全文获取类型
收费全文 | 4744145篇 |
免费 | 314269篇 |
国内免费 | 178784篇 |
专业分类
电工技术 | 255517篇 |
技术理论 | 125篇 |
综合类 | 254461篇 |
化学工业 | 696463篇 |
金属工艺 | 227936篇 |
机械仪表 | 254414篇 |
建筑科学 | 259133篇 |
矿业工程 | 107657篇 |
能源动力 | 133703篇 |
轻工业 | 390878篇 |
水利工程 | 97456篇 |
石油天然气 | 140204篇 |
武器工业 | 35128篇 |
无线电 | 509314篇 |
一般工业技术 | 583494篇 |
冶金工业 | 561657篇 |
原子能技术 | 62923篇 |
自动化技术 | 666735篇 |
出版年
2023年 | 42561篇 |
2022年 | 101248篇 |
2021年 | 144299篇 |
2020年 | 104107篇 |
2019年 | 85114篇 |
2018年 | 101926篇 |
2017年 | 111988篇 |
2016年 | 101905篇 |
2015年 | 120803篇 |
2014年 | 165332篇 |
2013年 | 267969篇 |
2012年 | 277222篇 |
2011年 | 315304篇 |
2010年 | 282124篇 |
2009年 | 282506篇 |
2008年 | 289215篇 |
2007年 | 280535篇 |
2006年 | 254771篇 |
2005年 | 212290篇 |
2004年 | 150015篇 |
2003年 | 114881篇 |
2002年 | 107914篇 |
2001年 | 99135篇 |
2000年 | 97259篇 |
1999年 | 80530篇 |
1998年 | 142227篇 |
1997年 | 100237篇 |
1996年 | 85133篇 |
1995年 | 66736篇 |
1994年 | 58026篇 |
1993年 | 49686篇 |
1992年 | 33053篇 |
1991年 | 29863篇 |
1990年 | 29759篇 |
1989年 | 28794篇 |
1988年 | 26716篇 |
1987年 | 24321篇 |
1986年 | 23656篇 |
1985年 | 25439篇 |
1984年 | 22062篇 |
1983年 | 20261篇 |
1982年 | 19144篇 |
1981年 | 19507篇 |
1980年 | 18744篇 |
1979年 | 16820篇 |
1978年 | 16238篇 |
1977年 | 22921篇 |
1976年 | 33658篇 |
1975年 | 14036篇 |
1974年 | 13029篇 |
排序方式: 共有10000条查询结果,搜索用时 171 毫秒
161.
Salehe Gomroki Zahra Yavari Ahmad Reza Abbasian Meissam Noroozifar 《International Journal of Applied Ceramic Technology》2021,18(6):2099-2110
The spongy nickel oxide (SNO) was synthesized the solution combustion method. The SNO was selected as a promoter to boost the catalytic activity of nanoraspberry-like palladium (NRPd) toward electrooxidation of five light fuels (LFs): methanol, ethanol, formaldehyde, formic acid, and ethylene glycol. The X-ray powder diffraction, Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscopy, and field emission scanning electron microscope techniques were used for the materials characterization. In comparison with nonpromoted Pd, the NRPd-SNO electrocatalyst shown an excellent efficiency in parameters like the electrochemical active surface area and anti-CO poisoning behavior. The turnover data and the parameters, including reaction order, activation energy, and the coefficients of electron transfer and diffusion, were evaluated for the each process of LFs electrooxidation. The outcome for NRPd-SNO activity toward LFs electrooxidation was compared to some reported electrodes. The SNO increases the removal of intermediates created in the oxidation of LFs that can poison the surface of palladium catalyst. This is due to the presence of the lattice oxygens in SNO structure and Ni switching between its high and low valances. The compatibility of the adsorption process of LFs on the surface of the NRPd-SNO catalyst with different isotherms was determined by studying the Tafel polarization and calculating the surface coverage. 相似文献
162.
Journal of Porous Materials - Solar vapor generation is considered a green and practical approach to take advantage of solar energy as a renewable source and provide pure water. However, developing... 相似文献
163.
Kathleen T. Lauser Amy L. Rueter Michelle A. Calabrese 《American Institute of Chemical Engineers》2022,68(12):e17850
While protein medications are promising for treatment of cancer and autoimmune diseases, challenges persist in terms of development and injection stability of high-concentration formulations. Here, the extensional flow properties of protein-excipient solutions are examined via dripping-onto-substrate extensional rheology, using a model ovalbumin (OVA) protein and biocompatible excipients polysorbate 20 (PS20) and 80 (PS80). Despite similar PS structures, differences in extensional flow are observed based on PS identity in two regimes: at moderate total concentrations where surface tension differences drive changes in extensional flow behavior, and at small PS:OVA ratios, which impact the onset of weakly elastic flow behavior. Undesirable elasticity is observed in ultra-concentrated formulations, independent of PS identity; higher PS contents are required to observe these effects than in analogous polymeric excipient solutions. These studies reveal novel extensional flow behaviors in protein-excipient solutions, and provide a straightforward methodology for assessing the extensional flow stability of new protein-excipient formulations. 相似文献
166.
