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31.
Sourav Haldar Mamata Kombrabail G. Krishnamoorthy Amitabha Chattopadhyay 《Journal of fluorescence》2010,20(1):407-413
Due to the inherent difficulty in crystallizing membrane proteins, approaches based on fluorescence spectroscopy have proved
useful in elucidating their conformational characteristics. The ion channel peptide gramicidin serves as an excellent prototype
for monitoring membrane protein conformation and dynamics due to a number of reasons. We have analyzed conformational heterogeneity
in membrane-bound gramicidin using fluorescence lifetime distribution analysis of tryptophan residues by the maximum entropy
method (MEM). MEM represents a model-free and robust approach for analyzing fluorescence lifetime distribution. In this paper,
we show for the first time, that fluorescence lifetime distribution analysis using MEM could be a convenient approach to monitor
conformational heterogeneity in membrane-bound gramicidin in particular and membrane proteins in general. Lifetime distribution
analysis by MEM therefore provides a novel window to monitor conformational transitions in membrane proteins. 相似文献
32.
Edward C. Eckels Deep Chaudhuri Soham Chakraborty Daniel J. Echelman Shubhasis Haldar 《Chemical science》2021,12(33):11109
DsbA is a ubiquitous bacterial oxidoreductase that associates with substrates during and after translocation, yet its involvement in protein folding and translocation remains an open question. Here we demonstrate a redox-controlled chaperone activity of DsbA, on both cysteine-containing and cysteine-free substrates, using magnetic tweezers-based single molecule force spectroscopy that enables independent measurements of oxidoreductase activity and chaperone behavior. Interestingly we found that this chaperone activity is tuned by the oxidation state of DsbA; oxidized DsbA is a strong promoter of folding, but the effect is weakened by the reduction of the catalytic CXXC motif. We further localize the chaperone binding site of DsbA using a seven-residue peptide which effectively blocks the chaperone activity. We found that the DsbA assisted folding of proteins in the periplasm generates enough mechanical work to decrease the ATP consumption needed for periplasmic translocation by up to 33%.Protein translocation is facilitated by DsbA chaperone in a redox-dependent manner. 相似文献
33.
Anindita Sikdar Swapnadip Roy Kakali Haldar Soma Sarkar Sujit S. Panja 《Journal of fluorescence》2013,23(3):495-501
A rhodamine B-based fluorescence probe (1) for the sensitive and selective detection of Cu2+ ion has been designed and synthesized using pyridine moiety. The optical properties of this compound have been investigated in acetonitrile-water binary solution (7:3 v/v). Compound 1 is found to be an excellent sensor for a biologically/physiologically very important transition metal ion (Cu2+) using only the two very different modes of measurements (absorption and emission); one case displayed intensity enhancement whereas in other case showed intensity depletion (quenching). A mechanistic investigation has been performed to explore the static nature of quenching process. The sensor has been found to be very effective in sensing Cu2+ ion inside living cells also. 相似文献
34.
Asim K. Bera Bishnu P. Mukhopadhyay Asok K. Pal U. Haldar S. Bhattacharya Asok Banerjee 《Journal of chemical crystallography》1998,28(7):509-516
The crystal structure of an octadecahydrated complex between two inosine 5-monophosphate (IMP) has been determined at atomic resolution, which reveals the hydrogen bonding and the coordination cooperativity of water molecules to nucleotide recognition. The crystal belongs to monoclinic space group P21 with cell dimensions a = 8.65(1), b = 21.90(1), c = 12.37(1)Å, and = 110.38(9)°. The ribose hydroxyls, purine N7, keto(O6) bonded water molecules W1, W2, W5, W6, W8 and the phosphate bridge forming water oxygens of W4, W7, W11 appear to play an invariant role in their hydrogen bonding interactions with the IMPs. The synergistic role of the water molecules W5, W6, W8 in the purine staking domain N27W5=2.583,O16W8=2.759,O2627W6=2.723 Åhave been clearly observed for the first time. The complexation of the water molecules through variable hydrogen bonding coordination indicate their functional involvement through extensive cooperative donor-acceptor network mechanism. The occurrence of hydrogen-bonded water spines, water bridges and their interplay in the structural association of IMPs could indicate the possible viability of those aquatic centers in the biological situation. 相似文献
35.
