全文获取类型
收费全文 | 103352篇 |
免费 | 9702篇 |
国内免费 | 6002篇 |
专业分类
电工技术 | 7892篇 |
技术理论 | 3篇 |
综合类 | 8125篇 |
化学工业 | 15749篇 |
金属工艺 | 5967篇 |
机械仪表 | 7165篇 |
建筑科学 | 8267篇 |
矿业工程 | 3123篇 |
能源动力 | 3154篇 |
轻工业 | 6769篇 |
水利工程 | 2105篇 |
石油天然气 | 5775篇 |
武器工业 | 1287篇 |
无线电 | 12064篇 |
一般工业技术 | 11563篇 |
冶金工业 | 4106篇 |
原子能技术 | 1251篇 |
自动化技术 | 14691篇 |
出版年
2024年 | 327篇 |
2023年 | 1560篇 |
2022年 | 2688篇 |
2021年 | 4099篇 |
2020年 | 3273篇 |
2019年 | 2638篇 |
2018年 | 2911篇 |
2017年 | 3260篇 |
2016年 | 2901篇 |
2015年 | 4272篇 |
2014年 | 5402篇 |
2013年 | 6361篇 |
2012年 | 6983篇 |
2011年 | 7659篇 |
2010年 | 7038篇 |
2009年 | 6732篇 |
2008年 | 6568篇 |
2007年 | 6156篇 |
2006年 | 6040篇 |
2005年 | 4984篇 |
2004年 | 3721篇 |
2003年 | 3319篇 |
2002年 | 3366篇 |
2001年 | 2956篇 |
2000年 | 2398篇 |
1999年 | 2270篇 |
1998年 | 1722篇 |
1997年 | 1466篇 |
1996年 | 1328篇 |
1995年 | 1082篇 |
1994年 | 856篇 |
1993年 | 659篇 |
1992年 | 566篇 |
1991年 | 345篇 |
1990年 | 297篇 |
1989年 | 220篇 |
1988年 | 168篇 |
1987年 | 99篇 |
1986年 | 90篇 |
1985年 | 62篇 |
1984年 | 38篇 |
1983年 | 36篇 |
1982年 | 43篇 |
1981年 | 27篇 |
1980年 | 22篇 |
1979年 | 10篇 |
1973年 | 4篇 |
1959年 | 6篇 |
1951年 | 6篇 |
1940年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 156 毫秒
51.
Synergistic flame retardant effects of activated carbon and molybdenum oxide in poly(vinyl chloride) 下载免费PDF全文
Mengjiao Zhang Weihong Wu Shaorui He Xue Wang Yunhong Jiao Hongqiang Qu Jianzhong Xu 《Polymer International》2018,67(4):445-452
The synergistic effects of activated carbon (AC) and molybdenum oxide (MoO3) in improving the flame retardancy of poly(vinyl chloride) (PVC) were investigated. The effects of AC, MoO3 and their mixture with a mass ratio of 1:1 on the flame retardancy and smoke suppression properties of PVC were studied using the limiting oxygen index and cone calorimeter tests. It was found that the flame retardancy of the relatively cheaper AC was slightly weaker than that of MoO3. In addition, the incorporation of AC and MoO3 greatly reduced the total heat release and improved smoke suppressant property of PVC composites. When the total content of AC and MoO3 was 10 phr, PVC/AC/MoO3 had the lowest peak heat release rate and peak smoke production rate values of 173.80 kW m?2 and 0.1472 m2 s?1, which represented reductions of 47.3 and 59.9%, respectively, compared with those of PVC. Furthermore, thermogravimetric analysis and gel content tests were used to analyze the flame retardant mechanism of AC and MoO3, with results showing that AC could promote early crosslinking in PVC. Char residue left after heating at 500 °C was analyzed using scanning electron microscopy and Raman spectroscopy, and the results showed that MoO3 produced the most compact char, with the smallest and most organized carbonaceous microstructures. © 2017 Society of Chemical Industry 相似文献
52.
53.
设计了一种以STM32F103微控制器为控制核心,基于24位高精度模数转换器的钻孔深度测量仪器。利用弹性波回波测距原理,通过测量出钻孔中钻杆的长度,实现钻孔深度的快速、无损、准确的测量,主要用于井下瓦斯抽放钻孔、探放水钻孔等煤矿通防工作的施工验收。仪器小巧轻便,操作简单,单人即可完成测量工作,节约下井的人力物力,提高生产效率,最长测量长度可达250米,误差不超过1米。 相似文献
54.
55.
56.
