全文获取类型
收费全文 | 168025篇 |
免费 | 12347篇 |
国内免费 | 6187篇 |
专业分类
电工技术 | 8919篇 |
技术理论 | 10篇 |
综合类 | 8831篇 |
化学工业 | 27458篇 |
金属工艺 | 10115篇 |
机械仪表 | 10203篇 |
建筑科学 | 9891篇 |
矿业工程 | 4040篇 |
能源动力 | 3714篇 |
轻工业 | 9430篇 |
水利工程 | 3181篇 |
石油天然气 | 9607篇 |
武器工业 | 1065篇 |
无线电 | 17647篇 |
一般工业技术 | 26912篇 |
冶金工业 | 11136篇 |
原子能技术 | 4851篇 |
自动化技术 | 19549篇 |
出版年
2024年 | 733篇 |
2023年 | 2390篇 |
2022年 | 4728篇 |
2021年 | 6336篇 |
2020年 | 4763篇 |
2019年 | 4059篇 |
2018年 | 5194篇 |
2017年 | 5626篇 |
2016年 | 5177篇 |
2015年 | 5703篇 |
2014年 | 7359篇 |
2013年 | 8974篇 |
2012年 | 9620篇 |
2011年 | 10315篇 |
2010年 | 8767篇 |
2009年 | 8603篇 |
2008年 | 8471篇 |
2007年 | 7957篇 |
2006年 | 7387篇 |
2005年 | 6302篇 |
2004年 | 4823篇 |
2003年 | 4749篇 |
2002年 | 4797篇 |
2001年 | 4369篇 |
2000年 | 3772篇 |
1999年 | 3374篇 |
1998年 | 2668篇 |
1997年 | 2229篇 |
1996年 | 1998篇 |
1995年 | 1756篇 |
1994年 | 1487篇 |
1993年 | 1269篇 |
1992年 | 1229篇 |
1991年 | 1093篇 |
1990年 | 1098篇 |
1989年 | 1022篇 |
1988年 | 901篇 |
1987年 | 845篇 |
1986年 | 765篇 |
1985年 | 719篇 |
1984年 | 701篇 |
1981年 | 668篇 |
1979年 | 736篇 |
1978年 | 777篇 |
1977年 | 739篇 |
1976年 | 755篇 |
1975年 | 713篇 |
1974年 | 719篇 |
1973年 | 723篇 |
1972年 | 705篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
41.
Qingna Gong Songtao Cao Yu Zhou Ruixin Wang Weizhou Jiao 《International Journal of Hydrogen Energy》2021,46(41):21442-21453
Ni2P nanoparticles and CdS nanorods were grew together on a mesoporous g-C3N4 through a facile in-situ solvothermal approach. Under visible light (λ > 400 nm), the as-prepared ternary PCN–CdS-5% Ni2P composite displays a high H2 evolution rate with 2905.86 μmol g?1 h?1, which is about 14, 18 and 279 times that of PCN–CdS, PCN–Ni2P and PCN, respectively. The enhanced photocatalytic activity is mainly attributed to the improved separation efficiency of the photocarriers by the type II PCN–CdS heterojunction and the effective extraction of photogenerated electrons by Ni2P. Meanwhile, Ni2P acts as co-catalyst to provide the photocatalytic active site for hydrogen reduction. In addition, PCN–CdS-5% Ni2P composite exerts good stability in 12-h cycles. 相似文献
42.
卫星导航地基增强系统(GBAS)是国际民航组织重点推进的新技术。为全面借鉴国际上 GBAS 技术的发展与应用,本文介绍了 GBAS 组成、原理和优缺点,研究了国内外 GBAS 研究与应用的发展,结合中国民航目前的运行需求提出了 GBAS 应用建议,为 GBAS 发展应用提供了参考。 相似文献
43.
Wireless Personal Communications - The existing long term evolution networks originally designed for human-to-human communications are hard to tackle numerous and bursty random access requests from... 相似文献
44.
45.
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
46.
47.
48.
49.
Lü Qing Xu Bin Yu Yang Zhan Wei Zhao Yu Zheng Jun Ji Jian 《Bulletin of Engineering Geology and the Environment》2021,80(8):6513-6525
Bulletin of Engineering Geology and the Environment - Many uncertainties exist in pile-stabilized slopes which make their design substantially complicated. In this paper, a first-order reliability... 相似文献
50.
Lihua Lou Weijie Yu Ronald J. Kendall Ernest Smith Seshadri S. Ramkumar 《应用聚合物科学杂志》2020,137(30):49213
A tensile properties testing study was conducted to understand the influence of thickness, cross-head speed (speed of testing), gauge length (GL; specimen test length), and sample shape on important tensile properties of polyvinyl alcohol (PVA) nanofiber webs. The effects of each testing parameter on load at break, extension at break, Young's modulus, and tensile stress–strain curve of PVA nanofiber webs are analyzed. The Welch two sample t-tests show the significant difference among tested data. Using interaction plots, two-way analysis of variance, and margin mean plots, the interaction effects among testing parameters have been analyzed. Of all the factors, cross-head speed, the interaction among GL, and sample thickness (GL: Thickness) and the interaction among GL, testing speed and sample thickness (GL: Speed: Thickness) have significant influence on the tensile properties of PVA nanofiber webs. Moreover, the hypothesized model of mechanism of tensile strain–stress curve of PVA nanofiber webs has been proposed. Based on the model, the tensile strain–stress curve can be split into three stages: linear elastic, partial break up, and complete breakage. This study will provide a better understanding of tensile testing parameters' effects and their interaction effects on the tensile properties of nanowebs. 相似文献