全文获取类型
收费全文 | 465篇 |
免费 | 13篇 |
专业分类
电工技术 | 4篇 |
综合类 | 3篇 |
化学工业 | 75篇 |
金属工艺 | 3篇 |
机械仪表 | 16篇 |
建筑科学 | 17篇 |
能源动力 | 5篇 |
轻工业 | 80篇 |
水利工程 | 2篇 |
石油天然气 | 5篇 |
无线电 | 59篇 |
一般工业技术 | 60篇 |
冶金工业 | 97篇 |
自动化技术 | 52篇 |
出版年
2023年 | 7篇 |
2022年 | 8篇 |
2021年 | 23篇 |
2020年 | 5篇 |
2019年 | 7篇 |
2018年 | 8篇 |
2017年 | 14篇 |
2016年 | 5篇 |
2015年 | 5篇 |
2014年 | 4篇 |
2013年 | 20篇 |
2012年 | 12篇 |
2011年 | 20篇 |
2010年 | 17篇 |
2009年 | 18篇 |
2008年 | 10篇 |
2007年 | 23篇 |
2006年 | 17篇 |
2005年 | 9篇 |
2004年 | 16篇 |
2003年 | 10篇 |
2002年 | 10篇 |
2001年 | 7篇 |
2000年 | 9篇 |
1999年 | 7篇 |
1998年 | 26篇 |
1997年 | 12篇 |
1996年 | 17篇 |
1995年 | 17篇 |
1994年 | 4篇 |
1993年 | 9篇 |
1992年 | 8篇 |
1991年 | 11篇 |
1990年 | 3篇 |
1989年 | 4篇 |
1988年 | 7篇 |
1987年 | 8篇 |
1986年 | 5篇 |
1984年 | 7篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1981年 | 2篇 |
1980年 | 5篇 |
1979年 | 4篇 |
1978年 | 9篇 |
1977年 | 3篇 |
1976年 | 3篇 |
1975年 | 2篇 |
1974年 | 2篇 |
1972年 | 3篇 |
排序方式: 共有478条查询结果,搜索用时 15 毫秒
11.
Vikki Ambrose John H Miller Stuart J Dickson Scott Hampton Penelope Truman Rodney A Lea Jefferson Fowles 《Nicotine & tobacco research》2007,9(8):793-799
The effect of total particulate matter (TPM) from cigarette smoke on the expression and binding properties of nicotinic acetylcholine receptors (nAChRs) was investigated using a human neuroblastoma cell line (SH-SY5Y). TPM but not nicotine on its own inhibited cell growth at nicotine concentrations above 5 microM. To examine effects on nAChR expression, intact cells were incubated with 3H-epibatidine, and a Bmax of 13 fmoles/10(5) cells (7.8 x 10(4) binding sites/cell) was measured in unexposed cells as well as in cells treated with 2 microM nicotine alone or with TPM containing 2 microM nicotine. Using Scatchard analysis, we measured a Kd of 0.3 nM for 3H-epibatidine binding to nAChRs. This Kd was increased to 1.3 nM by addition of nicotine or TPM extract, both at 2 microM nicotine. Bmax, however, was unaffected, suggesting competitive binding of nicotine to its receptor. Short-term and prolonged 3-day exposures of SH-SY5Y cells to either TPM or nicotine at nicotine concentrations ranging from 0.2 microM to 20 microM increased specific binding, suggesting upregulation of nAChR expression. Most significant, binding was consistently greater in cells pretreated with TPM than in cells pretreated with nicotine. We conclude that TPM contains compounds that are toxic to cells at high concentrations (cell growth inhibition) but that do not compete with nicotine for binding to nAChRs (Scatchard analysis). These non-nicotinic compounds are capable of increasing the expression of one or more of the nAChR subunits. Furthermore, our cell culture assay provides a useful in vitro model for assessing the relative addictiveness of different tobacco products, including that of non-nicotine components. 相似文献
12.
