全文获取类型
收费全文 | 10160篇 |
免费 | 2039篇 |
国内免费 | 370篇 |
专业分类
电工技术 | 1725篇 |
综合类 | 378篇 |
化学工业 | 2600篇 |
金属工艺 | 568篇 |
机械仪表 | 150篇 |
建筑科学 | 116篇 |
矿业工程 | 237篇 |
能源动力 | 1218篇 |
轻工业 | 79篇 |
水利工程 | 13篇 |
石油天然气 | 80篇 |
武器工业 | 28篇 |
无线电 | 1710篇 |
一般工业技术 | 2999篇 |
冶金工业 | 417篇 |
原子能技术 | 146篇 |
自动化技术 | 105篇 |
出版年
2024年 | 96篇 |
2023年 | 857篇 |
2022年 | 377篇 |
2021年 | 713篇 |
2020年 | 836篇 |
2019年 | 713篇 |
2018年 | 595篇 |
2017年 | 642篇 |
2016年 | 622篇 |
2015年 | 488篇 |
2014年 | 553篇 |
2013年 | 528篇 |
2012年 | 473篇 |
2011年 | 728篇 |
2010年 | 500篇 |
2009年 | 448篇 |
2008年 | 388篇 |
2007年 | 530篇 |
2006年 | 431篇 |
2005年 | 374篇 |
2004年 | 327篇 |
2003年 | 261篇 |
2002年 | 247篇 |
2001年 | 147篇 |
2000年 | 136篇 |
1999年 | 128篇 |
1998年 | 72篇 |
1997年 | 64篇 |
1996年 | 63篇 |
1995年 | 39篇 |
1994年 | 34篇 |
1993年 | 24篇 |
1992年 | 25篇 |
1991年 | 20篇 |
1990年 | 10篇 |
1989年 | 17篇 |
1988年 | 5篇 |
1987年 | 5篇 |
1986年 | 6篇 |
1985年 | 6篇 |
1984年 | 6篇 |
1983年 | 7篇 |
1982年 | 12篇 |
1979年 | 1篇 |
1978年 | 1篇 |
1975年 | 1篇 |
1974年 | 1篇 |
1959年 | 1篇 |
1954年 | 1篇 |
1951年 | 9篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
由于干态聚合物电解质目前还不能满足聚合物锂离子电池的应用要求,人们致力于开发含液体增塑剂的聚合物电解质,包括凝胶型和微孔型两类体系。本文综述了含液聚合物电解质的最新进展,重点论述了各种新体系和新方法。 相似文献
2.
A quantum chemical study of the binding of Li+ cation to polyalkyloxides has been carried out. The lithium cation interaction with three polyalkyloxides (polyethylene oxide (PEO), polytrimethylene oxide (PTMO), and polypropylene oxide (PPO)) has been investigated using ab initio molecular orbital theory at the HF/6-31G* level with molecular models for the polymers. Coordination by one to six oxygens was considered. In addition, higher level calculations were carried out using G3(MP2) theory for coordination of Li+ by one oxygen. For coordination of lithium by one oxygen, the binding energy ordering is PTMO>PPO>PEO, with PTMO having the largest lithium cation affinity. The same ordering is found for larger coordination numbers with the exception of coordination by six oxygens, where the ordering changes due to the steric interactions. 相似文献
3.
4.
5.
添加剂对尖晶石型锰酸锂性质表征的影响 总被引:1,自引:0,他引:1
以LiOH·H_20和MnO_2为原料,分别掺入H_2BO_3、Al_2O_3、SiO_2和P_2O_5等添加剂,用固相分段法制备尖晶石型锰酸锂。结果表明,SiO_2和P_2O_5可以有效地改善LiMn_2O_4的电化学性能,H_3BO_3对锰酸锂的电化学性能影响不大,而Al_2O_3破坏了LiMn_2O_4的电化学性能。面扫描结果显示,Si或P元素各自都均匀地分散于LiMn_2O_4的物相中。从元素电负性和原子半径的角度分析了B、Si、P和Al元素对尖晶石型LiMn_2O_4结构和性能的影响。 相似文献
6.
7.
超动型长寿命铅蓄电池池的几点建议 总被引:1,自引:1,他引:0
报导了国内外起动用长寿命铅酸蓄电池的概况,根据笔多年积累的经验并针对这类电池的应用特点,具体介绍了起动型铅酸蓄电池在原辅材料,零部件,生产设备和制造工艺等方面如何采取有效措施以提高这类电池的使用寿命。 相似文献
8.
H. Perez-Blanco 《International Journal of Refrigeration》1993,16(6):429-433
The search for high-efficiency, gas-fired cooling cycles has led to the development of dual-loop absorption machines with cooling coefficients of performance (COPs) in the 1.2 to 1.7 range. This increased performance may call for high generator temperatures, new working fluids or new materials of construction. In most cases, two different sets of working fluids are required. The conceptual design presented here is aimed at obtaining high efficiencies with relatively low temperatures, employing only one set of fluids. The concept consists of two loops coupled in a configuration aimed at minimizing the loss of thermodynamic availability incurred when transferring refrigerant between the loops. The working fluid pair is a solution of lithium bromide-water. The calculated COPs are of the order of 1.8. The cycle relies on an elaborate evaporator-absorber combination. The paper presents the conceptual design, the critical assumptions, and the performance calculations for the concept. 相似文献
9.
Anionic copolymerizations of styrene (M1) with excess 1-(4-dimethyl-aminophenyl)-1-phenylethylene (M2) were conducted in benzene at 25°C for 24h, using sec-butyllithium as initiator. Narrow molecular weight distribution copolymers with M?;n = 16.1 × 103 g/mol (M?w/M?n = 1.04) and 38.2 × 103g/mol (M?w/M?n = 1.05), and 24 and 38 moles of M2 per macromolecule, respectively, were characterized by size exclusion chromatography, 1H NMR spectroscopy and DSC. The monomer reactivity ratio, r1 = 5.6, was obtained from the copolymer composition at complete consumption of M1, assuming that the rate constant k22 =0,i.e. r2 =0. The polymers exhibited Tg values of 128 and 119°C, respectively, which correspond to an estimated Tg = 217°C for the hypothetical homopolymer of M2. 相似文献
10.
Ying Bai Yanfeng Yin Na Liu Bingkun Guo Hongjun Shi Jianyong Liu Zhaoxiang Wang Liquan Chen 《Journal of power sources》2007
As the continuance of our series study on LiCoO2 surface modification, the complicated traditional surface coating method is replaced with simple addition of amorphous YPO4 and Al2O3 in commercial LiCoO2 or in commercial electrolyte based on our understanding to the improvement mechanism of surface modification. Comprehensive studies by X-ray photoelectron spectroscopy (XPS), gas chromatography and mass spectroscopy (GC–MS), inductively coupled plasma (ICP) and Fourier transformed infrared (FTIR) indicate that the products of spontaneous reaction between the additive and the LiPF6 based electrolyte are responsible for the performance improvements. 相似文献