全文获取类型
收费全文 | 207653篇 |
免费 | 2498篇 |
国内免费 | 575篇 |
专业分类
电工技术 | 3554篇 |
综合类 | 146篇 |
化学工业 | 32231篇 |
金属工艺 | 10334篇 |
机械仪表 | 7058篇 |
建筑科学 | 4025篇 |
矿业工程 | 2161篇 |
能源动力 | 4708篇 |
轻工业 | 13005篇 |
水利工程 | 2936篇 |
石油天然气 | 7733篇 |
武器工业 | 22篇 |
无线电 | 21676篇 |
一般工业技术 | 45617篇 |
冶金工业 | 34502篇 |
原子能技术 | 6625篇 |
自动化技术 | 14393篇 |
出版年
2021年 | 2115篇 |
2019年 | 2063篇 |
2018年 | 3763篇 |
2017年 | 3792篇 |
2016年 | 4067篇 |
2015年 | 2281篇 |
2014年 | 3857篇 |
2013年 | 8882篇 |
2012年 | 5764篇 |
2011年 | 7328篇 |
2010年 | 5923篇 |
2009年 | 6559篇 |
2008年 | 6699篇 |
2007年 | 6546篇 |
2006年 | 5624篇 |
2005年 | 5163篇 |
2004年 | 4665篇 |
2003年 | 4592篇 |
2002年 | 4403篇 |
2001年 | 4498篇 |
2000年 | 4215篇 |
1999年 | 4226篇 |
1998年 | 10210篇 |
1997年 | 7208篇 |
1996年 | 5525篇 |
1995年 | 4153篇 |
1994年 | 3616篇 |
1993年 | 3849篇 |
1992年 | 2997篇 |
1991年 | 3008篇 |
1990年 | 2903篇 |
1989年 | 2862篇 |
1988年 | 2874篇 |
1987年 | 2521篇 |
1986年 | 2582篇 |
1985年 | 2864篇 |
1984年 | 2695篇 |
1983年 | 2563篇 |
1982年 | 2304篇 |
1981年 | 2276篇 |
1980年 | 2347篇 |
1979年 | 2364篇 |
1978年 | 2384篇 |
1977年 | 2487篇 |
1976年 | 2876篇 |
1975年 | 2190篇 |
1974年 | 2073篇 |
1973年 | 2170篇 |
1972年 | 1941篇 |
1971年 | 1758篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
62.
Ramesh Shruthy Stephen Jancy Radhakrishnan Preetha 《International Journal of Food Science & Technology》2021,56(8):3991-3999
In this study, the cellulose nanoparticles (CNP) isolated from potato peel were used for reinforcement of polyvinyl alcohol (PVA)-based active packaging film. The above film was used to pack the raw prawns (Penaeus monodon) at −20 °C, and the colour change, protein content, TVB-N, TMA and microbial analysis were done at regular interval for prawns stored in CNP-PVA active packaging film. A significant difference was observed in the quality of prawns stored in potato CNP-PVA film compared with prawns packed and stored in polyethylene film. The newly designed active packaging with CNP and fennel seed oil enhanced the shelf life of prawns up to two months for both HOSO (head on shell on) prawn and PD (peeled and deveined) prawn. Hence, the study recommends the potato peel CNP-PVA film with fennel seed oil as better choice to extend the shelf life of the prawns during storage compared with polyethylene packaging. 相似文献
63.
64.
V. I. Zubkov O. V. Kucherova I. N. Yakovlev A. V. Solomonov 《Russian Microelectronics》2015,44(3):203-209
An automated system for integrated electrophysical and optical studies of semiconductor nanoheterostructures, which operates in a wide temperature range from 15 to 475 K, is designed. The setup is intended to measure the temperature and frequency admittance and electroluminescence spectra of light-emitting diode and laser chips formed on substrates of diameter up to 50.2 mm, and the distribution of parameters over the wafer. The setup includes the closed-cycle helium cryogenic station, LCR meter, and temperature controller. The characterization results of nanoheterostructures with InGaN/GaN multiple quantum wells, which are used for creating highly efficient white and blue light-emitting diodes, are presented. 相似文献
65.
I. N. Andronov Yu. I. Ryabkov N. P. Bogdanov N. A. Severova A. N. Danilov I. V. Churilina 《Russian Metallurgy (Metally)》2015,2015(10):778-784
The influence of the thermal cycling conditions on the thermal-cycling creep of a TN-1 alloy and the related irreversible deformations is studied. The conditions under which an anomalous increase in the irreversible deformations begins are determined. The structural mechanism of the irreversible deformations of an equiatomic alloy is shown to be analogous to the structural mechanism of metal creep at high temperatures: it predominantly has a dislocation character. It is proposed to use the effect of anomalous increase in the deformation of materials with reversible martensitic transformations for forming parts made of these materials at low temperatures. 相似文献
66.
67.
68.
V. A. Eremenko V. N. Karpov V. V. Timonin N. G. Barnov I. O. Shakhtorin 《Journal of Mining Science》2015,51(6):1113-1125
The authors have determined the causes of drop in performance of induced block caving using fans of blastholes 105 mm in diameter and single blastholes 250 mm in diameter, as well as the sources of increased drilling cost and expansion of start-up time of production blocks in Abakan underground mine. Alternatives of improvement in drilling efficiency under current conditions are discussed. 相似文献
69.
Sleptsov V. V. Kukushkin D. Yu. Kulikov S. N. Diteleva A. O. 《Russian Engineering Research》2021,41(5):416-418
Russian Engineering Research - Thin-film vacuum technology permits the creation of new electrode materials on the basis of a flexible carbon matrix with a highly developed surface. Supercapacitor... 相似文献
70.
D. Kherifi H. Belhouchet S. Ramesh K.Y. Sara Lee A. Kenzour S. Djoualah M.K.G. Abbas Y.H. Wong S. Ramesh 《Ceramics International》2021,47(12):16483-16490
In this work, the sintering behaviour of fluorapatite (FAp)–silicate composites prepared by mixing variable amounts of natural quartz (2.5 wt% to 20 wt%) and FAp was studied. The composites were pressureless sintered in air at temperatures from 1000 °C to 1350 °C. The effects of temperatures on the densification, phase formation, chemical bonding and Vickers hardness of the composites were evaluated. All the samples exhibited mixed phase, comprising FAp and francolite as the major constituents along with some minor phases of cristobalite, wollastonite, dicalcium silicate and/or whitlockite dependent on the quartz content and sintering temperature. The composite containing 2.5 wt% quartz exhibited the best sintering properties. The highest bulk density of 3 g/cm3 and a Vickers hardness of >4.2 GPa were obtained for the 2.5 wt% quartz–FAp composite when sintered at 1100 °C. The addition of quartz was found to alter the microstructure of the composites, where it exhibited a rod-like morphology when sintered at 1000 °C and a regular rounded grain structure when sintered at 1350 °C. A wetted grain surface was observed for composites containing high quartz content and was believed to be associated with a transient liquid phase sintering. 相似文献