为解决市场主流充电器缺少电池容量检测功能以及电池充满电量后不能自动断电等问题,设计了一种以MSP430单片机为控制核心、DS1302为外围时钟电路芯片、具有检测电池容量功能的充电器,并给出了单元模块设计电路和配套的软件流程图。实验表明,该充电器可对锂电池、镍镉电池进行充电和放电,并提供两种电池容量检测方式,在采用传统电池容量检测方式测量时误差不超过5%;快速检测方式因节省时间,误差稍大。 相似文献
13.
Geórgia Bertoni Pompeu Ariane Vendemiatti Priscila Lupino Gratão Salete Aparecida Gaziola Peter John Lea 《Food Biotechnology》2013,27(1):55-64
Lysine is an essential amino acid normally present in very low concentration in cereal seeds. In previous reports we have studied the metabolism of lysine in several distinct high-lysine maize mutants and observed drastic variations in the activity of saccharopine dehydrogenase (SDH), a key enzyme involved in lysine degradation. We have now analyzed the activity of SDH using non-denaturing polyacrylamide gel electrophoresis (PAGE) to identify possible isoenzymes that could explain the patterns of activity previously observed. The results indicated the presence of at least two SDH isoenzymes, one contributing to approximately 90% of the total enzyme activity and a minor form only present in the wild type lines and the opaque-1 mutant. The results suggest that the differences in total SDH activity among the genotypes tested are due to alterations in the predominant SDH isoenzymic form, which is likely to be the bifunctional polypeptide containing lysine 2-oxoglutarate reductase. 相似文献
14.
Daniela M. Ushizima Hrishikesh A. Bale E. Wes Bethel Peter Ercius Brett A. Helms Harinarayan Krishnan Lea T. Grinberg Maciej Haranczyk Alastair A. Macdowell Katarzyna Odziomek Dilworth Y. Parkinson Talita Perciano Robert O. Ritchie Chao Yang 《JOM Journal of the Minerals, Metals and Materials Society》2016,68(11):2963-2972
15.
Inf rarotspektroskopie von Wasser in Schlacken. Chemischer Bindungszustand von Wasser in Schlacken, Abhängigkeit der integralen Extinktion der OH-Banden vom Wasserdampfpartialdruck. Wasserstoff beim ESU-Verfahren. 相似文献
16.
Justin Salminen Peter Blomberg Jarno Mäkinen Lea Räsänen 《American Institute of Chemical Engineers》2015,61(9):2739-2748
Mining and metals processing are not invisible activities and are heavy industries, which require energy, water, chemicals, and land area. Recently more emphasis is given to environmental and societal aspects in mining and processing. Development of good practices with improved resource efficiency, new recovery methods and sustainability thinking are increasingly required. This work shows pH titration method for acid mine drainage (AMD) water incorporated with aqueous thermodynamic model for selective metals precipitation from complex solution. Also two examples on gold recovery methods from aqueous streams are shown: biosorption using fungal matter and solvent extraction using a task‐specific ionic liquid. By understanding chemical thermodynamics and natural phenomena, there is a better chance of developing solutions for environmental problems and new industrial processes. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2739–2748, 2015 相似文献
17.
Tandy S Bossart K Mueller R Ritschel J Hauser L Schulin R Nowack B 《Environmental science & technology》2004,38(3):937-944
Metal pollution of soils is widespread across the globe, and the clean up of these soils is a difficulttask. One possible remediation technique is ex-situ soil washing using chelating agents. Ethylenediaminetetraacetic acid (EDTA) is a very effective chelating agent for this purpose but has the disadvantage that it is quite persistent in the environment due to its low biodegradability. The aim of our work was to investigate the biodegradable chelating agents [S,S]-ethylenediaminedisuccinic acid (EDDS), iminodisuccinic acid (IDSA), methylglycine diacetic acid (MGDA), and nitrilotriacetic acid (NTA) as potential alternatives and compare them with EDTA for effectiveness. Kinetic experiments showed for all metals and soils that 24 h was the optimum extraction time. Longer times only gave minor additional benefits for heavy metal extraction but an unwanted increase in iron mobilization. For Cu at pH 7, the order of the extraction efficiency for equimolar ratios of chelating agent to metal was EDDS > NTA> IDSA > MGDA > EDTA and for Zn it was NTA > EDDS > EDTA >MGDA > IDSA. The comparatively low efficiency of EDTA resulted from competition between the heavy metals and co-extracted Ca. For Pb the order of extraction was EDTA > NTA >EDDS due to the much stronger complexation of Pb by EDTA compared to EDDS. At higher concentration of complexing agent, less difference between the agents was found and less pH dependence. There was an increase in heavy metal extraction with decreasing pH, but this was offset by an increase in Ca and Fe extraction. In sequential extractions EDDS extracted metals almost exclusively from the exchangeable, mobile, and Mn-oxide fractions. We conclude that the extraction with EDDS at pH 7 showed the best compromise between extraction efficiency for Cu, Zn, and Pb and loss of Ca and Fe from the soil. 相似文献
18.