167.
Jinfeng Zeng Zhiting Liu Hanbo Zou Wei Yang Haosen Fan Haijun Yu Shengzhou Chen 《金属学报(英文版)》2021,34(8):1153-1162
A appropriate size with three-dimension(3 D) channels for lithium diffusion plays an important role in constructing highperforming LiNi_(0.5)Mn_(1.5)O_4(LNMO) cathode materials, as it can not only reduce the transport path of lithium ions and electrons, but also reduce the side effects and withstand the structural strain in the process of repetitive Li~+ intercalation/deintercalation. In this work, an e fficient method for designing the hollow LNMO microsphere with 3 D channels structure by using polyethylene oxide(PEO) as soft template agent assisted solvothermal method is proposed. Experimental results indicate that PEO can make the reagents mingle evenly and nucleate slowly in the solvothermal process, thus obtaining a homogeneous distribution of carbonate precursors. In the final LNMO products, the hollow 3 D channels structure obtained by the decomposition of PEO and carbonate precursor in the calcination can provide abundant electroactive zones and electron/ion transport paths during the charge/discharge process, which benefits to improve the cycling performance and rate capability. The LNMO prepared by adding 1 g PEO possesses the most outstanding electrochemical performance, which presented an excellent discharge capacity of 143.1 mAh g~(-1) at 0.1 C and with a capacity retention of 92.2% after 100 cycles at 1 C. The superior performance attributed to the 3 D channels structure of hollow microspheres, which provide uninterrupted conductive systems and therefore achieve the stable transfer for electron/ion. 相似文献
168.
Kai Liu Chenyang Zhou Jiaming Hu Song Zhang Qingqing Zhang Ce Sun Yusheng Shi Huajun Sun Changxia Yin Yuzhen Zhang Yu Fu 《Journal of the European Ceramic Society》2021,41(12):5909-5917
A digital light processing (DLP) technology has been developed for 3D printing lead-free barium titanate (BTO) piezoelectric ceramics. By comparing the curing and rheological properties of slurries with different photosensitive monomer, a high refractive index monomer acryloyl morpholine (ACMO) was chosen, and a design and preparation method of BTO slurry with high solid content, low viscosity and high curing ability was proposed. By further selecting the printing parameters, the single-layer exposure time was reduced and the forming efficiency has been greatly improved. Sintered specimens were obtained after a nitrogen-air double-step debinding and furnace sintering process, and the BTO ceramics fabricated with 80 wt% slurry shows the highest relative density (95.32 %) and piezoelectric constant (168.1 pC/N). Furthermore, complex-structured BTO ceramics were prepared, impregnated by epoxy resin and finally assembly made into hydrophones, which has significance for the future design and manufacture of piezoelectric ceramic-based composites that used in functional devices. 相似文献
169.
Hui Liu Yaohui Fu Jinhai Yuan Lei Yu Zhefei Wang Quan Liu Bo Wei Xuhong Wang 《Ceramics International》2021,47(12):16570-16578
To provide a basis for the high-temperature oxidation of ultra-high temperature ceramics (UHTCs), the oxidation behavior of Zr3[Al(Si)]4C6 and a novel Zr3[Al(Si)]4C6-ZrB2-SiC composite at 1500 °C were investigated for the first time. From the calculation results, the oxidation kinetics of the two specimens follow the oxidation dynamic parabolic law. Zr3[Al(Si)]4C6 exhibited a thinner oxide scale and lower oxidation rate than those of the composite under the same conditions. The oxide scale of Zr3[Al(Si)]4C6 exhibited a two-layer structure, while that of the composite exhibited a three-layer structure. Owing to the volatilization of B2O3 and the active oxidation of SiC, a porous oxide layer formed in the oxide scale of the composite, resulting in the degradation of its oxidation performance. Furthermore, the cracks and defects in the oxide scale of the composite indicate that the reliability of the oxide scale was poor. The results support the service temperature of the obtained ceramics. 相似文献
170.
Khadijeh Pourkhanali Gholam Khayati 《Theoretical Foundations of Chemical Engineering》2021,55(6):1169-1177
Theoretical Foundations of Chemical Engineering - The importance of aqueous two-phase systems has been increased recently as a method with greater performance capability in separation and... 相似文献