全文获取类型
收费全文 | 143篇 |
免费 | 8篇 |
专业分类
化学 | 118篇 |
晶体学 | 5篇 |
力学 | 2篇 |
数学 | 1篇 |
物理学 | 25篇 |
出版年
2024年 | 1篇 |
2023年 | 3篇 |
2022年 | 7篇 |
2021年 | 4篇 |
2020年 | 8篇 |
2019年 | 8篇 |
2018年 | 9篇 |
2017年 | 11篇 |
2016年 | 10篇 |
2015年 | 3篇 |
2014年 | 5篇 |
2013年 | 8篇 |
2012年 | 10篇 |
2011年 | 15篇 |
2010年 | 5篇 |
2009年 | 7篇 |
2008年 | 6篇 |
2007年 | 8篇 |
2006年 | 1篇 |
2005年 | 3篇 |
2004年 | 2篇 |
2003年 | 8篇 |
2002年 | 2篇 |
1999年 | 1篇 |
1988年 | 2篇 |
1987年 | 1篇 |
1986年 | 1篇 |
1977年 | 1篇 |
1972年 | 1篇 |
排序方式: 共有151条查询结果,搜索用时 15 毫秒
41.
Nath Surjatapa Bhattacharya Barnali Sarkar Utpal Singh T. Sanjoy 《Journal of fluorescence》2022,32(4):1321-1336
Journal of Fluorescence - In this work, a donor–acceptor substituted aromatic system ((E)-N-((E)-3-(4 (dimethylamino)phenyl) allylidene)-4-(trifluoromethyl) benzenamine (DPATB) has been... 相似文献
42.
Barnali Dutta Basile F. E. Curchod Pablo Campomanes Dr. Euro Solari Dr. Rosario Scopelliti Dr. Ursula Rothlisberger Prof. Kay Severin Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(28):8400-8409
Cyclopentadienyl–ruthenium half‐sandwich complexes with η2‐bound alkyne ligands have been suggested as catalytic intermediates in the early stages of Ru‐catalyzed reactions with alkynes. We show that electronically unsaturated complexes of the formula [RuCl(Cp^)(η2‐RC≡CR′)] can be stabilized and crystallized by using the sterically demanding cyclopentadienyl ligand Cp^ (Cp^=η5‐1‐methoxy‐2,4‐tert‐butyl‐3‐neopentyl‐cyclopentadienyl). Furthermore we demonstrate that [RuCl2(Cp^)]2 is an active and regioselective catalyst for the [2+2+2] cyclotrimerization of alkynes. The first elementary steps of the reaction of mono(η2‐alkyne) complexes containing {RuCl(Cp*)} (Cp*=η5‐C5Me5) and {RuCl(Cp^)} fragments with alkynes were investigated by DFT calculations at the M06/6‐31G* level in combination with a continuum solvent model. Theoretical results are able to rationalize and complement the experimental findings. The presence of the sterically demanding Cp^ ligand increases the activation energy required for the formation of the corresponding di(η2‐alkyne) complexes, enhancing the initial regioselectivity, but avoiding the evolution of the system towards the expected cyclotrimerization product when bulky substituents are present. Theoretical results also show that the electronic structure and stability of a metallacyclic intermediate is strongly dependent on the nature of the substituents present in the alkyne. 相似文献
43.
Bis(diisopropyl) thiophosphoryl disulfide (DIPDIS) being a rubber accelerator has a definite role as a coupling agent in the silica filled polychloroprene rubber with ethylene propylene diene rubber (CR‐EPDM) blends. Diethylene glycol can further improve the beneficial effect of DIPDIS in silica filled CR‐EPDM blends. Two‐stage vulcanization technique further improves the physical properties of silica filled CR‐EPDM blends. The results have been compared with non‐reinforcing calcium carbonate filled systems. Scanning electron microscopy (SEM) studies further indicate the coherency and homogeneity in the silica filled CR‐EPDM blend vulcanizates obtained from this two‐stage process. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
44.
45.
Multiple emissions have been observed from benzil under different conditions in solutions at room temperature as well as in low temperature glass matrices at 77 K. Low temperature emission has been monitored in rigid matrices frozen under different conditions of illumination. Steady state and time-resolved results together with the ab initio quantum chemical calculations provide, for the first time, the assignments of the different fluorescence bands to the different geometries and∕or electronic states of the fluorophore molecule. It is revealed that the skew form of benzil emits from the first (S(1)) as well as the second excited singlet (S(2)) states depending on the excitation wavelength, while the relaxed transplanar conformer fluoresces only from the S(1) state. The yet unexplored emission band peaking at around 360 nm has been assigned to originate from the S(2) state. Ab initio calculations using the density functional theory at B3LYP∕6-31G?? level corroborate well with the experimental observations. 相似文献
46.
We adopt the potential harmonics expansion method for anab initio solution of the many-body system in a Bose condensate containing interacting bosons. Unlike commonly adopted mean-field theories,
our method is capable of handling two-body correlation properly. We disregard three- and higher-body correlations. This simplification
is ideally suited to dilute Bose Einstein condensates, whose number density is required to be so small that the interparticle
separation is much larger than the range of two-body interaction to avoid three- and higher-body collisions, leading to the
formation of molecules and consequent instability of the condensate. In our method we can incorporate realistic finite range
interactions. We calculate energies of low-lying states of a condensate containing23Na atoms and some thermodynamical properties of the condensate. 相似文献
47.
Following Flaschka and Newell, the inverse problem for Painleve IV is formulated with the help of similarity variables. The Painleve IV arises as the eliminant of the two second-order ordinary differential equations originating from the nonlinear Schrödinger equation. Asymptotic expansions are obtained near the singularities at zero and infinity of the complex eigenvalue plane. The corresponding analysis then displays the Stokes phenomena. The monodromy matrices connecting the solutionY
j
, in the sectorS
j
to that inS
j
+1 are fixed in structure by the imposition of certain conditions. It is then shown that a deformation keeping the monodromy data fixed leads to the nonlinear Schrödinger equation. While Flaschka and Newell did not make any absolute determination of the Stokes parameters, the present approach yields the values of the Stokes parameters in an explicit way, which in turn can determine the matrix connecting the solutions near zero and infinity. Finally, it is shown that the integral equation originating from the analyticity and asymptotic nature of the problem leads to the similarity solution previously determined by Boiti and Pampinelli. 相似文献
48.
Chowdhury Ipsita Hazra Ghosh Sourav Roy Mouni Naskar Milan Kanti 《Journal of Sol-Gel Science and Technology》2015,74(1):199-207
Journal of Sol-Gel Science and Technology - Silver nanoparticles (AgNPs) dispersible in water were synthesized at room temperature in the presence of carambola fruit extract at different pH. The... 相似文献
49.
50.
Krishnendu B. Sahu Arindam Maity Shyamal Mondal Rupankar Paira Pritam Saha Subhendu Naskar Abhijit Hazra Sukdeb Banerjee Nirup B. Mondal 《Journal of heterocyclic chemistry》2013,50(Z1):E148-E155
A basic alumina‐supported microwave assisted simple methodology has been developed for the synthesis of aryl‐heteroaryl methanes (benzylated quinolones) via transition metal catalyzed cross‐coupling reaction of halo substituted polynuclear oxa‐aza quinolones with benzyl indium, an organometallic reagent easily derived from commercially available benzyl bromide. 相似文献