全文获取类型
收费全文 | 17017篇 |
免费 | 1394篇 |
国内免费 | 789篇 |
专业分类
电工技术 | 585篇 |
技术理论 | 5篇 |
综合类 | 2031篇 |
化学工业 | 4324篇 |
金属工艺 | 305篇 |
机械仪表 | 826篇 |
建筑科学 | 3339篇 |
矿业工程 | 915篇 |
能源动力 | 871篇 |
轻工业 | 926篇 |
水利工程 | 354篇 |
石油天然气 | 648篇 |
武器工业 | 43篇 |
无线电 | 371篇 |
一般工业技术 | 1065篇 |
冶金工业 | 1136篇 |
原子能技术 | 67篇 |
自动化技术 | 1389篇 |
出版年
2024年 | 87篇 |
2023年 | 215篇 |
2022年 | 497篇 |
2021年 | 494篇 |
2020年 | 582篇 |
2019年 | 413篇 |
2018年 | 368篇 |
2017年 | 448篇 |
2016年 | 525篇 |
2015年 | 559篇 |
2014年 | 1109篇 |
2013年 | 1053篇 |
2012年 | 1357篇 |
2011年 | 1304篇 |
2010年 | 1112篇 |
2009年 | 1044篇 |
2008年 | 840篇 |
2007年 | 1111篇 |
2006年 | 1057篇 |
2005年 | 853篇 |
2004年 | 688篇 |
2003年 | 627篇 |
2002年 | 502篇 |
2001年 | 402篇 |
2000年 | 327篇 |
1999年 | 300篇 |
1998年 | 216篇 |
1997年 | 177篇 |
1996年 | 123篇 |
1995年 | 121篇 |
1994年 | 95篇 |
1993年 | 67篇 |
1992年 | 78篇 |
1991年 | 63篇 |
1990年 | 36篇 |
1989年 | 33篇 |
1988年 | 45篇 |
1987年 | 28篇 |
1986年 | 27篇 |
1985年 | 45篇 |
1984年 | 28篇 |
1983年 | 28篇 |
1981年 | 7篇 |
1980年 | 11篇 |
1966年 | 7篇 |
1964年 | 7篇 |
1961年 | 9篇 |
1959年 | 8篇 |
1956年 | 8篇 |
1951年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Anaerobic co-digestion of food waste and FOG with sewage sludge – realising its potential in Ireland
Olumide Wesley Awe Yaqian Zhao Ange Nzihou Doan Pham Minh Nathalie Lyczko 《The International journal of environmental studies》2018,75(3):496-517
The severe environmental pollution in many countries is caused by indiscriminate discharge of large quantities of food waste (FW), fat oil and grease (FOG) and sewage sludge (SS) to the environment. There are many possible treatment routes, but anaerobic digestion (AD) is now well accepted for treating several kinds of organic wastes. But AD of FW alone presents some operational challenges because of substrates and variability. Anaerobic co-digestion of two or more substrates is better than single substrate digestion. This can use a plant’s unused capacity, in line with the trend to renewable energy. Co-digestion technology, although well established in many European countries, is still in its infancy in Ireland. There are problems with different regulatory arrangements. They should be resolved. The paper reviews anaerobic co-digestion technology is reviewed, with special focus on possible application in Ireland. 相似文献
2.
3.
4.
Gerd J. Hahn 《国际生产研究杂志》2020,58(5):1425-1441
The Fourth Industrial Revolution – also known as Industry 4.0 (i4.0) – comprises the digitalisation of the industrial sector. This paper uses the theoretical lens of supply chain innovation (SCI) to investigate the implications of i4.0 on supply chain management. For these purposes, the method of structured content analysis is applied to more than 200 use cases of i4.0-enabled SCI introduced by both established and startup companies. i4.0-enabled SCI manifests along three dimensions: process, technology, and business architecture. The key findings of this study can be summarised as follows: first, i4.0-enabled SCI extends the initial focus on productivity improvements in SC processes towards scalability and flexibility. Second, extant i4.0 solutions rely mostly on analytics and smart things while omitting smart people technology and the human-centric approach associated with the i4.0 paradigm. Third, established companies adopt i4.0 merely to sustain their existing business architectures while startup companies radically change their operating models, relying heavily on data analytics and the platform economy. Consequently, established companies pursue a problem-driven, engineering-based approach to SCI while startup companies follow an ‘asset-light’, business-driven approach. Lastly, there are two distinct approaches to digitalising operational SC processes: platform-based crowdsourcing of standard processes and on-demand provision of customised services. 相似文献
5.
