全文获取类型
收费全文 | 31469篇 |
免费 | 4979篇 |
国内免费 | 2027篇 |
专业分类
电工技术 | 2997篇 |
技术理论 | 2篇 |
综合类 | 3156篇 |
化学工业 | 2724篇 |
金属工艺 | 1370篇 |
机械仪表 | 2262篇 |
建筑科学 | 4161篇 |
矿业工程 | 2700篇 |
能源动力 | 1944篇 |
轻工业 | 3696篇 |
水利工程 | 1914篇 |
石油天然气 | 2775篇 |
武器工业 | 425篇 |
无线电 | 2086篇 |
一般工业技术 | 2467篇 |
冶金工业 | 1827篇 |
原子能技术 | 343篇 |
自动化技术 | 1626篇 |
出版年
2024年 | 309篇 |
2023年 | 793篇 |
2022年 | 1538篇 |
2021年 | 1680篇 |
2020年 | 1812篇 |
2019年 | 1367篇 |
2018年 | 1194篇 |
2017年 | 1386篇 |
2016年 | 1455篇 |
2015年 | 1485篇 |
2014年 | 2118篇 |
2013年 | 1900篇 |
2012年 | 2316篇 |
2011年 | 2430篇 |
2010年 | 1843篇 |
2009年 | 1777篇 |
2008年 | 1478篇 |
2007年 | 1724篇 |
2006年 | 1544篇 |
2005年 | 1338篇 |
2004年 | 1114篇 |
2003年 | 965篇 |
2002年 | 787篇 |
2001年 | 649篇 |
2000年 | 614篇 |
1999年 | 518篇 |
1998年 | 404篇 |
1997年 | 318篇 |
1996年 | 289篇 |
1995年 | 264篇 |
1994年 | 208篇 |
1993年 | 175篇 |
1992年 | 125篇 |
1991年 | 99篇 |
1990年 | 94篇 |
1989年 | 67篇 |
1988年 | 46篇 |
1987年 | 45篇 |
1986年 | 24篇 |
1985年 | 19篇 |
1984年 | 18篇 |
1983年 | 11篇 |
1982年 | 13篇 |
1981年 | 8篇 |
1980年 | 14篇 |
1966年 | 7篇 |
1964年 | 14篇 |
1962年 | 6篇 |
1959年 | 10篇 |
1957年 | 6篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
92.
介绍气化效率高、有利于环保、具有一定竞争力的Shell煤气化工艺原理、技术特点及关键设备。建议尽快实现关键技术和设备的国产化。 相似文献
93.
分析了景德镇民营陶瓷企业发展特点及其目前存在的问题,并就加快今后景德镇民营陶瓷企业发展步伐提出了几点建议。 相似文献
94.
95.
Gerontechnology acceptance by elderly Hong Kong Chinese: a senior technology acceptance model (STAM)
Ke Chen 《Ergonomics》2014,57(5):635-652
The purpose of this study was to develop and test a senior technology acceptance model (STAM) aimed at understanding the acceptance of gerontechnology by older Hong Kong Chinese people. The proposed STAM extended previous technology acceptance models and theories by adding age-related health and ability characteristics of older people. The proposed STAM was empirically tested using a cross-sectional questionnaire survey with a sample of 1012 seniors aged 55 and over in Hong Kong. The result showed that STAM was strongly supported and could explain 68% of the variance in the use of gerontechnology. For older Hong Kong Chinese, individual attributes, which include age, gender, education, gerontechnology self-efficacy and anxiety, and health and ability characteristics, as well as facilitating conditions explicitly and directly affected technology acceptance. These were better predictors of gerontechnology usage behaviour (UB) than the conventionally used attitudinal factors (usefulness and ease of use).
Practitioner Summary: Previous studies have not given much consideration to age-related health and associated abilities when examining acceptance of technology by the ageing population. By encompassing conventional technology acceptance constructs together with age-related health and ability characteristics, the present study was able to identify more factors affecting gerontechnology acceptance by older Hong Kong Chinese. 相似文献
96.
