全文获取类型
收费全文 | 3632篇 |
免费 | 232篇 |
国内免费 | 12篇 |
专业分类
电工技术 | 53篇 |
综合类 | 2篇 |
化学工业 | 746篇 |
金属工艺 | 140篇 |
机械仪表 | 189篇 |
建筑科学 | 67篇 |
矿业工程 | 2篇 |
能源动力 | 134篇 |
轻工业 | 304篇 |
水利工程 | 20篇 |
石油天然气 | 8篇 |
无线电 | 691篇 |
一般工业技术 | 740篇 |
冶金工业 | 367篇 |
原子能技术 | 28篇 |
自动化技术 | 385篇 |
出版年
2024年 | 7篇 |
2023年 | 25篇 |
2022年 | 57篇 |
2021年 | 119篇 |
2020年 | 88篇 |
2019年 | 67篇 |
2018年 | 115篇 |
2017年 | 115篇 |
2016年 | 123篇 |
2015年 | 100篇 |
2014年 | 143篇 |
2013年 | 232篇 |
2012年 | 216篇 |
2011年 | 253篇 |
2010年 | 188篇 |
2009年 | 194篇 |
2008年 | 188篇 |
2007年 | 155篇 |
2006年 | 132篇 |
2005年 | 95篇 |
2004年 | 92篇 |
2003年 | 90篇 |
2002年 | 57篇 |
2001年 | 94篇 |
2000年 | 73篇 |
1999年 | 59篇 |
1998年 | 151篇 |
1997年 | 114篇 |
1996年 | 78篇 |
1995年 | 61篇 |
1994年 | 62篇 |
1993年 | 51篇 |
1992年 | 33篇 |
1991年 | 40篇 |
1990年 | 23篇 |
1989年 | 28篇 |
1988年 | 23篇 |
1987年 | 11篇 |
1986年 | 13篇 |
1985年 | 7篇 |
1984年 | 12篇 |
1983年 | 13篇 |
1982年 | 12篇 |
1981年 | 9篇 |
1980年 | 11篇 |
1979年 | 5篇 |
1977年 | 8篇 |
1976年 | 13篇 |
1974年 | 3篇 |
1973年 | 3篇 |
排序方式: 共有3876条查询结果,搜索用时 15 毫秒
121.
Organic whey as a source of Lactobacillus strains with selected technological and antimicrobial properties 下载免费PDF全文
Anna Rzepkowska Dorota Zielińska Aleksandra Ołdak Danuta Kołożyn‐Krajewska 《International Journal of Food Science & Technology》2017,52(9):1983-1994
Twenty‐five strains, isolated from raw, non‐pasteurised, organic whey samples, were identified phenotypically and genotypically. Biochemical tests were performed, and enzyme profiles, antibiotic resistance and antimicrobial properties were investigated. Sixteen strains were identified as genus Lactobacillus. Based on 16S rDNA gene sequence, the strains were identified as Lb. plantarum and Lb. fermentum. All of the strains had β‐galactosidase activity, and some of them reduced nitrate content. All strains utilised carbohydrates. The tested strains were characterised by low or average lipolytic and esterolytic activity. Moreover, the strains showed low proteolytic activity which is advantageous for their use as starter cultures for foods with low protein content. Strains Lb. fermentum S20, SM1, SM3, S2R and Lb. plantarum SM5 produced harmful N‐acetyl‐β‐glucosaminidase; moreover, the strain S20 produced also β‐glucuronidase. None of the strains produced α‐chymotrypsin. In phenotypic studies, most of the test strains were susceptible to gentamicin, ampicillin, tetracycline, chloramphenicol, penicillin and erythromycin. Strains Lb. plantarum S1 and Lb. fermentum S4, S7, S8, S10, SM1 and SM3 did not possess any transfer resistance genes. Antagonistic activity of the culture LAB strains was assessed as high or moderate in relation to the indicator strains, with the greatest zones of inhibition for E.coli and the smallest for L. monocytogenes ATCC 15313. This study reveals that the LAB strains isolated from organic whey have high potential for food application. Some strains of species Lb. fermentum (S4, S7, S8, S10) have been identified as the best candidates. 相似文献
122.
