全文获取类型
收费全文 | 14082篇 |
免费 | 738篇 |
国内免费 | 336篇 |
专业分类
电工技术 | 121篇 |
综合类 | 445篇 |
化学工业 | 5165篇 |
金属工艺 | 1863篇 |
机械仪表 | 340篇 |
建筑科学 | 179篇 |
矿业工程 | 197篇 |
能源动力 | 1246篇 |
轻工业 | 462篇 |
水利工程 | 18篇 |
石油天然气 | 102篇 |
武器工业 | 77篇 |
无线电 | 813篇 |
一般工业技术 | 3136篇 |
冶金工业 | 589篇 |
原子能技术 | 87篇 |
自动化技术 | 316篇 |
出版年
2024年 | 31篇 |
2023年 | 668篇 |
2022年 | 369篇 |
2021年 | 341篇 |
2020年 | 729篇 |
2019年 | 705篇 |
2018年 | 322篇 |
2017年 | 697篇 |
2016年 | 663篇 |
2015年 | 758篇 |
2014年 | 904篇 |
2013年 | 999篇 |
2012年 | 1202篇 |
2011年 | 1017篇 |
2010年 | 708篇 |
2009年 | 916篇 |
2008年 | 344篇 |
2007年 | 914篇 |
2006年 | 802篇 |
2005年 | 300篇 |
2004年 | 130篇 |
2003年 | 177篇 |
2002年 | 188篇 |
2001年 | 168篇 |
2000年 | 133篇 |
1999年 | 126篇 |
1998年 | 49篇 |
1997年 | 19篇 |
1996年 | 45篇 |
1995年 | 45篇 |
1994年 | 42篇 |
1993年 | 32篇 |
1992年 | 42篇 |
1991年 | 37篇 |
1990年 | 32篇 |
1989年 | 30篇 |
1988年 | 61篇 |
1987年 | 140篇 |
1986年 | 114篇 |
1985年 | 40篇 |
1984年 | 21篇 |
1983年 | 14篇 |
1982年 | 8篇 |
1981年 | 20篇 |
1980年 | 14篇 |
1979年 | 15篇 |
1978年 | 9篇 |
1977年 | 7篇 |
1976年 | 8篇 |
1973年 | 1篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
91.
轻量化是降低铝质易拉罐生产成本、促进技术进步的重要手段。分析了实现铝质易拉罐轻量化的主要技术途径,包括减薄铝板材厚度和减小罐口直径2个方面。在此基础上,探讨了改善铝板材冶金质量与变形性能、优化罐型并改进工装模具等实现轻量化的关键技术。 相似文献
92.
Shuai Huang Lixin Yu Kangliang Peng Youjun Zhao Jindi Wang Mengmeng Shang 《Journal of the American Ceramic Society》2021,104(11):5848-5858
To enhance the display quality of light-emitting diodes (LEDs), it is of great significance to exploit green/yellow-emitting phosphors with narrow emission band, high quantum yield, and excellent color purity to satisfy the application. Herein, orthophosphate-based green/yellow-emitting Na3Tb(PO4)2:Ce3+/Eu2+ (NTPO:Ce3+/Eu2+) phosphors have been successfully synthesized by a facile solid-state reaction method. The absorption band of NTPO samples was extended to the near-ultraviolet region and the absorption efficiency was significantly improved owing to a highly efficient energy transfer from Ce3+/Eu2+ ion to Tb3+ ion in NTPO host certified by time-resolved PL spectra. Upon 300 nm excitation, the NTPO:Ce3+ is characterized by ultra-narrow-band green emission of Tb3+ with an absolute quantum yield of 94.5%. Unexpectedly, NTPO:Eu2+ emits bright yellow light with a color purity of 73% as a result of the blending of green light emission from Tb3+ and red light emission from Eu3+. The thermal stability has been improved by controlling the stoichiometric ratio of Na+. The prototype white LED used yellow-emitting NTPO:Eu2+ phosphor has higher color-rendering index (Ra = 83.5), lower correlated color temperature (CCT = 5206 K), and closer CIE color coordinates (0.338, 0.3187) to the standard white point at (0.333, 0.333) than that used green-emitting NTPO:Ce3+ phosphor, indicating the addition of the yellow light component improved the Ra of the trichromatic (RGB) materials. 相似文献
93.
