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   363351篇
  免费   28288篇
  国内免费   14219篇
电工技术   20283篇
技术理论   33篇
综合类   22688篇
化学工业   59894篇
金属工艺   20962篇
机械仪表   22978篇
建筑科学   28710篇
矿业工程   10987篇
能源动力   10235篇
轻工业   22832篇
水利工程   6429篇
石油天然气   23141篇
武器工业   2853篇
无线电   41656篇
一般工业技术   43400篇
冶金工业   18851篇
原子能技术   3697篇
自动化技术   46229篇
  2024年   619篇
  2023年   5334篇
  2022年   8186篇
  2021年   13560篇
  2020年   10285篇
  2019年   8628篇
  2018年   9858篇
  2017年   11273篇
  2016年   9906篇
  2015年   13942篇
  2014年   17507篇
  2013年   21338篇
  2012年   23076篇
  2011年   25443篇
  2010年   22041篇
  2009年   21047篇
  2008年   20552篇
  2007年   20034篇
  2006年   20645篇
  2005年   17968篇
  2004年   11673篇
  2003年   10047篇
  2002年   9458篇
  2001年   8285篇
  2000年   8672篇
  1999年   10061篇
  1998年   8374篇
  1997年   7114篇
  1996年   6579篇
  1995年   5542篇
  1994年   4558篇
  1993年   3299篇
  1992年   2657篇
  1991年   1994篇
  1990年   1496篇
  1989年   1181篇
  1988年   966篇
  1987年   646篇
  1986年   497篇
  1985年   362篇
  1984年   250篇
  1983年   167篇
  1982年   181篇
  1981年   141篇
  1980年   118篇
  1979年   58篇
  1978年   34篇
  1977年   32篇
  1976年   54篇
  1973年   21篇
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
1.
2.
Zhang  Junbao  Huang  Haojun  Yang  Changlin  Liu  Jizhao  Fan  Yinting  Yang  Guan 《Wireless Networks》2022,28(3):1301-1312
Wireless Networks - Although centrality is widely used to differentiate the importance of nodes for social-aware routing in mobile opportunistic networks (MONs), it is destination-agnostic since...  相似文献   
3.
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   
4.
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   
5.

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   
6.
7.
8.
Thermal action in extraction process had effects on characteristic tryptic peptides identification and gelling properties of porcine gelatin. SDS-PAGE, HPLC-LTQ/Orbitrap high-resolution mass spectrometry, texture analyser and rheometer were used to evaluate collagen depolymerisation degree, characteristic tryptic peptides and gelling properties of gelatins prepared in various thermal actions. Results showed that with increasing temperature and time, depolymerisation degree enlarged, while gel strength, gelling and melting temperature decreased. Mass spectra showed that 47 and 49 common characteristic tryptic peptides were identified in gelatins extracted at 50 °C and 100 °C with various times, respectively. Moreover, 34 common characteristic tryptic peptides were identified in all gelatin samples. Further comparison between this work and our previous investigations yielded 20 common characteristic tryptic peptides, which stably exist in various thermal actions. These common characteristic tryptic peptides may be very helpful for the accurate authentication of porcine gelatin.  相似文献   
9.
10.
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   
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