全文获取类型
收费全文 | 57631篇 |
免费 | 5923篇 |
国内免费 | 2833篇 |
专业分类
电工技术 | 3702篇 |
技术理论 | 4篇 |
综合类 | 3878篇 |
化学工业 | 9028篇 |
金属工艺 | 3684篇 |
机械仪表 | 4082篇 |
建筑科学 | 4469篇 |
矿业工程 | 1841篇 |
能源动力 | 1840篇 |
轻工业 | 4174篇 |
水利工程 | 1253篇 |
石油天然气 | 3031篇 |
武器工业 | 594篇 |
无线电 | 6574篇 |
一般工业技术 | 6810篇 |
冶金工业 | 2805篇 |
原子能技术 | 838篇 |
自动化技术 | 7780篇 |
出版年
2024年 | 140篇 |
2023年 | 965篇 |
2022年 | 1628篇 |
2021年 | 2451篇 |
2020年 | 1895篇 |
2019年 | 1643篇 |
2018年 | 1841篇 |
2017年 | 1946篇 |
2016年 | 1826篇 |
2015年 | 2465篇 |
2014年 | 3084篇 |
2013年 | 3635篇 |
2012年 | 4191篇 |
2011年 | 4385篇 |
2010年 | 3833篇 |
2009年 | 3686篇 |
2008年 | 3508篇 |
2007年 | 3255篇 |
2006年 | 3121篇 |
2005年 | 2620篇 |
2004年 | 1953篇 |
2003年 | 1774篇 |
2002年 | 1838篇 |
2001年 | 1600篇 |
2000年 | 1253篇 |
1999年 | 1266篇 |
1998年 | 851篇 |
1997年 | 716篇 |
1996年 | 650篇 |
1995年 | 563篇 |
1994年 | 420篇 |
1993年 | 346篇 |
1992年 | 267篇 |
1991年 | 185篇 |
1990年 | 144篇 |
1989年 | 97篇 |
1988年 | 105篇 |
1987年 | 46篇 |
1986年 | 60篇 |
1985年 | 26篇 |
1984年 | 22篇 |
1983年 | 12篇 |
1982年 | 14篇 |
1981年 | 7篇 |
1980年 | 7篇 |
1979年 | 11篇 |
1977年 | 7篇 |
1975年 | 5篇 |
1970年 | 6篇 |
1951年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
41.
Shilin Du Yichen Dong Feiqiang Guo Beile Tian Songbo Mao Lin Qian Chengyun Xin 《International Journal of Hydrogen Energy》2021,46(27):14138-14147
The potential of using high metals containing coal gangue and lignite to prepare high-activity coal char-based catalysts is investigated for effective biomass tar decomposition. Loose structure and rough surface are formed for these char-based catalysts with heterogeneous distribution of a large number of inorganic particles. In the biomass tar decomposition, the performance of the coal char-based catalysts is significantly influenced by the content of the metals in the raw materials and coal gangue char (GC) with the ash content as high as 50.80% exhibits the highest activity in this work. A high biomass tar conversion efficiency of 93.5% is achieved at 800 °C along with a significant increase in the fuel gas product. During the five-time consecutive tests, the catalytic performance of GC increases a little at the second or third times reuse and remains relatively stable, showing the remarkable stability of the catalyst in biomass tar decomposition applications. 相似文献
42.
根据水泥烧成热耗的组成,降低高温设备表面散热是降低水泥烧成热耗的重要途径之一,而减少高温窑炉墙壁的热传导可有效降低设备的表面散热。本文在介绍无机内保温涂层隔热原理的基础上,对保温涂层的应用效果进行了对比研究,通过在传统耐火隔热材料的基础上增加新型无机内保温涂层,可有效降低高温设备外表面温度,减少水泥生产中的散热损失,达到节能降耗的目的。 相似文献
43.
Dong Liu Xia Ke Zhong-Ce Hu Yu-Guo Zheng 《Journal of Bioscience and Bioengineering》2021,131(5):518-524
44.
Yuanzhi Jiang Yangyang Shi Rui Li Feng Hang Jianxin Zhao Hao Zhang Wei Chen 《International Journal of Food Science & Technology》2021,56(9):4690-4699
Lactobacillus plantarum proliferates inefficiently in milk, mainly because of its lack of cell envelope proteases and its inability to hydrolyse proteins in milk. Our previous study showed that this strain could grow well in milk with the addition of oat and malt extracts. To investigate the usage and preference for polypeptides and oligopeptides for this strain, sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), o-phthaldialdehyde (OPA), high-performance liquid chromatography (HPLC), plate counting and other methods were used in this study. The results showed that proteins in fermented milk cannot be absorbed and utilised by L. plantarum, whereas polypeptides and oligopeptides provide available nitrogen sources for their growth. Short-chain peptides were more conducive to absorption and utilisation than long-chain peptides. In particular, peptides with molecular weights in the range of 200–1400 Da in the oat extract and 100–700 Da in the malt extract were preferentially absorbed and utilised. 相似文献
45.
