首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2707篇
  免费   180篇
  国内免费   65篇
电工技术   15篇
综合类   70篇
化学工业   640篇
金属工艺   13篇
机械仪表   107篇
建筑科学   89篇
矿业工程   28篇
能源动力   138篇
轻工业   1497篇
水利工程   34篇
石油天然气   56篇
武器工业   1篇
无线电   31篇
一般工业技术   116篇
冶金工业   56篇
原子能技术   12篇
自动化技术   49篇
  2024年   9篇
  2023年   57篇
  2022年   86篇
  2021年   152篇
  2020年   132篇
  2019年   141篇
  2018年   115篇
  2017年   111篇
  2016年   122篇
  2015年   99篇
  2014年   153篇
  2013年   302篇
  2012年   172篇
  2011年   205篇
  2010年   103篇
  2009年   127篇
  2008年   90篇
  2007年   149篇
  2006年   147篇
  2005年   91篇
  2004年   83篇
  2003年   59篇
  2002年   39篇
  2001年   28篇
  2000年   24篇
  1999年   16篇
  1998年   16篇
  1997年   12篇
  1996年   17篇
  1995年   11篇
  1994年   9篇
  1993年   8篇
  1992年   7篇
  1991年   9篇
  1990年   6篇
  1989年   5篇
  1988年   2篇
  1987年   8篇
  1986年   1篇
  1985年   7篇
  1984年   5篇
  1983年   5篇
  1982年   3篇
  1981年   3篇
  1980年   3篇
  1978年   1篇
  1976年   2篇
排序方式: 共有2952条查询结果,搜索用时 171 毫秒
21.
《能源学会志》2020,93(5):2006-2016
In this experimental study, a physically pre-treated trommel fines feedstock, containing 44 wt% non-volatiles (ash and fixed carbon) and 56 wt% volatile matter (dry basis), was subjected to fast pyrolysis to recover energy from its organic load, using a 300 g h−1 bubbling fluidized bed (BFB) fast pyrolysis rig. A physical pre-treatment method (including crushing, grinding and sieving) was used to prepare a 0.5–2 mm sized trommel fines feedstock to make it suitable for fast pyrolysis in the BFB reactor. Experimental results from the fast pyrolysis process showed that the highest yield of organic liquid was obtained at around a temperature of 500 °C. However, both char and gas yields increased dramatically at temperatures above 500 °C, as a result of enhanced cracking of organic vapours, which reduced the yield of liquid products. Overall, energy recovery from the pyrolysis products (liquid and gas products as well as char pot residues) ranged from 63 to 70%, generally increasing with temperature. A large proportion of the high ash content (36 wt%) of the feedstock was found in the char pot (>62%), while smaller proportions were found in the reactor bed and some liquid products. The char pot ash residues composed mostly of non-hazardous earth materials and may be applied in bulk construction materials e.g. cement manufacture. Although, there was no problem with the pyrolysis rig during 1 h of operation, longer periods of operation would require periodic removal of accumulated solid residues and/or char pot modification to ensure continuous rig operation and process safety.  相似文献   
22.
刘韬  高明  杨帆  王准  张鑫  王佳慧  张勋 《化学试剂》2020,42(1):71-75
建立了人参、西洋参中凝胶色谱-固相萃取-液相色谱-串联质谱法测定蚜灭磷、吡虫啉、涕灭威、甲基内吸磷、甲硫威、辛硫磷6种农药的分析方法。样品经丙酮超声提取,凝胶色谱(GPC)净化后,固相萃取(SPE)净化,在HPLC/MS/MS多反应监测(MRM)模式下进行了定性和定量分析方法。在上述检测方法条件下,所测的6种农药的最低检出限为0.01 mg/kg,回收率范围为79.2%~107.3%,线性范围为0.01~0.2 mg/kg。  相似文献   
23.
Post-growth graphene transfer to a variety of host substrates for circuitry fabrication has been among the most popular subjects since its successful development via chemical vapor deposition in the past decade. Fast and reliable evaluation tools for its morphological characteristics are essential for the development of defect-free transfer protocols. The implementation of conventional techniques, such as Raman spectroscopy, atomic force microscopy (AFM), and transmission electron microscopy in production quality control at an industrial scale is difficult because they are limited to local areas, are time consuming, and their operation is complex. However, through a one-shot measurement within a few seconds, phase-shifting interferometry (PSI) successfully scans ≈1 mm2 of transferred graphene with a vertical resolution of ≈0.1 nm. This provides crucial morphological information, such as the surface roughness derived from polymer residues, the thickness of the graphene, and its adhesive strength with respect to the target substrates. Graphene samples transferred via four different methods are evaluated using PSI, Raman spectroscopy, and AFM. Although the thickness of the nanomaterials measured by PSI can be highly sensitive to their refractive indices, PSI is successfully demonstrated to be a powerful tool for investigating the morphological characteristics of the transferred graphene for industrial and research purposes.  相似文献   
24.
为考察接触剂对减压渣油接触裂化反应的影响,以石家庄减压渣油为原料,采用热解色谱(Py GC)和热重质谱(TG MS)分别评价无孔无酸接触剂(A)、有孔无酸接触剂(B)和有孔有酸接触剂(C)的孔结构、酸性,以及接触剂上油膜厚度对减压渣油裂化反应条件和反应产物的影响。结果表明,与无孔接触剂相比,接触剂上孔道的引入,使减压渣油分子能进入到孔径大于10 nm的孔道进行初步裂化,初步裂化产物能够进入孔径小于10 nm的孔道内进行二次裂化,生成更小分子。在A剂上减压渣油的油膜厚度对其热裂化反应产物的分布和生焦率没有明显影响;在B剂上减压渣油热裂化反应强度增强,生焦率增大至12%~13%;在C剂上,随着减压渣油油膜厚度的减小,其裂化产物中C12-和C12~C20馏分相对质量分数增大,C20+馏分相对质量分数减小,生焦率增大。TG MS结果表明,接触剂上酸中心的引入大大降低了减压渣油的起始裂化温度。  相似文献   
25.
