全文获取类型
收费全文 | 620545篇 |
免费 | 59221篇 |
国内免费 | 25878篇 |
专业分类
电工技术 | 36293篇 |
技术理论 | 66篇 |
综合类 | 42319篇 |
化学工业 | 109767篇 |
金属工艺 | 34018篇 |
机械仪表 | 38651篇 |
建筑科学 | 48337篇 |
矿业工程 | 19345篇 |
能源动力 | 16799篇 |
轻工业 | 45999篇 |
水利工程 | 11603篇 |
石油天然气 | 37881篇 |
武器工业 | 4887篇 |
无线电 | 69620篇 |
一般工业技术 | 72965篇 |
冶金工业 | 30737篇 |
原子能技术 | 6134篇 |
自动化技术 | 80223篇 |
出版年
2024年 | 2008篇 |
2023年 | 8356篇 |
2022年 | 15309篇 |
2021年 | 22617篇 |
2020年 | 18073篇 |
2019年 | 16041篇 |
2018年 | 18215篇 |
2017年 | 20685篇 |
2016年 | 19380篇 |
2015年 | 26012篇 |
2014年 | 32531篇 |
2013年 | 39245篇 |
2012年 | 40555篇 |
2011年 | 44110篇 |
2010年 | 39857篇 |
2009年 | 37526篇 |
2008年 | 36339篇 |
2007年 | 34946篇 |
2006年 | 35022篇 |
2005年 | 30604篇 |
2004年 | 21165篇 |
2003年 | 18434篇 |
2002年 | 16901篇 |
2001年 | 15043篇 |
2000年 | 15230篇 |
1999年 | 15801篇 |
1998年 | 12209篇 |
1997年 | 10237篇 |
1996年 | 9624篇 |
1995年 | 7997篇 |
1994年 | 6442篇 |
1993年 | 4457篇 |
1992年 | 3508篇 |
1991年 | 2699篇 |
1990年 | 2082篇 |
1989年 | 1686篇 |
1988年 | 1321篇 |
1987年 | 792篇 |
1986年 | 643篇 |
1985年 | 417篇 |
1984年 | 313篇 |
1983年 | 229篇 |
1982年 | 232篇 |
1981年 | 178篇 |
1980年 | 174篇 |
1979年 | 81篇 |
1978年 | 44篇 |
1977年 | 46篇 |
1976年 | 64篇 |
1973年 | 22篇 |
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
151.
152.
聚乙二醇-三聚氰胺甲醛和聚乙烯醇半互穿网络的构建及表征 总被引:1,自引:0,他引:1
为提高三聚氰胺甲醛(MF)树脂制品的柔韧性,以聚乙二醇接枝三聚氰胺(M-PEG)替代部分三聚氰胺,并与甲醛、聚乙烯醇(PVA)在碱性条件下合成了聚乙二醇-三聚氰胺甲醛(PEG-MF)与PVA的半互穿聚合物网络体系(SemiIPN)。采用红外光谱、拉曼光谱、热重分析、差示扫描量热法等手段对Semi-IPN的微观结构进行了剖析,并分析了PEG、PVA等柔性链段对Semi-IPN黏度、游离甲醛含量、柔韧性等性能的影响。结果表明,PVA作为线型结构贯穿于聚乙二醇-三聚氰胺甲醛树脂交联网络体系结构中,形成了半互穿网络结构;所形成的Semi-IPN的热分解温度比MF树脂降低了60℃左右;Semi-IPN的韧性比纯MF树脂提高了800%,最高可达到19.700kJ/m2。 相似文献
153.
154.
SPEEK/cSMM membrane for simultaneous electricity generation and wastewater treatment in microbial fuel cell 下载免费PDF全文
155.
Efficacy of Crude and Purified Chitinases (SsChi50) Extracted from Offal Red Scorpion Fish in Biological Control of Chickpea Weevil (Callosobruchus maculatus L.) 下载免费PDF全文
156.