Tiesong Xu Minghui Zhong Xiaolin Liang Jia Liu Bin Yan Jing Xiao Kai Jiao Xiange Wang Nian Si Zhongda Pan Zheming Zhao Xunsi Wang Peiqing Zhang Qiuhua Nie Shengchuang Bai Rongping Wang Junjie Zhang 《Journal of the American Ceramic Society》2021,104(11):5671-5678
Extinction ratio (ER) is one of the important parameters to characterize the polarization-maintaining (PM) performance of the fiber. In this paper, we report the preparation and properties of a novel chalcogenide microstructure fiber with a high ER. We fabricate a preform using a peeled-off extrusion method. The core and cladding material of the fiber are Ge9As23Se68 and Ge10As22Se68. The preform was drawn into a fiber with an average ER of −17.08 dB. The loss of the fiber is less than 2 dB over 5.20–8.55 μm, and the minimum loss of the fiber is 0.57 dB/m at 6.2 μm. Moreover, a flat mid-infrared supercontinuum spectrum spanning from 1.53 to 12.50 μm is generated by pumping an 18-cm-long PM fiber for the first time. 相似文献
94.
As a representative polyoxamide, poly(hexamethylene oxamide) (PA62) has good comprehensive performance. However, the high Tm (330°C) creates an obstacle for processing. To improve the processability of PA62, poly(hexamethylene terephthalate/hexamethylene oxamide) alternating copolyamide (alt-PA6T/62) was synthesized by hexamethylene diamine-terminated 6T6-diamine and dibutyl oxalate via solution/solid state polycondensation. Random copolyamide (ran-PA6T/62) was also synthesized for comparison. The structure and properties of the copolymer were analyzed by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR) spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Wide-angle X-ray diffraction (WAXD) and the saturated water absorption test. The NMR results confirm the alternating structure of alt-PA6T/62. The DSC and TGA results demonstrate that the novel alternating copolyamide alt-PA6T/62 (Tm = 321°C, T5 = 420°C) exhibited better thermal properties than those of ran-PA6T/62 (Tm = 294°C, T5 = 412°C). The saturated water absorption of alt-PA6T/62 was found to be 3.2 wt%. These results revealed that the novel alt-PA6T/62 had an alternating sequence distribution, showed a high melting point as well as good processability and thermal stability, and possessed low saturated water absorption and excellent dimensional stability. 相似文献
95.
Qianyu Yang Chen Gao Xuemei Zhang Xingyu Zhao Yiqing Fu Chihui Tsou Chunyan Zeng Li Yuan Zejun Pu Yiqing Xia Yuping Sheng Yu Fang 《应用聚合物科学杂志》2021,138(13):50308
Shape memory hydrogels (SMHs) can fix the hydrogels in a provisional shape and restore the initial shape under external stimulation. Herein, a dual-responsive shape memory hydrogel with dual-responsive swelling and self-healing properties is presented in this work. The SMHs were fabricated by one-step emulsion copolymerization of acrylic acid (AAc), acrylamide (AAm) and stearyl methacrylate (SMA). Sodium alginate (SA) was introduced as an interpenetrating polymer in the network. With ionic cross-linking between -COO− and Fe3+ or saline-reinforced hydrophobic association, the hydrogels can be fixed in a provisional shape, which can be restored by immersing the hydrogels in vitamin C solution or pure water, respectively. When the as-prepared hydrogels were immersed in FeCl3 solutions, additional ionic cross-linking between Fe3+ and -COO− could be formed, thus constructing the dual physically cross-linked (DPC) network, which endows the hydrogels with excellent fracture stress (2.6 MPa) and toughness (5.47 MJ/m3). Besides, the reversible physical cross-linkings endowed the hydrogel with outstanding self-healing capability. Furthermore, the pH and saline responsive swelling properties of the SMHs are additional fantastic properties. Therefore, we believe that this simple strategy provides a great opportunity for the preparation of SMHs with multiple intellectual performances. 相似文献
96.
In this paper, aramid fiber (AF)/ethylene-propylene-diene monomer (EPDM) microcellular foams added with different content of AF are prepared by the supercritical foaming method. The effect of the AF content on the rheological behavior, mechanical properties, thermal properties and cellular structure of the AF/EPDM microcellular foams has been systematically studied. The research illustrates that compared with pure EPDM, the AF/EPDM matrix has greater viscosity and modulus, which is conducive to reduce the cell size and increase its density. And the thermal stability of EPDM foams is improved with the addition of aramid fiber. Meanwhile, when the content of AF is added to 1 wt%, the AF/EPDM microcellular foam exhibits a relatively low thermal diffusion coefficient and apparent density with the thermal conductivity to 0.06 W/mK. When the AF is added to 5 wt%, the tensile strength of the AF/EPDM microcellular foam increases to 1.95 MPa, which is improved by 47% compared with that of the pure EPDM foam. Furthermore, when the compressive strain reaches to 50%, the compressive strength of the AF/EPDM microcellular foam is 0.48 MPa, improved by 296% compared with that of the pure EPDM foam. 相似文献
97.
