHS do not adequately meet the needs of those with sensory impairments. Now, with visual impairment set to increase globally and acknowledging the recognised link between quality of dwelling and wellbeing, this article aims to examine the experiences of visually impaired people living in lifetime homes. The objectives are to investigate existing lifetime homes and to identify whether LTHS meet occupants’ needs. Qualitative semi-structured interviews were carried out with six visually impaired people living in homes designed to LTHS in Northern Ireland. Collected data was analysed using interpretative phenomenological analysis identifying three super-ordinate themes: (1) living with visual impairment; (2) design considerations and (3) coping strategies. A core theme of balance between psychological and physical needs emerged through interconnection of super-ordinate themes. Although there are benefits to living in lifetime homes, negative aspects are also apparent with occupants employing several coping strategies to overcome difficulties. Whilst residents experience negative emotions following visual impairment diagnoses, results suggest that occupants still regard their homes as key places of security and comfort in addition to then highlighting the need for greater consideration of specific individual needs within general guidelines. 相似文献
95.
A pulsed CO2 laser-based system, operating at a wavelength of 10.6 μm, was used as a cleaning tool to remove particles as small as 0.1 μm from hydrophilic, oxidized silicon surfaces. The laser beam served as a fast heating source to induce the explosive evaporation of a water film deposited on the particle-contaminated surface. The resulting explosive forces were high enough to expel particles from the surface efficiently. The contaminant particles used were 0.1 μm alumina, 0.1-0.2 μm silica, and 0.1 μm polystyrene latex.
For each of these, the cleaning efficiency was monitored as a function of the laser fluence, the thickness of the deposited water film and the number of cleaning cycles. Whatever the nature of the particles, the cleaning efficiency was characterized by an upper limit of the energy density, determined to be 1.5 J/cm2, at which substrate damage occurred. At all lower laser fluences, the removal efficiency was particle-dependent.
The thickness of the deposited water film was varied by changing the time of exposure of the surface to water vapor, the vapor flow being fixed at 4700 ml/min. An exposure time of 1.5 s was found to be the most effective. Increasing the number of cleaning cycles permitted the evaluation of the effect of the zeta potentials of the particles with respect to that of the surface. 相似文献
For each of these, the cleaning efficiency was monitored as a function of the laser fluence, the thickness of the deposited water film and the number of cleaning cycles. Whatever the nature of the particles, the cleaning efficiency was characterized by an upper limit of the energy density, determined to be 1.5 J/cm2, at which substrate damage occurred. At all lower laser fluences, the removal efficiency was particle-dependent.
The thickness of the deposited water film was varied by changing the time of exposure of the surface to water vapor, the vapor flow being fixed at 4700 ml/min. An exposure time of 1.5 s was found to be the most effective. Increasing the number of cleaning cycles permitted the evaluation of the effect of the zeta potentials of the particles with respect to that of the surface. 相似文献
96.
Modern field programmable gate array (FPGA) chips, with their larger memory capacity and reconfigurability potential, are opening new frontiers in rapid prototyping of embedded systems. With the advent of high-density FPGAs, it is now possible to implement a high-performance VLIW (very long instruction word) processor core in an FPGA. With VLIW architecture, the processor effectiveness depends on the ability of compilers to provide sufficient ILP (instruction-level parallelism) from program code. This paper describes research result about enabling the VLIW processor model for real-time processing applications by exploiting FPGA technology. Our goals are to keep the flexibility of processors to shorten the development cycle, and to use the powerful FPGA resources to increase real-time performance. We present a flexible VLIW VHDL processor model with a variable instruction set and a customizable architecture which allows exploiting intrinsic parallelism of a target application using advanced compiler technology and implementing it in an optimal manner on FPGA. Some common algorithms of image processing were tested and validated using the proposed development cycle. We also realized the rapid prototyping of embedded contactless palmprint extraction on an FPGA Virtex-6 based board for a biometric application and obtained a processing time of 145.6 ms per image. Our approach applies some criteria for co-design tools: flexibility, modularity, performance, and reusability. 相似文献
97.
Cathy Keys 《The Journal of Architecture》2016,21(1):68-89
Whilst it is generally recognised that hospitals designed in major Australian centres have drawn heavily on British and American precedent since colonial settlement, little research has been undertaken on these connections in terms of remotely located, small-scale, cottage hospitals. This study of the Australian Inland Mission's cottage hospital Adelaide House (1926) contributes to our understanding of strategies used to design hospital environments in the early twentieth century through critical analysis of historical documents and existing literature. Preliminary findings suggest that the adoption or adaptation of international design precedent to meet inland Australian conditions was informed by ideas about climate, gender and race, and, to some extent, the advice of field-experienced nursing sisters. 相似文献
98.
A polymer modified with succinic anhydride has been investigated for the adsorption of cadmium (II) on a freshly precipitated aluminium (III) hydroxide floc. The proportion of chelate attached to the polymer is varied to determine the relationship between carboxyl and amino groups on the polyelectrolyte, in terms of enhanced adsorption of cadmium (II) on a hydrous aluminium floc. The presence of polyelectrolyte enhanced the adsorption of 3.3 ppm Cd (II) on a 333 ppm Al (III) floc at every concentration of polyelectrolyte investigated. The proportion of succinic anhydride attached to the polymer had an impact on the increased adsorption of Cd (II) on an Al (III) floc observed. A decreasing proportion of succinic anhydride to polymer resulted in a decrease in the amount of cadmium adsorbed on the floc. Above pH 8, a decrease in the % Cd (II) adsorbed on the floc and % Al (III) retained within the floc decreases with the presence of polyelectrolyte as a result of the formation of soluble Cd-Polyethylenimine-succinic acid (PEISA) complexes. When the Al-PEISA combination was applied to a complex matrix where Cd (II), Cu (II) and Ni (II) ions competed for adsorption, enhanced adsorption was observed for Cd (II) and Ni (II). At pH 7, dissolution of the floc observed with the addition of discrete chelates was not observed with the addition of polyelectrolytes. 相似文献
99.
100.
Fully quantitative analyses of DRIFTS data are required when the surface concentrations and the specific rate constants of reaction (or desorption) of adsorbates are needed to validate microkinetic models. The relationship between the surface coverage of adsorbates and various functions derived from the signal collected by DRIFTS is discussed here. The Kubelka-Munk and pseudoabsorbance (noted here as absorbance, for the sake of brevity) transformations were considered, since those are the most commonly used functions when data collected by DRIFTS are reported. Theoretical calculations and experimental evidence based on the study of CO adsorption on Pt/SiO2 and formate species adsorbed on Pt/CeO2 showed that the absorbance (i.e., = log 1/R', with R' = relative reflectance) is the most appropriate, yet imperfect, function to give a linear representation of the adsorbate surface concentration in the examples treated here, for which the relative reflectance R' is typically > 60%. When the adsorbates lead to a strong signal absorption (e.g., R' < 60%), the Kubelka-Munk function is actually more appropriate. The absorbance allows a simple correction of baseline drifts, which often occur during time-resolved data collection over catalytic materials. Baseline corrections are markedly more complex in the case of the other mathematical transforms, including the function proposed by Matyshak and Krylov (Catal. Today 1995, 25, 1-87), which has been proposed as an appropriate representation of surface concentrations in DRIFTS spectroscopy. 相似文献