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   4857941篇
  免费   336413篇
  国内免费   189245篇
电工技术   264629篇
技术理论   127篇
综合类   273641篇
化学工业   689139篇
金属工艺   235119篇
机械仪表   262991篇
建筑科学   279328篇
矿业工程   117636篇
能源动力   136882篇
轻工业   396951篇
水利工程   103496篇
石油天然气   145785篇
武器工业   36202篇
无线电   523652篇
一般工业技术   591516篇
冶金工业   569431篇
原子能技术   64839篇
自动化技术   692235篇
  2023年   43099篇
  2022年   93770篇
  2021年   142524篇
  2020年   106784篇
  2019年   88115篇
  2018年   105749篇
  2017年   116289篇
  2016年   108747篇
  2015年   132678篇
  2014年   180519篇
  2013年   279302篇
  2012年   287141篇
  2011年   326372篇
  2010年   292821篇
  2009年   292362篇
  2008年   298490篇
  2007年   289852篇
  2006年   262837篇
  2005年   219714篇
  2004年   158452篇
  2003年   122179篇
  2002年   113214篇
  2001年   102972篇
  2000年   97419篇
  1999年   80109篇
  1998年   141140篇
  1997年   99671篇
  1996年   83737篇
  1995年   67956篇
  1994年   58923篇
  1993年   50839篇
  1992年   34148篇
  1991年   30684篇
  1990年   30299篇
  1989年   29279篇
  1988年   27033篇
  1987年   24253篇
  1986年   23591篇
  1985年   25320篇
  1984年   21891篇
  1983年   20075篇
  1982年   18997篇
  1981年   19355篇
  1980年   18566篇
  1979年   16616篇
  1978年   16092篇
  1977年   22728篇
  1976年   33599篇
  1975年   13989篇
  1974年   12870篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
41.
Journal of Materials Science: Materials in Electronics - This work presents an interesting fabrication route toward development of pressure sensing patch by utilizing electrically conductive cotton...  相似文献   
42.
Journal of Materials Science: Materials in Electronics - Gum kondagogu (GK), a natural biopolymer was successfully employed in the synthesis of trimetallic (AgAuPd) nanocomposites and characterized...  相似文献   
43.

The non-centrosymmetric space group organic nonlinear optical single crystal of 4-chloro-2-nitroaniline (4Cl2NA) was developed by slow evaporation method at 40 °C. Grown 4Cl2NA was monoclinic structure with Pc space group which was recognized by single-crystal XRD analysis. An intermolecular contact of 4Cl2NA was visually analysed by Hirshfeld surface analysis. Active functional groups and their respective vibrations were identified by FTIR and FT-Raman spectral analysis. Optical properties were evaluated by UV–Visible spectral analysis. Thermal TG/DTA thermogram analysis and mechanical Vickers hardness analysis revealed that the synthesis material was thermally stable up to 115 °C and mechanical work hardness coefficient (n?=?2.98) confirmed the grown crystal was soft material. Laser beam-irradiated LDT analysis expressed the laser utility limitation of the 4Cl2NA crystal. The NLO second harmonic generation efficiency was tested by Kurtz Perry powder method.

  相似文献   
44.
Journal of Materials Science: Materials in Electronics - The influences of the selenium (Se) growth condition on the electronic level structure including deep defects and further on the...  相似文献   
45.
Journal of Materials Science: Materials in Electronics - 0.95(Li0.02Na0.50K0.48)(Nb0.95Sb0.05)O3–0.05AgTaO3@BaZrO3 (LNKNbSAT@BZ) lead-free ceramics were prepared via a sol–gel...  相似文献   
46.
Journal of Materials Science: Materials in Electronics - Layered transition metal dichalcogenides hold tunable and promising photoelectrochemical properties. MoSe2 is a potential candidate of the...  相似文献   
47.
Journal of Materials Science: Materials in Electronics - In this study, Mn3O4 thin films were grown by Successive Ionic Layer Adsorption and Reaction Technique (SILAR) with 20 and 50...  相似文献   
48.

Cr doped ZnAl2O4 spinel samples were prepared by the traditional solid state reaction and co-precipitation synthetic route, and the results suggest that the co-precipitation method has some superiority in contrast to the solid state reaction method. XRD, FT-IR, and XPS spectra confirmed that the well-crystallized spinel cubic phase of ZnAl2O4: Cr3+ samples were successfully formed. The morphology of the samples was investigated by FE-SEM and FE-TEM, and the results show that the samples by the co-precipitation route can generate a smaller size of particles compared to the solid state reaction. Photoluminescence excitation spectra monitored at 686 nm are comprised of two broad excitation bands near 530 nm and 395 nm, and the emission spectra show emissions ranging from 640 to 780 nm, due to the 2E?→?4A2 spin-forbidden transition of Cr3+ ions in spinel lattices. The optimized concentration monitored at 686 nm is 1%, while at 693 nm is 3.5%. Compared with the samples by solid state reaction method, the samples by co-precipitation method show preferable luminescent properties, such as the higher photoluminescence intensity and higher quantum efficiency. Several phosphor-converted LEDs were to investigate the applicability of the prepared samples. The results confirm that the phosphor has potential applications in plant growth and supplementing the red region in white-LEDs and the phosphors prepared by co-precipitation are more suitable to be used in phosphor-converted LED devices due to their preferable luminescent properties.

  相似文献   
49.
Journal of Materials Science: Materials in Electronics - Pure PVDF has higher breakdown strength but low dielectric and ferroelectric properties. Thus, we synthesized the LaFeO3 and GdFeO3...  相似文献   
50.
周忠彬  高金霞  袁宝慧 《爆破器材》2022,51(5):20-23,30
针对压制成型的PBX炸药装药,选择CT无损检测、巴西实验和扫描电镜检测等技术,对比研究了室温和加热两种温度下压制成型的炸药装药内部质量、静态力学性能和细观破坏形式。结果表明,加热压制有利于改善炸药装药的内部质量,可避免产生初始损伤,且提高了装药的力学性能。细观尺度上,室温压制成型的装药主要发生界面脱黏破坏,加热压制成型装药的主要破坏形式是穿晶断裂。  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