全文获取类型
收费全文 | 115754篇 |
免费 | 11490篇 |
国内免费 | 6198篇 |
专业分类
电工技术 | 8323篇 |
技术理论 | 8篇 |
综合类 | 8138篇 |
化学工业 | 17946篇 |
金属工艺 | 6848篇 |
机械仪表 | 7531篇 |
建筑科学 | 9071篇 |
矿业工程 | 4027篇 |
能源动力 | 3424篇 |
轻工业 | 8339篇 |
水利工程 | 2441篇 |
石油天然气 | 6809篇 |
武器工业 | 1381篇 |
无线电 | 13403篇 |
一般工业技术 | 12320篇 |
冶金工业 | 5659篇 |
原子能技术 | 1507篇 |
自动化技术 | 16267篇 |
出版年
2024年 | 611篇 |
2023年 | 1991篇 |
2022年 | 3960篇 |
2021年 | 5506篇 |
2020年 | 4008篇 |
2019年 | 3226篇 |
2018年 | 3636篇 |
2017年 | 4017篇 |
2016年 | 3596篇 |
2015年 | 5097篇 |
2014年 | 6316篇 |
2013年 | 7345篇 |
2012年 | 8410篇 |
2011年 | 8896篇 |
2010年 | 7977篇 |
2009年 | 7443篇 |
2008年 | 7236篇 |
2007年 | 6695篇 |
2006年 | 6585篇 |
2005年 | 5599篇 |
2004年 | 3609篇 |
2003年 | 2724篇 |
2002年 | 2564篇 |
2001年 | 2103篇 |
2000年 | 2217篇 |
1999年 | 2298篇 |
1998年 | 1659篇 |
1997年 | 1439篇 |
1996年 | 1406篇 |
1995年 | 1237篇 |
1994年 | 939篇 |
1993年 | 658篇 |
1992年 | 542篇 |
1991年 | 401篇 |
1990年 | 330篇 |
1989年 | 258篇 |
1988年 | 231篇 |
1987年 | 147篇 |
1986年 | 130篇 |
1985年 | 76篇 |
1984年 | 66篇 |
1983年 | 47篇 |
1982年 | 43篇 |
1981年 | 44篇 |
1980年 | 32篇 |
1979年 | 11篇 |
1978年 | 11篇 |
1977年 | 11篇 |
1976年 | 17篇 |
1959年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
71.
Qiang Xia Tao Feng Xiaowei Lou Ying Wang Yangying Sun Daodong Pan Jinxuan Cao 《International Journal of Food Science & Technology》2020,55(2):669-680
As a decisive attribute, flavour could be influenced by HP treatments through multiple physical and chemical pathways within the high pressure (HP)-assisted meat curing process. This investigation aimed to identify the major pathway influencing volatile flavour patterns of two representative vinasse-cured duck (VCD) products with HP treatments (150–300 MPa/15 min), including wet and dry types, by employing headspace fingerprinting as an untargeted approach. Results suggested that HP treatments greatly lowered moisture contents and increased Warner-Bratzler shear force and thiobarbituric acid reactive substances of the cured samples. According to multivariate models, the volatile flavour patterns of the HP-processed VCD could be clearly separated from the unprocessed samples, but the VCD pressurised at different intensities represented similar volatile fingerprinting, which was validated by e-nose analysis. The discriminant analysis (OPLS-DA) model outlined vinasse-derived ethanol, acetic acid, 3-methyl-1-butanol, 2-methyl-1-butanol, phenethyl alcohol and 2-methyl-3-octanone as the major discriminant aromas across the unpressurised and pressurised samples. 相似文献
72.
Ha ABDEL MAKSOUD Mk MAHFOUZ Mi SOLIMAN Mohamed G ELHARRIF M ABBASS Ma EL-BADRY 《Biocell》2020,44(1):111-115
Pyrethroid esters are widely used as insecticides worldwide. In this study, we aimed to evaluate the harmful
effect of deltamethrin on the male reproductive system through the assessment of reproductive hormones, inflammatory
markers, and testicular function. To achieve our aim, eighty male 7-9-week-old, Wistar rats were taken, weighed, and
divided into four experimental groups. The first group was kept as a control group, and the other three groups were
given deltamethrin orally at different concentrations (0.87, 8.7, and 17.4 mg/kg body weight) for nine weeks. The results
indicated that deltamethrin administration associated with a significant decrease in reproductive hormones, especially
FSH, LH, and significant elevation in the interleukin 2 (IL2), interleukin 6 (IL6), histamine, and cortisol levels. Also, the
significance of inhibition of sperm motility and viability, decreased testis weights, sperm count, and fructose in semen
were noted. These findings clarify the harmful effect of deltamethrin on the male reproductive system by producing a
significant alteration in reproductive hormones, inflammatory markers as well as testicular function. 相似文献
73.
74.
