全文获取类型
收费全文 | 227125篇 |
免费 | 17803篇 |
国内免费 | 8906篇 |
专业分类
电工技术 | 12373篇 |
技术理论 | 25篇 |
综合类 | 14268篇 |
化学工业 | 37745篇 |
金属工艺 | 13152篇 |
机械仪表 | 14608篇 |
建筑科学 | 17515篇 |
矿业工程 | 7442篇 |
能源动力 | 6430篇 |
轻工业 | 13611篇 |
水利工程 | 3623篇 |
石油天然气 | 16556篇 |
武器工业 | 1673篇 |
无线电 | 25049篇 |
一般工业技术 | 27103篇 |
冶金工业 | 12559篇 |
原子能技术 | 2266篇 |
自动化技术 | 27836篇 |
出版年
2024年 | 413篇 |
2023年 | 3612篇 |
2022年 | 5268篇 |
2021年 | 8593篇 |
2020年 | 6960篇 |
2019年 | 5902篇 |
2018年 | 6638篇 |
2017年 | 7492篇 |
2016年 | 6706篇 |
2015年 | 8911篇 |
2014年 | 11326篇 |
2013年 | 13368篇 |
2012年 | 14403篇 |
2011年 | 15621篇 |
2010年 | 13570篇 |
2009年 | 12828篇 |
2008年 | 12526篇 |
2007年 | 12005篇 |
2006年 | 12483篇 |
2005年 | 10852篇 |
2004年 | 7335篇 |
2003年 | 6289篇 |
2002年 | 5498篇 |
2001年 | 4904篇 |
2000年 | 5406篇 |
1999年 | 6414篇 |
1998年 | 5381篇 |
1997年 | 4397篇 |
1996年 | 4122篇 |
1995年 | 3491篇 |
1994年 | 2796篇 |
1993年 | 1945篇 |
1992年 | 1524篇 |
1991年 | 1203篇 |
1990年 | 923篇 |
1989年 | 723篇 |
1988年 | 528篇 |
1987年 | 324篇 |
1986年 | 264篇 |
1985年 | 188篇 |
1984年 | 130篇 |
1983年 | 98篇 |
1982年 | 119篇 |
1981年 | 98篇 |
1980年 | 70篇 |
1979年 | 36篇 |
1978年 | 26篇 |
1977年 | 20篇 |
1976年 | 35篇 |
1973年 | 13篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
92.
Zhang Nan Zhao Man Liu Guangfa Wang Jiaoyang Chen Yunzhi Zhang Zhengjian 《Journal of Materials Science》2022,57(19):8687-8700
Journal of Materials Science - A green modification method for effectively enhancing toughness of PLA was established. Herein, alkaline lignin (LG) was firstly alkylated with dodecane, and then... 相似文献
94.
Minghui Gu Yanchao Wei Yang Jiao Dequan Zhang Yongfeng Liu 《International Journal of Food Science & Technology》2022,57(6):3532-3543
To investigate the inner mechanisms of meat quality differences between high-quality (HQ) and low-quality (LQ), a comparative quantitative study between longissimus thoracis and external intercostals of goat muscle was performed from proteome to phosphorylated proteome using RP-HPLC in combination with the ‘isobaric tag’ for relative and absolute quantitation (iTRAQ) labelling strategy. Altogether, 1441 proteins were identified in our study, of which 673 were phosphoproteins, and a total of twenty were common differentially expressed proteins. Myosin, carbonic anhydrase, and phosphoglucomutase could be used as proteins marker for HQ and LQ meat. Bioinformatics analysis showed that these proteins exhibited different rates for glycolysis and oxidative phosphorylation reaction, thus causing the different pH and NADH change rates, and resulting in better colour, tenderness, and water retention in HQ meat. The release of Ca2+ and adenosine triphosphate changed the meat quality through calcium signalling. Our finding provides a comprehensive view of proteome changes and their phosphorylation levels in goat muscle, involved in producing meats of different muscle parts. It also gives a better understanding of the regulation of protein on various biological processes that determine the final meat quality attributes. 相似文献
95.