North Carolina rock phosphate (NCRP) (highly carbonate—substituted apatite) was ground to produce three samples with different particle size distributions. The effectiveness of these fertilizers was compared with the effectiveness of superphosphate in a field experiment and three glasshouse experiments using lateritic soils from south-western Australia. Non-reactive Queensland rock phosphate (low carbonate-substituted apatite from the Duchess deposit) was also used in the pot experiments. Bicarbonate-soluble phosphorus extracted from the soil is widely used in Western Australia to predict plant yields from previously-applied fertilizer dressings. For both field and pot experiments bicarbonate-extractable phosphorus (soil test value) was measured and related to subsequent plant yields.As calculated from the initial slope of the relationship between yield and the level of P applied, finely powdered NCRP was about 5–32% as effective as freshly-applied superphosphate in the year of application and also for two years after application in the field experiment, and for two successive crops in the three pot experiments. For both field and pot experiments, finely powdered NCRP, was at best, 1.5–2.0 times as effective as granular NCRP. Relative to freshly-applied superphosphate, the effectiveness of rock phosphates usually decreased with increasing level of application.For each of the crops in the field experiment, the relationships between yield and phosphorus content of plants (i.e. internal efficiency curves) were similar for all fertilizers. Thus the low effectiveness of the rock phosphates relative to superphosphate was solely due to much less phosphorus being taken up by plants. By contrast, in the pot experiments internal efficiency curves differed for different fertilizers. This is attributed to differences in the rate of phosphorus uptake by plant roots during the early stages of plant growth.For both field and pot experiments, soil test calibrations (the relationship between yield and soil test value) differed for rock phosphates and superphosphate. For superphosphate, soil test calibrations also differed for the three different years after the initial application of this fertilizer in the field experiment. For the second crop in the pot experiment, soil test calibrations differed for superphosphate applied at different times (before the first and the second crop). These results point out the difficulty of applying soil testing procedures to soils that have experienced different histories of fertilizer application. 相似文献
97.
Faliang Zhang Yongchun Luo Anqiang Deng Zhaohui Tang Long Kang Jianhong Chen 《Electrochimica acta》2006,52(1):24-32
(La, Ce, Pr, Nd)2MgNi9 hydrogen storage alloys were prepared through induction melting followed by a long annealing treatment. The structure and electrochemical properties of annealed alloys have been investigated by orthogonal design experiments. Both the individual effects of each substituting element and their interaction in alloys were studied systemically. It has been shown that the structure of main phase in alloys belongs to PuNi3-type with a space group R-3m. Substituting rare-earth elements have a significant effect on both the phase structure of alloys and microstructure. The anisotropic change in the crystal structure of alloys can cause the acceleration of pulverization of alloy particles and result in the deterioration of the cyclic stability of alloy electrodes. Misch metals can raise the plateau pressure of hydrogen absorption/desorption. The discharge capacity of alloy ranges from 342.97 to 380.68 mAh g−1 depending on the sort and content of substituting elements. Both cerium and neodymium can obviously reduce the discharge capacity of alloy electrodes. When compared to the La2MgNi9 alloy electrode, mish metals can significantly improve the high rate dischargeability of alloy electrodes. The improvement of the kinetic characteristic of alloy electrodes mainly results from the increase of the hydrogen diffusion rate in alloy bulk. 相似文献
98.
本文研究了炭黑-环氧树脂复合材料的制备工艺及炭黑填充率对材料电阻率的影响。实验结果表明,加入表面活性剂,明显改善了炭黑在环氧树脂中分布的均匀性。炭黑-环氧树脂材料具有明显的渗流效应,正温度系数效应即PTC效应,非线性伏安特性和电磁波屏蔽效应。 相似文献
99.
T. Hoshikawa 《Electrochimica acta》2006,51(25):5286-5294
Effects of the electrolyte of DSCs on impedance spectra were evaluated by changing concentration of redox couple, viscosity, and additives to electrolyte. The relation with current-voltage characteristics (I-V characteristics) was investigated. In many cases, the impedance component attributed to charge transfer at TiO2|electrolyte interface demonstrated strong relation with the I-V characteristics. The recombination of electrons in TiO2 with I3− in electrolyte was a key factor in determining performance of DSCs. To evaluate the effect of I3−, diffusion-limiting current in the electrolyte for various viscosities was evaluated by cyclic voltammetry. When the short circuit current (SCC) was almost equal to the diffusion-limiting current, strong influence of the diffusion coefficient on the impedance spectra was observed: impedance arcs were enlarged as the diffusion coefficient was decreased. On the other hand, when the diffusion-limiting current was larger than the SCC, photo-excitation and electron injection processes became dominating factors in the DSCs performance. The SCC was regulated by the charge recombination process at TiO2|electrolyte interface, and thus the impedance component ω3 was related to the performance in such condition. 相似文献
100.