This study investigates the co-digestion of poultry manure (PM) with sugar beet pulp residues (SBPR) obtained from saccharification and dewatering of sugar beet pulp. The laboratory-scale experiments were conducted under batch and semi-continuous conditions at mesophilic temperatures (35 °C). Batch tests gave specific biogas and methane yields of 590 dm3/kgVSfed and 423 dm3CH4/kgVSfed, respectively for SBPR, whereas the corresponding values for PM were 434 dm3/kgVSfed and 300 dm3CH4/kgVSfed. The co-digestion of PM with SBPR was found to increase biogas and methane yields compared to the manure alone. In semi-continuous reactor experiments, the highest methane yield of 346 dm3 CH4/kgVSfed was achieved for the mixture containing poultry manure with 50% SBPR (weight basis) and a solids retention time (SRT) of 20 days. However, when poultry manure was digested as a sole feedstock, the biogas production was inhibited by ammonia, whereas the co-digestion of PM with 25% SBPR was slightly affected by volatile fatty acids, which concentrations exceeded 4000 g/m3.  相似文献   
26.
Shrimp residues were dried (65 °C), grounded, and posteriorly used as an ingredient to the production of ‘spiced shrimp flour’ and ‘shrimp flavoured biscuits’. Both products were packed in modified atmosphere (100% N2) and stored for 180 days (25 °C) for shelf life evaluation. The centesimal composition, physicochemical, microbiological and sensory analyses were carried out in triplicate. The microbiological analysis (residue and shrimp flour) was within the limits of the legislation, confirming the hygienic–sanitary care during processing. The protein content was the most outstanding (40.13% for the spiced shrimp flour and 20.52% for the shrimp flavoured biscuits). The microbiological evaluation for the ‘spiced shrimp flour’ and ‘shrimp flavoured biscuits’ was below the legal limit, and both products were accepted by sensory analysis. The shelf life evaluation demonstrated stability for 6 months. Thus, we concluded that the Litopenaeus vannamei shrimp residue is a promising ingredient in the food industry.  相似文献   
27.
Agricultural residue could become a potential biomass source for energy production because it is available every year in areas accessible to tractors and vehicles. The aim of this work was to quantify the biomass available and its fuel characteristics, considering pruning residue from management of five main vine varieties planted in northwest Italy (barbera, dolcetto, cortese, cabernet sauvignon, and moscato) for a period of 15 years (from 2000 to 2014). Throughout the test period, pruning residue production ranged between 0.45 and 1.34 kg (1850–5360 kg ha−1) per plant. The average higher heating value of the five vine varieties tested ranged from 17.92 to 18.02 MJ kg−1, whereas the lower calorific value ranged between 7.34 and 7.96 MJ kg−1. The average ash content was approximately 3.85%. No statistical difference in biofuel characteristics was found between the vine varieties considered. This study highlights the high potential of vineyard pruning residue as a biofuel for energy production. In contrast, it is of considerable importance to know that biomass production can vary considerably between vine varieties and between years. This latter aspect is very important because, according to reference years, it is possible to under- or overestimate biomass production.  相似文献   
28.
顾学斌 《广东化工》2012,39(3):105-106
纵观海洋防污剂发展史,我们可以发现它和农药之间有着不解之缘,也可以说农药的发展推动了防污剂的发展。文章对曾经用过、正在使用、有可能应用为海洋防污剂的农药品种逐一介绍。  相似文献   
29.
Wood biomass in Serbia is traditionally used for energy. However, the manner of its use is outdated, and efficiency is very low. Annually over 3.5 million m3 of wood is cut down for energy needs in Serbia. In order to better exploit all forms of woody biomass, especially the one that is now treated as waste, and in order to fulfil the obligations from the outlined Convention on Climate Change it is necessary to switch to a modern way of production and utilization of woody biomass. Serbia is now at the very beginning of this process. This paper gives an overview and an analysis of the possibilities of utilization of wood waste as a renewable source of energy and the problems that producers in Serbia are facing due to undeveloped markets and excessive funds that are needed to start the production of briquettes and pellets. The ecological and economical advantages of using woody biomass, as well the possible support measures for the use of woody biomass in Serbia are also the topic of this paper. The present situation in this area, the manner of waste management in sawmills and the reasons for the necessity of future development of this industrial production are also briefly described.  相似文献   
30.
Pesticide residues caused great threat to human body health, and all countries protected the health of human body by specifying its upper limit. However, pesticide residues were generally very low, similar to trace analysis and as low as millionth or less, the content determination of pesticide residues was a troublesome problem. With the application and promotion of tandem mass spectrometry, it was able to do trace analysis. GC–EI/MS/MS was a common method for the determination of pesticide residues. The multiple reaction monitoring (MRM) mode was the most common quantitative method used in GC–EI/MS/MS. It has the characteristics of high sensitivity, good reproducibility, high accuracy, strong anti-interference and high ion flux. Multiple-twin precursor ions, product ions and collision energy of thirty-four pesticides were provided for MRM. It could play an important role in developing MRM method for the quantifying of 34 kinds of pesticide. Meanwhile, the development of MRM method for the quantifying of other compounds could also refer to this paper.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号