全文获取类型
收费全文 | 6010篇 |
免费 | 299篇 |
国内免费 | 27篇 |
专业分类
电工技术 | 168篇 |
综合类 | 11篇 |
化学工业 | 1425篇 |
金属工艺 | 182篇 |
机械仪表 | 203篇 |
建筑科学 | 163篇 |
矿业工程 | 4篇 |
能源动力 | 475篇 |
轻工业 | 625篇 |
水利工程 | 71篇 |
石油天然气 | 59篇 |
武器工业 | 2篇 |
无线电 | 618篇 |
一般工业技术 | 1129篇 |
冶金工业 | 446篇 |
原子能技术 | 40篇 |
自动化技术 | 715篇 |
出版年
2024年 | 18篇 |
2023年 | 113篇 |
2022年 | 200篇 |
2021年 | 353篇 |
2020年 | 226篇 |
2019年 | 262篇 |
2018年 | 280篇 |
2017年 | 245篇 |
2016年 | 274篇 |
2015年 | 189篇 |
2014年 | 265篇 |
2013年 | 541篇 |
2012年 | 340篇 |
2011年 | 410篇 |
2010年 | 268篇 |
2009年 | 232篇 |
2008年 | 189篇 |
2007年 | 169篇 |
2006年 | 140篇 |
2005年 | 95篇 |
2004年 | 95篇 |
2003年 | 102篇 |
2002年 | 84篇 |
2001年 | 79篇 |
2000年 | 90篇 |
1999年 | 58篇 |
1998年 | 136篇 |
1997年 | 92篇 |
1996年 | 84篇 |
1995年 | 68篇 |
1994年 | 57篇 |
1993年 | 55篇 |
1992年 | 24篇 |
1991年 | 47篇 |
1990年 | 44篇 |
1989年 | 39篇 |
1988年 | 48篇 |
1987年 | 38篇 |
1986年 | 32篇 |
1985年 | 30篇 |
1984年 | 30篇 |
1983年 | 25篇 |
1982年 | 23篇 |
1981年 | 19篇 |
1979年 | 18篇 |
1978年 | 17篇 |
1976年 | 14篇 |
1974年 | 9篇 |
1973年 | 10篇 |
1972年 | 10篇 |
排序方式: 共有6336条查询结果,搜索用时 9 毫秒
141.
The tetracycline (TC) resistance gene tet(M) was monitored in bacteria isolated from Japanese coastal and off-shore marine sediments. The high rate of occurrence of TC resistant (TC(r)) bacteria (120 microg mL(-1) TC) was observed at frequency ranges between 0.0-0.08% in Tokyo Bay, 1.67-1.82% in Sagami Bay and 0.0-4.35% in the open Pacific Ocean. The tet(M) gene was PCR amplified from the TC(r) isolates, showing 127 of 209 isolates (60.8%) as positive. The rate of occurrence of tet(M) was between 32.0-96.0%, 21.1 -28.0% and 0.0-83.3% in the isolates from Tokyo Bay, Sagami Bay and the open Pacific Ocean, respectively. The tet(M) positive isolates belonged to 4 orders of bacteria. Bacillales was the most dominant order (121 strains) among tet(M) possessing bacteria, followed by Actinomycetales (three strains), Flavobacteriales (one strain) and Pseudomonadales (one strain). This indicates that tet(M) is present in various bacterial species and suggests that marine sediments are a natural reservoir of the tet(M) gene. Nucleotide sequence of the tet(M) revealed that two genotypes of tet(M) were found in the bacteria. The two genotypes were placed in genetically distant branches of the phylogenetic tree, suggesting that the two tet(M)s have different origins. 相似文献
142.
