全文获取类型
收费全文 | 115122篇 |
免费 | 10061篇 |
国内免费 | 5510篇 |
专业分类
电工技术 | 7042篇 |
技术理论 | 13篇 |
综合类 | 8120篇 |
化学工业 | 19279篇 |
金属工艺 | 6256篇 |
机械仪表 | 7155篇 |
建筑科学 | 9761篇 |
矿业工程 | 3401篇 |
能源动力 | 3557篇 |
轻工业 | 7893篇 |
水利工程 | 2218篇 |
石油天然气 | 6897篇 |
武器工业 | 990篇 |
无线电 | 13014篇 |
一般工业技术 | 13716篇 |
冶金工业 | 5253篇 |
原子能技术 | 1303篇 |
自动化技术 | 14825篇 |
出版年
2024年 | 494篇 |
2023年 | 2016篇 |
2022年 | 3526篇 |
2021年 | 4858篇 |
2020年 | 3649篇 |
2019年 | 3122篇 |
2018年 | 3461篇 |
2017年 | 3867篇 |
2016年 | 3493篇 |
2015年 | 4560篇 |
2014年 | 5874篇 |
2013年 | 6818篇 |
2012年 | 7623篇 |
2011年 | 8007篇 |
2010年 | 7287篇 |
2009年 | 6926篇 |
2008年 | 6747篇 |
2007年 | 6267篇 |
2006年 | 6306篇 |
2005年 | 5251篇 |
2004年 | 3658篇 |
2003年 | 3190篇 |
2002年 | 3050篇 |
2001年 | 2829篇 |
2000年 | 2726篇 |
1999年 | 2867篇 |
1998年 | 2206篇 |
1997年 | 1854篇 |
1996年 | 1699篇 |
1995年 | 1432篇 |
1994年 | 1219篇 |
1993年 | 862篇 |
1992年 | 708篇 |
1991年 | 529篇 |
1990年 | 453篇 |
1989年 | 347篇 |
1988年 | 252篇 |
1987年 | 165篇 |
1986年 | 147篇 |
1985年 | 92篇 |
1984年 | 64篇 |
1983年 | 43篇 |
1982年 | 50篇 |
1981年 | 35篇 |
1980年 | 30篇 |
1979年 | 10篇 |
1976年 | 3篇 |
1970年 | 2篇 |
1959年 | 4篇 |
1951年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
91.
92.
93.
Thermal analysis of montmorillonites modified with quaternary phosphonium and ammonium surfactants 总被引:2,自引:4,他引:2
The thermal stability of seven organically modified montmorillonites (‘organoclays’) has been investigated using differential thermal analysis, differential scanning calorimetry, and thermogravimetry in conjunction with X-ray diffractometry. Six organoclays were synthesised by replacing the interlayer inorganic cations, initially present, with quaternary phosphonium and ammonium surfactant cations. The samples modified with tetrabutylphosphonium (TBP), and butyltriphenylphosphonium (BTPP) ions have an appreciably higher thermal stability than the octadecyltrimethylammonium (ODTMA)-modified clays. Thus, in the case of TBP- and BTPP-modified montmorillonites, the onset temperature of decomposition is close to 300 °C. Samples modified with hexadecyltributylphosphonium (HDTBP) ions have a lower onset temperature of decomposition of 225 °C. In comparison, the onset temperature for ODTMA-montmorillonites (obtained at different concentrations of ODTMA-bromide) ranges from 158 to 222 °C, being highest where the concentration of intercalated surfactant is lowest. The onset temperature for a commercial alkylsilane-treated quaternary ammonium-modified organoclay (S-BEN N-400FP) is 207 °C. The basal spacing of the TBP- and BTPP-modified clays is 1.7–1.8 nm, indicating a monolayer arrangement of quaternary phosphonium ions in the interlayer space, while the value of 2.5 nm for HDTBP-montmorillonite indicates a more open structure. The ODTMA-modified samples have basal spacings ranging from 1.9 to 2.1 nm, indicative of a bilayer to pseudo-trilayer arrangement. The exceptionally high basal spacing of 3.4 nm for the S-BEN N-400FP organoclay might be due to interlayer penetration of organosilane hydrolysis products during synthesis. The thermal properties of organoclays are apparently related to the nature of the surfactants and their arrangement in the interlayer space of montmorillonite. 相似文献
94.
