全文获取类型
收费全文 | 158篇 |
免费 | 9篇 |
国内免费 | 1篇 |
专业分类
化学 | 106篇 |
力学 | 22篇 |
数学 | 17篇 |
物理学 | 23篇 |
出版年
2023年 | 4篇 |
2022年 | 1篇 |
2021年 | 12篇 |
2019年 | 8篇 |
2018年 | 3篇 |
2017年 | 2篇 |
2016年 | 5篇 |
2015年 | 6篇 |
2014年 | 8篇 |
2013年 | 10篇 |
2012年 | 10篇 |
2011年 | 14篇 |
2010年 | 6篇 |
2009年 | 6篇 |
2008年 | 10篇 |
2007年 | 9篇 |
2006年 | 12篇 |
2005年 | 9篇 |
2004年 | 7篇 |
2003年 | 5篇 |
2002年 | 3篇 |
2000年 | 2篇 |
1999年 | 1篇 |
1998年 | 1篇 |
1996年 | 1篇 |
1994年 | 1篇 |
1991年 | 3篇 |
1989年 | 1篇 |
1987年 | 2篇 |
1986年 | 1篇 |
1983年 | 1篇 |
1981年 | 2篇 |
1980年 | 1篇 |
1979年 | 1篇 |
排序方式: 共有168条查询结果,搜索用时 15 毫秒
11.
12.
A strategy for selection of reference materials in stable oxygen isotope analyses of solid materials
The propagation of uncertainties associated with the stable oxygen isotope reference materials through a multi-point normalisation procedure was evaluated in this study using Monte Carlo (MC) simulation. We quantified the normalisation error for a particular selection of reference materials and their number of replicates, when the choice of standards is restricted to either nitrates, sulphates or organic reference materials alone, and in comparison with when this restriction was relaxed. A lower uncertainty in stable oxygen isotope analyses of solid materials performed using High-Temperature Pyrolysis (HTP) can be readily achieved through an optimal selection of reference materials. Among the currently available certified reference materials the best performing pairs minimising the normalisation errors are USGS35 and USGS34 for nitrates; IAEA-SO-6 and IAEA-SO-5 for sulphates; and IAEA-601 and IAEA-602 for organic materials. The normalisation error can be reduced further--by approximately half--if each of these two analysed reference materials is replicated four times. The overall optimal selection among all nine considered reference materials is the IAEA-602 and IAEA-SO-6 pair. If each of these two reference materials is replicated four times the maximum predicted normalisation error will equal 0.22‰, the minimum normalisation error 0.12‰, and the mean normalisation error 0.15‰ over the natural range of δ(18)O variability. We argue that the proposed approach provides useful insights into reference material selection and in assessing the propagation of analytical error through normalisation procedures in stable oxygen isotope studies. 相似文献
13.
Swapnil B. Ambade Rajaram S. Mane Anil V. Ghule Go-Woon Lee Ramphal Sharma Oh-shim Joo Rohan B. Ambade Soo-Hyoung Lee Sung-Hwan Han 《Journal of photochemistry and photobiology. A, Chemistry》2011,217(1):267-270
Enhanced photosensitization in presence of CdS nanoparticles is achieved in electrochemically deposited ZnO nanoplates and N3 loaded dye-sensitized solar cells. Chemically embedded CdS nanoparticles act as a sandwiching layer between ZnO nanoplates and dye molecules by overcoming current limiting serious Zn2+/dye insulating complex formation and CdS photo-corrosion issues. The X-ray diffraction and the scanning electron microscopy confirm the ZnO with vertically aligned nanoplates, perpendicular to the substrate surface. Amorphous CdS is monitored using electron dispersive X-ray analysis. The low and high resolution transmission electron microscope images confirm the presence of CdS nanoparticles over ZnO nanoplates which later is supported by an increase in optical absorbance and shift in band edge. About 400% increase in solar conversion efficiency with this cascade arrangement is achieved when compared with without CdS which could be fascinating while designing solid state solar cells in presence of suitable p-type layer. 相似文献
14.
