全文获取类型
收费全文 | 78889篇 |
免费 | 8328篇 |
国内免费 | 5346篇 |
专业分类
电工技术 | 5677篇 |
技术理论 | 3篇 |
综合类 | 7836篇 |
化学工业 | 11759篇 |
金属工艺 | 4962篇 |
机械仪表 | 4785篇 |
建筑科学 | 6796篇 |
矿业工程 | 2823篇 |
能源动力 | 2522篇 |
轻工业 | 6867篇 |
水利工程 | 1992篇 |
石油天然气 | 3557篇 |
武器工业 | 835篇 |
无线电 | 8712篇 |
一般工业技术 | 7679篇 |
冶金工业 | 3431篇 |
原子能技术 | 1121篇 |
自动化技术 | 11206篇 |
出版年
2024年 | 353篇 |
2023年 | 1337篇 |
2022年 | 2576篇 |
2021年 | 3476篇 |
2020年 | 2589篇 |
2019年 | 2283篇 |
2018年 | 2380篇 |
2017年 | 2540篇 |
2016年 | 2214篇 |
2015年 | 3269篇 |
2014年 | 3929篇 |
2013年 | 4630篇 |
2012年 | 5178篇 |
2011年 | 5308篇 |
2010年 | 5108篇 |
2009年 | 4767篇 |
2008年 | 4779篇 |
2007年 | 4564篇 |
2006年 | 4117篇 |
2005年 | 3225篇 |
2004年 | 2940篇 |
2003年 | 3776篇 |
2002年 | 5148篇 |
2001年 | 4357篇 |
2000年 | 2265篇 |
1999年 | 1474篇 |
1998年 | 713篇 |
1997年 | 632篇 |
1996年 | 607篇 |
1995年 | 484篇 |
1994年 | 404篇 |
1993年 | 270篇 |
1992年 | 224篇 |
1991年 | 136篇 |
1990年 | 121篇 |
1989年 | 86篇 |
1988年 | 68篇 |
1987年 | 40篇 |
1986年 | 43篇 |
1985年 | 32篇 |
1984年 | 25篇 |
1983年 | 14篇 |
1982年 | 12篇 |
1981年 | 15篇 |
1980年 | 19篇 |
1979年 | 8篇 |
1965年 | 4篇 |
1959年 | 9篇 |
1951年 | 15篇 |
排序方式: 共有10000条查询结果,搜索用时 320 毫秒
41.
42.
ZHAO Pengfei TIAN Yuming LIU Aiping KONG Xiangchen CHAI Yuesheng LI Zhangang BAI Pinbo 《中国耐火材料》2015,(2):36-41
Based on the needs of the market,a new 52 MPa medium-density and high-strength ceramic proppant was prepared by adopting third grade bauxite and clay as raw materials and using the solid phase sintering method,and the effect of the firing temperature on the microstructure,phase composition and mechanical properties of the ceramic proppant was studied. The broken resistance mechanism of this ceramic proppant was also discussed. The results show that the main phases of the prepared ceramic proppant are mullite and corundum; the broken rates are 3. 92% and 7. 21% under 52 MPa and69 MPa,respectively. 相似文献
43.
Catalytic Hydrocracking of a Bitumen‐Derived Asphaltene over NiMo/γ‐Al2O3 at Various Temperatures
下载免费PDF全文
![点击此处可从《化学工程与技术》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Hydrocracking of a bitumen‐derived asphaltene over NiMo/γ‐Al2O3 was investigated in a microbatch reactor at varying temperatures. The molar kinetics of asphaltene cracking reaction was examined by fitting the experimental data. Below a defined temperature, the molar reaction showed the first‐order kinetic feature while at higher temperatures secondary reactions such as coke formation became significant, causing deviation of the reaction behavior from the proposed first‐order kinetic model. Selectivity analysis proved that dominant products varied from gases to liquids to gases with increasing temperature, shifting the dominant reaction from C–S bonds cleavage to C–C bonds cleavage. 相似文献
44.
Sumeng Wei Yuling Yang Xiao Feng Shanshan Li Lei Zhou Jingyu Wang Xiaozhi Tang 《International Journal of Food Science & Technology》2020,55(7):2691-2699
Structures and properties of myofibrillar protein gel prepared at different power (300–800 W) were evaluated. Amino acid analysis demonstrated that changes in microwave power did not alter primary structure of gel. However, an increase in microwave power could change higher structures of gel. As microwave power increased, α-helix content decreased and β-sheet content increased. Increased microwave power probably facilitated protein to unfold and expose the internal groups, causing surface hydrophobicity and the formation of disulphide bonds were enhanced, which indicated changes in tertiary and quaternary structures of protein. At 500 W, gel had the best ultrastructure where surface morphology, springiness and water holding capacity reached the optimum. Our findings suggested that microwave at an appropriate power (500 W) could change higher structures of myofibrillar protein gel to achieve desired processing and quality protein gel characteristics. 相似文献
45.
Fei Li Xin-Gang Wang Xiao Huang Ji-Xuan Liu Weichao Bao Guo-Jun Zhang Hongzhi Wang 《Journal of the European Ceramic Society》2018,38(14):4806-4813
We present a straightforward method via sol-gel process using polyethylene glycol (PEG) as phase separation inducer to prepare zirconium carbide/silicon carbide (ZrC/SiC) porous monoliths. Organic/inorganic hybrid gels are prepared using zirconium oxychloride, furfuryl alcohol, and tetraethyl orthosilicate as major starting materials. In the presence of PEG, crack-free hybrid monoliths are obtained by drying the wet gels under ambient pressure, whereas in the absence of PEG, the wet gels break into pieces as expected. PEG plays a key role in maintaining the macroscopic shape of the monoliths. After ceramization at 1300–1500?°C, ZrC/SiC porous monoliths are obtained. SEM and mercury intrusion porosimetry data show that PEG also has strong influence on the microstructures of the monoliths. The compressive strengths of the ceramic monoliths are in the range of 0.3 to 0.7?MPa. And their compressive behavior starts to differ due to the changes in their microstructures, especially the pore structure. 相似文献
46.
48.
49.
50.
通过对粉煤灰砖抗折强度测量结果不确定度的评定,分析出影响试验结果的各种因素,为提高检测水平和精确度提供指导。 相似文献