全文获取类型
收费全文 | 2649篇 |
免费 | 195篇 |
国内免费 | 11篇 |
专业分类
电工技术 | 43篇 |
综合类 | 9篇 |
化学工业 | 768篇 |
金属工艺 | 45篇 |
机械仪表 | 62篇 |
建筑科学 | 91篇 |
矿业工程 | 5篇 |
能源动力 | 218篇 |
轻工业 | 370篇 |
水利工程 | 44篇 |
石油天然气 | 15篇 |
无线电 | 319篇 |
一般工业技术 | 461篇 |
冶金工业 | 62篇 |
原子能技术 | 16篇 |
自动化技术 | 327篇 |
出版年
2024年 | 14篇 |
2023年 | 75篇 |
2022年 | 133篇 |
2021年 | 252篇 |
2020年 | 166篇 |
2019年 | 129篇 |
2018年 | 194篇 |
2017年 | 173篇 |
2016年 | 170篇 |
2015年 | 122篇 |
2014年 | 159篇 |
2013年 | 219篇 |
2012年 | 170篇 |
2011年 | 209篇 |
2010年 | 111篇 |
2009年 | 111篇 |
2008年 | 66篇 |
2007年 | 65篇 |
2006年 | 59篇 |
2005年 | 39篇 |
2004年 | 35篇 |
2003年 | 38篇 |
2002年 | 23篇 |
2001年 | 10篇 |
2000年 | 9篇 |
1999年 | 8篇 |
1998年 | 7篇 |
1997年 | 7篇 |
1996年 | 5篇 |
1995年 | 11篇 |
1994年 | 8篇 |
1993年 | 7篇 |
1992年 | 9篇 |
1991年 | 7篇 |
1990年 | 3篇 |
1989年 | 5篇 |
1987年 | 2篇 |
1986年 | 4篇 |
1984年 | 4篇 |
1983年 | 1篇 |
1982年 | 6篇 |
1981年 | 3篇 |
1980年 | 1篇 |
1979年 | 2篇 |
1978年 | 1篇 |
1976年 | 1篇 |
1973年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有2855条查询结果,搜索用时 15 毫秒
101.
Didem Yıldırım Cem Ozic Dr. Yunus Ensari 《Chembiochem : a European journal of chemical biology》2023,24(12):e202300065
Oxyfunctionalization of non-activated carbon bonds by P450 monooxygenases has drawn great industrial attraction. Self-sufficient P450s containing catalytic heme and reductase domains in a single polypeptide chain offer many advantages since they do not require external electron transfer partners. Here, we report the first P450 enzyme identified and expressed from Azorhizobium caulinodans. Firstly, expression conditions of P450 AZC1 were optimized for enhanced expression in E.coli. The highest P450 content was obtained in E.coli Rosetta DE3 plysS when it was incubated in TB media supplemented with 0.75 mM IPTG, 0.5 mM ALA, and 0.75 mM FeCl3 at 25 °C for 24 hours. Subsequently, the purified enzyme showed a broad substrate spectrum including fatty acids, linear and cyclic alkanes, aromatics, and pharmaceuticals. Finally, P450 AZC1 showed optimal activity at pH 6.0 and 40 °C and a broad pH and temperature profile, making it a promising candidate for industrial applications. 相似文献
102.
Shafirah Samsuri Nurul Aini Amran Norshafika Yahya 《Chemical Engineering Communications》2016,203(3):345-363
Progressive freeze concentration (PFC) is a process where only a large single ice crystal is formed in the system and grown on the cooling surface so that the separation between the ice crystal and the mother solution is very easy. This makes the system very simple and leads to a lower cost. The conventional setup of PFC produces ice with high purity but lower productivity than suspension freeze concentration (SFC). The volume of ice produced is also usually low. Hence, continued areas of the development for PFC system include the quest for improved productivity and better efficiency. Different kinds of design have been investigated, which are easy to operate and cost-effective besides the ability to obtain high quality of product and better efficiency of the system. The PFC system is recognized as a good alternative if high-quality products can be produced with higher productivity. In this article, previous researches on PFC designs were reviewed for the purpose of providing an understanding on methods of designing a PFC system and also to provide references for future application of PFC. 相似文献
103.
Tasnuva Sarwar Tunna Kashif Ghafoor Sahena Ferdosh Juliana Md Jaffri Fahad Y Al-Juhaimi 《分离科学与技术》2018,53(2):243-260
Supercritical fluid extraction (SFE) using carbon dioxide (CO2) and liquid CO2 using Soxhlet (CO2-Soxhlet) extraction were employed to extract three (3) antidiabetic compounds viz. stigmasterol, quercetin, and avicularin from Mimosa pudica. Various extraction parameters were studied. Extracts were analyzed pharmacologically, qualitatively and quantitatively to ascertain enrichment levels. All three antidiabetic compounds were effectively enriched under optimized conditions of temperature 60°C, pressure 40 MPa, co-solvent ratio 30%, and CO2 flow rate of 5 ml min?1. SFE was found to be the better method for enrichment of the antidiabetic compounds than the CO2-Soxhlet method. Extraction conditions were seen to affect the enrichment of desired compounds. 相似文献
104.
