全文获取类型
收费全文 | 17617篇 |
免费 | 2918篇 |
国内免费 | 1063篇 |
专业分类
电工技术 | 121篇 |
综合类 | 1409篇 |
化学工业 | 10075篇 |
金属工艺 | 843篇 |
机械仪表 | 212篇 |
建筑科学 | 637篇 |
矿业工程 | 929篇 |
能源动力 | 871篇 |
轻工业 | 1344篇 |
水利工程 | 195篇 |
石油天然气 | 1349篇 |
武器工业 | 44篇 |
无线电 | 208篇 |
一般工业技术 | 1909篇 |
冶金工业 | 872篇 |
原子能技术 | 379篇 |
自动化技术 | 201篇 |
出版年
2024年 | 78篇 |
2023年 | 288篇 |
2022年 | 562篇 |
2021年 | 759篇 |
2020年 | 800篇 |
2019年 | 708篇 |
2018年 | 716篇 |
2017年 | 762篇 |
2016年 | 859篇 |
2015年 | 813篇 |
2014年 | 1047篇 |
2013年 | 1336篇 |
2012年 | 1671篇 |
2011年 | 1252篇 |
2010年 | 943篇 |
2009年 | 1010篇 |
2008年 | 767篇 |
2007年 | 1022篇 |
2006年 | 1013篇 |
2005年 | 714篇 |
2004年 | 648篇 |
2003年 | 565篇 |
2002年 | 471篇 |
2001年 | 393篇 |
2000年 | 378篇 |
1999年 | 277篇 |
1998年 | 248篇 |
1997年 | 234篇 |
1996年 | 196篇 |
1995年 | 145篇 |
1994年 | 177篇 |
1993年 | 130篇 |
1992年 | 117篇 |
1991年 | 92篇 |
1990年 | 64篇 |
1989年 | 58篇 |
1988年 | 52篇 |
1987年 | 48篇 |
1986年 | 28篇 |
1985年 | 34篇 |
1984年 | 30篇 |
1983年 | 21篇 |
1982年 | 15篇 |
1981年 | 7篇 |
1980年 | 9篇 |
1979年 | 4篇 |
1977年 | 3篇 |
1976年 | 2篇 |
1959年 | 4篇 |
1951年 | 26篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
吸附制冷循环的热力计算及热力学评价方法探讨 总被引:4,自引:0,他引:4
在化工吸附,吸附热力学及Polanyi吸附位势理论的基础上,介绍吸附制冷基本型循环,推演其参数坐标图,进而分析,给出其主要性能指标的热力计算,然后以热力学的逆卡诺循环和内可逆三热源循环模型为指针,对此制冷循环进行考察。并结合热力计算对其热力学完善性做出评价,从而给出了吸附制冷基本型循环合适的热力学评价方法。 相似文献
42.
43.
44.
Shihong XU Pengshou XU Mingrong JI Xianming LIU Maosheng MA Jingsheng ZHU Yuheng ZHANG Structure Research Laboratory University of Science Technology of China Hefei ChinaZhenjia XU Institute of Semiconductor Academia Sinica Beijing China 《材料科学技术学报》1993,9(6):437-440
The alkali-metal Na adsorption on Si(100)2×1 surface and its promoted oxidation and Si oxidegrowth have been investigated by means of thermal desorption,work function,Auger electronspectroscopy and photoemission electron spectroscopy.The experimental data showed that therewas a new state,interface electron state,near the Fermi level after the deposition of Na atoms.It wasfound that the presence of Na always caused an increase of the oxygen initial uptake whereas thepromotion of Si oxide growth was observed only at the coverage of Na greater than 0.5 ML.A newmechanism of Na-promoted Si oxide growth is suggested in this paper. 相似文献
45.
There is a need for developing low cost, easily and abundantly available, yet efficient, adsorbents for the removal of phosphates during the tertiary treatment of wastewaters. The tamarind nut shell activated carbon (TNSAC) prepared on a laboratory scale has been used to evaluate its performance for phosphate adsorption. This paper describes the laboratory production of this adsorbent material in its various forms, and discusses the effects of the TNSAC process variables (the unrinsed and rinsed forms of the TNSAC and the impregnation ratio) on its performance in adsorbing phosphate. The material has been shown to be a good alternative adsorbent. As much as 95% phosphate removal by the unrinsed TNSAC is possible in about 30 min under the test conditions. The phosphate adsorbing capacity is about two times higher for the unrinsed TNSAC in comparison to the rinsed TNSAC. The adsorption rates, however, transit to extremely low rates towards the end when equilibrium conditions could be attained in about 2 h contact time. The phosphate removal mechanics are adsorption and precipitation/ion exchange when unrinsed TNSAC is used, and adsorption alone for the rinsed TNSAC. The maximum phosphate removal is found to take place at an impregnation ratio of 1.0 for both forms of the TNSAC. 相似文献
46.