Xu Wang Yujie Zhong Qian Sun Dongqing Qi Fuxue Yan Quangang Xian Dong Wang Kui Du Jingyang Wang 《Journal of the American Ceramic Society》2019,102(4):2176-2186
The microstructure evolution and growth behavior of the Al2O3/Y3Al5O12(YAG)/ZrO2 ternary eutectic ceramics during directional solidification were well investigated. During directional solidification of the Al2O3/YAG/ZrO2 ternary eutectic ceramics, {} Al2O3 paralleled with {001}ZrO2 while they did not parallel with {001}YAG at the same time in the competitive growth stage. All of the interfaces parallel to each other finally. The area percentage of the Al2O3/ZrO2 and YAG/ZrO2 interfaces are 40.4 ± 0.2% and 30.8 ± 0.1%, respectively, higher than that of the Al2O3/YAG (28.8 ± 0.2%). The content of Al2O3 and YAG phases are 39.9% and 41.1%, respectively, almost double of that of ZrO2. The interfaces of Al2O3/ZrO2 and YAG/ZrO2 are shorter and more dispersed than that of the Al2O3/YAG. It was found that the interfacial energy of Al2O3/ZrO2 and YAG/ZrO2 interfaces are lower than that of Al2O3/YAG. It can be concluded that interfacial energy plays a decisive role in affecting the crystallographic orientation and interfaces distribution in the Al2O3/YAG/ZrO2 eutectic since the interfaces of Al2O3/ZrO2 and YAG/ZrO2 with lower interfacial energy can be formed more easily during directional solidification. Therefore, the contents of Al2O3/ZrO2 and YAG/ZrO2 interfaces are higher. This study can provide theoretical guidance for interface design of multi-phase materials. 相似文献
46.
In this study, 30 subjects were exposed to different combinations of air temperature (Ta: 24, 27, and 30°C) and CO2 level (8000, 10 000, and 12 000 ppm) in a high-humidity (RH: 85%) underground climate chamber. Subjective assessments, physiological responses, and cognitive performance were investigated. The results showed that as compared with exposure to Ta = 24°C, exposure to 30°C at all CO2 levels caused subjects to feel uncomfortably warm and experience stronger odor intensity, while increased mental effort and greater intensity of acute health symptoms were reported. However, no significant effects of Ta on task performance or physiological responses were found. This indicated that subjects had to exert more effort to maintain their performance in an uncomfortably warm environment. Increasing CO2 from 8000 to 12 000 ppm at all Ta caused subjects to report higher rates of headache, fatigue, agitation, and feeling depressed, although the results were statistically significant only at 24 and 27°C. The text typing performance and systolic blood pressure (SBP) decreased significantly at this exposure, whereas diastolic blood pressure (DBP) and thermal discomfort increased significantly. These effects suggest higher arousal/stress. No significant interaction effect of Ta and CO2 concentration on human responses was identified. 相似文献
47.
Chen Jianxin Deng Hongmei Zheng Dongliang Pan Yanlin Si Shufang Zhang Yuemin Yang Pingxiong Chu Junhao 《Journal of Materials Science: Materials in Electronics》2021,32(8):10151-10159
Journal of Materials Science: Materials in Electronics - The composite materials in the form of (1-x)BaTiO3-xSrFe0.5Nb0.5O3((1-x)BT-xSFN) are synthesized via the solid-state reaction route.... 相似文献
48.
董磊 《建设科技(建设部)》2021,(2):56-59,64
为发挥装配式IRF体系自身优势,施工现场需研发与体系相适应的施工技术.这对施工总承包单位在施工场地平面布置、预制构件安装、施工组织等方面提出了需求.装配式IRF体系依托天津葛沽镇定向安置房2018-03项目,研发出与施工技术相适应的工装系统,总结完善了高层建筑装配式IRF体系施工流程,进一步验证了体系的可行性. 相似文献
49.
Song Won Joon Youn Gyu Seong Cha Dong Jin 《Journal of Mechanical Science and Technology》2021,35(9):4261-4270
Journal of Mechanical Science and Technology - Here, a procedure that uses in-situ data recorded by two microphones placed inside an operating gas turbine combustor to determine the reflection... 相似文献
50.