全文获取类型
收费全文 | 412篇 |
免费 | 15篇 |
专业分类
化学 | 316篇 |
晶体学 | 1篇 |
力学 | 1篇 |
数学 | 41篇 |
物理学 | 68篇 |
出版年
2023年 | 5篇 |
2022年 | 3篇 |
2021年 | 15篇 |
2020年 | 13篇 |
2019年 | 21篇 |
2018年 | 19篇 |
2017年 | 20篇 |
2016年 | 24篇 |
2015年 | 16篇 |
2014年 | 25篇 |
2013年 | 39篇 |
2012年 | 27篇 |
2011年 | 37篇 |
2010年 | 18篇 |
2009年 | 11篇 |
2008年 | 16篇 |
2007年 | 30篇 |
2006年 | 15篇 |
2005年 | 19篇 |
2004年 | 15篇 |
2003年 | 11篇 |
2002年 | 10篇 |
2001年 | 2篇 |
2000年 | 3篇 |
1998年 | 3篇 |
1997年 | 1篇 |
1994年 | 2篇 |
1993年 | 1篇 |
1991年 | 2篇 |
1989年 | 1篇 |
1987年 | 1篇 |
1983年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有427条查询结果,搜索用时 185 毫秒
71.
Hydrogen Bonding between Metal‐Ion Complexes and Noncoordinated Water: Electrostatic Potentials and Interaction Energies 下载免费PDF全文
Jelena M. Andrić Majda Z. Misini‐Ignjatović Dr. Jane S. Murray Prof. Peter Politzer Prof. Snežana D. Zarić 《Chemphyschem》2016,17(13):2035-2042
The hydrogen bonding of noncoordinated water molecules to each other and to water molecules that are coordinated to metal‐ion complexes has been investigated by means of a search of the Cambridge Structural Database (CSD) and through quantum chemical calculations. Tetrahedral and octahedral complexes that were both charged and neutral were studied. A general conclusion is that hydrogen bonds between noncoordinated water and coordinated water are much stronger than those between noncoordinated waters, whereas hydrogen bonds of water molecule in tetrahedral complexes are stronger than in octahedral complexes. We examined the possibility of correlating the computed interaction energies with the most positive electrostatic potentials on the interacting hydrogen atoms prior to interaction and obtained very good correlation. This study illustrates the fact that electrostatic potentials computed for ground‐state molecules, prior to interaction, can provide considerable insight into the interactions. 相似文献
72.
Jovana Šakota Rosić Jelena Munćan Ivana Mileusnić Boris Kosić Lidija Matija 《Soft Materials》2016,14(4):264-271
The aim of this study was to determine if it is possible to distinguish between the groups of spoiled and unspoiled soft contact lenses using near-infrared spectroscopy and new analytical approach – Aquaphotomics. Using the principal component analysis, it was established that the absorbance spectra of worn and new contact lenses are differed at water absorption band related to hydration of proteins. Detection of proteins thus was performed indirectly by using vibrations of water molecules. This exploratory study showed that near-infrared spectroscopy and Aquaphotomics have potential for non-invasive, chemical-free detection of protein deposits on hydrated soft contact lenses. 相似文献
73.
Dragan Vujovic Jelena Popovic Djordjevic Milovan Velickovic Vele Tesevic 《Natural product research》2016,30(8):987-990
This work aimed to evaluate the total contents of polyphenolics (the Ribereau-Gayon–Maurié procedure), anthocyanins (using pH differential method) and tannins (the Nègre procedure) as well as the content of phenolic acids (using UPLC/MS chromatography), respectively of the wines obtained from three new Merlot clone candidates in the perennial clonal selection. The aforementioned chemical parameters were determined in the samples covering the period 2009–2012. In comparison both with the standard Merlot wine (mother vine) and the wines obtained from other two clone candidates, the Merlot wine of the clone candidate No. 022 was found to have the highest total content of all three examined components 1.89 ± 0.05 g/L (polyphenolics), 185.59 ± 5.00 mg/L (anthocyanins) and 1.11 ± 0.03 g/L (tannins), as well as six phenolic acids including gallic acid (25.49 ± 0.27 mg/L). These findings are in good agreement with the observed trend for the viticultural parameters indicating the clone candidate No. 022 as more promising than mother. 相似文献
74.
75.
