全文获取类型
收费全文 | 198184篇 |
免费 | 21630篇 |
国内免费 | 13260篇 |
专业分类
电工技术 | 17042篇 |
技术理论 | 4篇 |
综合类 | 17371篇 |
化学工业 | 27082篇 |
金属工艺 | 12693篇 |
机械仪表 | 13797篇 |
建筑科学 | 16569篇 |
矿业工程 | 6999篇 |
能源动力 | 5856篇 |
轻工业 | 16098篇 |
水利工程 | 5197篇 |
石油天然气 | 9244篇 |
武器工业 | 2437篇 |
无线电 | 23685篇 |
一般工业技术 | 19379篇 |
冶金工业 | 8033篇 |
原子能技术 | 2508篇 |
自动化技术 | 29080篇 |
出版年
2024年 | 1049篇 |
2023年 | 3287篇 |
2022年 | 6735篇 |
2021年 | 9123篇 |
2020年 | 6776篇 |
2019年 | 5151篇 |
2018年 | 5731篇 |
2017年 | 6764篇 |
2016年 | 5870篇 |
2015年 | 8885篇 |
2014年 | 11217篇 |
2013年 | 13324篇 |
2012年 | 15687篇 |
2011年 | 16340篇 |
2010年 | 15196篇 |
2009年 | 14347篇 |
2008年 | 14447篇 |
2007年 | 13686篇 |
2006年 | 12417篇 |
2005年 | 9633篇 |
2004年 | 6786篇 |
2003年 | 5481篇 |
2002年 | 5255篇 |
2001年 | 4657篇 |
2000年 | 3765篇 |
1999年 | 2722篇 |
1998年 | 1651篇 |
1997年 | 1350篇 |
1996年 | 1245篇 |
1995年 | 1073篇 |
1994年 | 865篇 |
1993年 | 543篇 |
1992年 | 441篇 |
1991年 | 317篇 |
1990年 | 257篇 |
1989年 | 226篇 |
1988年 | 161篇 |
1987年 | 105篇 |
1986年 | 92篇 |
1985年 | 45篇 |
1984年 | 38篇 |
1983年 | 32篇 |
1982年 | 34篇 |
1981年 | 45篇 |
1980年 | 46篇 |
1979年 | 32篇 |
1977年 | 9篇 |
1976年 | 10篇 |
1959年 | 12篇 |
1951年 | 20篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
目的研究热风辅助射频(hot air-assisted radio frequency,HA-RF)干燥过程中维生素C随温度变化的降解动力学模型。方法在6.5 cm极板间距和60℃热风系统条件下进行HA-RF干燥,重点研究胡萝卜丁中维生素C在干燥过程中的降解动力学,包括脱氢抗坏血酸(dehydroascorbic acid,DHAA)和抗坏血酸(ascorbic acid,AA)。总维生素C含量采用2,4-硝基苯肼分光光度法测定,AA采用2,6-二氯吲哚酚滴定法测定。结果HA-RF干燥过程中维生素C的降解规律符合一级可逆模型,其降解活化能为40.54 kJ/mol。DHAA活化能为35.83 kJ/mol,表明DHAA的稳定性低于AA。结论本研究使用的干燥温度为62.5~77.5℃,较高的干燥温度下维生素C降解速率较高,较低处理温度下的降解过程具有更好的模型适应度(R2>0.98)。 相似文献
42.
The fracture behaviour and morphologies of high-strength boron steel were investigated at different temperatures at a constant strain rate of 0.1 s-1 based on isothermal tensile tests. Fracture mechanisms were also analyzed based on the relationship between microstructure transformation and continuous cooling transformation(CCT) curves. It is found that 1) fractures of the investigated steel at high temperatures are dimple fractures; 2) the deformation of high-strength boron steel at high temperatures accelerates diffusion transformations; thus, to obtain full martensite, a higher cooling rate is needed; and 3) the investigated steel has the best plasticity when the deformation temperature is 750 °C. 相似文献
43.
A contact layer element for large deformations 总被引:1,自引:0,他引:1
44.
Lü Qing Xu Bin Yu Yang Zhan Wei Zhao Yu Zheng Jun Ji Jian 《Bulletin of Engineering Geology and the Environment》2021,80(8):6513-6525
Bulletin of Engineering Geology and the Environment - Many uncertainties exist in pile-stabilized slopes which make their design substantially complicated. In this paper, a first-order reliability... 相似文献
45.
46.
