全文获取类型
收费全文 | 432521篇 |
免费 | 4261篇 |
国内免费 | 822篇 |
学科分类
工业技术 | 437604篇 |
出版年
2021年 | 4007篇 |
2019年 | 3933篇 |
2018年 | 12294篇 |
2017年 | 12634篇 |
2016年 | 11244篇 |
2015年 | 4784篇 |
2014年 | 7717篇 |
2013年 | 16533篇 |
2012年 | 12593篇 |
2011年 | 18718篇 |
2010年 | 15987篇 |
2009年 | 16215篇 |
2008年 | 16758篇 |
2007年 | 17595篇 |
2006年 | 10393篇 |
2005年 | 11121篇 |
2004年 | 10078篇 |
2003年 | 9797篇 |
2002年 | 8845篇 |
2001年 | 8301篇 |
2000年 | 8130篇 |
1999年 | 7541篇 |
1998年 | 16284篇 |
1997年 | 11990篇 |
1996年 | 8840篇 |
1995年 | 7041篇 |
1994年 | 6383篇 |
1993年 | 6672篇 |
1992年 | 5354篇 |
1991年 | 5430篇 |
1990年 | 5357篇 |
1989年 | 5146篇 |
1988年 | 5076篇 |
1987年 | 4751篇 |
1986年 | 4717篇 |
1985年 | 5162篇 |
1984年 | 4940篇 |
1983年 | 4726篇 |
1982年 | 4398篇 |
1981年 | 4424篇 |
1980年 | 4497篇 |
1979年 | 4683篇 |
1978年 | 4800篇 |
1977年 | 5009篇 |
1976年 | 5755篇 |
1975年 | 4439篇 |
1974年 | 4454篇 |
1973年 | 4539篇 |
1972年 | 4043篇 |
1971年 | 3685篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
63.
Puneet Parmar Nicolas Lopez-Villalobos John T. Tobin Eoin Murphy Frank Buckley Shane V. Crowley Alan L. Kelly Laurence Shalloo 《International Journal of Food Science & Technology》2021,56(5):2415-2422
The objective of this study was to determine the effect of temperature on whole milk density measured at four different temperatures: 5, 10, 15, and 20 °C. A total of ninety-three individual milk samples were collected from morning milking of thirty-two Holstein Friesian dairy cows, of national average genetic merit, once every two weeks over a period of 4 weeks and were assessed by Fourier transform infrared spectroscopy for milk composition analysis. Density of the milk was evaluated using two different analytical methods: a portable density meter DMA35 and a standard desktop model DMA4500M (Anton Paar GmbH, UK). Milk density was analysed with a linear mixed model with the fixed effects of sampling period, temperature and analysis method; triple interaction of sampling period x analysis method x temperature; and the random effect of cow to account for repeated measures. The effect of temperature on milk density (ρ) was also evaluated including temperature (t) as covariate with linear and quadratic effects within each analytic method. The regression equation describing the curvature and density–temperature relationship for the DMA35 instrument was ρ = 1.0338−0.00017T−0.0000122T2 (R2 = 0.64), while it was ρ = 1.0334 + 0.000057T−0.00001T2 (R2 = 0.61) for DMA4500 instrument. The mean density determined with DMA4500 at 5 °C was 1.0334 g cm−3, with corresponding figures of 1.0330, 1.0320 and 1.0305 g cm−3 at 10, 15 and 20 °C, respectively. The milk density values obtained in this study at specific temperatures will help to address any bias in weight–volume calculations and thus may also improve the financial and operational control for the dairy processors in Ireland and internationally. 相似文献
64.
Kharitonov D. S. Makarova I. V. Osipenko M. A. Yanushevskii V. I. Wrzesińska A. Bobowska I. Kurilo I. I. 《Protection of Metals and Physical Chemistry of Surfaces》2020,56(1):113-124
Protection of Metals and Physical Chemistry of Surfaces - The stage mechanism of manganese-containing conversion coatings (MCCs) formation on the surface of AD31 alloy (AA6063) in acidic (pH 3)... 相似文献
65.
Kobrakov K. I. Kurnetsov D. N. Ruchkina A. G. Sharpar N. M. 《Theoretical Foundations of Chemical Engineering》2020,54(5):1052-1056
Theoretical Foundations of Chemical Engineering - New research results, as well as those published earlier by the authors, on the synthesis of azo compounds based on nitroanilines obtained by the... 相似文献
66.
A. Amala Jeya Ranchani V. Parthasarathy Chechia Hu Yi-Feng Lin 《Chemical Engineering Communications》2020,207(6):871-886
AbstractAn eco-friendly catalyst system was synthesized using three step reaction. The Cu nanoparticles bridged aminoclay catalyst was analyzed using various analytical techniques. The structure of the catalyst was confirmed by FTIR and XRD. The synthesized catalyst system was used for the reduction of p-nitrophenol (NP), Cr(VI), and fluorescein (Flur) dye individually, as well as in their mixture forms. The kapp value was computed to access the efficiency of the catalyst. The results indicated that the kapp value of the individual system is higher than that of the mixture systems due to the absence of the complex formation reaction. The catalytic performance of the catalyst was also tested for the Schiff base (SB) formation between poly(ethyleneglycol) (PEG) and aniline (ANI) in an oxygen atmosphere. The 1H-NMR spectroscopy result indicates that the present catalyst system produced 86% yield. 相似文献
67.
Bukin A. N. Moseeva V. S. Marunich S. A. 《Theoretical Foundations of Chemical Engineering》2020,54(5):1102-1106
Theoretical Foundations of Chemical Engineering - The development of a thermostable hydrophobic platinum catalyst is an important scientific and practical problem. The purpose of this work is to... 相似文献
68.
A. L. Rudenko V. V. Mishakin A. V. Gonchar K. V. Kurashkin A. E. Fomin 《Power Technology and Engineering (formerly Hydrotechnical Construction)》2020,53(6):687-689
At the hydroelectric unit No. 11 of the Nizhnekamsk hydroelectric power plant, the filling wedges of a rotor were investigated by ultrasound in the free st 相似文献
69.
The basic stages in the life cycle of a batch of complex engineering products are considered: design, production, operation, and disposal. A priori cost assessment for each stage is discussed. The cost aggregation in the consideration of multiple stages is analyzed. Requirements on the assessment are formulated. Methodological and implementation aspects of the assessment tools are outlined. The conclusion is that it is expedient to predict the costs on the basis of mathematical models of the product batch in an operational environment. The integration of multiple cost estimates is addressed. 相似文献
70.
Simonov M. Yu. Pertsev A. S. Shaimanov G. S. Simonov Yu. N. 《Metal Science and Heat Treatment》2020,61(9-10):601-609
Metal Science and Heat Treatment - The structure, the strength characteristics and the impact toughness at different temperatures up to –100°C of tubular billets from steel 35 are... 相似文献