Abdul Qadir Shah Tasneem Gul Kazi Muhammad Balal Arain Muhammad Khan Jamali Hassan Imran Afridi Nusrat Jalbani Ghulam Abbas kandhro Jameel Ahmed Baig Raja Adil sarfraz Rehana ansari 《Food chemistry》2009
The purpose of this study was to estimate total arsenic concentration in different tissues (leg, breast, liver and heart) of broiler chicken by hydride generation atomic absorption spectrometry (HGAAS) and graphite furnace atomic absorption spectrometry (GFAAS), prior to microwave assisted acid digestion. The accuracy of the techniques was evaluated by using certified reference material DORM-2. The percentage recoveries of total As were observed as 100.6% and 99.4% for HGAAS and GFAAS, respectively. The precision of the techniques, expressed as relative standard deviation, was observed as 1.71% and 4.18% for HGAAS and GFAAS measurements, respectively. The limits of detection for HGAAS and GFAAS were 0.025 μg/g and 0.052 μg/g, respectively. The concentrations of total arsenic in different tissues of broiler chicken were found in the range of 2.19–5.28, 2.15–5.22, 2.97–7.17 and 2.68–6.36 μg/g for leg, breast, liver and heart tissues, respectively. At a mean level of chicken consumption (60 g/person/day), people may ingest in the range of 72.0–85.1 μg arsenic/person/day from chicken alone. 相似文献
143.
The effects of physical refining on the formation of 3-monochloropropane-1,2-diol esters in relation to palm oil minor components 总被引:2,自引:0,他引:2
The formation of 3-monochloropropane-1,2-diol (3-MCPD) esters in refined palm oil during deodorisation is attributed to the intrinsic composition of crude palm oil. Utilising D-optimal design, the effects of the degumming and bleaching processes on the reduction in 3-MCPD ester formation in refined palm oil from poor-quality crude palm oil were studied relative to the palm oil minor components that are likely to be their precursors. Water degumming remarkably reduced 3-MCPD ester formation by up to 84%, from 9.79 mg/kg to 1.55 mg/kg. Bleaching with synthetic magnesium silicate caused a further 10% reduction, to 0.487 mg/kg. The reduction in 3-MCPD ester formation could be due to the removal of related precursors prior to the deodorisation step. The phosphorus content of bleached palm oil showed a significant correlation with 3-MCPD ester formation. 相似文献
144.
Jung‐Hwa Choi Jin‐Won Kang A. T. M. Mijanur Rahman Seung Ju Lee 《Journal of the Institute of Brewing》2016,122(1):143-146
High‐pressure treatment, which is an effective means of enhancing enzymatic reactions, was implemented during beer mashing to increase the production yield of fermentable sugar (FS). The malt solution was heated (62, 67, and 72°C) under pressure [0.1 (1 atm), 2, 50 and 100 MPa], and the FS was measured. The amount of FS reached an equilibrium level, which was the highest at 67°C and at 2 MPa. The pressures were 2, 50, 100, and 0.1 MPa in decreasing order of FS amount at 67°C. The temperatures were 67, 72 and 62°C in decreasing order of FS amount at 2 MPa. With a mechanistic approach, only the effect of pressure on gelatinization was analysed. The gelatinization degrees were also higher at pressures higher than 0.1 MPa. This observation highlights the positive effect (increasing the FS yield) of high‐pressure treatment on beer mashing. Copyright © 2015 The Institute of Brewing & Distilling 相似文献
145.
Potential Use of FTIR-ATR Spectroscopic Method for Determination of Virgin Coconut Oil and Extra Virgin Olive Oil in Ternary Mixture Systems 总被引:1,自引:0,他引:1
The aim of this study was to investigate the feasibility of Fourier-transform infrared (FTIR) spectroscopy combined with multivariate
calibrations of partial least square (PLS) and principle component regression (PCR) for analysis of virgin coconut oil (VCO)
in the ternary mixture with palm oil (PO) and olive oil, and for analysis of extra virgin olive oil (EVOO) mixed with soybean
oil (SO) and corn oil (CO). The spectra of individual oils and their blends with certain concentrations were scanned using
horizontal attenuated total reflectance accessory at mid-infrared region of 4,000–650 cm−1. The optimal frequency regions selected for calibration models were based on its ability to give the highest values of coefficient
of determination (R
2) and the lowest values of root mean standard error of calibration (RMSEC). PLS was slightly better for quantitative analysis
of VCO and EVOO compared with PCR. VCO in ternary mixtures is successfully determined at frequency region of 1,200–1,000 using
second derivative FTIR spectra with R
2 and RMSEC values of 0.999 and 0.200, respectively. Meanwhile, EVOO is best determined at 1,200–1,000 using first derivative
FTIR spectra with R
2 and RMSEC values of 0.999 and 0.975, respectively. The results showed that FTIR spectroscopy offers accurate and reliable
technique for quantitative analysis of VCO and EVOO in ternary systems. In addition, the developed method can be used for
the monitoring of VCO and EVOO adulteration with cheaper oils like PO in VCO as well as SO and CO in EVOO. 相似文献
146.
