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91.
Chandan Adhikary Rajesh Bera Buddhadeb Dutta Sreyashi Jana Gabriele Bocelli Andrea Cantoni Siddhartha Chaudhuri Subratanath Koner 《Polyhedron》2008
Three copper(II) Schiff-base complexes, [Cu(L1)(H2O)](ClO4) (1), [Cu(L2)] (2) and [Cu(L3)] (3) have been synthesized and characterized [where HL1 = 1-(N-ortho-hydroxy-acetophenimine)-2-methyl-pyridine], H2L2 = N,N′-(2-hydroxy-propane-1,3-diyl)-bis-salicylideneimine and H2L3 = N,N′-(2,2-dimethyl-propane-1,3-diyl)-bis-salicylideneimine]. The structure of complex 1 has been determined by single crystal X-ray diffraction analysis. In complex 1, the copper(II) ion is coordinated to one oxygen atom and two nitrogen atoms of the tridentate Schiff-base ligand, HL1. The fourth coordination site of the central metal ion is occupied by the oxygen atom from a water molecule. All the complexes exhibit high catalytic activity in the oxidation reactions of a variety of olefins with tert-butyl-hydroperoxide in acetonitrile. The catalytic efficacy of the copper(II) complexes towards olefin oxidation reactions has been studied in different solvent media. 相似文献
92.
Fraser-Reid B Chaudhuri SR Jayaprakash KN Lu J Ramamurty CV 《The Journal of organic chemistry》2008,73(24):9732-9743
Lipomannan (LM) is one of the domains of lipoarabinomannan (LAM) glycolipids, the latter being one of several cell surface organic molecules that fortify mycobacterial species against external attack. Some members of mycobacterial families are pathogenic, most notably Mycobacterium tuberculosis and Mycobacterium leprae, while others are nonpathogenic, and used in the clinic, such as Mycobacterium smegmatis. Additional biological significance arises from the fact that LM has been implicated in several health disorders outside of those associated with mycobacterial pathogens, notably for treatment of bladder cancer. LM is comprised of a heavily lipidated phosphoinositide dimannoside headgroup, from which a mannan array, of varied complexity, extends. The latter consists of a 1,6-alpha-linked backbone flanked at position O2, not necessarily regularly, with alpha-linked mannosides. This paper gives an example of lipomannan synthesis in which all of the sugar components, whether functioning as donors or acceptors, are obtained from n-pentenyl orthoesters, themselves in turn prepared in three easy steps from D-mannose. Assembly of the mannan array is facilitated by the exquisite regioselectivity occasioned by the use of ytterbium triflate/N-iodosuccinimide as the trigger for reaction of n-pentenyl orthoesters. 相似文献
93.
94.
Roychoudhury S Blondelle SE Collins SM Davis MC McKeever HD Houghten RA Parker CN 《Molecular diversity》1998,4(3):173-182
Bacterial resistance to antibiotics is emerging as amajor concern to the medical community. Theappearance of several antibiotic-resistant strains,including multidrug-resistant Staphylococcusaureus, raises the prospect that infections by thesebacteria could soon become untreatable with currentlyavailable antibiotics. In order to address thisproblem, increased emphasis is being placed on thediscovery of novel classes of antibacterial agentsthat inhibit novel molecular targets using sources ofcompounds not yet exploited for antibiotic drugdiscovery. Novel classes of compounds can now berapidly investigated using combinatorial chemistryapproaches. This report describes the identificationof novel antibacterial compounds from a combinatoriallibrary of N-acetylated, C-amidated D-amino acidhexapeptides. This library of compounds was screenedfor inhibitors of CheA, a member of the bacterialtwo-component signal transduction kinase family. Several peptides with apparent IC50 values in thelow micromolar range were identified. In addition toinhibiting CheA, these peptides inhibited mammalianprotein kinase C (from rat brain) with comparablepotency. Finally, these peptides were also found tohave significant antibacterial properties, althoughthe true mechanism by which they exhibited inhibitionof bacterial growth remains uncertain. 相似文献
95.
Simon G. Bott Alan P. Marchand Vijay R. Gadgil 《Journal of chemical crystallography》1995,25(5):215-218
The structure of the cyclic sulfite derived from the reaction of thionyl chloride withendo-8-hydroxy-exo-8-(endo-8-hydroxypentacyclo[5.4.0.0.2,6.03,10.05,9]undec-exo-8-yl)pentacyclo-[5.4.0.0.2,6.03,10.05,9]undecane is reported. All bond lengths and angles are consistent with the strained cage geometry. A static disorder of the terminal oxygen was found to be present. 相似文献
96.
