全文获取类型
收费全文 | 83241篇 |
免费 | 8450篇 |
国内免费 | 4163篇 |
专业分类
电工技术 | 5716篇 |
技术理论 | 7篇 |
综合类 | 5941篇 |
化学工业 | 13904篇 |
金属工艺 | 4527篇 |
机械仪表 | 5282篇 |
建筑科学 | 6889篇 |
矿业工程 | 2530篇 |
能源动力 | 2563篇 |
轻工业 | 6302篇 |
水利工程 | 1649篇 |
石油天然气 | 4087篇 |
武器工业 | 809篇 |
无线电 | 9976篇 |
一般工业技术 | 9916篇 |
冶金工业 | 3520篇 |
原子能技术 | 1024篇 |
自动化技术 | 11212篇 |
出版年
2024年 | 454篇 |
2023年 | 1645篇 |
2022年 | 3121篇 |
2021年 | 3968篇 |
2020年 | 2984篇 |
2019年 | 2484篇 |
2018年 | 2714篇 |
2017年 | 3012篇 |
2016年 | 2596篇 |
2015年 | 3612篇 |
2014年 | 4433篇 |
2013年 | 5081篇 |
2012年 | 5630篇 |
2011年 | 5758篇 |
2010年 | 5286篇 |
2009年 | 5108篇 |
2008年 | 4952篇 |
2007年 | 4354篇 |
2006年 | 4392篇 |
2005年 | 3523篇 |
2004年 | 2454篇 |
2003年 | 2204篇 |
2002年 | 2247篇 |
2001年 | 1979篇 |
2000年 | 1834篇 |
1999年 | 1907篇 |
1998年 | 1468篇 |
1997年 | 1249篇 |
1996年 | 1137篇 |
1995年 | 934篇 |
1994年 | 773篇 |
1993年 | 559篇 |
1992年 | 502篇 |
1991年 | 342篇 |
1990年 | 273篇 |
1989年 | 244篇 |
1988年 | 159篇 |
1987年 | 109篇 |
1986年 | 72篇 |
1985年 | 67篇 |
1984年 | 43篇 |
1983年 | 38篇 |
1982年 | 41篇 |
1981年 | 20篇 |
1980年 | 28篇 |
1979年 | 13篇 |
1978年 | 6篇 |
1977年 | 8篇 |
1976年 | 5篇 |
1951年 | 12篇 |
排序方式: 共有10000条查询结果,搜索用时 187 毫秒
2.
Sinan Zhang Yadonga Zhao Xueshuang Yao Zhenhong Zheng Chuyao Zheng Zhuo Jiang 《International Journal of Food Science & Technology》2022,57(7):4245-4253
Ripe carambolas are hard to store and transport, while freeze-dried ones are easy to store. However, its long production time leads to higher costs. This study shows that high hydrostatic pressure (HHP) treatment could shorten the freeze-drying time of carambola slices. After HHP treatment (25–250 MPa), the drying time of the fresh sample can be shortened by 33.3–44.4% and the distribution of water and pigment in tissues is much uniform. With the increment of the pressure, 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radical scavenging rate are increased. At 250 MPa, the total phenolic content (TPC) increased from 11.34 to 13.36 mg GAE g−1, and the total flavonoid content (TFC) of the control sample was increased from 10.77 to 12.73 mg RE g−1. Compared with the untreated sample, HHP treatment can enhance the flavour and shorten the freeze-drying time. This work guides the application of HHP technology for drying food processing. 相似文献
3.
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
4.
盾构隧道施工物料无人运输有助于提升运输效率、降低运输成本、减少运输安全事故率。与公路汽车无人驾驶、港口车辆无人驾驶、轨道交通无人驾驶等逐步成熟的无人驾驶技术不同,在隧道场景下实施施工物料无人运输存在运输物料种类繁多、运输调度困难、地下定位信号拒止、狭窄车道频繁会车、行车路面工况复杂、地上地下联动响应慢等诸多挑战。从实现盾构隧道施工物料无人运输的关键问题分析入手,综述当前盾构隧道施工物料运输方式、运输需求、无人运输发展现状及存在的挑战,提出盾构隧道施工物料无人运输的五大关键技术:多种类物料智能货控能效管理技术,无人化垂直装卸门机控制技术,多传感器融合同步定位与地图构建技术,隧道复杂环境路径规划与自主避障技术,隧-地一体化联动响应的高可靠性无线通信技术。 相似文献
5.
