全文获取类型
收费全文 | 62623篇 |
免费 | 6595篇 |
国内免费 | 3988篇 |
专业分类
电工技术 | 4390篇 |
技术理论 | 3篇 |
综合类 | 5197篇 |
化学工业 | 9773篇 |
金属工艺 | 3814篇 |
机械仪表 | 4136篇 |
建筑科学 | 4825篇 |
矿业工程 | 2079篇 |
能源动力 | 1841篇 |
轻工业 | 5095篇 |
水利工程 | 1327篇 |
石油天然气 | 2815篇 |
武器工业 | 636篇 |
无线电 | 7490篇 |
一般工业技术 | 7089篇 |
冶金工业 | 2627篇 |
原子能技术 | 813篇 |
自动化技术 | 9256篇 |
出版年
2024年 | 252篇 |
2023年 | 1007篇 |
2022年 | 1956篇 |
2021年 | 2783篇 |
2020年 | 2059篇 |
2019年 | 1751篇 |
2018年 | 1885篇 |
2017年 | 2024篇 |
2016年 | 1894篇 |
2015年 | 2711篇 |
2014年 | 3321篇 |
2013年 | 3936篇 |
2012年 | 4538篇 |
2011年 | 4584篇 |
2010年 | 4314篇 |
2009年 | 3997篇 |
2008年 | 3840篇 |
2007年 | 3671篇 |
2006年 | 3471篇 |
2005年 | 2941篇 |
2004年 | 2163篇 |
2003年 | 2168篇 |
2002年 | 2628篇 |
2001年 | 2280篇 |
2000年 | 1606篇 |
1999年 | 1275篇 |
1998年 | 789篇 |
1997年 | 695篇 |
1996年 | 548篇 |
1995年 | 486篇 |
1994年 | 387篇 |
1993年 | 253篇 |
1992年 | 226篇 |
1991年 | 180篇 |
1990年 | 134篇 |
1989年 | 114篇 |
1988年 | 81篇 |
1987年 | 48篇 |
1986年 | 37篇 |
1985年 | 28篇 |
1984年 | 17篇 |
1983年 | 5篇 |
1982年 | 19篇 |
1981年 | 13篇 |
1980年 | 25篇 |
1979年 | 13篇 |
1978年 | 7篇 |
1977年 | 7篇 |
1959年 | 14篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
11.
Effects of different carbon sources and C/N values on nonvolatile taste components of Pleurotus eryngii 下载免费PDF全文
Wen Li Xiaobei Li Yan Yang Feng Zhou Yanfang Liu Shuai Zhou Hailong Yu 《International Journal of Food Science & Technology》2015,50(11):2360-2366
Pleurotus eryngii, the second largest industrial cultivation mushroom in China, is usually cultivated on substrates mainly consisting of sawdust and corncob. In this study, experiments were performed to determine the effects of different carbon sources and C/N values on nonvolatile taste components of P. eryngii. The effects of different carbon sources on nonvolatile taste components levels revealed that sawdust was beneficial to high levels of crude protein, amino acids, 5′‐nucleotides and equivalent umami concentration, while corncob was beneficial to high contents of carbohydrate, polysaccharides and trehalose. At the similar C/N values, relatively higher sawdust content was beneficial to umami amino acid production, while relatively higher corncob content was beneficial to high contents of carbohydrate, polysaccharides and mannitol. Higher C/N value was beneficial to high levels of crude protein, amino acids, 5′‐nucleotides and equivalent umami concentration, while lower C/N value was beneficial to high contents of carbohydrate, polysaccharides and trehalose. These results provided information for P. eryngii fruit body industrial cultivation to obtain specific nonvolatile taste components with high levels. 相似文献
12.
13.
针对基站柜式空调耗电量大的问题,创造性地使用基站分布式冷却的方式,达到精确送风,节能高效的目的.在应用实践中检验了分布式冷却系统实际节能量和应用效果,总结出分布式冷却系统应用场景和范围,为更大范围推广应用DCS分布式冷却系统提供实践依据. 相似文献
14.
15.
16.
Weikang Dong Ruishi Qi Tiansheng Liu Yi Li Ning Li Ze Hua Zirui Gao Shuyuan Zhang Kaihui Liu Jiandong Guo Peng Gao 《Advanced materials (Deerfield Beach, Fla.)》2020,32(46):2002014
Hyperbolic phonon polaritons (HPhPs) in orthorhombic-phase molybdenum trioxide (α-MoO3) show in-plane hyperbolicity, great wavelength compression, and ultralong lifetime, therefore holding great potential in nanophotonic applications. However, its polaritonic response in the far-infrared (FIR) range remains unexplored due to challenges in experimental characterization. Here, monochromated electron energy loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM) is used to probe HPhPs in α-MoO3 in both mid-infrared (MIR) and FIR frequencies and correlate their behaviors with microstructures and orientations. It is found that low structural symmetry leads to various phonon modes and multiple Reststrahlen bands (RBs) over a broad spectral range (over 70 meV) and in different directions (55–63 meV and 119–125 meV along the b-axis, 68–106 meV along the c-axis, and 101–121 meV along the a-axis). These HPhPs can be selectively excited by controlling the direction of swift electrons. These findings provide new opportunities in nanophotonic and optoelectronic applications, such as directed light propagation, hyperlenses, and heat transfer. 相似文献
17.
19.
Wei-Li Xie Xiao-Dong Zhang Wen-Hui Liu Qi Xie Guang-Wu Wen Xiao-Xiao Huang Jian-Dong Zhu Fei-Xiang Ma 《稀有金属(英文版)》2019,(3)
SiC nano wires were fabricated on the silicon substrate dipped with a layer of Ni catalyst at 900 ℃ by gas pressure annealing processing. The morphologies and crystal structures were determined by scanning electron microscopy(SEM), transmission electron microscopy(TEM)and X-ray diffraction(XRD). The results show that the assynthesized nanowires are β-SiC single crystalline with diameter range of 50-100 nm, and length of tens of micron by directly annealing at 900 ℃. The SiC nano wires grow along the [111] direction with highly uniform morphology. And the possible growth mechanism of SiC nano wires is proposed.The present work provides an efficient strategy for the production of high-quality SiC nano wires. 相似文献
20.
Baofu Qiu Xiaoming Duan Zhuo Zhang Delong Cai Ning Liao Peigang He Dechang Jia Yu Zhou 《Ceramics International》2021,47(1):73-79
The effects of La2O3–Al2O3–SiO2 addition on the thermal conductivity, coefficient of thermal expansion (CTE), Young's modulus and cyclic thermal shock resistance of hot-pressed h-BN composite ceramics were investigated. The samples were heated to 1000 °C and then quenched to room temperature with 1–50 cycles, and the residual flexural strength was used to evaluate cyclic thermal shock resistance. h-BN composite ceramics containing 10 vol% La2O3–Al2O3 and 20 vol% SiO2 addition exhibited the highest flexural strength, thermal conductivity and relatively low CTE, which were beneficial to the excellent thermal shock resistance. In addition, the viscous amorphous phase of ternary La2O3–Al2O3–SiO2 system could accommodate and relax thermal stress contributing to the high thermal shock resistance. Therefore, the residual flexural strength still maintained the value of 234.3 MPa (86.9% of initial strength) after 50 cycles of thermal shock. 相似文献