全文获取类型
收费全文 | 824篇 |
免费 | 41篇 |
国内免费 | 17篇 |
专业分类
电工技术 | 17篇 |
综合类 | 31篇 |
化学工业 | 532篇 |
金属工艺 | 15篇 |
机械仪表 | 20篇 |
建筑科学 | 7篇 |
矿业工程 | 9篇 |
能源动力 | 13篇 |
轻工业 | 47篇 |
石油天然气 | 19篇 |
无线电 | 18篇 |
一般工业技术 | 118篇 |
冶金工业 | 8篇 |
原子能技术 | 7篇 |
自动化技术 | 21篇 |
出版年
2024年 | 1篇 |
2023年 | 20篇 |
2022年 | 17篇 |
2021年 | 22篇 |
2020年 | 21篇 |
2019年 | 25篇 |
2018年 | 13篇 |
2017年 | 25篇 |
2016年 | 26篇 |
2015年 | 23篇 |
2014年 | 22篇 |
2013年 | 52篇 |
2012年 | 51篇 |
2011年 | 42篇 |
2010年 | 36篇 |
2009年 | 32篇 |
2008年 | 37篇 |
2007年 | 61篇 |
2006年 | 68篇 |
2005年 | 39篇 |
2004年 | 44篇 |
2003年 | 39篇 |
2002年 | 37篇 |
2001年 | 18篇 |
2000年 | 19篇 |
1999年 | 20篇 |
1998年 | 13篇 |
1997年 | 11篇 |
1996年 | 8篇 |
1995年 | 7篇 |
1994年 | 6篇 |
1993年 | 10篇 |
1992年 | 7篇 |
1991年 | 2篇 |
1990年 | 1篇 |
1982年 | 3篇 |
1979年 | 2篇 |
1976年 | 1篇 |
1951年 | 1篇 |
排序方式: 共有882条查询结果,搜索用时 15 毫秒
51.
Jianwei Ren Nicholas M. Musyoka Henrietta W. Langmi Brian C. North Mkhulu Mathe Xiangdong Kang 《International Journal of Hydrogen Energy》2014
The fabrication of core–shell nanocrystals by incorporating microporous UiO-66 into mesoporous MIL-101 is reported. The growth of the core–shell MIL-101@UiO-66 nanocrystals was observed and supported by TEM and PXRD. The accessible pore volumes of the individual metal-organic framework (MOF) components and the core–shell hybrid crystals were also characterized. The hydrogen storage capacity exhibited by the resulting core–shell nanocrystals was 26% and 60% higher than those of pure phase MIL-101 and UiO-66, respectively. Finally, the fabricated core–shell MIL-101@UiO-66 structure exhibited a high degree of moisture tolerance. 相似文献
52.
Membranes with outstanding performance that are applicable in harsh environments are needed to broaden the current range of organic dehydration applications using pervaporation. Here, well‐intergrown UiO‐66 metal‐organic framework membranes fabricated on prestructured yttria‐stabilized zirconia hollow fibers are reported via controlled solvothermal synthesis. On the basis of the adsorption–diffusion mechanism, the membranes provide a very high flux of up to ca. 6.0 kg m?2 h?1 and excellent separation factor (>45 000) for separating water from i ‐butanol (next‐generation biofuel), furfural (promising biochemical), and tetrahydrofuran (typical organic). This performance, in terms of separation factor, is one to two orders of magnitude higher than that of commercially available polymeric and silica membranes with equivalent flux. It is comparable to the performance of commercial zeolite NaA membranes. Additionally, the membrane remains robust during a pervaporation stability test (≈300 h), including exposure to harsh environments (e.g., boiling benzene, boiling water, and sulfuric acid) where some commercial membranes (e.g., zeolite NaA membranes) cannot survive. 相似文献
53.
N. K. Pramanik R. S. Haldar Y. K. Bhardwaj S. Sabharwal U. K. Niyogi R. K. Khandal 《应用聚合物科学杂志》2011,122(1):193-202
Nylon 66 has been transformed into a material with significantly improved properties like hardness, tensile strength, and flexural modulus by processing it under the optimized dose rate of electron beam in the presence of suitable crosslinkers. Furthermore, percent water absorption of nylon 66 was reduced substantially on irradiation. Thermogravimetric analysis revealed that thermal stability of nylon 66 improved with increasing dose of radiation. Improvement of mechanical and thermal properties and reduction of water absorption of nylon 66 were due to the crosslinking of polyamide molecules made possible by the high energy radiation. Increase of crosslinking with increasing radiation dose was verified by the increase of gel content at higher doses. Differential scanning calorimetry showed that both melting and crystallization temperatures along with percent crystallinity of nylon 66 were decreased with the increasing dose of radiation leading to the development of more amorphous character in this semicrystalline polymer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011. 相似文献
54.
