全文获取类型
收费全文 | 567987篇 |
免费 | 67226篇 |
国内免费 | 46843篇 |
专业分类
电工技术 | 51755篇 |
技术理论 | 5篇 |
综合类 | 62332篇 |
化学工业 | 69573篇 |
金属工艺 | 39605篇 |
机械仪表 | 41300篇 |
建筑科学 | 44651篇 |
矿业工程 | 24788篇 |
能源动力 | 14983篇 |
轻工业 | 59147篇 |
水利工程 | 19543篇 |
石油天然气 | 20560篇 |
武器工业 | 9432篇 |
无线电 | 60729篇 |
一般工业技术 | 46242篇 |
冶金工业 | 21743篇 |
原子能技术 | 9206篇 |
自动化技术 | 86462篇 |
出版年
2024年 | 2878篇 |
2023年 | 8844篇 |
2022年 | 22195篇 |
2021年 | 28781篇 |
2020年 | 20626篇 |
2019年 | 14350篇 |
2018年 | 15378篇 |
2017年 | 17523篇 |
2016年 | 15626篇 |
2015年 | 25622篇 |
2014年 | 32540篇 |
2013年 | 37910篇 |
2012年 | 48518篇 |
2011年 | 50590篇 |
2010年 | 48221篇 |
2009年 | 45627篇 |
2008年 | 47043篇 |
2007年 | 45685篇 |
2006年 | 38848篇 |
2005年 | 31573篇 |
2004年 | 22543篇 |
2003年 | 14622篇 |
2002年 | 13574篇 |
2001年 | 12263篇 |
2000年 | 9651篇 |
1999年 | 3801篇 |
1998年 | 1230篇 |
1997年 | 973篇 |
1996年 | 789篇 |
1995年 | 682篇 |
1994年 | 489篇 |
1993年 | 471篇 |
1992年 | 394篇 |
1991年 | 271篇 |
1990年 | 254篇 |
1989年 | 276篇 |
1988年 | 181篇 |
1987年 | 120篇 |
1986年 | 116篇 |
1985年 | 58篇 |
1984年 | 75篇 |
1983年 | 61篇 |
1982年 | 57篇 |
1981年 | 95篇 |
1980年 | 183篇 |
1979年 | 119篇 |
1965年 | 16篇 |
1964年 | 10篇 |
1959年 | 115篇 |
1951年 | 119篇 |
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
61.
材料化学专业英语是材料化学专业最重要的专业课程之一,专业英语的学习可为学生的专业论文写作和国际交流奠定坚实的基础。该研究对当前材料化学专业英语教学中存在的一些问题进行了分析,并从教学内容、教学方法、教师素质等方面就如何提高材料化学专业英语的教学效果进行了探讨,以期对改善教学质量和提高学生学习兴趣等方面有所促进。 相似文献
62.
Bin Feng Xin Jiang Guisheng Zou Wengan Wang Tianming Sun Heng Yang Guanlei Zhao Mingye Dong Yu Xiao Hongwei Zhu Lei Liu 《Advanced functional materials》2021,31(29):2102359
The realization of liquid metal-based wearable systems will be a milestone toward high-performance, integrated electronic skin. However, despite the revolutionary progress achieved in many other components of electronic skin, liquid metal-based flexible sensors still suffer from poor sensitivity due to the insufficient resistance change of liquid metal to deformation. Herein, a nacre-inspired architecture composed of a biphasic pattern (liquid metal with Cr/Cu underlayer) as “bricks” and strain-sensitive Ag film as “mortar” is developed, which breaks the long-standing sensitivity bottleneck of liquid metal-based electronic skin. With 2 orders of magnitude of sensitivity amplification while maintaining wide (>85%) working range, for the first time, liquid metal-based strain sensors rival the state-of-art counterparts. This liquid metal composite features spatially regulated cracking behavior. On the one hand, hard Cr cells locally modulate the strain distribution, which avoids premature cut-through cracks and prolongs the defect propagation in the adjacent Ag film. On the other hand, the separated liquid metal cells prevent unfavorable continuous liquid-metal paths and create crack-free regions during strain. Demonstrated in diverse scenarios, the proposed design concept may spark more applications of ultrasensitive liquid metal-based electronic skins, and reveals a pathway for sensor development via crack engineering. 相似文献
63.
