全文获取类型
收费全文 | 1840篇 |
免费 | 67篇 |
国内免费 | 4篇 |
专业分类
电工技术 | 7篇 |
化学工业 | 201篇 |
金属工艺 | 16篇 |
机械仪表 | 24篇 |
建筑科学 | 14篇 |
矿业工程 | 2篇 |
能源动力 | 28篇 |
轻工业 | 233篇 |
水利工程 | 4篇 |
石油天然气 | 7篇 |
无线电 | 41篇 |
一般工业技术 | 116篇 |
冶金工业 | 1117篇 |
原子能技术 | 10篇 |
自动化技术 | 91篇 |
出版年
2024年 | 5篇 |
2023年 | 9篇 |
2022年 | 24篇 |
2021年 | 35篇 |
2020年 | 28篇 |
2019年 | 30篇 |
2018年 | 27篇 |
2017年 | 43篇 |
2016年 | 39篇 |
2015年 | 32篇 |
2014年 | 30篇 |
2013年 | 49篇 |
2012年 | 49篇 |
2011年 | 75篇 |
2010年 | 34篇 |
2009年 | 42篇 |
2008年 | 41篇 |
2007年 | 33篇 |
2006年 | 28篇 |
2005年 | 26篇 |
2004年 | 20篇 |
2003年 | 18篇 |
2002年 | 19篇 |
2001年 | 13篇 |
2000年 | 7篇 |
1999年 | 24篇 |
1998年 | 332篇 |
1997年 | 231篇 |
1996年 | 138篇 |
1995年 | 71篇 |
1994年 | 64篇 |
1993年 | 56篇 |
1992年 | 12篇 |
1991年 | 18篇 |
1990年 | 8篇 |
1989年 | 14篇 |
1988年 | 22篇 |
1987年 | 14篇 |
1986年 | 9篇 |
1985年 | 9篇 |
1983年 | 3篇 |
1982年 | 7篇 |
1981年 | 10篇 |
1980年 | 8篇 |
1978年 | 8篇 |
1977年 | 30篇 |
1976年 | 60篇 |
1972年 | 1篇 |
1967年 | 1篇 |
1954年 | 1篇 |
排序方式: 共有1911条查询结果,搜索用时 15 毫秒
1.
Tallison O. Abreu Roterdan F. Abreu Felipe F. do Carmo Wellington V. de Sousa Helenilson de O. Barros José E.V. de Morais João P.C. do Nascimento Marcelo A.S. da Silva Sergei Trukhanov Alex Trukhanov Larissa Panina Charanjeet Singh Antonio S.B. Sombra 《Ceramics International》2021,47(11):15424-15432
This work presents the dielectric properties of YNbO4 (YNO)–TiO2 composites in the microwave range. X-ray diffraction analysis demonstrates that the addition of TiO2 to YNO results in the formation of a Y(Nb0.5Ti0.5)2O6 phase. In the microwave range, the values of permittivity and dielectric loss did not present major changes with the increment of TiO2. Moreover, the addition of TiO2 results in an improvement in the thermal stability of YNO, with YNO63 demonstrating a resonant frequency of ?8.96 ppm.°C?1. We utilised numerical simulations to evaluate the behaviour of these materials as dielectric resonator antennae and it is found that they exhibit a reflection coefficient below ?10 dB at the resonant frequency, with a realised gain of 4.94 – 5.76 dBi, a bandwidth of 665–1050 MHz and a radiation efficiency above 84%. Our results indicate that YNO–TiO2 composites are interesting candidates for microwave operating devices. 相似文献
2.
