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91.
Jasmin Sultana Nageshwar D. Khupse Srijita Chakrabarti Pronobesh Chattopadhyay Diganta Sarma 《Tetrahedron letters》2019,60(16):1117-1121
Using catalytic amount of Ag2CO3 a simple, efficient and copper free green protocol has been developed to synthesize 1,4-disubstituted 1,2,3-triazoles regioselectively. Here, the cationic surfactant, cetylpyridinium chloride (CPyCl) in water provides a micellar media and accelerates the subsequent Ag(I)-catalysed azide-alkyne cycloaddition (AgAAC) reaction by increasing the concentration of reactants in the micellar pseudophase. Our method is found to be environmentally friendly from E-factor measurement. The surfactant, CPyCl is found to be nontoxic. 相似文献
92.
Guang Huang Claribel Murillo Solano Yuxin Su Nameer Ezzat Shino Matsui Liuyu Huang Debopam Chakrabarti Yu Yuan 《Tetrahedron letters》2019,60(26):1736-1740
A rapid and efficient synthesis of 2-vinylquinolines via trifluoromethanesulfonamide-mediated olefination of 2-methylquinoline and aldehyde under microwave irradiation is reported. Biological evaluation of these scaffolds demonstrates that 2-vinylquinolines 3x-3z possess excellent antimalarial activities against chloroquine-resistant Dd2 strain of Plasmodium falciparum (IC50 < 100 nM). 相似文献
93.
We report novel phase behavior for a system of disclike ellipsoidal particles interacting via a pair potential. We identify a structural phase transition between two hexagonal columnar phases, both tilted, induced by spatial ordering of the tilt about the columnar axis and positional correlations between neighboring columns upon cooling. The local minima of the potential energy surface support irregular helical arrangements of the discoids about the columnar axis for the high-temperature hexagonal columnar phase, and a tilted arrangement for both phases. Our study demonstrates that dispersion-repulsion forces corresponding to oblate ellipsoids are sufficient to produce a columnar phase that is tilted and helical. 相似文献
94.
The polycrystalline sample of LiFe1/2Ni1/2VO4 was prepared by a standard solid-state reaction technique and confirmed by X-ray diffractometry. LiFe1/2Ni1/2VO4 has orthorhombic crystal structure whose dielectric and electric modulus properties were studied over a wide frequency range (100 Hz–1 MHz) at different temperatures (296–623 K) using a complex impedance spectroscopy (CIS) technique. The frequency and temperature dependence of dielectric constant (εr) and tangent loss (tan δ) of LiFe1/2Ni1/2VO4 are studied. The variation of εr as a function frequency at different temperatures exhibits a dispersive behavior at low frequencies. The variation of the εr as a function of temperature at different frequencies shows the dielectric anomaly in εr at 498 K with maximum value of dielectric constant 274.49 and 96.86 at 100 kHz and 1 MHz, respectively. Modulus analysis was carried out to understand the mechanism of the electrical transport process, which indicates the non-exponential type of conductivity relaxation in the material. The activation energy calculated from electric modulus spectra is 0.38 eV. 相似文献
95.
Ramya Ramachandran Swetha Ramesh Srinath Ramkumar Arunaloke Chakrabarti Utpal Roy 《Applied biochemistry and biotechnology》2018,186(4):917-936
In the pursuit of new antifungal compounds, five coproduced lipopeptide variants (AF1 to AF5) from wild-type Bacillus subtilis RLID 12.1 were identified in our previous study. Out of five, AF4 was identified as a novel lead molecule belonging to the bacillomycin family showing less cytotoxicity at its respective minimum inhibitory concentrations (MIC) evaluated against 81 strains of Candida and Cryptococcus species (including clinical isolates); besides this, AF4 purified in the present study exhibited encouraging MIC values against 10 clinical mycelial fungi. Aiming for a selective production augmentation of AF4 lipopeptide variant, a new fermentation media comprising malt extract (1.01%), dextrose (0.55%), peptone (1.79%), MnSO4 (2 mM), and NaCl (0.5%) was formulated. Maximum production of 954.8?±?10.8 mg/L was achieved with 44% selectivity at 30 °C compared to unoptimized conditions (186.4?±?6.1 mg/L). Use of calcium alginate beads in the formulated media during the onset of lipopeptide production resulted in an augmentation in the selectivity of the most efficacious AF4 variant to about 72% presumably due to attenuation of other coproduced lipopeptide variants AF1 and AF2. Difference in yield of lipopeptides varied with bead size, bead preparation ratios, and sodium alginate concentrations. Use of Ca-alginate beads in the upstream production process of the lead AF4 variant may be considered as a novel strategy to address the potential challenge that may arise during the scale-up and downstream processing steps. Another significant finding derived from the study is that the proportion of bacillomycin variants of B. subtilis RLID 12.1 could be controlled by temperature and metal ions under static and shaking conditions. 相似文献
96.