Thirty randomly selected Aeromonas isolates from food and the environment in Abu Dhabi, United Arab Emirates, were characterized for putative virulence determinants, such as production of cytotoxin, cytotonic toxin, and hemolysin and their capacity to adhere to and invade Henle 407 cells in vitro. Seventy percent of the tested isolates were cytotoxin producers, and 80% were hemolytic. Cytotoxin was produced by 6 of 7 A. hydrophila strains, 6 of 13 A. caviae strains, and 6 of 7 A. veronii bv. sobria strains, mostly from food sources. A. schubertii, A. jandaei, and A. trota also produced both cytotoxin and hemolysin. All of the 30 isolates tested adhered to Henle 407 cells, but none were able to invade the cells, as determined with the in vitro assay. However, no significant correlation of the presence of these putative virulence factors was found among these aeromonad food isolates. 相似文献
147.
To understand the contribution of submarine groundwater discharge (SGD) to the coastal mass budgets of Hg and monomethylmercury (MMHg), preliminary mass balance estimates were made for Hwasun and Bangdu Bays on Jeju Island, known to have large SGD due to the high permeability of the volcanic rocks. The mass balance results indicate that SGD is a main source of Hg in Hwasun Bay (23 ± 14 × 10(-2) mol yr(-1), 34%) and Bangdu Bay (23 ± 20 × 10(-2) mol yr(-1), 67%), although the contribution from atmospheric deposition was considerable (25% for Hwasun and 23% for Bangdu). MMHg was also discharged primarily from submarine groundwater at Hwasun (0.30 ± 0.17 × 10(-2) mol yr(-1), 55%) and Bangdu (0.65 ± 0.49 × 10(-2) mol yr(-1), 64%), which was higher than atmospheric deposition (6% for Hwasun and 2% for Bangdu) and sediment diffusion flux (5% for Hwasun and 3% for Bangdu). The overall mass balance results suggest that, although there are large spatial variations in SGD rates throughout the region, the coastal mass budgets of Hg and MMHg need to include SGD as well as atmospheric deposition and sediment diffusion as primary sources of Hg and MMHg. 相似文献
148.
149.
Soheila Faraji Afidah Abdul Rahim Norita Mohamed Coswald Stephen Sipaut 《北京科技大学学报(英文版)》2011,18(5):615-622
Cu-P-silicon carbide(SiC)composite coatings were deposited by means of electroless plating.The effects ofpH values,temperature,and different concentrations of sodium hypophosphite(NaH2PO2·H2O),nickel sulfate(NiSO4·6H2O),sodium citrate(C6H5Na3O7·2H2O)and SiC on the deposition rate and coating compositions were evaluated,and the bath formulation for Cu-P-SiC composite coatings was optimised.The coating compositions were determined using energy-dispersive X-ray analysis(EDX).The corresponding optimal operating parameters for depositing Cu-P-SiC are as follows:pH 9; temperature,90℃; NaH2PO2·H2O concentration,125 g/L; NiSO4·6H2O concentration,3.125 g/L; SiC concentration,5 g/L; and C6H5Na3O7·2H2O concentration,50 g/L.The surface morphology of the coatings analysed by scanning electron microscopy(SEM)shows that Cu particles are uniformly distributed.The hardness and wear resistance of Cu-P composite coatings are improved with the addition of SiC particles and increase with the increase of SiC content. 相似文献
150.
Khan Humaira Rashid Akram Bilal Aamir Muhammad Malik Muhammad Azad Tahir Asif Ali Choudhary Muhammad Aziz Akhtar Javeed 《Journal of Materials Science: Materials in Electronics》2021,32(16):20946-20954
Journal of Materials Science: Materials in Electronics - A photoelectrochemical (PEC) water splitting ability of pure ZnO and manganese-incorporated ZnO thin films fabricated via a simple... 相似文献