Quality enhancement of the abundant under‐valued crustacean,lobster krill (Munida spp.), during its chilled storage
下载免费PDF全文
![点击此处可从《International Journal of Food Science & Technology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Bibiana García‐Soto José M. Miranda Jorge Barros‐Velázquez Santiago P. Aubourg 《International Journal of Food Science & Technology》2015,50(3):708-716
Lobster krill (Munida genus) represents an under‐valued crustacean frequently caught on European fishing banks. In this work, its sensory, microbiological and biochemical qualities were evaluated during chilled storage. Additionally, the effects of a prestorage antimelanosic treatment consisting of soaking in sodium metabisulphite (SMB) solutions at two different concentrations (0.25% and 0.75%) were also studied. SMB prestorage treatment provided lobster specimens that still exhibited acceptable sensory quality after 10 days of storage, while control specimens were unacceptable at that time. SMB treatment also resulted in a significant (P < 0.05) inhibition of microbial growth, mainly of Enterobacteriaceae, psychrotrophes and proteolytic bacteria. Low lipid oxidation levels were observed for all batches; however, a significantly higher (P < 0.05) retention of polyunsaturated fatty acids was found in SMB‐treated lobster, especially in the 0.75% SMB batch. The results presented here open the way to the potential commercialisation of currently under‐utilised lobster krill as a chilled product. 相似文献
3.
4.
ESR spin trapping was used to investigate the reaction of rabbit cytochrome P450 (P450) 1A2 with cumene hydroperoxide. Cumene hydroperoxide-derived peroxyl, alkoxyl, and carbon-centered radicals were formed and trapped during the reaction. The relative contributions of each radical adduct to the composite ESR spectrum were influenced by the concentration of the spin trap. Computer simulation of the experimental data obtained at various 5,5-dimethyl-1-pyrroline N-oxide (DMPO) concentrations was used to quantitate the contributions of each radical adduct to the composite ESR spectrum. The alkoxyl radical was the initial radical produced during the reaction. Experiments with 2-methyl-2-nitrosopropane identified the carbon-centered adducts as those of the methyl radical, hydroxymethyl radical, and a secondary carbon-centered radical. The reaction did not require NADPH-cytochrome P450 reductase or NADPH. It is concluded that the reaction involves the initial homolytic scission of the peroxide O-O bond to produce the cumoxyl radical. Methyl radicals were produced from the beta-scission of the cumoxyl radical. The peroxyl adduct was not observed in the absence of molecular oxygen. We conclude that the DMPO peroxyl radical adduct detected in the presence of oxygen was due to the methylperoxyl radical formed by the reaction of the methyl radical with oxygen. At a higher P450 concentration, a protein-derived radical adduct was also detected. 相似文献
5.
Cyclo 3 Fort is used in the treatment of chronic venous insufficiency. In this study, the effects of Cyclo 3 Fort, 2, 10 and 50 mg/kg, were studied in cheek pouch preparations from diabetic hamsters. The mean arteriolar diameter in animals receiving Cyclo 3 Fort, 10 and 50 mg/kg, was significantly greater than in control animals (p < 0.05), and the mean venule diameter was significantly lower in animals receiving the 50 mg/kg dose than in the control group. This suggests that Cyclo 3 Fort, 50 mg/kg/day, has a venotonic effect in diabetic animals. The venoarteriolar reflex was studied by measuring the internal diameter of arterioles during venular occlusion. The reflex was impaired in animals treated with either placebo or 2 mg/kg, but this was reversed by treatment with Cyclo 3 Fort, 10 and 50 mg/kg. 相似文献
6.
7.
8.
LA Pérula de Torres J Martínez de la Iglesia J Espejo Espejo MV Rubio Cuadrado I Enciso Berge FJ Fonseca del Pozo JM Aranda Lara 《Canadian Metallurgical Quarterly》1997,20(8):425-434
OBJECTIVE: To describe the health status of a population over 60 years and to study their relationship with several socio-demographic variables. DESIGN: A cross-sectional study, population based. SETTINGS: A community. PARTICIPANTS: A randomized sample of 1,103 non institutionalized people over 60 years living in the city of Cordoba (Spain). MEASUREMENTS AND MAIN RESULTS: By mean of a personal interview at home we used the OARS-MFAQ-VE questionnaire. Low self-rated health was associated with the age, to be female sex, a low cultural background, and a low income. Only 5.2% of the study people do not suffered any illness and 56% state that their health problems are major problems for doing their current activities. 4.9% declared to have some degree of physical incapacity. 3.7% of elderly population has an important cognitive deficit. CONCLUSIONS: The majority of elderly people has good health. Age is related with a poor health. Women have more health problems than men. 相似文献
9.
10.