在80 MHz~1 GHz频段,单个功率管输出功率能达到100 W以上,为研制输出功率400 W的功率放大器,文中设计了四路功率合成器。该合成器需要实现功率容量大、工作频带宽、体积小的设计目标。在功率容量方面,文中采用悬置带状线结构,其功率容量远远大于微带线结构;在工作频带方面,采用切比雪夫九节阻抗变换器,将工作带宽拓宽为80 MHz~1 GHz;在体积方面,文中合成器的功率合成部分采用Y型节级联实现四路功率合成,阻抗变换部分采用切比雪夫阻抗变换器进行阻抗变换,该结构相较于磁环巴伦功率合成器,不但具有损耗小、平坦度高的优点,而且通过将阻抗变换器设计成曲折的形状,进一步缩小了合成器体积。仿真与实测结果显示该合成器在80 MHz~1 GHz范围内还具有较高的平坦度,合成效率可达90%以上。 相似文献
65.
66.
Myelodysplastic syndromes (MDS) are highly heterogeneous myeloid neoplasms, and a large number of
patients are difficult to diagnose and classify by blood and bone marrow examination. As a surface marker of
granulocyte, studies have shown CD10 can be used to define the degree of granulocyte maturation in MDS patients.
However, whether it can be used for differential diagnosis of MDS and other hematological diseases remains
inconclusive. To explore the value of CD10 for differential diagnosis of MDS, 60 newly diagnosed MDS, 20 aplastic
anemia (AA) patients, and 35 iron-deficient anemia (IDA) patients were selected for this study. Bone marrow (BM)
specimens were processed for surface marker analysis and labeled with pre-conjugated monoclonal antibodies. Stained
cells were detected by flow cytometry. Our results indicated that CD10-positive granulocytes were significantly
decreased in BM of MDS patients than AA and IDA patients, and the level of CD10-positive mature granulocytes was
not associated with the clinical stages of malignancy. Receiver operating characteristic (ROC) areas under the curve
(AUC) of CD10-positive granulocytes was 0.86 and 0.85, respectively, in MDS patients than the IDA group and AA
group with good specificity and sensitivity. Further, CD10-positive granulocytes were increased after effective
treatment. In conclusion, we found the decrease in CD10-positive granulocytes has a differential diagnostic value of MDS. 相似文献
67.
为了建立适用于书画打印宣纸印刷质量的预测模型,本研究测量了14种书画打印宣纸的粗糙度、白度、不透明度、定量、光泽度和针对宣纸特别设定的帘纹深浅以及帘纹疏密度等表面物理参量,并在相同条件下,使用喷墨打印设备输出并测量印品色度值,利用总变差模型构建去除帘纹色差的测定方法,得到与人眼视觉特征相符的色差。运用GRNN广义回归神经网络结合书画打印宣纸表面物理参量与宣纸去帘纹后的色差值,建立预测模型。结果表明,该模型能够在仅测量书画打印宣纸表面物理参量的情况下,便能较为准确地预测书画打印宣纸印刷质量,为书画打印宣纸印刷前的选纸工作提供指导依据。 相似文献
68.
69.
70.
Yuchuan Lei 《传热工程》2020,41(9-10):768-778
AbstractA numerical study of condensation heat transfer in curved square and triangle microchannels with various curvatures is conducted. The model is based on the volume of fluid approach and user-defined routines. The predictive accuracy of the numerical results is assessed by comparing the heat transfer coefficient with available correlation. After the validation, the effects of the mass flux and heat flux on heat transfer coefficient are analyzed in detail. Increasing mass flux could strengthen heat transfer performance, while wall heat flux has little effect on condensation heat transfer coefficient. The curved microchannels show an advantage in heat transfer enhancement comparing with the straight ones, and the enhancement performs better in curved microchannels with larger curvatures. Besides, the heat transfer performance could be enhanced in triangle microchannels in comparison with square microchannels. 相似文献