全文获取类型
收费全文 | 83411篇 |
免费 | 8976篇 |
国内免费 | 5093篇 |
专业分类
电工技术 | 6979篇 |
技术理论 | 3篇 |
综合类 | 6841篇 |
化学工业 | 11734篇 |
金属工艺 | 5361篇 |
机械仪表 | 5708篇 |
建筑科学 | 6362篇 |
矿业工程 | 2604篇 |
能源动力 | 2532篇 |
轻工业 | 6072篇 |
水利工程 | 2135篇 |
石油天然气 | 4011篇 |
武器工业 | 1124篇 |
无线电 | 9865篇 |
一般工业技术 | 8684篇 |
冶金工业 | 3783篇 |
原子能技术 | 1042篇 |
自动化技术 | 12640篇 |
出版年
2024年 | 339篇 |
2023年 | 1123篇 |
2022年 | 2361篇 |
2021年 | 3340篇 |
2020年 | 2512篇 |
2019年 | 1939篇 |
2018年 | 2149篇 |
2017年 | 2639篇 |
2016年 | 2508篇 |
2015年 | 3578篇 |
2014年 | 4500篇 |
2013年 | 5177篇 |
2012年 | 6458篇 |
2011年 | 6799篇 |
2010年 | 6416篇 |
2009年 | 6096篇 |
2008年 | 5996篇 |
2007年 | 5617篇 |
2006年 | 5231篇 |
2005年 | 4287篇 |
2004年 | 3247篇 |
2003年 | 2966篇 |
2002年 | 3075篇 |
2001年 | 2685篇 |
2000年 | 1704篇 |
1999年 | 1260篇 |
1998年 | 717篇 |
1997年 | 627篇 |
1996年 | 519篇 |
1995年 | 397篇 |
1994年 | 305篇 |
1993年 | 215篇 |
1992年 | 165篇 |
1991年 | 119篇 |
1990年 | 105篇 |
1989年 | 79篇 |
1988年 | 49篇 |
1987年 | 44篇 |
1986年 | 28篇 |
1985年 | 13篇 |
1984年 | 21篇 |
1983年 | 15篇 |
1982年 | 15篇 |
1981年 | 11篇 |
1980年 | 10篇 |
1979年 | 6篇 |
1978年 | 2篇 |
1975年 | 3篇 |
1959年 | 7篇 |
1951年 | 5篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
21.
22.
23.
24.
In this study, 30 subjects were exposed to different combinations of air temperature (Ta: 24, 27, and 30°C) and CO2 level (8000, 10 000, and 12 000 ppm) in a high-humidity (RH: 85%) underground climate chamber. Subjective assessments, physiological responses, and cognitive performance were investigated. The results showed that as compared with exposure to Ta = 24°C, exposure to 30°C at all CO2 levels caused subjects to feel uncomfortably warm and experience stronger odor intensity, while increased mental effort and greater intensity of acute health symptoms were reported. However, no significant effects of Ta on task performance or physiological responses were found. This indicated that subjects had to exert more effort to maintain their performance in an uncomfortably warm environment. Increasing CO2 from 8000 to 12 000 ppm at all Ta caused subjects to report higher rates of headache, fatigue, agitation, and feeling depressed, although the results were statistically significant only at 24 and 27°C. The text typing performance and systolic blood pressure (SBP) decreased significantly at this exposure, whereas diastolic blood pressure (DBP) and thermal discomfort increased significantly. These effects suggest higher arousal/stress. No significant interaction effect of Ta and CO2 concentration on human responses was identified. 相似文献
25.