Nityananda Saha Dhiman Kumar Sau Siddhartha Chaudhuri Parikshit Chandra Mandal 《Transition Metal Chemistry》2005,30(5):532-540
New iron(III) complexes of 5-methyl-3-formylpyrazole 3-hexamethyleneiminylthiosemicarbazone (HMPz3Hex), [Fe(MPz3Hex)2]X · nH2O (where X = Cl, NO3or ClO4 and n = 1–2) have been synthesized and physico-chemically characterized by magnetic data (polycrystalline state), electronic, i.r. and e.p.r. spectral studies. The reported complexes are all cationic electrolytes (1:1) containing two moles of monodeprotonated title ligand and an anionic counterpart. I.r. spectra (4000–200 cm?1) indicate coordination to the central iron(III) ion via the pyrazolyl (tertiary) ring nitrogen, azomethine nitrogen and thiolato sulphur atoms of the primary ligand molecule. E.p.r. data (r.t. and l.n.t.) show the presence of a low-spin iron(III) cation with d xz 2 d xz 2 d xz 1 configuration. Cyclic voltammograms of iron(III) complexes indicate a reversible Fe+3/Fe+2 couple. X-ray data of [Fe(MPz3Hex)2]ClO4 · 2H2O (P1, triclinic) authenticate a FeN4S2 distorted octahedral coordination with the two azomethine nitrogens trans to each other; the pyrazolyl nitrogens and thiolato sulphurs are in cis-positions, indicating an unusual rotation about the azomethine (C=N) double bond of the free HMPz3Hex during complexation with iron(III). 相似文献
97.
Peptide Conjugates of a Nonsteroidal Anti‐Inflammatory Drug as Supramolecular Gelators: Synthesis,Characterization, and Biological Studies 下载免费PDF全文
Rajdip Roy Dr. Jolly Deb Dr. Siddhartha Sankar Jana Prof. Parthasarathi Dastidar 《化学:亚洲杂志》2014,9(11):3196-3206
Indomethacin ( IND ), which is a well‐known nonsteroidal anti‐inflammatory drug (NSAID), was conjugated with various naturally occurring amino acids. Most of these bioconjugates were capable of gelling pure water, a solution of NaCl (0.9 wt %), and phosphate‐buffered saline (pH 7.4), as well as a few organic solvents. The gels were characterized by table‐top and dynamic rheology, and electron microscopy. Variable‐temperature 1H NMR spectroscopy studies on a selected gel were performed to gain insights into the self‐assembly process during gel formation. Both 1D and 2D hydrogen‐bonded networks were observed in the single‐crystal structures of two of the gelators. Plausible biological applications of the hydrogelators were evaluated with the ultimate aim of drug delivery in a self‐delivery fashion. All hydrogelators were stable in phosphate‐buffered saline at pH 7.4 at 37 °C, and biocompatible in mouse macrophage RAW 264.7 cell line (3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay). Two of the most biocompatible hydrogelators displayed an anti‐inflammatory response comparable to that of the parent drug IND in prostaglandin E2 assay. Release of the bioconjugates into the bulk solvent interfaced with the corresponding hydrogels indicated their plausible future application in drug delivery. 相似文献
98.
99.
Sirin Sahana Chandrakanta Bandyopadhyay Siddhartha Chaudhuri 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(12):1450-1451
The crystal structure of the title compound, C32H24O4, contains three fused dihydropyran rings (A, B and C); ring A is fused with a benzene ring while the other two rings, B and C, are fused with naphthalene rings. Ring A adopts a half‐chair conformation with an equatorial methoxy group, whereas ring B assumes a distorted half‐chair conformation, the A/B ring junction being trans. Ring C adopts a distorted half‐boat conformation and is nearly orthogonal to ring B. Ring C is inclined to the best plane of ring A at an angle of 112.1 (1)°. 相似文献
100.
Current–voltage characteristics of long-wave infrared (LWIR) InAs/GaSb strained layer superlattice photodiodes (cut-off wavelength ∼10 μm), passivated with different surface passivants, have been modeled and simulated using ATLAS software from SILVACO. The simulated results are fitted to previous experimental results obtained on unpassivated devices and those passivated by silicon-dioxide (SiO2), silicon nitride (SixNy) and zinc sulfide (ZnS). Surface parameters in terms of surface recombination velocity, shunt resistance and interface trap density are extracted for different passivants. The performance of silicon-dioxide passivated diode is solely dominated by a shunt leakage path with a shunt resistance value of 0.56 Ω-cm2. Extracted electron and hole surface recombination velocities have values of 105 cm/s and 107 cm/s for unpassivated, 103 cm/s and 105 cm/s for SixNy passivated and 102 cm/s and 103 cm/s for ZnS passivated devices. Interface trap density follows a similar trend with values of 1015 cm−2, 8.5 × 1014 cm−2 and 1010 cm−2 for unpassivated, SixNy passivated and ZnS passivated devices respectively. The suitability and limitations of the simulation tool are discussed. 相似文献