Coir (Cocos nucifera) is a natural fibre known to retain its strength and resist biodegradation far better than other industrial natural fibres. However, systematic studies in this discipline are scarce. Geotextiles are usually exposed to diverse pH, salinity, moisture, and microbial association conditions. In the present work, specific surface modifications of coir geotextiles using a natural agent (cashew nut shell liquid) have been carried out to enhance their long-term performance depending on the end applications. The modified and unmodified geotextiles were subjected to acidic, alkaline, and neutral pH conditions, saline conditions, alternate wetting and drying cycles, and thermal cycles for the assessment of their durability, measured in terms of tensile strength. In situ soil burial studies in a tropical climate were conducted in specially prepared soil to follow the biodegradation behaviour of geotextiles at various depths. The surface-modified geotextiles were found to resist adverse chemical, physical, and biological conditions much better than the unmodified geotextiles. Alkaline conditions marginally accelerated the degradation rates when compared to acidic environments. The saline conditions, as well as alternate wetting and drying conditions, resulted in marginal loss of tensile strength (<7%). The surface-modified geotextiles buried within lower depths of soil under field conditions retained 70–80% of their initial tensile strength after 12 months, whereas the unmodified geotextiles lost 88% strength in four months. The positive impact of surface modification on durability is confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The results indicate the excellent potential of suitably surface-modified coir geotextiles for long-term use in adverse conditions. 相似文献
19.
Environmental chemistry of aminopolycarboxylate chelating agents 总被引:1,自引:0,他引:1
Nowack B 《Environmental science & technology》2002,36(19):4009-4016
Aminopolycarboxylate chelating agents are under scrutiny due to their influence on metal availability and mobility and in particular due to their persistence in the environment. In this review chelate adsorption, metal-mobilization, metal-exchange, mineral dissolution, reactive transport, photodegradation, and chemical degradation are all shown to be substantially affected by the chelated metal ion. The different reactivities of the metal-complexes have to be considered when assessing the reactions of chelating agents in the environment because they occur in natural waters predominantly in the form of metal complexes. Knowing the speciation of chelating agents in natural waters is therefore crucial for predicting their environmental fate. Despite this importance, only a few speciation measurements have been reported for natural waters, and model calculations have been frequently used instead. These calculations are, however, complicated by slow metal-exchange reactions that result in a nonequilibrium speciation and by the presence of naturally occurring ligands that compete with the chelating agents for available metals. The basis for a refined risk assessment of aminocarboxylate chelates should be the actual speciation in the natural water directly determined by analytical methods. The discussion of the influence of chelates on metal availability and fate also has to include the potential presence of other aminopolycarboxylate chelating agents besides the well-known EDTA and NTA. 相似文献
20.
The ease with which molten solder wets and spreads on the appropriate metallic surfaces of electronic component assemblies during the manufacturing process is referred to broadly as the solderability of the component or printed circuit board. Two needs are evident: a traceable solderability measurement method giving reproducible data that predict process performance, and an agreed level of solderability which, for a given manufacturing process, will deliver an acceptably robust solder joint. This paper describes briefly present understanding of the mechanisms that govern solderability and the measurement methods most likely to prove acceptable to the electronics assembly industry 相似文献