Hong Wei Li Li Ya‐Li Ma Ru‐Xue Liu Shuang‐Yan Meng Li‐Tong Niu Zhe Zhang Zhi‐Wang Yang 《火与材料》2019,43(7):868-879
Through the simple precipitation of palygorskite (PGS) by zinc borate (ZB) (to make PGS@ZB) and the decoration of PGS@ZB by dodecylamine (N), a novel organic‐inorganic@inorganic hybrid flame retardant of PGS@ZB‐N was prepared and was incorporated with ethylene vinyl acetate copolymer (EVA) to improve its flame retardance. The structure and morphology of PGS@ZB‐N were characterized by Fourier transform infrared (FTIR) spectroscopy, X‐ray diffraction (XRD), and scanning electron microscopy (SEM), and it was confirmed that the PGS@ZB‐N hybrid had been successfully prepared. The flame retardancy and burning behavior of EVA/PGS@ZB‐N/EG (EG = expandable graphite) composite were studied through thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL‐94 (by the vertical burning test), and cone calorimeter test (CCT) characterizations. The prepared EVA/PGS@ZB‐N/EG composite obtained an LOI value of 41.2% with the addition of 30 wt% PGS@ZB‐N/EG. It was found that EVA/PGS@ZB‐N/EG was protected through a gas phase and condensed phase alternating synergistic effect mechanism. 相似文献
75.
Hai Huang Haichao An Haibo Ma Shenyan Chen 《International journal for numerical methods in engineering》2019,117(3):291-315
This work presents an engineering method for optimizing structures made of bars, beams, plates, or a combination of those components. Corresponding problems involve both continuous (size) and discrete (topology) variables. Using a branched multipoint approximate function, which involves such mixed variables, a series of sequential approximate problems are constructed to make the primal problem explicit. To solve the approximate problems, genetic algorithm (GA) is utilized to optimize discrete variables, and when calculating individual fitness values in GA, a second-level approximate problem only involving retained continuous variables is built to optimize continuous variables. The solution to the second-level approximate problem can be easily obtained with dual methods. Structural analyses are only needed before improving the branched approximate functions in the iteration cycles. The method aims at optimal design of discrete structures consisting of bars, beams, plates, or other components. Numerical examples are given to illustrate its effectiveness, including frame topology optimization, layout optimization of stiffeners modeled with beams or shells, concurrent layout optimization of beam and shell components, and an application in a microsatellite structure. Optimization results show that the number of structural analyses is dramatically decreased when compared with pure GA while even comparable to pure sizing optimization. 相似文献
76.
随着掘进工作面自动化程度的提高,掘进巷道速度也在日益加快,而现有的顺槽皮带机机尾移动缓慢且移动时工作量大,需要两三人配合操作,存在一定的安全隐患。针对以上问题,研发可调偏迈步式胶带自移机尾,具有与悬挂二运皮带转载机搭接行程长,可以迈步式前进,自动调偏等功能,同时,可以降低工人的劳动强度,加快巷道掘进速度。 相似文献
77.
人像智能分析指的是对视频或录像中的人像进行结构化和可视化分析,对目标人物进行性别、年龄、发型等特征的智能识别,这项技术在视频侦查中有极高的应用价值。人像识别早期的算法是通过人工提取特征,通过学习低级视觉特征来针对不同属性进行分类学习,这种基于传统方法的模型表现常常不尽如人意。在计算机视觉领域,通过海量图像数据学习的神经网络比传统方法有更丰富的信息量和特征可以被提取。文章尝试通过深度学习技术训练神经网络模型对行人进行检测和识别,对于衣着不同的行人进行智能识别,具有更好的鲁棒性,提升了视频人像识别的准确率,拓展了人工智能技术在身份识别领域的应用。 相似文献
78.
Xuezhi Wang Xue Sun Zhelun Ma Tianbiao Yu Wanshan Wang 《Ceramics International》2018,44(18):22301-22307
Vitrified bond CBN grinding wheels are being widely used due to their superior performance. Also, advantages of vitrified grinding wheels are high elastic modulus, stable chemical property, and low thermal expansion coefficient. Brittleness and low strength are key factors restricting the development of vitrified bond CBN grinding wheels. In this paper, the sintering in a high magnetic field was innovatively introduced into the manufacturing of vitrified bond CBN grinding wheels, and the effects of sintering in a high magnetic field on properties on vitrified bond and vitrified CBN composites were systematically investigated. Vitrified bond was characterized using three-point bending, scanning electron microscopy, X-ray diffraction. It was observed that microstructure of vitrified bond could be changed, grain orientation could be controlled and average grain size could be decreased in a high magnetic field, while vitrified bond strength could be simultaneously improved. High quality vitrified bond could be obtained by appropriately adjusting the strength and direction of high magnetic field. Results demonstrated that vitrified bond properties were improved when the magnetic field strength was 6?T. In order to highlight the high magnetic field effect on the vitrified CBN composites, the ordinary CBN abrasives and nickel plated CBN abrasives were used respectively. Microstructures, bending strengths of vitrified CBN composites were compared in different high magnetic fields. When the magnetic field strength was appropriate (less than 6?T), the binding characteristic of vitrified bond CBN composites with nickel plated CBN abrasives was greatly improved. The highest bending strength value of vitrified CBN composites was 79.5?MPa in 6?T high magnetic field. 相似文献
79.
80.