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   342篇
  免费   9篇
  国内免费   7篇
化学   270篇
力学   21篇
数学   20篇
物理学   47篇
  2023年   1篇
  2022年   4篇
  2021年   20篇
  2020年   18篇
  2019年   7篇
  2018年   20篇
  2017年   12篇
  2016年   31篇
  2015年   15篇
  2014年   31篇
  2013年   63篇
  2012年   23篇
  2011年   23篇
  2010年   10篇
  2009年   17篇
  2008年   15篇
  2007年   19篇
  2006年   8篇
  2005年   10篇
  2004年   6篇
  2003年   3篇
  2002年   1篇
  1973年   1篇
排序方式: 共有358条查询结果,搜索用时 31 毫秒
1.
International Journal of Theoretical Physics - In the present work, a novel approach was proposed to optimize the teleportation cost in Distributed Quantum Circuits (DQCs) by applying a new...  相似文献   
2.
Journal of Cluster Science - In this research, we used a fast and simple method for synthesis of calcium titanate (CaTiO3) and calcium ferrite (CaFe2O4) nanostructures: microwave assisted...  相似文献   
3.
Journal of Thermal Analysis and Calorimetry - This is a numerical study of heat transfer and flow in a counter-flow sinusoidal parallel-plate heat exchanger using metal foam in the channels’...  相似文献   
4.
Journal of Thermal Analysis and Calorimetry - For the first time, double phosphates(V) Zn3Cr4(PO4)6 and Mg3Cr4(PO4)6 were synthesized by non-waste solid-state reaction, performed in the temperature...  相似文献   
5.
Let \(G=(V,E)\) be a graph. A subset \(S\subseteq V\) is a k-dominating set of G if each vertex in \(V-S\) is adjacent to at least k vertices in S. The k-domination number of G is the cardinality of the smallest k-dominating set of G. In this paper, we shall prove that the 2-domination number of generalized Petersen graphs \(P(5k+1, 2)\) and \(P(5k+2, 2)\), for \(k>0\), is \(4k+2\) and \(4k+3\), respectively. This proves two conjectures due to Cheng (Ph.D. thesis, National Chiao Tung University, 2013). Moreover, we determine the exact 2-domination number of generalized Petersen graphs P(2kk) and \(P(5k+4,3)\). Furthermore, we give a good lower and upper bounds on the 2-domination number of generalized Petersen graphs \(P(5k+1, 3), P(5k+2,3)\) and \(P(5k+3, 3).\)  相似文献   
6.
Journal of Thermal Analysis and Calorimetry - In the current work, after generating experimental data points for different volume fraction of nanoparticles ( $$\phi$$ ) and different temperatures,...  相似文献   
7.
In this research, the main emphasis has been focused on the preparation of a novel Fe3O4-supported propane-1-sulfonic acid-grafted graphene oxide quantum dots (Fe3O4@GOQD-O-(propane-1-sulfonic acid)) that it was readily synthesized via a five-step procedure as a hitherto unreported magnetic nanocatalyst. This newly prepared Fe3O4@GOQD-O-(propane-1-sulfonic acid) nanocomposite was structurally well-established by different analytical techniques including Fourier transform infrared (FT-IR), X-ray diffraction (XRD), energy-dispersive X-ray (EDX), thermal gravimetric analysis (TGA), field emission gun-scanning electron microscope (FESEM), high-resolution transmission electron microscopy (HRTEM) and vibrating sample magnetometer (VSM) analyses. The high catalytic performance of this nanocomposite was exhibited in one-pot synthesis of dihydropyrano[2,3-c]pyrazole and 4H-chromene derivatives under mild conditions. Low reaction times, excellent yields of the products, benignity of the catalyst, easy reaction work-up and magnetic recyclability of the catalyst are the main advantages of the present protocol. Also, our research indicated that the Fe3O4@GOQD-O-(propane-1-sulfonic acid) could be reused up to five times without considerable loss of catalytic activity.  相似文献   
8.
A novel Cu (II) Schiff‐base complex immobilized on core‐shell magnetic Fe3O4 nanoparticles (Fe3O4@SPNC) was successfully designed and synthesized. The structural features of these nanoparticles were studied and confirmed by using various techniques including FT‐IR spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy‐dispersive X‐ray spectroscopy (EDS), vibrating sample magnetometer (VSM), X‐Ray diffraction (XRD), wavelength dispersive X‐ray spectroscopy (WDX), and inductively coupled plasma (ICP). These newly synthesized nanoparticles have been used as efficient heterogeneous catalytic system for one‐pot multicomponent synthesis of new pyrano[2,3‐b]pyridine‐3‐carboxamide derivatives. Notably, the catalyst could be easily separated from the reaction mixture by using an external magnet and reused for several successive reaction runs with no significant loss of activity or copper leaching. The present protocol benefits from a hitherto unreported MNPs‐immobilized Cu (II) Schiff‐base complex as an efficient nanocatalyst for the synthesis of newly reported derivatives of pyrano[2,3‐b]pyridine‐3‐carboxamide from one‐pot multicomponent reactions.  相似文献   
9.
Research on Chemical Intermediates - In this research, synthesis and characterization of a novel Schiff base Cu (II) complex immobilized on Fe3O4@SiO2 nanoparticles are reported. Then, the...  相似文献   
10.
Journal of Thermal Analysis and Calorimetry - Hot-rolled strips are cooled on the run-out table to achieve the customer-required mechanical properties. Cooling reduces the oxidation, which can...  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