全文获取类型
收费全文 | 272350篇 |
免费 | 24476篇 |
国内免费 | 15590篇 |
专业分类
电工技术 | 19192篇 |
技术理论 | 9篇 |
综合类 | 21534篇 |
化学工业 | 39767篇 |
金属工艺 | 17577篇 |
机械仪表 | 17993篇 |
建筑科学 | 17568篇 |
矿业工程 | 8672篇 |
能源动力 | 6450篇 |
轻工业 | 21251篇 |
水利工程 | 6552篇 |
石油天然气 | 13186篇 |
武器工业 | 2563篇 |
无线电 | 28256篇 |
一般工业技术 | 35418篇 |
冶金工业 | 14737篇 |
原子能技术 | 6614篇 |
自动化技术 | 35077篇 |
出版年
2024年 | 727篇 |
2023年 | 3851篇 |
2022年 | 8368篇 |
2021年 | 11517篇 |
2020年 | 8374篇 |
2019年 | 6513篇 |
2018年 | 7809篇 |
2017年 | 8621篇 |
2016年 | 7939篇 |
2015年 | 10417篇 |
2014年 | 13154篇 |
2013年 | 16152篇 |
2012年 | 18632篇 |
2011年 | 19750篇 |
2010年 | 17667篇 |
2009年 | 17454篇 |
2008年 | 17394篇 |
2007年 | 16764篇 |
2006年 | 14868篇 |
2005年 | 12439篇 |
2004年 | 9183篇 |
2003年 | 7716篇 |
2002年 | 7491篇 |
2001年 | 6831篇 |
2000年 | 5809篇 |
1999年 | 3995篇 |
1998年 | 2841篇 |
1997年 | 2353篇 |
1996年 | 2032篇 |
1995年 | 1817篇 |
1994年 | 1506篇 |
1993年 | 1311篇 |
1992年 | 1265篇 |
1991年 | 1120篇 |
1990年 | 1130篇 |
1989年 | 1054篇 |
1988年 | 922篇 |
1987年 | 845篇 |
1986年 | 772篇 |
1985年 | 722篇 |
1984年 | 706篇 |
1981年 | 690篇 |
1979年 | 753篇 |
1978年 | 777篇 |
1977年 | 740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 15 毫秒
91.
一次性医用手套是能够防止人们交叉感染的常用防护用品。随着新冠肺炎疫情在全球范围的迅速蔓延,疫情防控一线以及广大普通民众对一次性医用手套的需求与日俱增,其标准也受到广泛关注。本文对中国国家标准涉及一次性使用医用手套的4项产品标准进行了解读,并分析它们与国外同种产品标准间的对应关系以及重点指标的差异。 相似文献
92.
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
94.
95.
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
96.
Colour remains one of the key factors in presenting an object and, consequently, has been widely applied in retrieval of images based on their visual contents. However, a colour appearance changes with the change of viewing surroundings, the phenomenon that has not been paid attention yet while performing colour‐based image retrieval. To comprehend this effect, in this article, a chromatic contrast model, CAMcc, is developed for the application of retrieval of colour intensive images, cementing the gap that most of existing colour models lack to fill by taking simultaneous colour contrast into account. Subsequently, the model is applied to the retrieval task on a collection of museum wallpapers of colour‐rich images. In comparison with current popular colour models including CIECAM02, HSI and RGB, with respect to both foreground and background colours, CAMcc appears to outperform the others with retrieved results being closer to query images. In addition, CAMcc focuses more on foreground colours, especially by maintaining the balance between both foreground and background colours, while the rest of existing models take on dominant colours that are perceived the most, usually background tones. Significantly, the contribution of the investigation lies in not only the improvement of the accuracy of colour‐based image retrieval but also the development of colour contrast model that warrants an important place in colour and computer vision theory, leading to deciphering the insight of this age‐old topic of chromatic contrast in colour science. © 2014 Wiley Periodicals, Inc. Col Res Appl, 40, 361–373, 2015 相似文献
97.
98.
风积沙改性土的热膨胀特性对评价风积沙改性土路基温度稳定性至关重要.通过在风积沙中掺入不同质量的水泥、黏性土或聚丙烯纤维制成不同配比的改性土,测试改性土的热膨胀系数,研究外加材料的掺入量对改性土热膨胀特性的影响.试验结果表明:改性土的平均线膨胀系数随着水泥掺入量的增加总体呈增大趋势,随着聚丙烯纤维掺入量的增加而减小,随着黏性土掺入量的增加而增大.聚丙烯纤维的掺入可有效降低改性土的热膨胀系数.研究成果可为进一步优化改性土提供研究方向,为高温差沙漠地区工程建设中风积沙改性土温度裂缝的控制提供试验依据. 相似文献
99.