全文获取类型
收费全文 | 1798篇 |
免费 | 88篇 |
国内免费 | 51篇 |
专业分类
电工技术 | 205篇 |
综合类 | 111篇 |
化学工业 | 257篇 |
金属工艺 | 67篇 |
机械仪表 | 215篇 |
建筑科学 | 53篇 |
矿业工程 | 265篇 |
能源动力 | 113篇 |
轻工业 | 147篇 |
水利工程 | 16篇 |
石油天然气 | 117篇 |
武器工业 | 4篇 |
无线电 | 17篇 |
一般工业技术 | 94篇 |
冶金工业 | 168篇 |
原子能技术 | 12篇 |
自动化技术 | 76篇 |
出版年
2024年 | 1篇 |
2023年 | 9篇 |
2022年 | 28篇 |
2021年 | 39篇 |
2020年 | 39篇 |
2019年 | 17篇 |
2018年 | 25篇 |
2017年 | 23篇 |
2016年 | 37篇 |
2015年 | 44篇 |
2014年 | 115篇 |
2013年 | 112篇 |
2012年 | 140篇 |
2011年 | 146篇 |
2010年 | 109篇 |
2009年 | 108篇 |
2008年 | 87篇 |
2007年 | 126篇 |
2006年 | 114篇 |
2005年 | 115篇 |
2004年 | 80篇 |
2003年 | 88篇 |
2002年 | 61篇 |
2001年 | 63篇 |
2000年 | 49篇 |
1999年 | 40篇 |
1998年 | 20篇 |
1997年 | 31篇 |
1996年 | 13篇 |
1995年 | 13篇 |
1994年 | 12篇 |
1993年 | 4篇 |
1992年 | 10篇 |
1991年 | 2篇 |
1990年 | 4篇 |
1989年 | 6篇 |
1988年 | 3篇 |
1987年 | 2篇 |
1963年 | 1篇 |
1959年 | 1篇 |
排序方式: 共有1937条查询结果,搜索用时 453 毫秒
1.
Xi Zhao Hongyue Li Fangchao Cui Jinxiang Wang Shumin Yi Hongbo Mi Yanfang Lv Xuepeng Li Jianrong Li 《International Journal of Food Science & Technology》2022,57(7):4400-4410
Taking air freezing (AF) as the reference, the effects of four types of multi-compound freezing medium for cryogenic liquid quick-freezing (immersion freezing, IF) on the freezing rate, quality and myofibrillar protein (MP) denaturation of red drum (Sciaenops ocellatus) fillets during frozen storage (−18°C) from days 0 to 90 were studied. Samples were gathered on days 0, 15, 30, 45, 60 and 90 for analysis. The results showed that IF groups (IF-1: 20% ethanol, 30% propylene glycol, 10% sodium chloride aqueous solution; IF-2: 20% ethanol, 20% propylene glycol, 10% glycerol, 10% sodium chloride aqueous solution; IF-3: 20% ethanol, 20% propylene glycol, 10% polyethylene glycol, 10% sodium chloride aqueous solution; IF-4: 20% ethanol, 20% propylene glycol, 5% glycerol, 5% polyethylene glycol, 10% sodium chloride aqueous solution) significantly shortened the time to cross the formation zone of maximum ice crystals while the freezing rate was 6.13 times higher than the AF group after adding 30% propylene glycol as the freezing medium. Furthermore, compared with the AF group, the IF groups significantly reduced losses in the water-holding capacity, the myofibrillar fragmentation index, microstructure damage, texture characteristics, drip loss and water migration (P < 0.05). In addition, the MP of IF groups had higher maximum transition temperatures (Tmax1 and Tmax2), total sulfhydryl content, Ca2+-ATPase activity and relative α-helix content compared with the AF group. In conclusion, IF could significantly increase the freezing rate of red drum fillets, and slow down quality deterioration and denaturation of MP during frozen storage for 90 days (−18°C). In particular, IF-2 (20% ethanol, 20% propylene glycol, 10% glycerol, 10% sodium chloride aqueous solution) was found to be more suitable for the immersion freezing of marine fish among the four multi-compound freezing medium. 相似文献
2.
《Advanced Powder Technology》2022,33(12):103872
We investigate the transition evolution from the initial state with the random packing of the particles to the stable state in which successive avalanches exhibit consistent characteristics under the slumping regime. It is found that there exist three distinct stages in the transition evolution, considering the change of the volume fraction. The coordination number is almost unchanged during the transition evolution, which indicates the particle contact form is consistent in the three stages. The pause phenomena are discovered in some avalanches, and the probability of pause occurrence increases continuously in the three consecutive stages. We also explore the distribution of particles in the passive layer at the stable state. The particles in the middle region of the passive layer have the closest packing status, and the deeper the region is located, the later it reaches the stable state. 相似文献
3.
4.
5.
This paper performs a comprehensive analysis and calibration on the geometric error of the ultra-precision drum roll lathe with dual-spindle symmetrical structure and cross slider layout. Firstly, the volumetric error model which contains all geometric errors of the dual-spindle ultra-precision drum roll lathe (DSUPDRL) is developed based on the combination of the homogenous transfer matrix (HTM) and multi-body system (MBS) theory. Secondly, sensitivity analysis for the volumetric error model is conducted to identify the sensitive geometric error components of the DSUPDRL using an improved Sobol method based on the quasi-Monte Carlo algorithm. The result of sensitivity analysis laid the foundation for the subsequent geometric error calibration. Then, some sensitive error components along the X and Z directions are calibrated using a laser interferometer and a pair of inductance displacement probes. Besides the volumetric error model, the concentricity error caused by dual-spindle symmetrical structure is proposed and calibrated by the on-machine measurement using a classic reversal method. Finally, a large-scale roller mold with a diameter of 250 mm and a length of 600 mm is machined using the DSUPDRL after calibration. The experimental result shows that 1.4 μm/600 mm generatrix accuracy is obtained, which validate the effectiveness of the geometric error analysis and calibration. 相似文献
6.
7.
8.
阐述了焦炭塔常见损伤模式及其发生机理、主要表征、影响因素及控制措施。针对具体检验案例,分析了缺陷产生原因,对检验人员及使用单位如何做好焦炭塔的检维修工作提出了建议。 相似文献
9.
10.
根据锅炉给水泵平衡部件的损坏情况,分析了平衡装置对多级泵长周期运行的影响,经过计算论证,提出了理论间隙在实际应用中的问题,并结合设备结构实际情况建议采用新型平衡鼓,即带凹槽的平衡鼓形式。 相似文献