高光谱激光雷达谱位合一的角度效应分析 总被引:1,自引:0,他引:1
高光谱激光雷达以其谱位合一的技术优势为实现超三维精准遥感观测提供了可行途径,因此成为当前激光雷达与高光谱遥感领域共同大力推进的前沿发展方向。目前已有多型原型系统研发出来并得到了原理性验证,然而针对其数据处理核心环节问题的基础技术仍较为欠缺。典型问题之一是不同波段回波信号受激光入射角度的影响,该角度效应限制了高光谱激光雷达实现高性能遥感。以芬兰空间信息研究所高光谱激光雷达原型系统扫描桦树树干为例探讨了该角度效应,发现了不同激光波段对不同入射角度的回波强度响应模式,推导出了角度效应的基本规律及其精细尺度的统计规律,为后续该方向的系统研发、数据处理及信息提取等提供了可借鉴的底层机理与技术基础。 相似文献
26.
Bin Zhang Xuesong Jiang Fei Shen Xueming He Yong Fang Qiuhui Hu 《International Journal of Food Science & Technology》2021,56(6):2588-2595
This work intends to develop an online experimental system for screening of deoxynivalenol (DON) contamination in whole wheat meals by visible/near-infrared (Vis/NIR) spectroscopy and computer vision coupling technology. Spectral and image information of samples with various DON levels was collected at speed of 0.15 m s−1 on a conveyor belt. The two-type data were then integrated and subjected to chemometric analysis. Discriminant analysis showed that samples could be classified by setting 1000 μg kg−1 as the cut-off value. The best correct classified rate obtained in prediction was 93.55% based on fusion of spectral and image features, with reduced prediction uncertainty as compared to single feature. However, quantification of DON by quantitative analysis was not successful due to poor model performance. These results indicate that, although not accurate enough to provide conclusive result, this coupling technology could be adopted for rapid screening of DON contamination in cereals and feeds during processing. 相似文献
27.
Muhammad Sheeraz Mamoon Ur Rashid Asad Ali Fazli Akram Ho Jeong Lee Jin San Choi Jong-Seong Bae Yong Soo Kim Young-Han Shin Chang Won Ahn Tae Heon Kim 《Journal of the European Ceramic Society》2021,41(10):5155-5162
We demonstrate the structural evolution of polymorphic phases in Al2O3-inserted SrMnO3 ceramics synthesized by solid state reaction. While the 4H-hexagonal phase is predominant in pure SrMnO3 ceramics, a small amount of 6H-hexagonal polymorph is identified in addition to the primary 4H-hexagonal SrMnO3 and the secondary hexagonal SrAl2O4 phases in the as-sintered ceramics, evidenced by x-ray diffraction and subsequent Rietveld refinement analyses. The existence of the 6H-hexagonal SrMnO3 phase is corroborated using Raman spectroscopy. The chemical compositions and electronic structures of the Al2O3-inserted SrMnO3 compounds are also examined using energy dispersive spectroscopy and x-ray photoelectron spectroscopy, respectively. The first-principles calculations reveal that there is no clear difference between the total energies of 4H- and 6H-hexagonal polymorphs regardless of the presence/absence of Sr and oxygen vacancies. Possible origins are discussed with the estimation of actual strain based on the refined lattice parameter of 6H SrMnO3. 相似文献
28.
30.
Shibo Lv Yuyang Miao Dr. Dapeng Liu Prof. Fengling Song 《Chembiochem : a European journal of chemical biology》2020,21(15):2098-2110
Photothermal therapy (PTT) has attracted great attention due to its noninvasive and effective use against cancer. Various photothermal agents (PTAs) including organic and inorganic PTAs have been developed in the last decades. Organic PTAs based on small-molecule dyes exhibit great potential for future clinical applications considering their good biocompatibility and easy chemical modification or functionalization. In this review, we discuss the recent progress of organic PTAs based on small-molecule dyes for enhanced PTT. We summarize the strategies to improve the light penetration of PTAs, methods to enhance their photothermal conversion efficiency, how to optimize PTAs’ delivery into deep tumors, and how to resist photobleaching under repeated laser irradiation. We hope that this review can rouse the interest of researchers in the field of PTAs based on small-molecule dyes and help them to fabricate next-generation PTAs for noninvasive cancer therapy. 相似文献