Neural Processing Letters - In this article, the finite time (FT) synchronization problem of fractional order quaternion valued neural networks with time delay is investigated. Without separating... 相似文献
95.
Sun Yuxiang Yuan Bo Zhang Yongliang Zheng Wanwen Xia Qingfeng Tang Bojian Zhou Xianzhong 《International Journal of Control, Automation and Systems》2021,19(9):2984-2998
International Journal of Control, Automation and Systems - The reinforcement learning problem of complex action control in multiplayer online battlefield games has brought considerable interest in... 相似文献
96.
Uncertainties existing in the acoustic metamaterial may strongly affect its unusual properties. Aiming at this actuality, the interval model is introduced to treat with uncertainties existing in the acoustic metamaterial with Helmholtz resonators. Frequency intervals in which the sound intensity transmission coefficients are certainly less than the required value and the effective bulk moduli are certainly negative are defined as conservative approximations. Frequency intervals in which the sound intensity transmission coefficients may be less than the required value and the effective bulk moduli may be negative are defined as unsafe approximations. The proportion of the conservative approximation and the unsafe approximation is defined as an approximate precision. Based on the quantification of uncertainties of the sound intensity transmission coefficients and the negative effective bulk moduli, an optimization model for the interval acoustic metamaterial with Helmholtz resonators is constructed. Numerical results showed that even suffering from effects of interval parameters, unusual properties of the optimized acoustic metamaterial (such as the bandgap of the sound transmission and the negative effective bulk modulus) could be improved. 相似文献
97.
谢媛 《湖南工业职业技术学院学报》2015,(2):74-78
残疾人通常根据其政治、经济、精神和社会保障等利益需要进行利益表达。当残疾人的利益表达机制不完善、缺乏利益表达意识、社会利益输出不平衡等因素造成制度化利益表达受阻,残疾人只能无奈地选择非常规的、非制度化利益表达方式。通过健全残疾人社会保障服务体系、保证残疾人制度化利益表达渠道畅通、引导残疾人合理运用网络新媒体进行利益表达,是规避由非制度化利益表达造成的社会不和谐因子的有效途径。 相似文献
98.
宋子健 《武汉理工大学学报(材料科学英文版)》2014,29(2):329-333
The applicability of the rapid iodide migration test was systematically studied. Comparative experimental tests of different test conditions, including several external voltages, test durations, concrete ages and mixing proportions, were carried out to make clear the transport behaviors of iodide under parallel electric fields. Numerical simulations were also done using the finite element method to found the correlation between chloride and iodide transport behaviors. The test and numerical results show that the chloride transport behaviors of RIM and RCM tests have a good correlation under the several conditions used in the present paper. Moreover, the influence of external conditions (external voltages, test durations) on the test results is small. Thus, it can be concluded that the RIM method is available to determine the chloride penetration resistance of the chloride-eroded structural concrete. 相似文献
99.
根据城市居民对供水的可靠性、稳定性、经济节能性的需求,课题组提出了一种基于"双储"模式的供水系统,并按照本市德胜住宅小区的供水要求,设计了一套由储水池、气压罐、变频器、多台水泵机组等主要设备构成的全自动变频恒压供水系统.经过近半年的运行测试,系统有效地解决了传统供水方式中存在的问题,增强了系统的总体性能,有明显的节能效果. 相似文献
100.
Cheng Jiaqi Gong Junyi Yue Shuai Jiang Yao Hou Xiangjun Ma Jianjun Yao Yali Jiang Cairong 《Journal of Applied Electrochemistry》2021,51(8):1175-1188
Journal of Applied Electrochemistry - La-doped titanate materials have been widely investigated as alternative Ni-free anodes for solid oxide fuel cells (SOFCs). In this study, La0.4Sr0.6TiO3 (LST)... 相似文献