Quality enhancement of the abundant under‐valued crustacean,lobster krill (Munida spp.), during its chilled storage 下载免费PDF全文
Bibiana García‐Soto José M. Miranda Jorge Barros‐Velázquez Santiago P. Aubourg 《International Journal of Food Science & Technology》2015,50(3):708-716
Lobster krill (Munida genus) represents an under‐valued crustacean frequently caught on European fishing banks. In this work, its sensory, microbiological and biochemical qualities were evaluated during chilled storage. Additionally, the effects of a prestorage antimelanosic treatment consisting of soaking in sodium metabisulphite (SMB) solutions at two different concentrations (0.25% and 0.75%) were also studied. SMB prestorage treatment provided lobster specimens that still exhibited acceptable sensory quality after 10 days of storage, while control specimens were unacceptable at that time. SMB treatment also resulted in a significant (P < 0.05) inhibition of microbial growth, mainly of Enterobacteriaceae, psychrotrophes and proteolytic bacteria. Low lipid oxidation levels were observed for all batches; however, a significantly higher (P < 0.05) retention of polyunsaturated fatty acids was found in SMB‐treated lobster, especially in the 0.75% SMB batch. The results presented here open the way to the potential commercialisation of currently under‐utilised lobster krill as a chilled product. 相似文献
157.
Xiaoyan Qiu Yongqiang Zhang Haitao Wu Rui Yang Jun Yang Rongjuan Liu Yong Liu Zhiping Zhou Tongfan Hao Yijing Nie 《Polymer International》2019,68(2):218-224
The crystallization of capped ultrathin polymer films is closely dependent on film thickness and interfacial interaction. Using dynamic Monte Carlo simulations, the crystallization behaviors of polymer films confined between two substrates were investigated. The crystallization rate of confined polymers is reduced with high interfacial interactions. Above a critical strength of interfacial interaction, polymer crystallization in the thin film is inhibited within the simulation time scales. An increase in film thickness leads to a rise in critical interfacial interaction. In thicker films, the chains have more space to change conformation to form crystal stems. In addition, there are fewer absorbed segments in confined chains for the thicker films, and thus the chains have stronger ability to adjust their conformation. Therefore an increase in film thickness can cause a reduction in the entropic barrier required for the formation of crystals and thus an increase in the critical interfacial interaction. © 2018 Society of Chemical Industry 相似文献
158.
Chenxu Liu Shuguang Zhang Ruonan Ji Peng Wang Jin Zhang Yu Tian Yonggang Meng Yedong He 《Ceramics International》2019,45(4):4747-4755
Semiconductor particles doped Al2O3 coatings were prepared by cathode plasma electrolytic deposition in Al(NO3)3 electrolyte dispersed with SiC micro- and nano-particles (average particle sizes of 0.5–1.7?µm and 40?nm respectively). The effects of the concentrations and particle sizes of the SiC on the microstructures and tribological performances of the composite coatings were studied. In comparison with the case of dispersing with SiC microparticles, the dispersion of SiC nanoparticles in the coatings was more uniform. When the concentration of SiC nanoparticles was 5?g/L, the surface roughness of the composite coating was reduced by 63%, compared with that of the unmodified coating. Friction results demonstrated that the addition of 5?g/L SiC nanoparticles reduced the friction coefficient from 0.60 to 0.38 and decreased the wear volume under dry friction. The current density and bath voltage were measured to analyze the effects of SiC particles on the deposition process. The results showed that the SiC particles could alter the electrical behavior of the coatings during the deposition process, weaken the bombardment of the plasma, and improve the structures of the coatings. 相似文献
159.
Magnetic Resonance Materials in Physics, Biology and Medicine - To investigate the value of using diffusion-weighted imaging (DWI) and intravoxel incoherent motion DWI (IVIM-DWI) to assess the... 相似文献
160.
既有公共建筑能耗中,围护结构节能潜力巨大。以兰州某既有办公建筑为例,采用DeST-C软件模拟围护结构不同材料厚度、窗型,得出系列负荷,通过对数据分析、比较,得出如下结论:外墙外保温适宜材料为50mm的挤塑板,最大热负荷节能率为45.66%;屋面适宜保温材料为65mm的挤塑板,最大热负荷节能率为4.25%;外窗各个朝向全部更换玻璃,推荐选用内张膜中空玻璃(双膜),最大热负荷节能率为7.36%;单独更换南向外窗材料,推荐选用真空镀膜复合中空玻璃,最大热负荷节能率为1.78%。 相似文献