首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   62409篇
  免费   3830篇
  国内免费   705篇
电工技术   1417篇
技术理论   1篇
综合类   962篇
化学工业   12848篇
金属工艺   2825篇
机械仪表   4085篇
建筑科学   1996篇
矿业工程   394篇
能源动力   2480篇
轻工业   4827篇
水利工程   509篇
石油天然气   751篇
武器工业   89篇
无线电   9287篇
一般工业技术   12468篇
冶金工业   4486篇
原子能技术   823篇
自动化技术   6696篇
  2024年   70篇
  2023年   766篇
  2022年   987篇
  2021年   1981篇
  2020年   1489篇
  2019年   1496篇
  2018年   1807篇
  2017年   1841篇
  2016年   2101篇
  2015年   1787篇
  2014年   2716篇
  2013年   3806篇
  2012年   4048篇
  2011年   4674篇
  2010年   3562篇
  2009年   3596篇
  2008年   3456篇
  2007年   2895篇
  2006年   2729篇
  2005年   2293篇
  2004年   1985篇
  2003年   1966篇
  2002年   1876篇
  2001年   1561篇
  2000年   1361篇
  1999年   1306篇
  1998年   1883篇
  1997年   1272篇
  1996年   1055篇
  1995年   750篇
  1994年   621篇
  1993年   519篇
  1992年   395篇
  1991年   352篇
  1990年   324篇
  1989年   288篇
  1988年   245篇
  1987年   190篇
  1986年   150篇
  1985年   126篇
  1984年   108篇
  1983年   71篇
  1982年   46篇
  1981年   50篇
  1980年   43篇
  1979年   37篇
  1978年   33篇
  1977年   41篇
  1976年   69篇
  1973年   22篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
Feng  Wenran  Li  Zhen  Chen  Yingying  Chen  Jinyang  Lang  Haoze  Wan  Jianghong  Gao  Yan  Dong  Haitao 《Journal of Materials Science》2022,57(3):1881-1889
Journal of Materials Science - Although chalcogenide materials continue to generate considerable interest due to great potentials for various optoelectronic devices, annealing for a long time in...  相似文献   
2.
3.
4.
Multimedia Tools and Applications - The study presents a new approach to automate segmentation of clinically significant brain tumor and, to a certain extent, addresses two major issues associated...  相似文献   
5.
Food Science and Biotechnology - Various hilling materials (rice hulls, pine sawdust, and perlite) were compared to produce sprout vegetables using beach silvertop (Glehnia littoralis Fr. Schm. ex...  相似文献   
6.
Surface passivation treatment is a widely used strategy to resolve trap-mediated nonradiative recombination toward high-efficiency metal-halide perovskite photovoltaics. However, a lack of passivation with mixture treatment has been investigated, as well as an in-depth understanding of its passivation mechanism. Here, a systematic study on a mixed-salt passivation strategy of formamidinium bromide (FABr) coupled with different F-substituted alkyl lengths of ammonium iodide is demonstrated. It is obtained better device performance with decreasing chain length of the F-substituted alkyl ammonium iodide in the presence of FABr. Moreover, they unraveled a synergistic passivation mechanism of the mixed-salt treatment through surface reconstruction engineering, where FABr dominates the reformation of the perovskite surface via reacting with the excess PbI2. Meanwhile, ammonium iodide passivates the perovskite grain boundaries both on the surface and top perovskite bulk through penetration. This synergistic passivation engineer results in a high-quality perovskite surface with fewer defects and suppressed ion migration, leading to a champion efficiency of 23.5% with mixed-salt treatment. In addition, the introduction of the moisture resisted F-substituted groups presents a more hydrophobic perovskite surface, thus enabling the decorated devices with excellent long-term stability under a high humid atmosphere as well as operational conditions.  相似文献   
7.
8.
The production of hydrogen, a favourable alternative to an unsustainable fossil fuel remains as a significant hurdle with the pertaining challenge in the design of proficient, highly productive and sustainable electrocatalyst for both oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Herein, the dysprosium (Dy) doped copper oxide (Cu1-xDyxO) nanoparticles were synthesized via solution combustion technique and utilized as a non-noble metal based bi-functional electrocatalyst for overall water splitting. Due to the improved surface to volume ratio and conductivity, the optimized Cu1-xDyxO (x = 0.01, 0.02) electrocatalysts exhibited impressive HER and OER performance respectively in 1 M KOH delivering a current density of 10 mAcm?2 at a potential of ?0.18 V vs RHE for HER and 1.53 V vs RHE for OER. Moreover, the Dy doped CuO electrocatalyst used as a bi-functional catalyst for overall water splitting achieved a potential of 1.56 V at a current density 10 mAcm?2 and relatively high current density of 66 mAcm?2 at a peak potential of 2 V. A long term stability of 24 h was achieved for a cell voltage of 2.2 V at a constant current density of 30 mAcm?2 with only 10% of the initial current loss. This showcases the accumulative opportunity of dysprosium as a dopant in CuO nanoparticles for fabricating a highly effective and low-cost bi-functional electrocatalyst for overall water splitting.  相似文献   
9.
Abnormal levels of glutathione, a cellular antioxidant, can lead to a variety of diseases. We have constructed a near-infrared ratiometric fluorescent probe to detect glutathione concentrations in biological samples. The probe consists of a coumarin donor, which is connected through a disulfide-tethered linker to a rhodamine acceptor. Under the excitation of the coumarin donor at 405 nm, the probe shows weak visible fluorescence of the coumarin donor at 470 nm and strong near-infrared fluorescence of the rhodamine acceptor at 652 nm due to efficient Forster resonance energy transfer (FRET) from the donor to the acceptor. Glutathione breaks the disulfide bond through reduction, which results in a dramatic increase in coumarin fluorescence and a corresponding decrease in rhodamine fluorescence. The probe possesses excellent cell permeability, biocompatibility, and good ratiometric fluorescence responses to glutathione and cysteine with a self-calibration capability. The probe was utilized to ratiometrically visualize glutathione concentration alterations in HeLa cells and Drosophila melanogaster larvae.  相似文献   
10.
动力电池是当前新能源汽车中的核心零件,其性能,安全,可靠与耐久性直接影响整个车辆安全耐久性能,而电池系统的抗振动冲击特性是产品开发设计过程中需要满足的重要指标.文中着重阐述动力电池振动疲劳的测试验证策略与具体实施指导,为电池系统研发和测试工作提供重要参考.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号