本文以热分解型过氧化物——过氧化二异丙苯(简称DCP)为引发剂,研究了引发剂浓度、溶胀剂、浸渍时间、浸渍温度对尼龙-66纤维化学交联反应的影响。通过测定交联后纤维溶解性能的变化,确定纤维交联反应的程度:通过对纤维进行红外光谱、X射线广角衍射强度以及强伸度的测定,进一步阐明了化学交联纤维的结构和性能。 相似文献
55.
56.
根据锦纶—66帘子线对油剂的要求进行了该油剂的配方设计,调整了平滑剂与乳化剂的比例,合成了理想的耐热油剂,用于原丝和帘子布生产,各项物理性能指标合格,效果良好. 相似文献
57.
Lee?HuskeyEmail author Matthew?Berman Alexandra?Hill 《The Annals of Regional Science》2004,38(1):75-92
We investigate determinants of the pattern of recent migration of Alaska Natives between rural homelands and urban areas. A review of the literature on moving in the North American North suggests that economic opportunities draw migrants, although such opportunities must be viewed in the context of the mixed subsistence-cash economy prevailing in rural areas of the region. Consequently, we model Native migration as a simultaneous decision with labor market participation in a mixed economy. Estimated equations explaining individual Alaska Native migration choices using the U.S. Census Public Use Microdata Sample (PUMS) are consistent with the model, and also suggest that perceived opportunities differ between women and men.The authors acknowledge financial support from the National Science Foundation, grant OPP-9521459. An earlier version of this paper was presented to the 1998 annual meeting of the Western Regional Science Association 相似文献
58.
为了研究66 kV XLPE电力电缆的绝缘性能,文中采用自主设计的加速老化试验平台,同时对三根样品电缆分别进行两个阶段的电老化、热老化以及电热联合老化.利用等温松弛电流法(IRC)分别对加速老化前后的样品电缆进行试验,分析老化因子的改变,研究电缆的绝缘性能变化.试验结果表明:经过两个阶段的加速老化试验,电老化样品老化因子分别增加3.70%和4.21%,而热老化样品老化因子分别增加4.82%和23.42%,说明电应力和热应力在影响绝缘老化性能中,热应力的“贡献”更大,且温度越高,热应力起到的作用越大;电热联合双应力作用下的样品老化因子分别增加13.04%和37.50%,电热联合作用下老化因子变化远大于单一应力作用的样品老化因子变化,说明电、热两种应力存在某种协同作用,联合作用会加快电缆绝缘劣化. 相似文献
59.
Sara Stevenson 《History of Photography》2013,37(2):235-242
This article is prompted by the remarkable characteristic of nineteenth-century Scotland that circumstances congregate to give an unprecedentedly generous or democratic view of life. Four forms of communication – the statistical accounts, which were followed by the British census records, the boom in publishing, especially in newspapers and journals, and inexpensive communication promoted by the penny post, even the information in street directories and advertisements – all combine with the exploitation of photography to give us insights, which can be disconcertingly specific, acting as occasional spotlights on the landscape. This article is prompted by one particular letter from Robert Louis Stevenson, written when he was a young man, and is followed through two lines of connected thought: the practice of studio photography in Scotland and Stevenson's continuing interest in the photographic portrait. 相似文献
60.
Polyamide 66 fibers were thermoset in a torsion-bending deformation at various temperatures up to 240 °C. Some of the fibers were heat-set at constant length prior to the deformation at presetting temperatures of 150 °C and 200 °C to vary the structural state of the starting material. Fractional recovery was measured after various combinations of temperature and time. It was found that heat setting of PA66 is dominated by time-dependent stress relaxation exhibiting time-temperature equivalence. Increased crystallinity, and/or other molecular rearrangements occurring during presetting, impose additional constraints on molecular mobility, which delay onset of the flow regime and increase the time constant of relaxation at a given temperature. The thermosetting characteristics of PA66 fibers are very similar to those of poly(ethylene terephthalate) fibers. For both polymers, superposing the curves of fractional recovery vs. setting time at different temperatures produce satisfactory master curves, without the need for vertical shifting of the data. Arrhenius plots yield approximate activation energies for the thermosetting flow process of 35-65 kcal/mol in PA66 and 95-115 kcal/mol in PET. 相似文献