全文获取类型
收费全文 | 157篇 |
免费 | 5篇 |
专业分类
化学 | 131篇 |
数学 | 3篇 |
物理学 | 28篇 |
出版年
2023年 | 3篇 |
2022年 | 4篇 |
2021年 | 2篇 |
2020年 | 5篇 |
2019年 | 11篇 |
2018年 | 6篇 |
2017年 | 3篇 |
2016年 | 5篇 |
2015年 | 1篇 |
2014年 | 3篇 |
2013年 | 7篇 |
2012年 | 8篇 |
2011年 | 17篇 |
2010年 | 5篇 |
2009年 | 5篇 |
2008年 | 3篇 |
2007年 | 9篇 |
2006年 | 5篇 |
2005年 | 9篇 |
2004年 | 5篇 |
2003年 | 2篇 |
2002年 | 2篇 |
2001年 | 1篇 |
2000年 | 5篇 |
1999年 | 5篇 |
1998年 | 1篇 |
1997年 | 1篇 |
1993年 | 1篇 |
1986年 | 2篇 |
1985年 | 1篇 |
1983年 | 2篇 |
1982年 | 4篇 |
1977年 | 2篇 |
1976年 | 1篇 |
1974年 | 3篇 |
1973年 | 1篇 |
1972年 | 1篇 |
1966年 | 1篇 |
1963年 | 1篇 |
1962年 | 5篇 |
1959年 | 2篇 |
1958年 | 2篇 |
排序方式: 共有162条查询结果,搜索用时 15 毫秒
11.
Determination of pharmaceuticals, iodinated contrast media and musk fragrances in sludge by LC/tandem MS and GC/MS 总被引:1,自引:0,他引:1
Ternes TA Bonerz M Herrmann N Löffler D Keller E Lacida BB Alder AC 《Journal of chromatography. A》2005,1067(1-2):213-223
Analytical methods have been developed that allow for the determination of antiphlogistics, lipid regulators, the antiepileptic carbamazepine, cytostatic agents, the psychiatric drug diazepam and iodinated contrast media (ICM) as well as two major polycyclic musk fragrances HHCB (galaxolide) and AHTN (tonalide) in activated and digested sludge. The procedures consist of ultrasonic solvent extraction (USE) using methanol/acetone or pressurized liquid extraction (PLE) using 100% methanol. Clean-up was performed with C18ec material and silica gel followed by LC tandem MS (electrospray or atmospheric pressure chemical ionization) detection for pharmaceuticals and iodinated contrast media as well as GC/MS in the SIM mode for musk fragrances. Absolute recoveries from spiked activated sludge in general ranged from 88+/-4 to 119+/-20% for ICM and were 78+/-15 and 87+/-10% for the AHTN and HHCB, respectively. For the pharmaceuticals, absolute recoveries in activated sludge ranged between 43 and 78%. Subsequently, compensation of losses was carried out by using surrogate standards (acidic pharmaceuticals: fenoprop, neutral pharmaceuticals: dihydro-carbamazepine, musk fragrances: AHTN-D3). With one exception the recoveries were also adequate in digested sludge ranging from 43% to 120%. 相似文献
12.
13.
Recent experiments suggest that the Ising pyrochlore magnets Ho2Ti2O7 and Dy2Ti2O7 display qualitative properties of the nearest-neighbor "spin ice" model. We discuss the dipolar energy scale present in both these materials and discuss how spin-ice behavior can occur despite the presence of long-range dipolar interactions. We present results of numerical simulations and a mean field analysis of Ising pyrochlore systems. Based on our quantitative theory, we suggest that the spin-ice behavior in these systems is due to long-range dipolar interactions, and that the nearest-neighbor exchange in Dy2Ti2O7 is antiferromagnetic. 相似文献
14.
