全文获取类型
收费全文 | 308634篇 |
免费 | 3377篇 |
国内免费 | 1113篇 |
专业分类
电工技术 | 5365篇 |
综合类 | 2422篇 |
化学工业 | 43483篇 |
金属工艺 | 17248篇 |
机械仪表 | 13240篇 |
建筑科学 | 7174篇 |
矿业工程 | 2086篇 |
能源动力 | 6213篇 |
轻工业 | 19652篇 |
水利工程 | 3611篇 |
石油天然气 | 4784篇 |
武器工业 | 2篇 |
无线电 | 33687篇 |
一般工业技术 | 63231篇 |
冶金工业 | 40429篇 |
原子能技术 | 5448篇 |
自动化技术 | 45049篇 |
出版年
2021年 | 1217篇 |
2019年 | 1249篇 |
2018年 | 21909篇 |
2017年 | 21580篇 |
2016年 | 14750篇 |
2015年 | 2560篇 |
2014年 | 2995篇 |
2013年 | 7992篇 |
2012年 | 9363篇 |
2011年 | 21597篇 |
2010年 | 18951篇 |
2009年 | 16658篇 |
2008年 | 17265篇 |
2007年 | 19735篇 |
2006年 | 5176篇 |
2005年 | 9033篇 |
2004年 | 7148篇 |
2003年 | 6521篇 |
2002年 | 4910篇 |
2001年 | 4014篇 |
2000年 | 3844篇 |
1999年 | 3866篇 |
1998年 | 10220篇 |
1997年 | 7210篇 |
1996年 | 5473篇 |
1995年 | 4247篇 |
1994年 | 3618篇 |
1993年 | 3567篇 |
1992年 | 2598篇 |
1991年 | 2560篇 |
1990年 | 2384篇 |
1989年 | 2396篇 |
1988年 | 2339篇 |
1987年 | 2087篇 |
1986年 | 2037篇 |
1985年 | 2340篇 |
1984年 | 2158篇 |
1983年 | 1982篇 |
1982年 | 1856篇 |
1981年 | 1925篇 |
1980年 | 1772篇 |
1979年 | 1795篇 |
1978年 | 1754篇 |
1977年 | 2086篇 |
1976年 | 2661篇 |
1975年 | 1542篇 |
1974年 | 1535篇 |
1973年 | 1591篇 |
1972年 | 1338篇 |
1971年 | 1245篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
Venhryn Yu. I. Popovych I. D. Serednytski A. S. Kolomys O. F. Luchechko A. P. Strelchuk V. V. 《Journal of Materials Science: Materials in Electronics》2022,33(14):10715-10722
Journal of Materials Science: Materials in Electronics - The ZnO and TiO2 nanopowders have been prepared by means of the pulsed laser reactive ablation of metallic (Zn, Ti) targets. The Structural,... 相似文献
2.
Kalinina E. V. Kudoyarov M. F. Nikitina I. P. Dementyeva E. V. Zabrodskii V. V. 《Semiconductors》2022,56(3):184-188
Semiconductors - The results of the effect of irradiation with Ar ions on the structural, electrophysical, and optical characteristics of ultraviolet Cr/4H-SiC photodetectors in the spectral range... 相似文献
3.
Yusupov M. R. Umurakova K. E. Gantsev A. V. Akhmetov A. F. 《Chemistry and Technology of Fuels and Oils》2022,58(3):449-453
Chemistry and Technology of Fuels and Oils - This article considers the alternatives for treatment of the raffinate produced at a unit for the extraction of benzene-containing fractions and the... 相似文献
4.