Haldar S Raghuraman H Chattopadhyay A 《The journal of physical chemistry. B》2008,112(44):14075-14082
Melittin is a cationic hemolytic peptide isolated from the European honey bee, Apis mellifera. In spite of a number of studies, there is no consensus regarding the orientation of melittin in membranes. In this study, we used a melittin analogue that is covalently labeled at its amino terminal (Gly-1) with the environment-sensitive 1-dimethylamino-5-sulfonylnaphthalene (dansyl) group to obtain information regarding the orientation and dynamics of the amino terminal region of membrane-bound melittin. Our results show that the dansyl group in Dns-melittin exhibits red edge excitation shift in vesicles of 1,2-dioleoyl-sn-glycero-3-phosphocholine, implying its localization in a motionally restricted region of the membrane. This is further supported by wavelength-dependent anisotropy and lifetime changes and time-resolved emission spectra characterized by dynamic Stokes shift, which indicates relatively slow solvent relaxation in the excited state. Membrane penetration depth analysis using the parallax method shows that the dansyl group is localized at a depth of approximately 18 A from the center of the bilayer in membrane-bound Dns-melittin. Further analysis of dansyl and tryptophan depths in Dns-melittin shows that the tilt angle between the helix axis of membrane-bound melittin and the bilayer normal is approximately 70 degrees. Our results therefore suggest that melittin adopts a pseudoparallel orientation in DOPC membranes at low concentration. 相似文献
36.
Sarkar T Roy S Bhattacharya J Bhattacharya D Mitra CK Dasgupta AK 《Journal of colloid and interface science》2008,327(1):224-232
Gold nanoparticles show thermal hysteresis with properties such as surface plasmon absorption, conductivity, and zeta potential. The direction of the incremental change in plasmon peak position and its extinction depend on the nature of surface conjugation. The thermal profile of a surface plasmon resonance spectrum for nanoparticles may serve as a signature for the associated small molecule or macromolecule on which it is seeded. The thermal responses of zeta potential and conductivity profile are found to be independent of the surface conjugation with the later being subjected to a phase transition phenomenon as revealed by a temperature criticality. 相似文献
37.
Chaudhuri C Chang RY Chen WX Fang WC Cheng JP Whang TJ Tsai CC 《The journal of physical chemistry. A》2007,111(39):9764-9768
The 71Pig Rydberg state of Na2 correlating with the separated atom limit Na(3s) + Na(5p) has been observed using high-resolution cw optical-optical double resonance spectroscopy. A total of 104 identified rovibrational levels in the range v = 0-12 and 11 = J = 44 have been assigned to the 71Pig state. Dunham coefficients were determined, and the Rydberg-Klein-Rees potential curve in the range of R = 2.99-4.66 A was derived for the 71Pig state using the observed quantum levels. The important molecular properties are the potential minimum Te = 36 633.00(23) cm-1 at Re = 3.6313(29) A, omegae = 115.75(13) cm-1, and Be = 0.111 22(17) cm-1. A detailed discussion of this investigation of the 71Pig state is provided. 相似文献
38.
Banerjee J Haldar MK Manokaran S Mallik S Srivastava DK 《Chemical communications (Cambridge, England)》2007,(26):2723-2725
We report the synthesis and fluorescence properties of naphthalenesulfonamide derivatives as active site probes for carbonic anhydrases. 相似文献
39.
Samartzis PC Lin JJ Ching TT Chaudhuri C Lee SH Wodtke AM 《The Journal of chemical physics》2007,126(4):041101
We report evidence that cyclic-N(3) is exclusively produced in the 157-nm photolysis of ClN(3). Photoproduct translational energy measurements reveal a single-peaked distribution for an N(3)-formation channel with maximum and minimum translational energies matching the theoretically predicted minimum and maximum binding energies of cyclic-N(3), respectively. The absence of linear-N(3) greatly simplifies the data analysis. The zero-Kelvin heat of formation of cyclic-N(3) is derived experimentally (142+/-3.5 kcal/mol) and is in excellent agreement with the best existing determinations from other studies. 相似文献
40.
Chanchal Ghosh 《Journal of Physics and Chemistry of Solids》2009,70(6):1024-1029
Results of theoretical investigation on the structural and electronic properties of GaAs/AlAs and AlAs/GaAs core/shell nanoparticles are presented. We have considered relaxed structures of essentially spherical parts of the zinc-blende crystal structure. The electronic properties and the total energy were calculated using density-functional tight-binding method. Our results include the charge distribution, density of states (DOSs), electronic energy levels (in particular HOMO and LUMO), HOMO-LUMO gap, excitation spectra and their variation with shell thickness for both GaAs/AlAs and AlAs/GaAs core/shell systems. 相似文献