An investigation of sound absorption coefficient on sisal fiber poly lactic acid bio‐composites 下载免费PDF全文
Elammaran Jayamani Sinin Hamdan Md Rezaur Rahman Muhammad Khusairy Bin Bakri Akshay Kakar 《应用聚合物科学杂志》2015,132(34)
In this research, the mechanical, acoustical, thermal, morphological, and infrared spectral properties of untreated, heat and alkaline‐treated sisal fiber‐reinforced poly‐lactic‐acid bio‐composites were analyzed. The bio‐composite samples were fabricated using a hot press molding machine. The properties mentioned above were evaluated and compared with heat‐treated and alkaline‐treated sisal fibers. Composites with heat‐treated sisal fibers were found to exhibit the best mechanical properties. Thermo‐gravimetric analysis (TGA) was conducted to study the thermal degradation of the bio‐composite samples. It was discovered that the PLA‐sisal composites with optimal heat‐treated at 160°C and alkaline‐treated fibers possess good thermal stability as compared with untreated fiber. The results indicated that the composites prepared with 30wt % of sisal had the highest sound absorption as compared with other composites. Evidence of the successful reaction of sodium hydroxide and heat treatment of the sisal fibers was provided by the infrared spectrum and implied by decreased bands at certain wavenumbers. Observations based on scanning electron microscopy of the fracture surface of the composites showed the effect of alkaline and heat treatment on the fiber surface and improved fiber‐matrix adhesion. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42470. 相似文献
105.
Synthesis and Biological Evaluation of Ferrocenylquinoline as a Potential Antileishmanial Agent 下载免费PDF全文
Md Yousuf Debarati Mukherjee Abhishek Pal Somaditya Dey Supratim Mandal Dr. Chiranjib Pal Dr. Susanta Adhikari 《ChemMedChem》2015,10(3):546-554
The emergence of resistance against antileishmanial drugs in current use necessitates the search for new classes of antileishmanial compounds. Herein we report the design, synthesis, and evaluation of a novel ferrocenylquinoline for activity against Leishmania donovani. 7‐Chloro‐N‐[2‐(1H‐5‐ferrocenyl‐1,2,3‐triazol‐1‐yl)ethyl]quinolin‐4‐amine ( 1 ) was generated by coupling an iron(II) ethynylferrocene species with 4‐(2‐ethylazido)amino‐7‐chloroquinoline using click chemistry. The synthesized compound 1 was tested for its antileishmanial activity using both promastigote and amastigote stages of L. donovani. Compound 1 showed promising anti‐promastigote activity, with an IC50 value of 15.26 μM and no cytotoxicity toward host splenocytes. From the battery of tests conducted in this study, it appears that this compound induces parasite death by promoting oxidative stress and depolarizing the mitochondrial membrane potential, thereby triggering apoptosis. These results suggest that ferrocenylquinoline 1 is a suitable lead for the development of new antileishmanial drugs. 相似文献
106.
Reinforcement of graphene nanoplatelets on plasticized poly(lactic acid) nanocomposites: Mechanical,thermal, morphology,and antibacterial properties 下载免费PDF全文
Buong Woei Chieng Nor Azowa Ibrahim Wan Md Zin Wan Yunus Mohd Zobir Hussein Yoon Yee Then Yuet Ying Loo 《应用聚合物科学杂志》2015,132(11)
Plasticized poly(lactic acid) (PLA)‐based nanocomposites filled with graphene nanoplatelets (xGnP) and containing poly(ethylene glycol) (PEG) and epoxidized palm oil (EPO) with ratio 2 : 1 (2P : 1E) as hybrid plasticizer were prepared by melt blending method. The key objective is to take advantage of plasticization to increase the material ductility while preserving valuable stiffness, strength, and toughness via addition of xGnP. The tensile modulus of PLA/2P : 1E/0.1 wt % xGnP was substantially improved (30%) with strength and elasticity maintained, as compared to plasticized PLA. TGA analysis revealed that the xGnP was capable of acting as barrier to reduce thermal diffusion across the plasticized PLA matrix, and thus enhanced thermal stability of the plasticized PLA. Incorporation of xGnP also enhanced antimicrobial activity of nanocomposites toward Escherichia coli, Salmonella typhimurium, Staphylococcus aureus, and Listeria monocytogenes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41652. 相似文献
107.
Md. Zahid Hossain 《Nutrient Cycling in Agroecosystems》2001,61(1-2):197-204
Bangladesh is an agricultural country. About 80% of the total population live in rural areas. The contribution of agriculture
to the gross domestic product is 30%. Rice is the major food crop while jute, sugarcane and tea are the main cash crops. Other
important crops are wheat, tobacco, pulses, vegetables and fruits. Overall productivity in Bangladesh is stagnating or declining.
