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   265511篇
  免费   20541篇
  国内免费   10340篇
电工技术   14868篇
技术理论   22篇
综合类   16988篇
化学工业   43870篇
金属工艺   15081篇
机械仪表   16821篇
建筑科学   21780篇
矿业工程   7956篇
能源动力   7499篇
轻工业   16499篇
水利工程   4622篇
石油天然气   15884篇
武器工业   2018篇
无线电   30072篇
一般工业技术   31960篇
冶金工业   13478篇
原子能技术   2901篇
自动化技术   34073篇
  2024年   412篇
  2023年   3958篇
  2022年   5755篇
  2021年   9333篇
  2020年   7565篇
  2019年   6275篇
  2018年   7257篇
  2017年   8183篇
  2016年   7182篇
  2015年   9689篇
  2014年   12418篇
  2013年   15239篇
  2012年   16342篇
  2011年   17924篇
  2010年   15565篇
  2009年   15118篇
  2008年   14940篇
  2007年   13945篇
  2006年   14666篇
  2005年   12933篇
  2004年   8855篇
  2003年   7711篇
  2002年   7173篇
  2001年   6528篇
  2000年   6666篇
  1999年   7803篇
  1998年   6553篇
  1997年   5565篇
  1996年   5187篇
  1995年   4363篇
  1994年   3587篇
  1993年   2687篇
  1992年   2156篇
  1991年   1596篇
  1990年   1215篇
  1989年   1010篇
  1988年   803篇
  1987年   571篇
  1986年   384篇
  1985年   301篇
  1984年   184篇
  1983年   137篇
  1982年   164篇
  1981年   108篇
  1980年   89篇
  1979年   53篇
  1978年   31篇
  1977年   30篇
  1976年   44篇
  1975年   15篇
排序方式: 共有10000条查询结果,搜索用时 14 毫秒
1.
Wen  Pushan  He  Rui  Li  Xiang-Dan  Lee  Myong-Hoon 《Journal of Materials Science》2022,57(1):755-765
Journal of Materials Science - Three polyimides (PIs) were prepared from a diamine containing biphenyl ester group as a side chain and a corresponding dianhydride chosen from...  相似文献   
2.
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   
3.

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   
4.

This paper deals with a class of fast diffusion p-Laplace equation with logarithmic non-linearity in a bounded smooth domain with homogeneous Dirichlet boundary condition. By using energy estimates and some ordinary differential inequalities, we study the conditions on extinction and non-extinction of global solutions. The results of this paper extend and complete the previous studies on this equation.

  相似文献   
5.
6.
Hydrogen peroxide (H2O2) has been listed as one of the 100 most important chemicals in the world. However, huge amount of residual H2O2 is hard to timely decomposed into O2 and H2O under acidic condition, easily resulting in explosion hazard. Here, we reported a core–shell structure catalyst, that is graphene with Co N structure encapsulated Co nanoparticles. Co N graphene shell serves as the active site for the H2O2 decomposition, and Co core further enhance this decomposition. Benefiting from it, the H2O2 decomposition were close to 100% after 6 cycles without pH adjustment, which increased 6 orders of magnitude compared with no catalyst. At the same time, the O2 generation reached 99.67% in 2 h with little metal leaching, and ·OH has been greatly inhibited to only 0.08%. This work can cleanly remove H2O2 with little deep oxidation and protect the process of H2O2 utilization to achieve a safer world.  相似文献   
7.
8.
Wu  Zheng  Meng  Xuan  Shi  Li  Liu  Naiwang 《Journal of Porous Materials》2022,29(2):493-500
Journal of Porous Materials - In this work, a trifluoromethanesulfonic acid (TFOH) modified clay (TFOH-Clay) was developed for the removal of trace olefins in heavy naphtha. 5%TFOH-Clay can...  相似文献   
9.
陈尊凤  肖雄  黄伟健  吴超  王洳锦 《广东化工》2022,49(1):121-122,143
以消费者、行业专家、各品牌商以及全球各个美妆相关行业对纯净美妆的认识为依据,从配方设计、关键的原料筛选、生产过程、包材选择以及测试评估等方面,对如何实现纯净美妆产品进行了较为详细的阐述,无疑为纯净美妆的标准建立和定义提供很好的参考.  相似文献   
10.
International Journal of Wireless Information Networks - Source seeking problem has been faced in many fields, especially in search and rescue applications. We proposed a virtual structure-based...  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