Yin S Davis RA Shelper T Sykes ML Avery VM Elofsson M Sundin C Quinn RJ 《Organic & biomolecular chemistry》2011,9(19):6755-6760
Bioassay-guided fractionation of the CH(2)Cl(2)/MeOH extract of the Australian marine sponge Pseudoceratina sp. resulted in the purification of four new bromotyrosine alkaloids, pseudoceramines A-D (1-4), along with a known natural product, spermatinamine (5). The structures of 1-5 were determined by spectroscopic methods. Pseudoceramines A (1) and B (2) feature a rare bromotyrosyl-spermine-bromotyrosyl sequence, and pseudoceramine C (3) is the first example of bromotyrosine coupled with an N-methyl derivative of spermidine. Compounds 1-5 were screened for inhibition of toxin secretion by the type III secretion (T3S) pathway in Yersinia pseudotuberculosis. Compounds 2 and 5 inhibited secretion of the Yersinia outer protein YopE (IC(50) = 19 and 6 μM, respectively) and the enzyme activity of YopH (IC(50) = 33 and 6 μM, respectively). 相似文献
15.
Real time PCR is the mainstay of current nucleic acid assays, underpinning applications in forensic science, point-of-care diagnostics and detection of bioterrorism agents. Despite its broad utility, the search for new tests continues, inspired by second and third generation DNA sequencing technologies and fuelled by progress in single molecule fluorescence spectroscopy, nanotechnology and microfabrication. These new methods promise the direct detection of nucleic acids without the need for enzymatic amplification. In this feature article, we provide a chemist's perspective on this multidisciplinary area, introducing the concepts of single molecule detection then focussing on the selection of labels and probe chemistry suitable for generating a signal detectable by ultrasensitive fluorescence spectroscopy. Finally, we discuss the further developments that are required to incorporate these detection platforms into integrated 'sample-in-answer-out' instruments, capable of detecting many target sequences in a matter of minutes. 相似文献
16.
Rohan Abeyaratne 《Journal of Elasticity》1983,13(2):175-184
The equations governing the equilibrium of a finitely deformed elastic solid are derived from the Principle of Minimum Potential Energy. The possibility of the deformation gradient and the stresses being discontinuous across certain surfaces in the body — “equilibrium shocks” — is allowed for. In addition to the equilibrium equations, natural boundary conditions and traction continuity condition, a supplementary jump condition which is to hold across the surface of discontinuity is derived. This condition is shown to imply that a stable equilibrium shock must necessarily be dissipation-free. 相似文献
17.
Chemical investigations of the fermentation broth from the microfungus Xylaria sp. have afforded the new natural product 3-chloro-4-hydroxyphenylacetamide 1 and the previously reported fungal metabolite 3-chloro-4-hydroxyphenylacetic acid 2. This letter reports the isolation and full spectroscopic characterisation of compounds 1 and 2 by NMR, UV, IR and MS data. The crystal structure and one-pot synthesis of 3-chloro-4-hydroxyphenylacetamide are also reported. 相似文献
18.
Hanrahan JR Mewett KN Chebib M Matos S Eliopoulos CT Crean C Kumar RJ Burden P Johnston GA 《Organic & biomolecular chemistry》2006,4(13):2642-2649
A divergent synthesis of both diastereoisomers of (+/-)-(3-aminocyclopentane)alkylphosphinic acid is described. Both diastereoisomers are obtained in 5 steps from the key (+/-)-(3-hydroxycyclopent-1-ene)alkylphosphinate esters which are prepared via a palladium catalysed C-P bond forming reaction. 相似文献
19.
20.
T. Battumur Swapnil B. Ambade Rohan B. Ambade Pashupati Pokharel Dai Soo Lee Sung-Hwan Han Wonjoo Lee Soo-Hyoung Lee 《Current Applied Physics》2013,13(1):196-204
In order to enhance the capacitance of electrochemical capacitors, multiwalled carbon nanotubes (MWCNTs) and graphene nanosheets (GNS) were added to cobalt oxide (Co3O4) paste. The composite film based on Co3O4/MWCNT/GNS (95:4:1 wt%) exhibited a capacitance of 294 F/g while the capacitance of Co3O4/MWCNT (95:5 wt%) and pure Co3O4 film is 205 and 163 F/g, respectively. The enhanced capacitance of Co3O4/MWCNT/GNS composite film was attributed to the electrochemical contributions of the Co3O4 nanoparticle attached to the GNS as well as their significantly increased specific surface areas by MWCNTs. Furthermore, the composite films showed faradaic redox capacitive behavior to double-layer capacitive behavior due to the different nanostructures of the composites. 相似文献