Khaled Al-Farhany Mohammed A. Alomari Ahmed Al-Saadi Ali Chamkha Hakan F. Öztop Wael Al-Kouz 《亚洲传热研究》2022,51(2):1691-1710
In the current work, numerical simulations are achieved to study the properties and the characteristics of fluid flow and heat transfer of (Cu–water) nanofluid under the magnetohydrodynamic effects in a horizontal rectangular canal with an open trapezoidal enclosure and an elliptical obstacle. The cavity lower wall is grooved and represents the heat source while the obstacle represents a stationary cold wall. On the other hand, the rest of the walls are considered adiabatic. The governing equations for this investigation are formulated, nondimensionalized, and then solved by Galerkin finite element approach. The numerical findings were examined across a wide range of Richardson number (0.1 ≤ Ri ≤ 10), Reynolds number (1 ≤ Re ≤ 125), Hartmann number (0 ≤ Ha ≤ 100), and volume fraction of nanofluid (0 ≤ φ ≤ 0.05). The current study's findings demonstrate that the flow strength increases inversely as the Reynolds number rises, which pushes the isotherms down to the lower part of the trapezoidal cavity. The Nuavg rises as the Ri rise, the maximum Nuavg = 10.345 at Ri = 10, Re = 50, ϕ = 0.05, and Ha = 0; however, it reduces with increasing Hartmann number. Also, it increase by increasing ϕ, at Ri = 10, the Nuavg increased by 8.44% when the volume fraction of nanofluid increased from (ϕ = 0–0.05). 相似文献
5.
Kulikova M. V. Krylova A. Yu. Zhagfarov F. G. Krysanova K. O. 《Chemistry and Technology of Fuels and Oils》2022,58(2):327-332
Chemistry and Technology of Fuels and Oils - The review examines biomass of animal origin in terms of a potential renewable raw material for obtaining CO2-neutral fuel unaffecting the carbon... 相似文献
6.
Rukomoynikov A. A. Yuminov I. P. Khamitov A. I. Garifullin I. Sh. Agliullin Ya. F. 《Russian Engineering Research》2022,42(9):916-919
Russian Engineering Research - Systems are considered for the dehydration of petroleum so as to separate water–petroleum emulsions. In particular, the low-temperature microwave (UHF)... 相似文献
7.
Kravchenko V. F. Konovalov Ya. Yu. 《Journal of Communications Technology and Electronics》2022,67(8):952-964
Journal of Communications Technology and Electronics - A new design of wavelets based on the convolution of a compactly supported function with a rectangular pulse is proposed and theoretically... 相似文献
8.
Journal of Communications Technology and Electronics - A statistical study of the effectiveness of the non-threshold search procedure for a noise-like phase-shift keyed signal by the delay time is... 相似文献
9.
10.
Yang Hu Stephanie M. Sjoberg Chunpen Chen Amber L. Hauvermale Craig F. Morris Stephen R. Delwiche Ashley E. Cannon Camille M. Steber Zhiwu Zhang 《Comprehensive Reviews in Food Science and Food Safety》2022,21(3):2105-2117
This review examines the application, limitations, and potential alternatives to the Hagberg–Perten falling number (FN) method used in the global wheat industry for detecting the risk of poor end-product quality mainly due to starch degradation by the enzyme α-amylase. By viscometry, the FN test indirectly detects the presence of α-amylase, the primary enzyme that digests starch. Elevated α-amylase results in low FN and damages wheat product quality resulting in cakes that fall, and sticky bread and noodles. Low FN can occur from preharvest sprouting (PHS) and late maturity α-amylase (LMA). Moist or rainy conditions before harvest cause PHS on the mother plant. Continuously cool or fluctuating temperatures during the grain filling stage cause LMA. Due to the expression of additional hydrolytic enzymes, PHS has a stronger negative impact than LMA. Wheat grain with low FN/high α-amylase results in serious losses for farmers, traders, millers, and bakers worldwide. Although blending of low FN grain with sound wheat may be used as a means of moving affected grain through the marketplace, care must be taken to avoid grain lots from falling below contract-specified FN. A large amount of sound wheat can be ruined if mixed with a small amount of sprouted wheat. The FN method is widely employed to detect α-amylase after harvest. However, it has several limitations, including sampling variability, high cost, labor intensiveness, the destructive nature of the test, and an inability to differentiate between LMA and PHS. Faster, cheaper, and more accurate alternatives could improve breeding for resistance to PHS and LMA and could preserve the value of wheat grain by avoiding inadvertent mixing of high- and low-FN grain by enabling testing at more stages of the value stream including at harvest, delivery, transport, storage, and milling. Alternatives to the FN method explored here include the Rapid Visco Analyzer, enzyme assays, immunoassays, near-infrared spectroscopy, and hyperspectral imaging. 相似文献