全文获取类型
收费全文 | 567篇 |
免费 | 11篇 |
专业分类
化学 | 388篇 |
晶体学 | 30篇 |
力学 | 21篇 |
数学 | 29篇 |
物理学 | 110篇 |
出版年
2023年 | 3篇 |
2022年 | 6篇 |
2021年 | 8篇 |
2020年 | 9篇 |
2019年 | 11篇 |
2018年 | 19篇 |
2017年 | 14篇 |
2016年 | 12篇 |
2015年 | 18篇 |
2014年 | 28篇 |
2013年 | 37篇 |
2012年 | 43篇 |
2011年 | 52篇 |
2010年 | 20篇 |
2009年 | 24篇 |
2008年 | 29篇 |
2007年 | 23篇 |
2006年 | 52篇 |
2005年 | 26篇 |
2004年 | 22篇 |
2003年 | 8篇 |
2002年 | 12篇 |
2001年 | 4篇 |
2000年 | 11篇 |
1999年 | 7篇 |
1998年 | 5篇 |
1997年 | 7篇 |
1996年 | 8篇 |
1995年 | 6篇 |
1994年 | 6篇 |
1993年 | 7篇 |
1992年 | 9篇 |
1991年 | 6篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 3篇 |
1986年 | 1篇 |
1985年 | 3篇 |
1984年 | 2篇 |
1983年 | 1篇 |
1981年 | 1篇 |
1980年 | 2篇 |
1979年 | 2篇 |
1978年 | 2篇 |
1976年 | 1篇 |
1975年 | 1篇 |
1969年 | 1篇 |
1968年 | 2篇 |
排序方式: 共有578条查询结果,搜索用时 15 毫秒
101.
Basi V. Subba Reddy Nagendra Nath Yadav Nikhil Srivastava Jhillu S. Yadav Balasubramanian Sridhar 《Helvetica chimica acta》2012,95(1):76-86
Ionic liquids were found to be a suitable reaction medium for 1,4‐dipolar cycloaddition reactions of an isoquinoline, an activated alkyne, and a 4‐oxo‐4H‐1‐benzopyran‐3‐carboxaldehyde at room temperature to afford [1]benzopyrano‐pyrido‐isoquinoline (=9aH,15H‐benzo[a][1]benzopyrano[2,3‐h]quinolizine) derivatives selectively in good yields. The ionic liquid can be recovered and recycled in further runs without loss of activity. 相似文献
102.
Sridhar Madabhushi Raveendra JillellaKondal Reddy Godala Kishore Kumar Reddy MalluChina Ramanaiah Beeram Narsaiah Chinthala 《Tetrahedron letters》2012,53(39):5275-5279
An efficient and simple method for the synthesis of 2,2-disubstituted-2H-chromenes by one-step cyclocondensation of a phenol with a variety of 1,1-disubstituted propargyl alcohols using BF3·Et2O as the catalyst is described. 相似文献
103.
Maddimsetti Venkateswara RaoKotha kapu Sridhar Reddy Batchu Venkateswara Rao 《Tetrahedron letters》2012,53(45):5993-5995
An efficient strategy has been developed for the stereo selective synthesis of N-Boc-(2S,3S)-3-hydroxy-2-phenyl piperidine and N-Boc-safingol from benzaldehyde and N-Boc-imine. 相似文献
104.