Samarthya Bhagia Nidia C. Gallego Nitilaksha Hiremath David P. Harper Richard A. Lowden Richard R. Lowden Yunqiao Pu Uday Vaidya Soydan Ozcan Arthur J. Ragauskas 《应用聚合物科学杂志》2021,138(32):50797
High speed friction grinding has been used to grind plant and food substances in water but never been explored for grinding of thermoplastics like polylactic acid (PLA), low and high density polyethylene and polypropylene. Such grinding was investigated in this work and was made possible by using 0.5% guar gum solution instead of just water because increasing the viscosity of water reduced their settling and the speed of passing through the grinder. Tensile, flexural, and impact strengths of the plastics were studied and higher grinding efficiency of PLA could be explained by its low elongation-at-break compared to low density polyethylene, high density polyethylene, and polypropylene. The microplastics (2000–45 μm) were studied for mass and particle size distributions and by scanning electron microscopy, 13C CP/MAS NMR, Fourier transform infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. In addition, viscosity of guar gum and contact angles was measured. This new technology can produce finely ground microplastics (710–45 μm) for a variety of applications. 相似文献
98.
Junfeng Yue Xuejiao Fu Jun Lu Shuidong Zhang Dong Li Yi He Quan Wei Changhua Liu Lin Gan Ishak Ahmad Jin Huang 《应用聚合物科学杂志》2021,138(45):51330
Sustainable development strategy has aroused a great interest in biomass resources as alternative raw materials. A kind of biomass-derived poly(butylene succinate) (PBS), has been developed as porous foams to reduce resource exhaustion and meet lightweight demands. For fire-safety in-service, graphene oxide (GO) was functionalized by 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) to combine flame-retardant elements and heat-barrier function. Hence, a very low loading level of P-containing GO as only 5 wt% could reduce peak heat release rate (pHRR) and total heat release (THR) of PBS-based foams by 58.5% and 22.3%, respectively. Meanwhile, N-/P-doped mesoporous char with a specific surface area of 136 m2/g, which derived from combustion of flame-retardant foaming PBS, contributes to a potential of energy storage applications in the capacitor or the anode of Li-ion battery with long-term stability. Overall, the sustainability of bio-based polyester could integrate lightweight of foaming, and be extended to utilization after use via facile combustion inspired by flame-retardancy design. 相似文献
99.
A simple and feasible method to enhance the wear resistance of ultra-high molecular weight polyethylene (UHMWPE) fibers was reported. The graphite oxide (GO) prepared using improved Hummer's method was surface modified with hexadecylamine to improve its compatibility with UHMWPE. Combined with well-dispersion of modified-GO (m-GO) in dichloromethane and the fact that the viscosity of UHMWPE suspension can be decreased by dichloromethane, the well dispersed m-GO/dichloromethane was added into UHMWPE suspension to improve m-GO dispersion in UHMWPE fibers. Finally, UHMWPE fibers with different m-GO concentration were prepared using gel spinning technology. The effect of m-GO concentration on the structure and properties of modified UHMWPE fibers were investigated. The results indicated that the melting temperature and crystallinity of m-GO modified UHMWPE fibers increased with increasing of m-GO concentration, while the fiber's crystal sizes and orientation increased, thus the tensile strength of m-GO modified UHMWPE fibers remained almost undamaged. The introduction of m-GO is beneficial to the formation of smooth transfer film on fiber's surface, which enhanced the self-lubrication of UHMWPE fibers. Compared with pure UHMWPE fiber, the UHMWPE fiber containing 1.5 wt% m-GO had enhanced wear resistance by 55.4% and still maintained high tensile strength of 29.98 cN dtex−1. 相似文献
100.
为改善剑麻纤维(SF)与聚丙烯(PP)之间的相容性,在PP/SF复合材料中添加超支化聚酯(H101)、超支化环氧树脂(E102),研究了两种超支化聚合物(HBP)的热稳定性及对PP/SF复合材力学性能、熔体流动性和微观形貌的影响。热重分析表明,所使用的HBP均具有较好的热稳定性;扫描电子显微镜分析发现,HBP的加入使基体与纤维结合得更加紧密;力学性能测试表明,H101可不同程度地提高复合材料的拉伸、弯曲及冲击强度;E102可提高复合材料的拉伸及冲击强度,当E102含量为10%时,与PP/SF复合材料相比,冲击强度提高了72.24%。尽管HBP含量较高时复合材料的力学性能提高,但HBP会降低复合材料的熔体流动速率,选择HBP含量时需要综合考虑。 相似文献