全文获取类型
收费全文 | 15343篇 |
免费 | 1631篇 |
国内免费 | 363篇 |
专业分类
电工技术 | 109篇 |
综合类 | 1475篇 |
化学工业 | 3139篇 |
金属工艺 | 372篇 |
机械仪表 | 264篇 |
建筑科学 | 4022篇 |
矿业工程 | 4276篇 |
能源动力 | 133篇 |
轻工业 | 581篇 |
水利工程 | 160篇 |
石油天然气 | 525篇 |
武器工业 | 12篇 |
无线电 | 112篇 |
一般工业技术 | 525篇 |
冶金工业 | 1180篇 |
原子能技术 | 134篇 |
自动化技术 | 318篇 |
出版年
2024年 | 40篇 |
2023年 | 153篇 |
2022年 | 346篇 |
2021年 | 517篇 |
2020年 | 496篇 |
2019年 | 396篇 |
2018年 | 426篇 |
2017年 | 512篇 |
2016年 | 609篇 |
2015年 | 593篇 |
2014年 | 960篇 |
2013年 | 1026篇 |
2012年 | 1301篇 |
2011年 | 1257篇 |
2010年 | 801篇 |
2009年 | 823篇 |
2008年 | 738篇 |
2007年 | 851篇 |
2006年 | 788篇 |
2005年 | 659篇 |
2004年 | 567篇 |
2003年 | 508篇 |
2002年 | 420篇 |
2001年 | 393篇 |
2000年 | 346篇 |
1999年 | 288篇 |
1998年 | 227篇 |
1997年 | 321篇 |
1996年 | 173篇 |
1995年 | 162篇 |
1994年 | 121篇 |
1993年 | 101篇 |
1992年 | 102篇 |
1991年 | 63篇 |
1990年 | 58篇 |
1989年 | 56篇 |
1988年 | 52篇 |
1987年 | 24篇 |
1986年 | 13篇 |
1985年 | 6篇 |
1984年 | 7篇 |
1983年 | 4篇 |
1980年 | 16篇 |
1979年 | 7篇 |
1977年 | 1篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1963年 | 1篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Reliable prediction of flooding conditions is needed for sizing and operating packed extraction columns. Due to the complex interplay of physicochemical properties, operational parameters and the packing-specific properties, it is challenging to develop accurate semi-empirical or rigorous models with a high validity range. State of the art models may therefore fail to predict flooding accurately. To overcome this problem, a data-driven model based on Gaussian processes is developed to predict flooding for packed liquid-liquid and high-pressure extraction columns. The optimized Gaussian process for the liquid-liquid extraction column results in an average absolute relative error (AARE) of 15.23 %, whereas the algorithm for the high-pressure extraction column results in an AARE of 13.68 %. Both algorithms can predict flooding curves for different packing geometries and chemical systems precisely. 相似文献
2.
In this paper, the dynamic behaviors on the basis of simulation for high-purity heat integrated air separation column (HIASC) are studied. A nonlinear generic model control (GMC) scheme is proposed based on the nonlinear behavior analyses of a HIASC process, and an adaptive generic model control (AGMC) scheme is further presented to correct the model parameters online. Related internal model control (IMC) scheme and multi-loop PID (M-PID) scheme are also developed as the comparative base. The comparative researches are carried out among these linear and nonlinear control schemes in detail. The simulation research results show that the proposed AGMC schemes present advantages in both servo control and regulatory control for the high-purity HIASC. 相似文献
3.
4.
5.
Flotation has been used in industry for more than a half century as the primary technique for upgrading phosphate. While the flotation of phosphate was inefficient when oleic acid was used alone as a collector, therefore a mixed collector of oleic acid (HOl), linoleic acid (LA) and linolenic acid (LNA) was employed to improve the recovery of phosphate flotation. The batch flotation results showed that the optimal composition of the mixed collector was 54 wt.% HOl, 36 wt.% LA and 10 wt.% LNA. Additionally, the effect of pH on the mixed collector application was studied while considering the surface tension, contact angle and micro-flotation. The results showed that the mixed collector should be used at a pH of 9.5. Above a pH of 9.5, the adsorption of fatty acids dimers on the apatite surface hindered phosphate flotation. The influence of the mixed collector assembly on apatite flotation was also investigated. It was demonstrated that due to its low critical micelle concentration, a sufficiently hydrophobic apatite surface could be generated at a collector concentration of 60 mg/L. In addition, zeta potential experiments suggested that collector adsorption was governed by chemisorption. FTIR and XPS spectra studies further indicated that the chemical reaction involved the carboxyl groups of fatty acids and Ca species at the apatite surface for each fatty acid in the mixed collector. 相似文献
6.
7.
It is the aim of this paper to examine the effects of conditioning time on the flotation of hematite using three technical grade fatty acid reagents as providing additional evidence on their mechanism of interaction with the hematite surface. Various mechanisms have been postulated as occurring as conditioning time is increased. Both physical (e.g. conditioning time and power input) and chemical (nature, dispersion and solubility of the adsorbing species) contribute to the mechanisms of attachment of collector. In this paper, the mechanism of attachment of oleate to hematite can be readily explained by chemisorption, but the mechanism of attachment of lauric acid appears to be physical adsorption at neutral pH. The flotation of hematite with a mixture of tallow-type fatty acids (palmitic, stearic and oleic acids) is very sensitive to conditioning time, and suggests that, even though flotation is very effective at short conditioning times, it is very susceptible to the presence of fines and their associated high surface areas. It is therefore obvious that both the physical and chemical conditions contribute to the mechanisms of adsorption of fatty acids on iron-containing oxide minerals and must be understood in order to optimise the flotation of these minerals in an industrial situation. 相似文献
8.
根据延迟焦化装置露天栈桥的工程设计实践,围绕一炉两塔(一个加热炉两个焦炭塔)的焦化装置,分析了露天栈桥设计中的要点及难点,对其在平面布置、基础安排和吊车梁选型等设计方面做一些介绍和论述。 相似文献
9.
10.
本文以NH3-H2O系统Gibbs自由能、熵、焓和汽液相平衡的热力学模型为基础,用松弛法进行了无水氨精馏塔的模拟计算。改变无水氨采出比、回流比(直汽量)和进料板位置均影响蒸馏效果。 相似文献