Tae-Kyun Oh Sung Oh Seongdae Kim Jae Sung Park Nagarajan Vinod Kyung Min Jang Sei Chang Kim Chang Won Choi Suk-Min Ko Dong Kee Jeong Rajangam Udayakumar 《International journal of molecular sciences》2014,15(9):15571-15591
A full-length phytase gene (phy) of Aspergillus nidulans was amplified from the cDNA library by polymerase chain reaction (PCR), and it was introduced into a bacterial expression vector, pET-28a. The recombinant protein (rPhy-E, 56 kDa) was overexpressed in the insoluble fraction of Escherichia coli culture, purified by Ni-NTA resin under denaturing conditions and injected into rats as an immunogen. To express A. nidulans phytase in a plant, the full-length of phy was cloned into a plant expression binary vector, pPZP212. The resultant construct was tested for its transient expression by Agrobacterium-infiltration into Nicotiana benthamiana leaves. Compared with a control, the agro-infiltrated leaf tissues showed the presence of phy mRNA and its high expression level in N.
benthamiana. The recombinant phytase (rPhy-P, 62 kDa) was strongly reacted with the polyclonal antibody against the nonglycosylated rPhy-E. The rPhy-P showed glycosylation, two pH optima (pH 4.5 and pH 5.5), an optimum temperature at 45~55 °C, thermostability and broad substrate specificities. After deglycosylation by peptide-N-glycosidase F (PNGase-F), the rPhy-P significantly lost the phytase activity and retained 1/9 of the original activity after 10 min of incubation at 45 °C. Therefore, the deglycosylation caused a significant reduction in enzyme thermostability. In animal experiments, oral administration of the rPhy-P at 1500 U/kg body weight/day for seven days caused a significant reduction of phosphorus excretion by 16% in rat feces. Besides, the rPhy-P did not result in any toxicological changes and clinical signs. 相似文献
123.
Sónia Simões Filomena Viana Mustafa Koçak A. Sofia Ramos M. Teresa Vieira Manuel F. Vieira 《Journal of Materials Engineering and Performance》2012,21(5):678-682
In this article, the characterization of the interfacial structure of diffusion bonding a TiAl alloy is presented. The joining
surfaces were modified by Ni/Al reactive multilayer deposition as an alternative approach to conventional diffusion bonding.
TiAl substrates were coated with alternated Ni and Al nanolayers. The nanolayers were deposited by dc magnetron sputtering
with 14 nm of period (bilayer thickness). Joining experiments were performed at 900 °C for 30 and 60 min with a pressure of
5 MPa. Cross sections of the joints were prepared for characterization of their interfaces by scanning electron microscopy
(SEM), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM), high resolution TEM (HRTEM),
energy dispersive x-ray spectroscopy (EDS), and electron backscatter diffraction (EBSD). Several intermetallic compounds form
at the interface, assuring the bonding of the TiAl. The interface can be divided into three distinct zones: zone 1 exhibits
elongated nanograins, very small equiaxed grains are observed in zone 2, while zone 3 has larger equiaxed grains. EBSD analysis
reveals that zone 1 corresponds to the intermetallic Al2NiTi and AlNiTi, and zones 2 and 3 to NiAl. 相似文献
124.
In this study, anion exchange membranes having various quaternary ammonium groups were prepared by using a radiation-induced graft polymerization method and followed by subsequent treatment of films with amines. FT-IR and SEM-EDX techniques were employed to monitor the reaction progress. The cross-sectional distribution of the anionic exchange functional groups through the membranes has also been investigated using SEM-EDX technique. The results reveal that the anion exchange groups were found to be evenly distributed throughout the membranes. It was also observed that the physico-chemical properties of the anion exchange membranes such as water uptake, ionic conductivity, thermal stability, chemical stability, mechanical properties, and dimensional stability are largely influenced by the chemical structure of the quaternary ammonium moiety which is attached to the graft chains. Among the prepared anion exchange membranes, the membrane having mono-quaternized 1,4-diazabicyclo[2,2,2]octane moiety was found to have both enhanced chemical and dimensional stabilities, while the others having quaternized trimethylamine or bis-quaternized 1,4-diazabicyclo[2,2,2]octane have the decreased dimensional and chemical stabilities. 相似文献
125.
Nur Koçberber Kιlιç Pιnar Karacakaya Ergin Duygu Gönül Dönmez 《Water and Environment Journal》2012,26(1):94-99
Phenol removal levels of Synechocystis sp. were investigated in BG11 media with 10 mg/L triacontanol (TRIA) and without it to test whether the hormone could increase the removal efficiency by increasing biomass. The assays were performed to determine the effect of light on degradation, in media with 119.0–492.8 mg/L phenol under light and dark conditions. At increasing phenol concentrations, the degradation ranged between 98.5 and 100% regardless of a dark or a light condition. Experiments were carried out under light to determine the optimum pH for effective degradation. Optimum pH was found to be 6.5 at 200 mg/L phenol with or without TRIA. Phenol degradation was investigated in the 120.2–826.9 mg/L range. Although 377.4 mg/L phenol was completely degraded in hormone controls within 120 h, degradation was increased by TRIA, and the process was completed in 96 h. These data suggest that Synechocystis sp. has potential for use in the treatment of wastewaters containing phenol. 相似文献
126.