The increased concentration of CO2 due to continuous breathing and no discharge of human beings in the manned closed space, like spacecraft and submarines, can be a threat to health and safety. Effective removal of low concentration CO2 from the manned closed space is essential to meet the requirements of long-term space or deep-sea exploration, which is an international frontier and trend. Ionic liquids (ILs), as a widespread and green solvent, already showed its excellent performance on CO2 capture and absorption, indicating its potential application in low concentration CO2 capture. In this review, we first summarized the current methods and strategies for direct capture from low concentration CO2 in both the atmosphere and manned closed spaces. Then, the multi-scale simulation methods of CO2 capture by ionic liquids are described in detail, including screening ionic liquids by COSMO-RS methods, capture mechanism by density functional theory and molecular dynamics simulation, and absorption process by computational fluid dynamics simulation. Lastly, some typical IL-based green technologies for low concentration CO2 capture, such as functionalized ILs, co-solvent systems with ILs, and supported materials based on ILs, are introduced, and analyzed the subtle possibility in manned closed spaces. Finally, we look forward to the technology and development of low concentration CO2 capture, which can meet the needs of human survival in closed space and proposed that supported materials with ionic liquids have great advantages and infinite possibilities in the vital area. 相似文献
57.
Yong Pan Chen Zhu Wen Bin Zeng Pei Fu Chi Chen Bao Ming Xu Zhong Feng Gao 《Chembiochem : a European journal of chemical biology》2021,22(24):3431-3436
Rapid and sensitive point-of-care testing (POCT) is an extremely critical mission in practical applications, especially for rigorous military medicine, home health care, and in the third world. Here, we report a visual POCT method for adenosine triphosphate (ATP) detection based on Taylor rising in the corner of quadratic geometries between two rod surfaces. We discuss the principle of Taylor rising, demonstrating that it is significantly influenced by contact angle, surface tension, and density of the sample, which are controlled by ATP-dependent rolling circle amplification (RCA). In the presence of ATP, RCA reaction effectively suppresses Taylor-rising behavior, due to the increased contact angle, density, and decreased surface tension. Without addition of ATP, untriggered RCA reaction is favorable for Taylor rising, resulting in a significant height. With this proposed method, visual sensitive detection of ATP without the aid of other instruments is realized with only a 5 μL droplet, which has good selectivity and a low detection limit (17 nM). Importantly, this visual method provides a promising POCT tool for user-friendly molecular diagnostics. 相似文献
58.
Qianglong He Aiyang Wang Chun Liu Weimin Wang Hao Wang Zhengyi Fu 《Journal of the European Ceramic Society》2018,38(7):2832-2840
B4C-TiB2-SiC composites were fabricated via hot pressing using ball milled B4C, TiB2, and SiC powder mixtures as the starting materials. The impact of ball milling on the densification behaviors, mechanical properties, and microstructures of the ceramic composites were investigated. The results showed that the refinement of the powder mixtures and the removal of the oxide impurities played an important role in the improvement of densification and properties. Moreover, the formation of the liquid phases during the sintering was deemed beneficial for densification. The typical values of relative density, hardness, bending strength, and fracture toughness of the composites reached 99.20%, 32.84?GPa, 858?MPa and 8.21?MPa?m1/2, respectively. Crack deflection, crack bridging, crack branching, and microcracking were considered to be the potential toughening mechanisms in the composites. Furthermore, numerous nano-sized intergranular/intragranular phases and twin structures were observed in the B4C-TiB2-SiC composite. 相似文献
59.
Han Yan Gu Yi Chen Lei Li Bing Liu Xiang Ming Chen 《International Journal of Applied Ceramic Technology》2020,17(2):790-796
SrLa[Ga1−x(R0.5Ti0.5)x]O4 (R = Mg, Zn) ceramics were prepared by a standard solid state sintering method. The single-phase ceramics with K2NiF4-type layered perovskite structure and I4/mmm space group were obtained, indicating that SrLa(R0.5Ti0.5) and SrLaGaO4 can form the unlimited solid solutions. With increasing x for R = Mg and Zn, εr increases monotonously, the Qf value first increases and then decreases, while τf increases from a negative to a positive value. The optimized microwave dielectric properties were obtained as following: εr = 23.3, Qf = 89 400 GHz, τf = −0.8 ppm/°C for SrLa[Ga0.6(Mg0.5Ti0.5)0.4]O4 and εr = 23.3, Qf = 76 200 GHz, τf = 0.2 ppm/°C for SrLa[Ga0.7(Zn0.5Ti0.5)0.3]O4, indicating that the present solid solution ceramics are the promising candidates as microwave resonator materials for the telecommunication applications. 相似文献