全文获取类型
收费全文 | 150073篇 |
免费 | 13283篇 |
国内免费 | 7485篇 |
专业分类
电工技术 | 9893篇 |
技术理论 | 8篇 |
综合类 | 11128篇 |
化学工业 | 24330篇 |
金属工艺 | 9168篇 |
机械仪表 | 9534篇 |
建筑科学 | 12604篇 |
矿业工程 | 4389篇 |
能源动力 | 4019篇 |
轻工业 | 12317篇 |
水利工程 | 3117篇 |
石油天然气 | 7878篇 |
武器工业 | 1445篇 |
无线电 | 16131篇 |
一般工业技术 | 16407篇 |
冶金工业 | 6661篇 |
原子能技术 | 1775篇 |
自动化技术 | 20037篇 |
出版年
2024年 | 541篇 |
2023年 | 2327篇 |
2022年 | 4279篇 |
2021年 | 5966篇 |
2020年 | 4577篇 |
2019年 | 3683篇 |
2018年 | 4287篇 |
2017年 | 4784篇 |
2016年 | 4220篇 |
2015年 | 6069篇 |
2014年 | 7537篇 |
2013年 | 9130篇 |
2012年 | 10531篇 |
2011年 | 11266篇 |
2010年 | 9872篇 |
2009年 | 9578篇 |
2008年 | 9489篇 |
2007年 | 8889篇 |
2006年 | 8670篇 |
2005年 | 7359篇 |
2004年 | 5105篇 |
2003年 | 4316篇 |
2002年 | 4049篇 |
2001年 | 3510篇 |
2000年 | 3336篇 |
1999年 | 3402篇 |
1998年 | 2619篇 |
1997年 | 2125篇 |
1996年 | 2091篇 |
1995年 | 1711篇 |
1994年 | 1365篇 |
1993年 | 979篇 |
1992年 | 771篇 |
1991年 | 642篇 |
1990年 | 461篇 |
1989年 | 361篇 |
1988年 | 286篇 |
1987年 | 192篇 |
1986年 | 125篇 |
1985年 | 87篇 |
1984年 | 58篇 |
1983年 | 32篇 |
1982年 | 43篇 |
1981年 | 38篇 |
1980年 | 43篇 |
1979年 | 11篇 |
1976年 | 4篇 |
1973年 | 3篇 |
1959年 | 9篇 |
1951年 | 3篇 |
排序方式: 共有10000条查询结果,搜索用时 781 毫秒
51.
王虔虔在上任中建材(合肥)粉体科技装备有限公司(简称粉体公司)总经理之前,和分管部门的所有同事坐在同一间大办公室内。之所以和大家在同一个空间内工作,王虔虔是想更进一步拉近彼此之间的距离,以身作则潜移默化,传承公司文化,建立相互信任的团队。2012年,粉体公司决定向"提供系统解决方案的综合服务商"转变。 相似文献
52.
ABSTRACT This study investigates the effects of strain, strain rates, and forming directions (RD-rolling direction, TD-transverse direction, and ND-normal direction) on adiabatic shear, via dynamic impact compression tests using the Split Hopkinson Pressure Bar (SHPB) apparatus. A modified Johnson-Cook (J-C) constitutive model is proposed, which used to analyse the influence of the constitutive parameters on the sensitivity of adiabatic shear, employing a finite element software. The different sensitivities of adiabatic shear under different directions are explained by combining microscopic analysis and results from mechanical responses. The results show that the sensitivity of adiabatic shear can be related to the time of stress collapse in the following trend: ND?>?TD?>?RD; the sensitivities of these constitutive parameters on adiabatic shear are calculated and compared. 相似文献
53.
To realize joint optimization of spatial diversity and equalization combining in the intersymbol interference (ISI) channel, an iterative equalization combining algorithm is proposed. The proposed algorithm uses the coefficients of Turbo equalization to calculate the combination weights without estimating the signal to noise ratio in each diversity branch. The equalized symbols from different diversity branches are combined, and the extrinsic information output from the decoder is fed back to the equalizers, so as to exchange soft information between the equalizers and the decoder. The performance of the proposed algorithm is analyzed using the extrinsic information transfer (EXIT) chart and verified by simulations. Results show that our approach fully exploits time domain information from the multipath channel and spatial domain information from multi receiving antennas, which efficiently improve the performance of the receiver in the severe ISI channel. 相似文献
54.