K. Ravikumar B. Sridhar M. Mahesh V. V. Narayana Reddy 《Journal of chemical crystallography》2006,36(6):381-387
The crystal structures of isoxazole, 3-[[dihydro-2-[(Z)-2-oxohyrazono]-1H-imidazol-1-(3H)-yl]methyl-5-phenyl-,N-oxide] (C13H13N5O3) (I), isoxazole,3-[[dihydro-2-[(Z)-2-oxohyrazono]-1H-imidazol-1-(3H)-yl]-methyl-5-(4-methylphenyl)-,N-oxide] (C14H15N5O3) (II) and isoxazole, 3-[[dihydro-2-[(Z)-2-oxohyrazono]-1H-imidazol-1-(3H)-yl]-methyl-5-(2-methoxyphenyl)-,N-oxide] (C14H15N5O4) (III) have been determined by X-ray diffraction studies. The compound I, crystallized in triclinic space group with unit cell dimensions a = 7.2405(7) ?, b = 7.9936(8) ?, c = 11.6573(11) ?, α = 97.801(2)°, β = 90.884(2)°, γ = 96.250(2)° and Z = 2. Compound II crystallized in orthorhombic space group Pna21 with unit cell dimensions a = 10.1778(10) ?, b = 28.228(3) ?, c = 5.1206(5) ?, and Z = 4. Compound III crystallized in monoclinic space group P21/n with unit cell dimensions a = 7.8439(9) ?, b = 7.8544(9) ?, c = 23.534(3) ?, β = 99.464(2)° and Z = 4. For all three compounds, the five-membered imidazolidine ring adopts an envelope conformation. The crystal structures are stabilized by both the intramolecular N–H···O and intermolecular N–H···N hydrogen bonding. 相似文献
105.
Marcel Sihor Sridhar Gowrisankaran Alexandr Martaus Martin Motola Gilles Mailhot Marcello Brigante Olivier Monfort 《Molecules (Basel, Switzerland)》2022,27(24)
The preparation of anodic TiO2 nanotube layers has been performed using electrochemical anodization of Ti foil for 4 h at different voltages (from 0 V to 80 V). In addition, a TiO2 thin layer has been also prepared using the sol–gel method. All the photocatalysts have been characterized by XRD, SEM, and DRS to investigate the crystalline phase composition, the surface morphology, and the optical properties, respectively. The performance of the photocatalyst has been assessed in versatile photocatalytic reactions including the reduction of N2O gas and the oxidation of aqueous sulfamethoxazole. Due to their high specific surface area and excellent charge carriers transport, anodic TiO2 nanotube layers have exhibited the highest N2O conversion rate (up to 10% after 22 h) and the highest degradation extent of sulfamethoxazole (about 65% after 4 h) under UVA light. The degradation mechanism of sulfamethoxazole has been investigated by analyzing its transformation products by LC-MS and the predominant role of hydroxyl radicals has been confirmed. Finally, the efficiency of the anodic TiO2 nanotube layer has been tested in real wastewater reaching up to 45% of sulfamethoxazole degradation after 4 h. 相似文献
106.
A first principle study of hydrogen storage in titanium-doped small carbon clusters (C2nTin,n = 2–6)
Structural Chemistry - Hydrogen storage in Ti-doped small carbon clusters, C2nTin (n = 2–6), has been studied using density functional theory. Using the principle of maximum hardness (η)... 相似文献
107.
Sridhar Jagannathan 《国际流体数值方法杂志》1992,14(7):793-815
In the simulation of non-linear free surface flows in a finite domain a major concern is with the radiation condition to be applied at the ‘open’ boundary. No general theoretical radiation conditions are known to exist. In this paper a new open boundary condition is formulated based on energy flux equalization between the non-linear inner domain and a linear outer domain. The non-linear flow in the inner domain is solved numerically using a semi-Lagrangian procedure. The energy flux arriving at the open boundary is removed using a new open boundary condition which acts as a linear wave absorber. For the cases studied the performance of this boundary condition is found to be quite good. 相似文献
108.
109.
K. Sridhar 《Zeitschrift fur Physik C Particles and Fields》1988,38(3):449-452
It has been shown that a study of correlation between the average rapidity, 〈y〉, and transverse energy,E T , can be used to distinguish between different origins of large transverse energy events observed inp-Pb scattering in the HELIOS experiment. If the largeE T events are to be attributed to a nuclear dependence of structure functions then the hard scattering picture implies a positive correlation among the above two quantities, contrary to that seen in experiment. 相似文献
110.
Asymptotic behaviour of the moments of the first passage time (FPT) on a one-dimensional lattice holding a multifurcating
hierarchy of teeth is studied. There is a transition from ordinary to anomalous diffusion when the parameter controlling the
relative sizes of the teeth, is varied with respect to the furcating number of the hierarchy. The scaling behaviour of the
moments of FPT with the linear dimensions of the lattice segment indicates that in the anomalcus phase the probability density
of the FPT is multifractal. 相似文献