The implication of yield stagnation or declining productivity is severe, since these trends have occurred despite rapid growth
in the use of chemical fertilisers. Depletion of soil organic matter is the main cause of low productivity, which is considered
one of the most serious threats to the sustainability of agriculture in Bangladesh. In Bangladesh, most soils have less than
17 g/kg and some soils have less than 10 g/kg organic matter. Farmers realise that there is a problem with soil fertility
related to organic matter depletion. Farmers say that organic matter increases yield, reduces the production cost, improves
crop growth and the economy, increases water-holding capacity and improves the soil structure. They recognise soil with higher
organic matter content by darker brownish to black in colour. Some farmers are using fast-growing trees such as Flemingia macrophyla, Ipilipil (Leucaen leucophala), Glyricidia sepium, Boga Medula (Tephrosia candida), Dhol Kolmi (Ipomoea fistulosa), etc., as living fences, which can be used as fuel, fertiliser and fodder. To increase the soil organic matter, farmers
use green manure crops, compost, quick compost, cow dung, azolla, etc. However, fuel for cooking purposes is limited and cow
dung and crop residues are largely used as fuel. Crop residues are also used as fodder for livestock. Farmers expressed the
wish to learn more about organic fertilizer management. However, sufficient food should be produced to keep pace with population
growth. To alleviate the hunger and poverty is to increase the intensity of agricultural production and maintain favorable
ecological conditions. Therefore, more organic matter should be used in the farmers' fields to sustain the soil fertility
in an intensive farming system.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
108.
Mahtab Samadi Zurina Zainal Abidin Robiah Yunus Dayang Radiah Awang Biak Hiroyuki Yoshida Eng Hai Lok 《中国化学工程学报》2017,25(2):216-222
This study aimed to model the kinetic of hydro-distillation of Aquilaria malaccensis leaves oil in order to understand and optimize the extraction process. In addition, this study, for the first time, aimed to identify the chemical compositions of the A. malaccensis leave-oil. By assessing both first-order kinetic model and the model of simultaneous washing and diffusion, the result indicated that the model of simultaneous washing and diffusion better describes the hydro-distillation mechanism of the essential oil from A. malaccensis leaves.The optimum time, solid to liquid ratio, and the heating power for extracting the highest amount of essential oil were found to be around 3 h, 1:10(g·ml-1), and 300 W respectively. Yellow essential oil with a strong smell and a yield of 0.05 v/w was extracted by hydro-distillation Clevenger apparatus. Chemical compounds of the essential oil were analyzed using gas chromatography–mass spectroscopy(GC/MS), which resulted in identification of 42 compounds that constitute 93% of essential oil. Among the identified components,Pentadecanal(32.082%), 9-Octadecenal,(Z)(15.894%), and Tetradecanal(6.927%) were the major compounds.Considering the fact that all the identified major components possess pesticidal properties, A. malaccensis leaves can be regarded as a promising natural source for producing pesticides. 相似文献
109.
110.
Hamizah Md Rasid Nur Hanis Adila Azhar Siti Fairus M. Yusoff 《Journal of Polymer Research》2017,24(7):106
The modification of liquid natural rubber (LNR) has attracted interests among chemists as it brings improvements to several of its properties and widens its application to various fields. LNR can be modified into fluorinated LNR (F-LNR) which is of interest to industries due to its remarkable properties, including low surface energies, high thermal stabilities, together with its significant hydrophobic characters. In this work, a new route to prepare fluorinated rubber was presented. Hydroxylated LNR (OH-LNR) was initially synthesized in good yield via oxidation in the presence of tungsten complex catalyst and acetic acid with hydrogen peroxide as an oxidant. The optimum hydroxyl content of 57.0% was obtained within 6 h reaction time at 90 °C. In the second step, the esterification of OH-LNR using pentadecafluorooctanoyl chloride (PDFOC) under mild conditions was conducted, leading to LNR bearing fluoro groups in the side chain of LNR (F-LNR). ATR-FTIR spectroscopy was used to elucidate the structure and determine any changes in the functional groups that may have been induced during the reaction. 1H NMR spectroscopy was employed to reveal that a high fluorine content of 48.6% was obtained using 3:1 molar ratio of OH-LNR:PDFOC for 8 h at 50 °C. The microstructure of F-LNR was further analyzed using 19F NMR and 13C NMR spectroscopies, and the results confirmed the presence of fluorine in LNR. Thermogravimetric analyses also indicated that the modification improved thermal stability of the LNR. Contact angle measurements were also conducted to verify the hydrophobicity of the fluorinated rubber and the results obtained showed that F-LNR exhibited higher hydrophobicity than LNR. 相似文献