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   229223篇
  免费   3457篇
  国内免费   893篇
电工技术   3999篇
综合类   686篇
化学工业   36303篇
金属工艺   10805篇
机械仪表   7782篇
建筑科学   4927篇
矿业工程   2347篇
能源动力   5280篇
轻工业   15491篇
水利工程   3180篇
石油天然气   7920篇
武器工业   53篇
无线电   24002篇
一般工业技术   48264篇
冶金工业   38478篇
原子能技术   6797篇
自动化技术   17259篇
  2021年   2656篇
  2020年   1862篇
  2019年   2417篇
  2018年   4137篇
  2017年   4148篇
  2016年   4481篇
  2015年   2651篇
  2014年   4397篇
  2013年   9933篇
  2012年   6616篇
  2011年   8352篇
  2010年   6723篇
  2009年   7420篇
  2008年   7530篇
  2007年   7408篇
  2006年   6356篇
  2005年   5786篇
  2004年   5386篇
  2003年   5513篇
  2002年   5605篇
  2001年   5520篇
  2000年   4799篇
  1999年   4762篇
  1998年   11613篇
  1997年   8142篇
  1996年   6204篇
  1995年   4617篇
  1994年   3948篇
  1993年   4219篇
  1992年   3193篇
  1991年   3163篇
  1990年   3042篇
  1989年   2999篇
  1988年   3001篇
  1987年   2625篇
  1986年   2686篇
  1985年   3017篇
  1984年   2778篇
  1983年   2649篇
  1982年   2395篇
  1981年   2376篇
  1980年   2459篇
  1979年   2433篇
  1978年   2443篇
  1977年   2594篇
  1976年   3091篇
  1975年   2239篇
  1974年   2104篇
  1973年   2221篇
  1972年   1973篇
排序方式: 共有10000条查询结果,搜索用时 15 毫秒
1.
2.
3.
Refractories and Industrial Ceramics - The paper introduces a promising technology for utilizing a traditional scheme for implementing a flow-through micro-arc oxidation method to restore localized...  相似文献   
4.
Combustion, Explosion, and Shock Waves - Results of a numerical study of mixing, ignition, and combustion of a cold hydrogen jet propagating along the lower wall of a channel parallel to a...  相似文献   
5.
Multimedia Tools and Applications - The three-dimensional models of brain tumors serve as diagnostic assistance for physicians, surgeons, and radiologists. The proposed system establishes an...  相似文献   
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.
Mesenchymal stem cells (MSCs) are the main cell players in tissue repair and thanks to their self-renewal and multi-lineage differentiation capabilities, they gained significant attention as cell source for tissue engineering (TE) approaches aimed at restoring bone and cartilage defects. Despite significant progress, their therapeutic application remains debated: the TE construct often fails to completely restore the biomechanical properties of the native tissue, leading to poor clinical outcomes in the long term. Pulsed electromagnetic fields (PEMFs) are currently used as a safe and non-invasive treatment to enhance bone healing and to provide joint protection. PEMFs enhance both osteogenic and chondrogenic differentiation of MSCs. Here, we provide extensive review of the signaling pathways modulated by PEMFs during MSCs osteogenic and chondrogenic differentiation. Particular attention has been given to the PEMF-mediated activation of the adenosine signaling and their regulation of the inflammatory response as key player in TE approaches. Overall, the application of PEMFs in tissue repair is foreseen: (1) in vitro: to improve the functional and mechanical properties of the engineered construct; (2) in vivo: (i) to favor graft integration, (ii) to control the local inflammatory response, and (iii) to foster tissue repair from both implanted and resident MSCs cells.  相似文献   
9.
Semiconductors - Abstract—In our work, we carry out a structural-spectroscopic study of AlGaN/GaN epitaxial layers grown by molecular-beam epitaxy with nitrogen-plasma activation on a hybrid...  相似文献   
10.
Journal of Communications Technology and Electronics - In recent years, there has been a rapid improvement in photonics products due to the use of multilayer heterostructures grown on the basis of...  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