Biosolids reduction model by return activated sludge ozonation was validated by simulating nitrification data compiled from our pilot-scale and the literature studies. Then, a global sensitivity analysis (GSA) was performed to identify influential and non-influential parameters for biosolids reduction efficiency, change in specific nitrification activity (SNA), and alteration to expected nitrification stability. In general, the model outputs were sensitive to operational and ozone reaction parameters, but not to biochemical parameters. For operational parameters, mainly temperature and initial solids retention time (SRT) influenced all model outputs. For biosolids reduction, increase in the degradability of the influent COD decreased the reduction efficiency. For SNA, the changes were highly dependent on the influent TKN/COD ratio. Our findings also imply that the stability of the nitrification process in ozonated systems should be enhanced at constant MLVSS for warm temperatures, but could be reduced at temperatures below 12 °C and aerated SRTs below 10 days. 相似文献
6.
Combination of X-ray Digital Industrial Radiography (DIR) and Particle Tracking Velocimetry (PTV) techniques for local liquid velocity measurement (VLL) has been newly developed and successfully applied for trickle bed reactor (TBR). The technique was validated against newly developed fiber optical probe technique. This work attempts to highlight the applicability of this newly developed technique on a liquid–solid packed bed reactor. In this work, liquid was represented by water and solids were represented by EPS beads. The EPS beads were chosen because of its low density property. Three superficial liquid velocities (VSL) were applied to the system. The experiment was replicated four times. The digital industrial radiography (DIR) consists of a complementary metal oxide semiconductor (CMOS) digital detector and X-ray source. Results of this work suggest that the technique has been successfully applied and comparable with previous work that has been done in the literature. It also suggests that there will be a maximum measurable interstitial liquid velocity when it travel inside the packed bed. The measured VLL can have a maximum range that is between 4 and 4.7 times that of its VSL. For VSL=0.42±±2%, the VLL-Max is in between 1.7 cm/s and 1.9 cm/s, VSL=0.84±±2%, the VLL-Max is in between 3.6 cm/s and 4.0 cm/s, and for VSL=1.11±±2%, the VLL-Max is in between 4.3 cm/s and 4.8 cm/s. 相似文献
7.
针对工业控制系统传统单一检测算法模型对不同攻击类型检测率和检测速度不佳的问题,提出一种优化支持向量机和K-means++算法结合的入侵检测模型。首先利用主成分分析法(PCA)对原始数据集进行预处理,消除其相关性;其次在粒子群优化(PSO)算法的基础上加入自适应变异过程避免在训练的过程中陷入局部最优解;然后利用自适应变异粒子群优化(AMPSO)算法优化支持向量机的核函数和惩罚参数;最后利用密度中心法改进K-means算法与优化后的支持向量机组合成入侵检测模型,从而实现工业控制系统的异常检测。实验结果表明,所提方法在检测速度和对各类攻击的检测率上得到明显提升。 相似文献
8.
9.
Aline Kövilein Christin Kubisch Liyin Cai Katrin Ochsenreither 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2020,95(3):513-526
Malic acid derived from fossil resources is currently applied in the food and beverage industries with a medium global production capacity. However, in the transition from a fossil-based to a bio-based economy, biotechnologically produced l -malic acid may become an important platform chemical with many new applications, especially in the field of biopolymers. In this review, currently used petrochemical production routes to dl -malic acid are outlined and insights into possible bio-based alternatives for microbial l -malic acid production are provided. Besides ecological reasons, the possibility to produce enantiopure l -malic acid by microbial fermentation is the biggest advantage over chemical synthesis. State-of-the-art and open challenges concerning production host engineering, substrate choice and downstream processing are addressed. With regard to production hosts, a literature overview is given covering the leading natural production strains of Aspergillus, Ustilago and Aureobasidium, as well as Escherichia coli as the most important engineered recombinant host. The utilization of renewable substrates as an alternative to glucose is emphasized in particular as a key aspect for a competitive bio-based production. Out of the alternative substrates discussed in this review, the industrial side-streams crude glycerol and molasses seem to be most promising for large-scale l -malic acid production. © 2019 The Authors. Journal of Chemical Technology & Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. 相似文献
10.
通过对接轨站设置位置和布置图型主要影响因素的分析。按照能够充分反映接轨站作业特点的交接方式。对接轨站所采用的布置图型进行了归纳和分类。 相似文献