Tao Feng Mingde Tong Shuotian Yao Hejun Li Shifeng Wen Hongjiao Lin 《Journal of the European Ceramic Society》2021,41(1):158-166
Composites based on hafnium carbide and reinforced with continuous naked carbon fiber with and without PyC interface were prepared at low temperature by precursor infiltration and pyrolysis and chemical vapor deposition method. The microstructure, mechanical property, cyclic ablation and fiber bundle push-in tests of the composites were investigated. The results show that after three times ablation cycles, the bending strength of samples without PyC interface decreased by 63.6 %; the bending strength of samples with PyC interface only decreased by 37.8 %. The force displacement curve of the samples with PyC interface presented a well pseudoplastic deformation state. The mechanical behavior difference of two kinds of composites was due to crucial function of PyC interface phase including protection of fiber and weakening of fiber/matrix interface. 相似文献
6.
KH550, KH560, CTAB, and F127 were adopted to modify silicon (Si) to improve the dispersity and stability of Si in the polyacrylonitrile/dimethyl sulfoxide (PAN/DMSO) polymer solutions. The influence of surfactants on rheological behaviors of PAN/DMSO/Si blending polymer solutions was investigated by an advanced solution and melt rotation rheometer. The homogeneity and stability were also studied. The results showed that the surfactants could change the viscosity dependence of blending polymer solutions on shear rate, temperature and storage time by increase the steric hindrance of Si. Among the four solutions, PAN/DMSO/Si blending polymer solution with F127 exhibited the lowest viscosity, activation energy and the smallest structural viscosity index and exhibited the trend close to the Newtonian fluids. Moreover, PAN/DMSO/Si blending polymer solution with F127 exhibited the best dispersity and stability, indicating its best physical properties and machinability. 相似文献
7.
首都体育馆作为北京冬奥会的重要竞赛场馆,在改造过程中深入贯彻"绿色办奥"理念,采用二氧化碳制冰、LED照明、无障碍设施、新风系统、"海绵城市"等可持续性相关措施,为落成已经超过半个世纪的首都体育馆注入了新鲜的"绿色血液". 相似文献
8.
Developing the thermal stability of metal-based ceramic composites or their films has always been challenging and bottlenecks for the utilization of energy. In this paper, the novel mesh-like functional Al doped-MoO3 nanocomposite film with even distribution and high purity was firstly fabricated by the high-efficiency electrophoretic deposition and surface modification. The optimal suspension turned out to be the mixture of isopropanol and the additives of polyethyleneimine and benzoic acid. The microtopography, crystalline structure, environmental resistance and thermal stability were analyzed by field emission scanning electron microscope (FESEM), energy dispersive X-ray (EDX), X-ray diffractometer (XRD), exposure and droplet-impacting test, DSC analysis and ignition test, respectively. The water contact angle and sliding angle of product can reach ~170° and <1°, indicating the excellent anti-wetting property. In addition, the high heat-release (~3180 J/g) of product all kept almost unchangeable after six months exposure experiments, demonstrating the outstanding thermostability. The exquisite design idea here can perfectly match microelectromechanical system (MEMS), providing the valuable reference for fabricating other metal-based high-energy composites with long lifespan for real industrial applications. 相似文献
9.
10.
Qianying Hoo Xiaohu Wang Feng Yuan Xuewei Cao Tiewa Cao Maolin Zhang 《Journal of the European Ceramic Society》2021,41(6):3816-3822
Jingdezhen is famous for its bluish white (Qingbai) porcelains of the Song Dynasty, and those decorated with iron spots are distinctive among them. Herein, iron spots on a bluish white porcelain were investigated using a series of microscopic and spectroscopic characterizations. We found the decreasing iron content from more than 8 wt% to about 2 wt% during the glaze color transition from rusty to brown and finally into green, which built a connection on the coloring mechanism of iron-rich crystallized glaze and celadon glaze. We identified the rare ε-Fe2O3, a promising magnetic material, in both the dark brown crystals and the triangular crystals in the rusty area, which is its first discovery among bluish white porcelains. Based on these findings, we discussed the coloring mechanism of iron-spot decoration along with the physical form of the iron oxide crystals, indicating the partially reducing atmosphere during firing process. 相似文献