王玮 《上海第二工业大学学报》2015,(2):173-176
从探讨郭沫若的生平背景入手,介绍了他的翻译成就,并对郭沫若的翻译理论和翻译思想做出了初步的剖析。郭沫若的翻译实践主要可以从郭沫若译著《英诗译稿》和《浮士德》窥见一斑,而郭沫若的翻译理论则可从罗新璋所著的《翻译论集》和方克平所著的《溯洄从美:从批判理论到文学翻译》中探出精髓。对郭沫若翻译实践和理论的研究可以发现郭沫若的"创作论"的地位固然不可撼动,但其中对于创作的维度却并没有提出很好的标准。 相似文献
47.
Combination of heat treatment and chitosan coating to improve postharvest quality of wolfberry (Lycium barbarum)
下载免费PDF全文
![点击此处可从《International Journal of Food Science & Technology》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Zhaojun Ban Wenwen Wei Xiangzheng Yang Jianhua Feng Junfeng Guan Li Li 《International Journal of Food Science & Technology》2015,50(4):1019-1025
The synergistic application of hot water dip at 42 °C for 30 min and 1% chitosan coating on differentiation in postharvest quality traits, microstructure as well as microbiological evolution of wolfberry fruits was investigated. Fresh wolfberry fruits were stored at 2 ± 0.5 °C and 90% relative humidity (RH) for 28 days. Results indicated the combination of prestorage heat treatment and chitosan coating maintained higher levels of ascorbic acid, total phenolic contents and antioxidant capacity as well as lower decay, compared with untreated wolfberry fruits. The possible mechanism was that the heat treatment almost sealed open stomata to limit the sites of pathogen penetration into fruits independently, followed by the biofilm formed by chitosan which controlled secondary infections as well as slowed changes in fruit respiration and metabolic activity in wolfberries. The synergistically treated fruit also exhibited a higher acceptability obtained by sensory analysis after cold storage. In this sense, the integrated application of heat treatment and chitosan coating could be regarded as an effective strategy to extend storage life and maintain the postharvest quality of wolfberry fruits. 相似文献
48.
Thermally conductive polymers offer new possibilities for the heat dissipation in electric and electronic components, for example, by a three‐dimensional shaping of the heat sinks. To face safety regulations, improved fire performance of those components is required. In contrast to unfilled polymers, those materials exhibit an entirely different thermal behavior. To investigate the flammability, a phosphorus flame retardant was incorporated into thermally conductive composites of polyamide 6 and hexagonal boron nitride. The flame retardant decreased the thermal conductivity only slightly. However, the burning behavior changed significantly, due to a different heat propagation, which was investigated using a thermographic camera. An optimum content of hexagonal boron nitride for a sufficient thermal conductivity and fire performance was found between 20 and 30 vol%. The improvement of the fire performance was due to a faster heat release out of the pyrolysis zone and an earlier decomposition of the flame retardant. For higher contents of hexagonal boron nitride, the heat was spread faster within the part, promoting an earlier ignition and increasing the decomposition rate of the flame retardant. 相似文献
49.
Wei Mengnan Ban Boyuan Li Jingwei Sun Jifei Li Feifei Jiang Xuesong Chen Jian 《SILICON》2020,12(2):327-338
Silicon - A novel green cationic surfactant Poly (propylene glycol) bis (2-aminopropyl ether) (PEA) with multiple amine groups was utilized as a collector for flotation separation of quartz from... 相似文献
50.
Cerebral microbleeds and cognitive decline in a hemodialysis patient: Case report and review of literature
下载免费PDF全文
![点击此处可从《Hemodialysis international. International Symposium on Home Hemodialysis》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Lin Li Mark Fisher Wei‐Ling Lau Hamid Moradi Alexander Cheung Gaby Thai Jason Handwerker Kamyar Kalantar‐Zadeh 《Hemodialysis international. International Symposium on Home Hemodialysis》2015,19(3):E1-E7
Cerebral microbleeds (CMBs) are small hemosiderin deposits indicative of prior cerebral microscopic hemorrhage and previously thought to be clinically silent. Recent population‐based cross‐sectional studies and prospective longitudinal cohort studies have revealed association between CMB and cognitive dysfunction. In the general population, CMBs are associated with age, hypertension, and cerebral amyloid angiopathy. In the chronic kidney disease (CKD) population, diminished estimated glomerular filtration rate has been found to be an independent risk factor for CMB, raising the possibility that a uremic milieu may predispose to microbleeds. In the end‐stage renal disease (ESRD) population on hemodialysis, the incidence of microbleeds is significantly higher compared with a control group without history of CKD or stroke. We present an ESRD patient on chronic hemodialysis with a history of gradual cognitive decline and progressive CMBs. Through this case and literature review, we illustrate the need to develop detection and prediction models to treat this frequent development in ESRD patients. 相似文献