N,N'-Alkylmethylimidazolium cations have been separated in NACE when one of the N,N'-dialkylimidazolium salts (ionic liquids (ILs)) was used as an electrolyte additive to the organic solvent separation medium. The separated species were 1-methyl-, 1-ethyl-, 1-butyl-, 1-octyl-, 1-decyl-3-methylimidazolium and N-butyl-3-methylpyridinium cations and BGE composed of 1-ethyl-3-methylimidazolium ethylsulfate or 1-butyl-3-methylimidazolium trifluoroacetate [BMIm][FAcO] (A6; B2) diluted in ACN. It was demonstrated that contactless conductivity detection (CCD) may be applied to monitoring the separation process in nonaqueous separation media, allowing to use the UV light-absorbing imidazolium-based electrolyte additives. There could be marked three concentration regions of added ILs; at first ionic strength of BGE below 1-2 mM, and then the actual electrophoretic mobility of analytes rises from 0. At concentrations above 1-2 mM, the added IL facilitated separation. In concentration region of 1-20 mM, the actual electrophoretic mobility of analyzed imidazolium cations was increasing with decrease in separation medium ionic strength. At higher concentrations of BGE (above 30 mM), the conductivity of the separation media became too high for this detector. Some organic dyes were also successfully separated and detected by contactless conductivity detector in a 20 mM A6 separation electrolyte in ACN. 相似文献
76.
77.
Watanabe T Radulovic J Boretius S Frahm J Michaelis T 《Magnetic resonance imaging》2006,24(3):209-215
This magnetic resonance imaging (MRI) study describes mapping of the habenulo-interpeduncular pathway in living mice based on manganese-induced contrast. Six hours after intracerebroventricular microinjection of MnCl2, T1-weighted 3D MRI (2.35 T) at 117 mum isotropic resolution revealed a continuous pattern of anterograde labeling from the habenula via the fasciculus retroflexus to the interpeduncular nucleus. Alternatively, the less invasive systemic administration of MnCl2 allowed for monitoring of the dynamic uptake pattern of respective neural components with even higher reproducibility across animals. Time courses covered the range from 42 min to 24 h after injection. In conclusion, manganese-enhanced MRI may open new ways for functional assessments of the habenulo-interpeduncular system in animal models with cognitive impairment. 相似文献
78.
Jelena Đorović Zoran Marković Zorica D. Petrović Dušica Simijonović Vladimir P. Petrović 《Molecular physics》2017,115(19):2460-2468
The time-dependent density functional theory (TDDFT) was applied in conjunction with the natural bond orbital analysis to examine the UV-Vis properties of 10 phenolic Schiff bases. The calculations were performed with different functionals, but main discussion refers to results obtained at the B3LYP/6-311+G(d,p) level of theory. The approach based on the natural localised molecular orbital clusters indicates similar behaviour for majority of examined compounds. The HOMO (“highest occupied molecular orbital”) cluster is delocalised over the ring which is electron richer, the HOMO-1 cluster is spread over the other ring, whereas the LUMO (“lowest unoccupied molecular orbital”) cluster is situated on the imino group. The two bands at long wavelengths correspond to the HOMO → LUMO and HOMO-1 → LUMO transitions, i.e. from both A and B rings to the imino group. The next band originates from a transition from the imino group to the imino group. The band at the smallest wavelengths originates from a transition from the A ring to the A ring, or from the B ring to the B ring. Our findings are in very good agreement with the existing literature data. 相似文献
79.
Jelena Klinovaja Daniel Loss 《The European Physical Journal B - Condensed Matter and Complex Systems》2014,87(8):1-16
We study anisotropic stripe models of interacting electrons in the presence of magnetic fields in the quantum Hall regime with integer and fractional filling factors. The model consists of an infinite strip of finite width that contains periodically arranged stripes (forming supercells) to which the electrons are confined and between which they can hop with associated magnetic phases. The interacting electron system within the one-dimensional stripes are described by Luttinger liquids and shown to give rise to charge and spin density waves that lead to periodic structures within the stripe with a reciprocal wavevector 8k F in a mean field approximation. This wavevector gives rise to Umklapp scattering and resonant scattering that results in gaps and chiral edge states at all known integer and fractional filling factors ν. The integer and odd denominator filling factors arise for a uniform distribution of stripes, whereas the even denominator filling factors arise for a non-uniform stripe distribution. We focus on the ground state of the system, and identify the quantum Hall regime via the quantized Hall conductance. For this we calculate the Hall conductance via the Streda formula and show that it is given by σ H = νe 2/h for all filling factors. In addition, we show that the composite fermion picture follows directly from the condition of the resonant Umklapp scattering. 相似文献
80.
Jelena Tamuliene Liudmila G. Romanova Vasyl S. Vukstich Alexander V. Papp Alexander V. Snegursky 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2014,68(5):1-17
The fragmentation of the hydrated and anhydrous asparagine molecule (C4H8N2O3) under a low-energy electron impact was studied both experimentally and theoretically. The main emphasis was given to the mechanisms of the fragment production of these molecules. A special attention was paid to the energy characteristics of the ionic fragment yield. The geometrical parameters of the initial molecule rearrangement were also analyzed. 相似文献