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   269408篇
  免费   5663篇
  国内免费   1084篇
电工技术   4452篇
综合类   319篇
化学工业   41938篇
金属工艺   8595篇
机械仪表   7608篇
建筑科学   7411篇
矿业工程   591篇
能源动力   7868篇
轻工业   32493篇
水利工程   2278篇
石油天然气   1991篇
武器工业   10篇
无线电   34288篇
一般工业技术   48780篇
冶金工业   48401篇
原子能技术   3470篇
自动化技术   25662篇
  2022年   1384篇
  2021年   2675篇
  2020年   1840篇
  2019年   2218篇
  2018年   3210篇
  2017年   3240篇
  2016年   3590篇
  2015年   2710篇
  2014年   4499篇
  2013年   13347篇
  2012年   8023篇
  2011年   11099篇
  2010年   8459篇
  2009年   9327篇
  2008年   9781篇
  2007年   9685篇
  2006年   8845篇
  2005年   7979篇
  2004年   7625篇
  2003年   7535篇
  2002年   6945篇
  2001年   7258篇
  2000年   6531篇
  1999年   7049篇
  1998年   17085篇
  1997年   11817篇
  1996年   8922篇
  1995年   6744篇
  1994年   5893篇
  1993年   5704篇
  1992年   4072篇
  1991年   3834篇
  1990年   3599篇
  1989年   3427篇
  1988年   3344篇
  1987年   2647篇
  1986年   2524篇
  1985年   3206篇
  1984年   2830篇
  1983年   2588篇
  1982年   2382篇
  1981年   2416篇
  1980年   2246篇
  1979年   2068篇
  1978年   1904篇
  1977年   2217篇
  1976年   2804篇
  1975年   1599篇
  1974年   1503篇
  1973年   1572篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
1.
2.
Journal of Materials Science -  相似文献   
3.
Xiao  Zhu  Chen  Yanxun  Jiang  Hongbo  Hu  Zhenzhen  Lui  John C. S.  Min  Geyong  Dustdar  Schahram 《Wireless Networks》2022,28(7):3305-3322
Wireless Networks - Unmanned aerial vehicles (UAV) have been widely used in various fields because of their high mobility and portability. At the same time, due to the rapid development of...  相似文献   
4.
5.
6.
Journal of Chemical Ecology - Biocontrol agents such as parasitic wasps use long-range volatiles and host-associated cues from lower trophic levels to find their hosts. However, this chemical...  相似文献   
7.
A set of novel hydrazone derivatives were synthesized and analyzed for their biological activities. The compounds were tested for their inhibitory effect on the phosphorylating activity of the protein kinase CK2, and their antioxidant activity was also determined in three commonly used assays. The hydrazones were evaluated for their radical scavenging against the DPPH, ABTS and peroxyl radicals. Several compounds have been identified as good antioxidants as well as potent protein kinase CK2 inhibitors. Most hydrazones containing a 4-N(CH3)2 residue or perfluorinated phenyl rings showed high activity in the radical-scavenging assays and possess nanomolar IC50 values in the kinase assays.  相似文献   
8.
9.
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   
10.
Currently, the efficient detection of fingerprints is essential for the crime investigations. Revealing fingerprints is commonly achieved with fluorescent organic compounds but they are not efficient for fingerprint detection on porous or reflective surfaces. In order to solve the problem of collecting fingerprints on porous/reflective surfaces, inorganic phosphors have been employed, since they have characteristics of variable color emission, afterglow, high chemical stability and nano-size, which allow the fingerprint detection on any porous or non-porous surfaces. Due to these last properties, this review presents a summary about the use of phosphorescent and fluorescent phosphors for the detection of latent fingerprints. First, we discussed the main physical and chemical characteristics of the fingerprints which permit their detection and collection from any surface. After this, we presented the main morphological, structural and luminescent properties of the phosphorescent and fluorescent phosphors that allow their use for fingerprint detection. Later, we demonstrated with pictures of fingerprints (with and without light emission from the phosphors deposited on them) that both, phosphorescent and fluorescent phosphors can be used to visualize fingerprints with high resolution and high contrast without interference of the background surface, which is ideal for its collection and registration in the Automated Fingerprint Identification System (AFIS). We believe that this review could be useful to understand how to select an appropriate phosphorescent or fluorescent material for fingerprint detection depending on the type of surface (porous or non-porous, reflective or not reflective) where the fingerprint is deposited.  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