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21.
Tomasz Laskowski Zbigniew Rafiński Paweł Sowiński Jan Pawlak 《Magnetic resonance in chemistry : MRC》2012,50(5):347-349
The relative configurations of four stereogenic centers of the C33‐C42 fragment of niphimycin A were assigned as 2S*, 3R*, 4S* and 6S*, based upon 1H NMR analysis with double‐quantum filtered COSY and nuclear Overhauser spectroscopy experiments. These data were then correlated with absolute configurations at C36 and C38 of niphimycin A, which were declared previously as 36S and 38S [3]. This allowed for the assignment of the absolute configurations at C34 and C35 of niphimycin A as 34S and 35R. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
22.
Kasra Rafi 《Geometric And Functional Analysis》2007,17(3):936-959
We study how the length and the twisting parameter of a curve change along a Teichmüller geodesic. We then use our results
to provide a formula for the Teichmüller distance between two hyperbolic metrics on a surface, in terms of the combinatorial
complexity of curves of bounded lengths in these two metrics.
Received: October 2005 Revision: April 2006 Accepted: May 2006 相似文献
23.
M. Rafi S. Ahmed M. Aslam Khan M. Aslam Baig 《Zeitschrift für Physik A Hadrons and Nuclei》1985,320(3):369-373
We report new high resolution measurements on the photoabsorption spectra of BaH in the wavelength region 3,000 Å–3,800 Å using the second order of a 3.4 metre Ebert spectrograph and a High pressure xenon arc as the background source of continuum. Observations include two new electronic transitions of BaH and BaD, denoted asK 2 ∑-X 2 ∑ at 3,725 Å andL 2 Π —X 2 ∑ at 3,694 Å, which are forming an p-complex orginating from the 7p atomic state of barium. A rotational analysis of the band systems have been carried out and effective rotational constants are determined. 相似文献
24.
S.K. Sadrnezhaad Rafi Ali Rahimi Gholamreza Raisali Farhad Foruzanfar 《Journal of Non》2009,355(48-49):2400-2404
Mechanism of removal of lead from silicate glass containing 68.5 wt% PbO by 0.5 N HNO3 was investigated by incorporation of the chemical-analyses/weight-loss data into shrinking-core model (SCM) and minimization of the difference. Scanning electron microscopy (SEM), emission spectrometry with inductively coupled plasma (ICP), X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDS) were used to determine the compositional changes of the lead-silicate glass (LSG) samples. Dual inter-diffusion chemical reaction mechanisms having respective activation energies of 83.49 and 47.80 kJ/mol dominated the deleading process. 相似文献
25.
Fatimah Saeed Aldughaylibi Muhammad Asam Raza Sumaira Naeem Humera Rafi Mir Waqas Alam Basma Souayeh Mohd Farhan Muhammad Aamir Noushi Zaidi Tanveer Ahmad Mir 《Molecules (Basel, Switzerland)》2022,27(18)
This study was designed to check the potential of secondary metabolites of the selected plants; Citrullus colocynthis, Solanum nigrum, Solanum surattense, Calotropis procera, Agave americana, and Anagallis arvensis for antioxidant, antibacterial, antifungal, and antidiabetic agents. Plant material was soaked in ethanol/methanol to get the crude extract, which was further partitioned via solvent extraction technique. GCMS and FTIR analytical techniques were applied to check the compounds responsible for causing antioxidant, antimicrobial, and antidiabetic activities. It was concluded that about 80% of studied extracts/fractions were active against α-amylase, ranging from 43 to 96%. The highest activity (96.63%) was exhibited by butanol fractions of A. arvensis while the least response (43.65%) was shown by the aqueous fraction of C. colocynthis and the methanol fraction of fruit of S. surattense. The highest antioxidant activity was shown by the ethyl acetate fraction of Anagallis arvensis (78.1%), while aqueous as well as n-hexane fractions are the least active throughout the assay. Results showed that all tested plants can be an excellent source of natural products with potential antimicrobial, antioxidant, and antidiabetic potential. The biological response of these species is depicted as a good therapeutic agent, and, in the future, it can be encapsulated for drug discovery. 相似文献
26.