Pinakpani Chakrabarti Kailasam Venkatesan T. Stanley Cameron Türsen Demir Robert A. Shaw 《Journal of chemical crystallography》1985,15(3):229-245
The synthesis and selected aspects of the UV, IR, and1H NMR spectra of the title compound are described. The crystals of the title compound are triclinic witha=12.999(9),b=8.911(4),c=9.199(5) Å;=105.56(3),=113.50(4), =92.53(3)°;Z=2; space groupP¯1. Its X-ray crystal structure analysis provides information regarding the conformational features of the amide linkage when no intermolecular hydrogen bonding involving this group is present. The X-ray study shows that the C-N bond is longer [1.363(4) Å] than that found normally in peptide molecules. The compound shows a peculiar disorder involving one of the two amide groups present in the molecule. The conformation of theN-methyl acetanilide moiety and its relation to the1H NMR spectrum of the compound are discussed. 相似文献
97.
98.
We have studied the properties of various isomers of potassium clusters containing even number of atoms ranging from 2 to 20 at the ab initio level. The geometry optimization calculations of the isomers of each cluster are performed by using all-electron density functional theory with gradient corrected exchange-correlation functional. Using the optimized geometries of different isomers we investigate the evolution of binding energy, ionization potential, and static polarizability with the increasing size of the clusters. The polarizabilities are calculated by employing M?ller-Plesset perturbation theory and time-dependent density functional theory. The polarizabilities of dimer and tetramer are also calculated by employing large basis set coupled cluster theory with single and double excitations and perturbative triple excitations. The time-dependent density functional theory calculations of polarizabilities are carried out with two different exchange-correlation potentials: (i) an asymptotically correct model potential and (ii) within the local density approximation. A systematic comparison with the other available theoretical and experimental data for various properties of small potassium clusters mentioned above has been performed. These comparisons reveal that both the binding energy and the ionization potential obtained with gradient-corrected potential match quite well with the already published data. Similarly, the polarizabilities obtained with M?ller-Plesset perturbation theory and with model potential are quite close to each other and also close to experimental data. 相似文献
99.
This study describes the use of peptide vesicular platforms for the templated growth of fibrillar structures to craft hybrids that retain the gross morphological features of two discreet self-assembled peptides. A synthetic triskelion peptide, which results in the rapid emergence of self-assembled spherical structures, was employed as a template. Addition of either one of two different peptides, both of which form long filamentous structures when co-incubated with the triskelion solution, affords hybrids that retain the gross morphology of both the spherical and filamentous structures. It is surmised that this process is aided by hydrogen bonding and the interdigitation of aromatic residues, which leads to the growth of hybrid structures. We believe that observations concerning the surface-assisted growth of peptide fibrils and tubular structures from vesicular platforms may have ramifications for the design and development of peptide-based hybrid materials with controlled hierarchical structures. 相似文献
100.
Chandrasekhar V Nagarajan L Clérac R Ghosh S Senapati T Verma S 《Inorganic chemistry》2008,47(12):5347-5354
The reaction of Cu(ClO4)2. 6H2O with t-BuP(O)(OH)2 and 3,5-(CF3)2PzH in the presence of triethylamine afforded the dodecanuclear cage ([Et3NH]2[Cu12(mu-3,5-(CF3)2Pz)6(mu3-OH)6(mu-OH)3(mu3-t-BuPO3)2(mu6-t-BuPO3)3][t-BuPO2OH][C6H5CH3]2) (2). The molecular structure of this cage revealed that it possesses a barrel-shaped architechture. The cage structure is built by the cumulative coordination action of phosphonate, hydroxide, and pyrazolyl ligands. A similar reaction involving Cu(NO3)2. 3H2O, t-BuP(O)(OH)2, 3,5-dimethylpyrazole, and triethylamine afforded another dodecanuclear cage [Cu12(mu-DMPz)8(eta1-DMPzH)2(mu4-O)2(mu3-OH)4(mu3- t-BuPO3)4].3MeOH (3). The latter is crown-shaped and is built by the coordination of pyrazole, pyrazolyl, phosphonate, hydroxide, oxide, and methanol ligands. Both of the dodecanuclear cages are efficient nucleases in the presence of magnesium monoperoxyphthalate. 相似文献