Catherine Weetman Amelie Porzelt Prasenjit Bag Franziska Hanusch Shigeyoshi Inoue 《Chemical science》2020,11(18):4817
Main group multiple bonds have proven their ability to act as transition metal mimics in the last few decades. However, catalytic application of these species is still in its infancy. Herein we report the second neutral NHC-stabilised dialumene species by use of a supporting aryl ligand (3). Different to the trans-planar silyl-substituted dialumene (3Si), compound 3 features a trans-bent and twisted geometry. The differences between the two dialumenes are explored computationally (using B3LYP-D3/6-311G(d)) as well as experimentally. A high influence of the ligand''s steric demand on the structural motif is revealed, giving rise to enhanced reactivity of 3 enabled by a higher flexibility in addition to different polarisation of the aluminium centres. As such, facile activation of dihydrogen is now achievable. The influence of ligand choice is further implicated in two different catalytic reactions; not only is the aryl-stabilised dialumene more catalytically active but the resulting product distributions also differ, thus indicating the likelihood of alternate mechanisms simply through a change of supporting ligand.Ligand controlled reactivity: a trans-bent and twisted geometry enables dihydrogen activation and enhanced catalytic activity for NHC-stabilised dialumenes. 相似文献
15.
P. Majee G. Goswami M. K. Sen B. C. Bag 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,72(3):435-439
In this paper we have studied the directed motion of a Brownian particle
in a multiplicative noise
driven flashing ratchet system. Our investigation shows
the current (j) is either maximum or minimum
in the super-diffusion (SPD) region depending on the asymmetric character of the ratchet potential.
But the optimum behavior disappears for the symmetric
ratchet potential and there is a current inversion around the normal diffusion (ND). With increase of
half cycle period(tp/2) (which controls the on-off operation
mechanism of the potential), j
passes through a maximum and the peak height is the highest for the SPD. Also
at low asymmetry in the system, the mobility is more dominating for
the normal and the super-diffusion cases than the sub-diffusion.
For large asymmetry in the ratchet potential,
the diffusion control positive current
is larger for the ND compared to the other cases.
Finally, we observe that there is a maximum in the variation of current as a function of noise correlation time for
SPD. But it disappears for the other cases. 相似文献
16.
Dibyendu S. Bag Dhiraj Dutta T. C. Shami K. U. Bhasker Rao 《Journal of polymer science. Part A, Polymer chemistry》2009,47(9):2228-2242
A chiral monomer containing L ‐leucine as a pendant group was synthesized from methacryloyl chloride and L ‐leucine in presence of sodium hydroxide at 4 °C. The monomer was polymerized by free radical polymerization in propan‐2‐ol at 60 °C using 2,2′‐azobis isobutyronitrile (AIBN) as an initiator under nitrogen atmosphere. The polymer, poly(2‐(Methacryloyloxyamino)‐4‐methyl pentanoic acid) is thus obtained. The molecular weight of the polymer was determined to be: Mw is 6.9 × 103 and Mn is 5.6 × 103. The optical rotation of both chiral monomer and its polymer varies with the solvent polarity. The amplification of optical rotation due to transformation of monomer to polymer is associated with the ordered conformation of chiral monomer unit in the polymeric chain due to some secondary interactions like H‐bonding. The synthesized monomer and polymer exhibit intense Cotton effect at 220 nm. The conformation of the chain segments is sensitive to external stimuli, particularly the pH of the medium. In alkaline medium, the ordered chain conformation is destroyed resulting disordered random coils. The ordered coiling conformation is more firmly present on addition of HCl. The polymer exhibits swelling‐deswelling characteristics with the change of pH of the medium, which is reversible. The Cotton effect decreases linearly with the increase of temperature which is reversible on cooling. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2228–2242, 2009 相似文献
17.
Süheyla Çehreli Be?ir Tatlí Pelin Bagˇman 《The Journal of chemical thermodynamics》2005,37(12):1288-1293
(Liquid + liquid) equilibrium (LLE) data for (water + propionic acid + cyclohexanone) were measured under atmospheric pressure and at T = (293.2, 298.2 and 303.2) K. Phase diagrams were obtained by determining solubility and tie-line data. The LLE data of the ternary systems were predicted by UNIFAC method. Distribution coefficients and separation factors were evaluated over the immiscibility regions. 相似文献
18.
The molar absorptivity of diphenylthiocarbazone in cyclohexane is dramatically enhanced by the addition of small quantities of chloroform. This has been attributed to the formation of a 1:2 dithizone chloroform complex (formation constant 104.0) rather than simple nonspecific solvent effects. 相似文献
19.
20.