Second-law-based thermodynamic analysis of two-stage and mechanical-subcooling refrigeration cycles 总被引:1,自引:0,他引:1
Thermodynamic analysis of HFC-134a vapor-compression refrigeration cycles is investigated by both the first and second laws of thermodynamics. Second-law analysis is carried out for both two-stage and mechanical-subcooling refrigeration cycles. The analysis is performed on each of the system components to determine their individual contribution to the overall system irreversible losses. It is found that most of the losses are due to a low compressor efficiency. Irreversibilities of expansion valves and condenser are also significant. In addition, it is shown that the optimum inter-stage pressure for two-stage and mechanical-subcooling refrigeration systems is very close to the saturation pressure corresponding to the arithmetic mean of the refrigerant condensation and evaporation temperatures. These results are compared with the existing practice in the industry. Furthermore, theoretical results of a two-stage refrigeration system performance are also compared with experimental values for a CFC-22 system. 相似文献
47.
Matthew Caurie 《International Journal of Food Science & Technology》2005,40(3):295-303
An equation has been derived to calculate the water activity (Aw) of multicomponent mixtures of solutes and non‐solutes. The equation is based on a previous Caurie adsorption equation and it depends on the number of component ingredients and the initial moisture contents of the ingredients in the mixture. Solute and non‐solute/water interaction effects in solution were identified as playing important roles in determining accurate equilibrium Aws of the aqueous mixtures. The new equation allows for interaction effects in mixed solution/suspensions and has been tested on model foods (the data was taken from the literature) containing up to five solutes and non‐solute components. The equation displays a high degree of accuracy. Unlike the Ross equation, which applies only approximately to mixtures of dilute solutions, the new equation applies to mixtures at all solution concentrations and to wet solids. 相似文献
48.
A new method for analysis of trace mercury in water samples was developed, based on the combination of preconcentration/separation using dithizone-modified nanometer titanium dioxide (TiO2) as a solid phase extractant and determination by cold vapor atomic adsorption spectrometry (CVAAS). Dithizone was dissolved with alcohol and loaded on the surface of nano-sized TiO2 powders by stirring. The static adsorption behavior of Hg2 on the dithizone-modified nanoparticles was investigated in detail. It was found that excellent adsorption ratio for Hg2 could be obtained in the pH range of 7-8 with an oscillation time of 15 min, and a 5 mL of 3.5 mol·L-1 HCl solution could quantitatively elute Hg2 from nanometer TiO2 powder. Common coexisting ions caused no obvious influence on the determination of mercury. The mechanisms for the adsorption and desorption were discussed. The detection limit (3σ) for Hg2 was calculated to be 5 ng·L-1. The proposed method was applied to the determination of Hg2 in a mineral water sample and a Zhujiang River water sample. By the standard addition method, the average recoveries were found to be 94.4%-108.3% with RSD (n = 5) of 2.9%-3.5%. 相似文献
49.
详细介绍了进口的VPSA制氧装置的流程特点、工艺参数及主要设备的配置。实际运转证明 ,该制氧装置具有运行可靠、启动时间短、部分负荷性能优越、负荷转换速度快等优点 ,能满足金隆铜业有限公司的实际生产要求。 相似文献
50.
程银芳 《精细石油化工进展》2007,8(6):28-30
用壳聚糖和粉煤灰对含间甲酚的废水进行吸附处理,考察了壳聚糖的用量、振荡时间、振荡速度以及粉煤灰与壳聚糖的混合比对处理效果的影响.结果表明:在常温下,对于初始质量浓度为56 mg/L的间甲酚,当壳聚糖用量为3 g/L,以170 r/min的转速吸附振荡0.5 h,去除率可达到88%以上;在上述条件下,加入质量比4:1的粉煤灰与壳聚糖混合物5g/L时,间甲酚的去除率可达到91%. 相似文献