Pectin from Yuza (Citrus junos) pomace was extracted by using combined physical and enzymatic (CPE) treatment, and their characteristics were compared with those of chemically-extracted pectin. Their physico-chemical and thermo-mechanical properties were also investigated in a wheat flour–water system. The CPE extraction produced pectin with 55% of galaturonic acid and the extraction yield was 7.3%. Also, the pectin obtained by CPE extraction exhibited a higher degree of esterification (46%) than chemically-extracted pectin (41%), which was confirmed by FT-IR analysis. When the pectin solutions were subjected to steady-shear conditions, both samples had shear-thinning properties while high apparent viscosity was observed in the chemically-extracted pectin. Even though the use of both pectins raised the pasting parameters of wheat flour as well as its gelatinization temperature, less change in the pasting properties was found in the wheat flour–water system containing the pectin prepared by CPE treatment. The Mixolab results demonstrated that during mechanical shearing and thermal treatments, the dough samples containing chemically-extracted pectin exhibited enhanced mixing stability, strong protein network structure, and increased peak viscosity. 相似文献
127.
128.
Kei Noda Ko Okamura Junko Taniguchi Masaru Suzuki Mitsunori Hieda 《Journal of Low Temperature Physics》2013,171(5-6):638-643
We have carried out quartz crystal microbalance (QCM) experiments for 4He films on an exfoliated single-crystalline graphite using a 32 kHz tuning fork, and have measured the temperature dependence of the resonance frequency and the Q value for various areal densities and oscillation amplitudes. Comparing with the previous experiments for Grafoil, the decoupling of the films due to the slippage or the superfluidity was larger than that of Grafoil, and the competition between the slippage and the superfluidity was observed in three-atom thick films. Furthermore, it was found that the slippage is suppressed gradually at higher temperature than the superfluid onset T c , and that the relaxation time decreases at low temperatures while it obeys the Arrhenius law at high temperatures. These results suggest a precursor to the superfluidity of 4He films. 相似文献
129.
Suriyan Supapvanich Rachaya Arkajak Ko Yalai 《International Journal of Food Science & Technology》2012,47(12):2662-2670
The effects of hot CaCl2 dips on postharvest quality and bioactive compounds of fresh‐cut sweet leaf bush were investigated. The vegetable was dipped in 0.5% or 1.0% (w/v) of CaCl2 solutions at 40 °C for 30 s and the control was the untreated sample. Hot CaCl2 dips significantly delayed the weight loss, maintained the overall quality and inhibited the wiltness (P < 0.05). Both hot CaCl2 dips had no effect on the changes in lightness (L*) and delayed the decrease in greenness (‐a*) and total chlorophyll content and the increase in both yellowness (b*) and carotenoid content. Hot CaCl2 dips enhanced total antioxidants, total phenolics content and both AsA‐POD and G‐POD activities from 38.6, 0.44, 15.2 and 22.4 at day 0 to 55.3, 0.55, 50.5 and 362.4 at day 8, respectively. Moreover, hot CaCl2 dips also delayed the loss of DPPH free radical scavenging activity, total flavonoid, ascorbic acid and CAT activity when compared to other treatments during storage. This study showed that hot CaCl2 dip maintains postharvest quality and enhanced bioactive compounds of fresh‐cut sweet leaf bush during storage. 相似文献
130.
A chitosan-based carbon dioxide (CO2) indicator was developed to monitor freshness or quality of packaged foods during their storage, as elevated CO2 levels inside a package is one of the prime indicators of microbial spoilage of food. The objective of this proof-of-concept study, therefore, was to develop a chitosan-based CO2 indicator and to investigate its performance in different operating environments. For the enhancement of signal strength of indicator, 2-amino-2-methyl-1-propanol (AMP) was used as an additive to the chitosan solution. Aqueous chitosan–AMP suspensions were prepared by addition of chitosan (0.1%, 0.2% and 0.4%) and AMP (0%, 5%, 10% and 20%) to distilled water at pH 7.0. Thereafter, the aqueous chitosan suspensions were incubated under 100% and 20% CO2 test atmospheres. The aqueous solubility of chitosan, which in turn impacts the degree of transparency of the suspension, was tested at different pHs and time intervals, spectrometrically. The transparency of 0.2% chitosan aqueous suspension increased dramatically below pH 6.5 under 20% or 100% CO2 incubation. The addition of a 5% AMP concentration to the chitosan suspension was found optimal for maximum CO2 absorption and this, therefore, increased transparency by more than 90%. 相似文献