Syed Farooq Adil Mohamed E. Assal Mohammed Rafi Shaik Mufsir Kuniyil Azhar Hashmi Mujeeb Khan Aslam Khan Muhammad Nawaz Tahir Abdulrahman Al-Warthan Mohammed Rafiq H. Siddiqui 《应用有机金属化学》2020,34(8):e5718
Graphene–metal nanocomposites have been found to remarkably enhance the catalytic performance of metal nanoparticle-based catalysts. In continuation of our previous report, in which highly reduced graphene oxide (HRG)-based nanocomposites were synthesized and evaluated, we present nanocomposites of graphene oxide (GRO) and ZnO nanoparticle-doped MnCO3 ([ZnO–MnCO3/(1%)GRO]) synthesized via a facile, straightforward co-precipitation technique. Interestingly, it was noticed that the incorporation of GRO in the catalytic system could noticeably improve the catalytic efficiency compared to a catalyst (ZnO–MnCO3) without GRO, for aerial oxidation of benzyl alcohol (BzOH) employing O2 as a nature-friendly oxidant under base-free conditions. The impacts of various reaction factors were thoroughly explored to optimize reaction conditions using oxidation of BzOH to benzaldehyde (BzH) as a model substrate. The catalysts were characterized using X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, Energy dispersive X-ray spectroscopy (EDX), Brunauer-Emmett-Teller (BET), and Raman spectroscopy. The (1%)ZnO–MnCO3/(1%)GRO exhibited significant specific activity (67 mmol.g−1.hr−1) with full convversion of BzOH and >99% BzH selectivity within just 6 min. The catalytic efficiency of the (1%)ZnO–MnCO3/(1%)GRO nanocomposite was significantly better than the (1%)ZnO–MnCO3/(1%)HRG and (1%)ZnO–MnCO3 catalysts, presumably due to the existence of oxygen-possessing groups on the GRO surface and as well as a very high surface area that could have been instrumental in uniformly dispersing the active sites of the catalyst, i.e., ZnO–MnCO3. Under optimum circumstances, various kinds of alcohols were selectively transformed to respective carbonyls with full convertibility over the (1%)ZnO–MnCO3/(1%)GRO catalyst. Furthermore, the highly effective (1%)ZnO–MnCO3/(1%)GRO catalyst could be successfully reused and recycled over five consecutive runs with a marginal reduction in its performance and selectivity. 相似文献
27.
28.
Dana Mendelson Asaf Nachmias Samuel S. Watson 《Communications in Mathematical Physics》2014,329(1):29-56
We show that crossing probabilities in 2D critical site percolation on the triangular lattice in a piecewise analytic Jordan domain converge with power law rate in the mesh size to their limit given by the Cardy–Smirnov formula. We use this result to obtain new upper and lower bounds of ${e^{O(\sqrt{{\rm log}\,{\rm log} R})}\, R^{-1/3}}$ for the probability that the cluster at the origin in the half-plane has diameter R, improving the previously known estimate of R ?1/3+o(1). 相似文献
29.
Kalim Ullah Khan Samina Roohi Mohammad Rafi Rizwana Zahoor Zafar Iqbal Mushtaq Ahmad 《Journal of Radioanalytical and Nuclear Chemistry》2014,300(1):225-228
Labelling of 5-aminolevulinic acid (5-ALA) with 99mTc was achieved by using SnCl2·2H2O as reducing agent. Radiochemical purity and labelling efficiency was determined by instant thin layer chromatography/paper chromatography. Efficiency of labelling was dependent on many parameters such as amount of ligand, reducing agent, pH, and time of incubation. 99mTc labelled 5-ALA remained stable for 24 h in human serum. Tissue biodistribution of 99mTc-5-ALA was evaluated in Sprague–Dawley rats. Biodistribution study (% ID/g) in rats revealed that 99mTc-5-ALA was accumulated significantly in liver, spleen, stomach and intestine after half hour, 4 and 24 h. Significant activity was noted in bladder and urine at 4 h. High liver uptake of 99mTc-5-ALA makes it a promising liver imaging agent. 相似文献
30.
The behavior of the random graph G(n,p) around the critical probability pc = is well understood. When p = (1 + O(n1/3))pc the components are roughly of size n2/3 and converge, when scaled by n?2/3, to excursion lengths of a Brownian motion with parabolic drift. In particular, in this regime, they are not concentrated. When p = (1 ‐ ?(n))pc with ?(n)n1/3 →∞ (the subcritical regime) the largest component is concentrated around 2??2 log(?3n). When p = (1 + ?(n))pc with ?(n)n1/3 →∞ (the supercritical regime), the largest component is concentrated around 2?n and a duality principle holds: other component sizes are distributed as in the subcritical regime. Itai Benjamini asked whether the same phenomenon occurs in a random d‐regular graph. Some results in this direction were obtained by (Pittel, Ann probab 36 (2008) 1359–1389). In this work, we give a complete affirmative answer, showing that the same limiting behavior (with suitable d dependent factors in the non‐critical regimes) extends to random d‐regular graphs. © 2009 Wiley Periodicals, Inc. Random Struct. Alg., 2010 相似文献