双检合并技术在海底电缆地震资料处理中被广泛应用,可衰减电缆鬼波的影响。传统方式以水、陆检记录的波场记录相同为假设,电缆鬼波压制效果差,合并效果并不理想。在分析交叉鬼波化双检合并技术基本原理的基础上,综合利用水检资料与陆检鬼波褶积的结果和陆检资料与水检鬼波褶积的结果求取刻度算子,同时在地震资料处理中利用陆检资料标定水检资料,从而优化了交叉鬼波化双检合并技术。实际资料处理结果表明,改进后的技术可有效衰减电缆鬼波,分离出上行波场,大幅度拓宽地震资料频带,提高地震资料分辨率,从而提供更丰富的构造细节信息。 相似文献
55.
56.
Zhongyu Qiu Xiaowen Ge Naibao Huang Shixian Zhou Junjie Zhang Jiaping Xuan 《International Journal of Hydrogen Energy》2021,46(3):2952-2959
Polyethylene oxide (PEO)-polypropylene oxide (PPO)-polyethylene oxide block copolymer having different molecular weights are used as precursors of carbon materials to prepare Hollow -Derivatives carbon material as an electrocatalyst through block copolymer self-assembly. The composition and microstructure of the prepared catalysts are shown by Raman spectroscopy, X-ray diffraction (XRD), Test of nitrogen adsorption and desorption curves, High resolution transmission electron microscopy (HR-TEM) and scanning electron microscopy (HR-SEM). Oxygen was passed into alkaline electrolyte solution until the solution reached saturation state. With molecular weight increasing, the obtained sample gradually changed from block to hollow and spherical. When the molecular weight was 12600 g mol?1, the evenly hollow carbon nanocages was acquired (C-12600). In O2 saturated alkaline electrolyte (0.1 M KOH solution), C-12600's limited current density,half-wave potential and initial potential are 5.23 mA cm?2@0.4 V, 0.72 V and 0.81 V, respectively. And most important is that half-wave potential and onset potential have barely change after 2000 cycles of cyclic voltammetry. As a result, the porous carbon materials exhibited excellent electrocatalytic activity while maintaining high stability in alkaline KOH solution. 相似文献
57.
Ting Liu Huimin Zhang Panfei Ma Aimin Chang Hui Jiang 《Journal of the American Ceramic Society》2019,102(8):4393-4398
Core–shell structures have been proposed to improve the electrical properties of negative-temperature coefficient (NTC) thermistor ceramics. In this work, Al2O3-modified Co1.5Mn1.2Ni0.3O4 NTC thermistor ceramics with adjustable electrical properties were prepared through citrate-chelation followed by conventional sintering. Co1.5Mn1.2Ni0.3O4 powder was coated with a thin Al2O3 shell layer to form a core–shell structure. Resistivity (ρ) increased rapidly with increasing thickness of the Al2O3 layer, and the thermal constant (B) varied moderately between 3706 and 3846 K. In particular, Co1.5Mn1.2Ni0.3O4@Al2O3 ceramic with 0.08 wt% Al2O3 showed the increase of ρ double, and the change in its B was less than 140 K. The Co1.5Mn1.2Ni0.3O4@Al2O3 NTC ceramics showed high stability, and their grain size was relatively uniform due to the protection offered by the shell. The aging coefficient of the ceramic was less than 0.2% after aging for 500 hours at 125°C. Taken together, the results indicate that as-prepared Co1.5Mn1.2Ni0.3O4@Al2O3 NTC ceramics with a core–shell structure may be promising candidates for application as wide-temperature NTC thermistor ceramics. 相似文献
58.
Yu-Jiao Liu Xiao-Yang Fan Dr. Dong-Dong Zhang Yin-Zheng Xia Dr. Yan-Jun Hu Feng-Lei Jiang Prof. Fu-Ling Zhou Prof. Yi Liu 《ChemMedChem》2020,15(6):552-558
Based on the potential therapeutic value in targeting mitochondria and the fluorophore tracing ability, a fluorescent mitochondria-targeted organic arsenical PDT-PAO-F16 was fabricated, which not only visualized the cellular distribution, but also exerted anti-cancer activity in vitro and in vivo via targeting pyruvate dehydrogenase complex (PDHC) and respiratory chain complexes in mitochondria. In details, PDT-PAO-F16 mainly accumulated into mitochondria within hours and suppressed the activity of PDHC resulting in the inhibition of ATP synthesis and thermogenesis disorder. Moreover, the suppression of respiratory chain complex I and IV accelerated the mitochondrial dysfunction leading to caspase family-dependent apoptosis. In vivo, the acute promyelocytic leukemia was greatly alleviated in the PDT-PAO-F16 treated group in APL mice model. Our results demonstrated the organic arsenical precursor with fluorescence imaging and target-anticancer efficacy is a promising anticancer drug. 相似文献
59.
60.