Ziqian He Na Deng Bisheng Zheng Tong Li Rui Hai Liu Ling Yuan Wenzhi Li 《International Journal of Food Science & Technology》2022,57(7):4268-4276
The changes in polyphenol fractions after in vitro fermentation of apple peel polyphenol (APP) by gut microbiota as well as the effects of APP on the growth, pH value, short-chain fatty acids (SCFAs) production and intestinal flora composition of gut microbiota fermentation were firstly explored in this study. The relative abundance of Lactobacillus in the APP group was 49.55% with an increment of 49.40% compared with the blank group, while that of Bifidobacterium was 13.32%. Moreover, the flora produced 37.093 ± 0.478 mM of SCFAs including acetic acid, propionic acid, butyric acid and valeric acid during the process of fermentation, thus reduced the environmental pH value. In addition, polyphenol fractions in APP were altered by gut microbiota fermentation to some extent, for example, glycosides were hydrolysed to aglycones. These findings suggested APP as a potential prebiotic agent to alleviate the disorder of intestinal flora. 相似文献
96.
2021年9月16日,四川省泸县发生6.0级地震,对当地的文化遗产造成了不同程度的损坏。为掌握文化遗产在此次地震中的破坏情况,对古建筑、古桥、渡槽、摩崖造像、古遗址以及可移动文物进行震害调查,分析破坏原因,提出不同文化遗产的震害等级,并统计其在此次地震中破坏占比。研究结果表明:古建筑中木结构的震害较轻,砖木结构和石木结构的损伤较为严重,表现为墙体开裂、倾斜、倒塌和屋面损毁等破坏;古桥的桥面板产生裂缝和起壳,桥头堡基石发生移位;摩崖造像发生开裂、石像脱落,部分岩石发生坠落;古遗址的原有缝隙增大,石砌墙歪闪或倾斜;可移动文物与陈列台连接的金属卡件在地震下崩落。根据震害调查结果,将文化遗产的震害划分为4个等级,并对古建筑的维修与加固、摩崖造像的一体化监测、古桥的维护与应急抢险、可移动文物的隔震保护提出几点建议,为我国文化遗产的抗震保护提供参考。 相似文献
97.
98.
99.
Qing Li Jun Wang Jie Ma Meng Ni Fan Yang Peng Liu Kuo Yang Lee Hsing-I Hsiang Deyuan Shen Dingyuan Tang 《Journal of the American Ceramic Society》2022,105(5):3375-3381
High-efficiency Yb:Y2O3 laser ceramics were fabricated using the vacuum-sintering plus hot isostatic pressing (HIP) without sintering additives. High-purity well-dispersed nanocrystalline Yb:Y2O3 powder was synthesized using a modified co-precipitation method in-house. The green bodies were first vacuum sintered at a temperature as low as 1430°C and then HIPed at 1450°C. Finally, the samples were air annealed at 800°C for 10 h. Although no sintering aids were used, full density of the samples with excellent optical homogeneity and an inline transmission of 80% at 400 nm could be obtained. Moreover, photodarkening phenomenon was not detected in the ceramics. Preliminary laser experiment with the fabricated ceramics in a two-mirror cavity has demonstrated 32 W continuous-wave (CW) output at ∼1077 nm with an optical-to-optical conversion efficiency of 58.2%. To the best of our knowledge, this is so far the highest CW output power and optical-to-optical conversion efficiency achieved with the Yb3+-doped sesquioxide ceramics in a simple two-mirror cavity. 相似文献
100.
Fengjun Yin Xiaohui Yang Lei Zheng Ling Fang Sha Wang Hong Liu 《American Institute of Chemical Engineers》2022,68(6):e17669
Acid–base transport is integral to many important interfacial reactions in various fields of chemistry, but its theoretical foundation is lacked. Herein, a common acid–base transport model is established owing to the success in deriving buffer transport equations. This model is applicable to most buffer systems by flexibly integrating the transport equations in terms of buffer components, and is verified through the model relationships of buffer transport limiting current by using hydrogen evolution reaction experiments. Based on model calculations, two diagram approaches are proposed to depict the dynamic pH response and aid buffer operation optimizations. The model and methods allow us to quantify the rate-limiting effect of acid–base transport on interfacial reactions and to precisely control the effect through medium regulations. Furthermore, the model has laid the foundation of dynamic pH effect on species transformation and process mechanism, which can be of wide interest in the chemistry encompassing interfacial reactions. 相似文献