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31.
S. Chitra S. Viswanathan S. V. S. Rao P. K. Sinha 《Journal of Radioanalytical and Nuclear Chemistry》2011,287(3):955-960
Crystalline silicotitanate inorganic ion exchanger, with a sitinakite structure is candidate material for remediation of aqueous
nuclear waste streams. The syntheses of crystalline silicotitanate (CST) and Nb-substituted crystalline silcotitanate (Nb-CST)
were carried out under hydrothermal conditions and the products were characterized using techniques viz., XRD, SEM/EDS, DTA/TGA,
surface area respectively. Batch experiments were carried out to study the kinetics of uptake of 137Cs and 90Sr, to estimate the decontamination factor (DF) values and distribution coefficients (K
d) for the above synthesized CST and Nb-CST samples from actual radioactive waste solutions. The DF values for uptake of Cs
and Sr by Nb-CST after 24 h of equilibration was 355 and 136 whereas for CST it was found to be 40 and 176 respectively. The
K
d values for uptake of Cs and Sr for Nb-CST after 24 h of equilibration was found to be 35,490 and 13,500 mL/g respectively
whereas the K
d values for uptake of Cs and Sr for CST was found to be 4,025 and 17,525 mL/g respectively. The ion exchange capacity of Nb-CST
towards 90Sr and 137Cs was estimated to be 11.8 and 3.2 meq/g respectively whereas the ion exchange capacity of CST towards 90Sr and 137Cs was estimated to be 14.6 and 4.4 meq/g respectively. 相似文献
32.
33.
For two graphs G and H their wreath product ${G \otimes H}$ has the vertex set ${V(G) \times V(H)}$ in which two vertices (g 1, h 1) and (g 2, h 2) are adjacent whenever ${g_{1}g_{2} \in E(G)}$ or g 1 = g 2 and ${h_{1}h_{2} \in E(H)}$ . Clearly ${K_{m} \otimes I_{n}}$ , where I n is an independent set on n vertices, is isomorphic to the complete m-partite graph in which each partite set has exactly n vertices. A subgraph of the complete multipartite graph ${K_m \otimes I_n}$ containing vertices of all but one partite set is called partial factor. An H-frame of ${K_m \otimes I_n}$ is a decomposition of ${K_m \otimes I_n}$ into partial factors such that each component of it is isomorphic to H. In this paper, we investigate C 2k -frames of ${(K_m \otimes I_n)(\lambda)}$ , and give some necessary or sufficient conditions for such a frame to exist. In particular, we give a complete solution for the existence of a C 4p -frame of ${(K_m \otimes I_n)(\lambda)}$ , where p is a prime, as follows: For an integer m ≥ 3 and a prime p, there exists a C 4p -frame of ${(K_m \otimes I_n)(\lambda)}$ if and only if ${(m-1)n \equiv 0 ({\rm {mod}} {4p})}$ and at least one of m, n must be even, when λ is odd. 相似文献
34.
Kwan JC Ratnayake R Abboud KA Paul VJ Luesch H 《The Journal of organic chemistry》2010,75(23):8012-8023
Grassypeptolides A-C (1-3), a group of closely related bis-thiazoline containing cyclic depsipeptides, have been isolated from extracts of the marine cyanobacterium Lyngbya confervoides. Although structural differences between the analogues are minimal, comparison of the in vitro cytotoxicity of the series revealed a structure-activity relationship. When the ethyl substituent of 1 is changed to a methyl substituent in 2, activity is only slightly reduced (3-4-fold), whereas inversion of the Phe unit flanking the bis-thiazoline moiety results in 16-23-fold greater potency. We show that both 1 and 3 cause G1 phase cell cycle arrest at lower concentrations, followed at higher concentrations by G2/M phase arrest, and that these compounds bind Cu(2+) and Zn(2+). The three-dimensional structure of 2 was determined by MS, NMR, and X-ray crystallography, and the structure of 3 was established by MS, NMR, and chemical degradation. The structure of 3 was explored by in silico molecular modeling, revealing subtle differences in overall conformation between 1 and 3. Attempts to interconvert 1 and 3 with base were unsuccessful, but enzymatic conversion may be possible and could be a novel form of activation for chemical defense. 相似文献
35.
Dudka A. P. Chitra R. Choudhury R. R. Pisarevsky Yu. V. Simonov V. I. 《Crystallography Reports》2010,55(6):1060-1066
Crystallography Reports - An accurate X-ray diffraction study of a La3Ta0.25Zr0.50Ga5.25O14 single crystal (a = 8.2574(4) Å, c = 5.1465(4) Å, sp. gr. P321, Z = 1, R/R w = 0.62/0.57% for... 相似文献
36.
Raman spectroscopic studies of dl-serine and dl-valine under static high pressures have been carried out up to 8 and 7 GPa, respectively to understand the behaviour of hydrogen bonds in these compounds. The discontinuous changes in the pressure dependence of some of the Raman modes of dl-serine at 1.5 GPa are interpreted to be due to molecular rearrangements brought about by changes in the hydrogen bonding interactions. Our results of the pressure dependence of N–H?O librational modes in dl-valine at 3 GPa suggest changes in the nature of hydrogen bonding interactions across this pressure. 相似文献
37.
The action of concentrated sulphuric acid on (, R = H or CO2Me, R′ = H) generates the cation (, R = H or CO2Me, R′ = H); the stereoisomer (, R = H, R′ = H) is unaffected. This is an alternative procedure of some utility for the preparation of some cation salts, notably of (, R = CO2Me, R′ = H). 相似文献
38.
The salts (Y=H, OMe, Me) react with RLi(R=Me, n-Bu, i-Pr, t-Bu) in CH2Cl2 at low temperature to give and in excellent yields. Nucleophilic addition at the 1-position of (Y=OMe) has been observed for the first time. 相似文献
39.
R. Chitra Vijay Thiruvenkatam R. R. Choudhury M. V. Hosur T. N. Guru Row 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(1):o11-o13
The title bis(glycyl‐l ‐aspartic acid) oxalate complex {systematic name: bis[2‐(2‐ammonioacetamido)butanedioic acid] oxalate 0.4‐hydrate}, 2C6H11N2O5+·C2O42−·4H2O, crystallizes in a triclinic space group with the planar peptide unit in a trans conformation. The asymmetric unit consists of two glycyl‐l ‐aspartic acid molecules with positively charged amino groups and neutral carboxyl groups, and an oxalate dianion. The twist around the C—Cα bond indicates that both the peptide molecules adopt extended conformations, while the twist around the N—Cα bond shows that one has a folded and the other a semi‐extended state. The present complex can be described as an inclusion compound with the dipeptide molecule as the host and the oxalate anion as the guest. The usual head‐to‐tail sequence of aggregation is not observed in this complex, as is also the case with the glycyl‐l ‐aspartic acid dihydrate molecule. The study of aggregation and interaction patterns in binary systems is the first step towards understanding more complex phenomena. This further leads to results that are of general interest in bimolecular aggregation. 相似文献
40.
D. J. Goyal Chitra Agashe M. G. Takwale V. G. Bhide 《Journal of Crystal Growth》1993,130(3-4):567-570
Antimony-doped tin oxide films were deposited by spray pyrolysis on Corning 7059 substrates. The structural and electrical properties of the films deposited with different doping levels were studied. Relative variations in the structural properties were explained on the basis of structure factor calculations. The results show that the incorporation of antimony atoms takes place only at substitutional sites. As expected, the substitutional replacement of tin by antimony atoms increased appreciably the free carrier density of the film. 相似文献