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311.
The liquid-solid equilibrium temperature in the binary systems between n-dotriacontane and methyl or ethyl octadecanoate and methyl nonadecanoate are determined in order to obtain the interchange parameters between CH3 or CH2 and COO groups, by means of the statistics of group interaction. 相似文献
312.
P. Caramella F.Marinone Albini D. Vitali Nelson G. Rondan Yun-Dong Wu Timothy R. Schwartz K.N. Houk 《Tetrahedron letters》1984,25(18):1875-1878
Benzonitrile oxide cycloadds preferentially to the substituents of -3,5-di-X-cyclopentenes, where X = OMe, OAc, OCOPh, Br, Cl, and OH. Higher stereoselectivities are found for -2,5-di-X-2,5-dihydrofurans. The origins of these selectivities, and contrasts with acyclic and cyclobutene analogs, are described. 相似文献
313.
New NMR experiments for the measurement of side-chain dynamics in high molecular weight ( approximately 100 kDa) proteins are presented. The experiments quantify (2)H spin relaxation rates in (13)CH(2)D or (13)CHD(2) methyl isotopomers and, for applications to large systems, offer significant gains both in sensitivity (2-3-fold) and resolution over previously published HSQC schemes. The methodology has been applied to investigate Ile dynamics in the 723-residue, single polypeptide chain enzyme, malate synthase G. Methyl-axis order parameters, S(axis), characterizing the amplitudes of motion of the methyl groups, have been derived from both (13)CH(2)D and (13)CHD(2) probes and are in excellent agreement. The distribution of order parameters is trimodal, reflecting the range of dynamics that are available to Ile residues. A reasonable correlation is noted between and inverse temperature factors from X-ray studies of the enzyme. The proposed methodology significantly extends the range of protein systems for which side-chain dynamics can be studied. 相似文献
314.
Hellberg F Zhaunerchyk V Ehlerding A Geppert WD Larsson M Thomas RD Bannister ME Bahati E Vane CR Osterdahl F Hlavenka P af Ugglas M 《The Journal of chemical physics》2005,122(22):224314
This paper presents results concerning measurements of the dissociative recombination (DR) of dihydrogen sulfide ions. In combination with the ion storage ring CRYRING an imaging technique was used to investigate the breakup dynamics of the three-body channel in the DR of 32SD2(+). The two energetically available product channels S(3P) + 2D(2S) and S(1D) + 2D(2S) were both populated, with a branching fraction of the ground-state channel of 0.6(0.1). Information about the angle between the two deuterium atoms upon dissociation was obtained together with information about how the available kinetic energy was distributed between the two light fragments. The recombination cross sections as functions of energy in the interval of 1 meV to 0.3 eV in the center-of-mass frame are presented for 34SH2(+). The thermal rate coefficient for the DR of 34SH2(+) was determined to be (4.8+/-1.0) x 10(-7)(T/300)(-0.72+/-0.1) cm3 s(-1) over this interval. 相似文献
315.
Targeting a Dark Excited State of HIV‐1 Nucleocapsid by Antiretroviral Thioesters Revealed by NMR Spectroscopy 下载免费PDF全文
Dr. Lalit Deshmukh Dr. Vitali Tugarinov Dr. Daniel H. Appella Dr. G. Marius Clore 《Angewandte Chemie (International ed. in English)》2018,57(10):2687-2691
HIV‐1 nucleocapsid (NCp7) is a two Cys2HisCys zinc knuckle (N‐Zn and C‐Zn) protein that plays a key role in viral replication. NCp7 conformational dynamics is characterized by NMR relaxation dispersion and chemical exchange saturation transfer measurements. While the N‐Zn knuckle is conformationally stable, the C‐Zn knuckle interconverts on the millisecond timescale between the major state, in which the zinc is coordinated by three cysteines and a histidine, and two folded minor species (with populations around 1 %) in which one of the coordination bonds (Cys413‐Sγ‐Zn or His421‐N?2‐Zn) is hydrolyzed. These findings explain why antiretroviral thioesters specifically disrupt the C‐Zn knuckle by initial acylation of Cys413, and show that transient, sparsely‐populated (“dark”), excited states of proteins can present effective targets for rational drug design. 相似文献
316.
Zhaunerchyk V Ehlerding A Geppert WD Hellberg F Thomas RD Larsson M Viggiano AA Arnold ST Osterdahl F Hlavenka P 《The Journal of chemical physics》2004,121(21):10483-10488
The dissociative recombination of Na(+)(D(2)O) ion has been studied at the heavy-ion storage ring CRYRING (Manne Siegbahn Laboratory, Stockholm University). The cross section has been measured as a function of center-of-mass energy ranging from 1 meV to 0.1 eV and found to have an E(-1.37) dependence. The rate coefficient has been deduced to be (2.3+/-0.32)x10(-7)(T(e)/300)(-0.95+/-0.01) cm(3) s(-1) for T(e)=50-1000 K. The branching ratios have been measured at 0 eV. Of the four energetically accessible dissociation channels, three channels are found to occur although the channel that breaks the weak Na(+)-D(2)O bond is by far dominant. 相似文献
317.
Maxym V. Vasylyev Sylvain Gatard Itsik Bar-Nahum Leonid Konstantinovski Ellen J. Wachtel Ronny Neumann 《Journal of Cluster Science》2006,17(2):235-243
Organic–inorganic hybrid compounds were prepared by the reaction of a tin chloride-substituted polyoxometalate, [PSn(Cl)W11O39]4− with tris(2-aminoethyl)amine, and poly(propylene)imine (DAB-Am) tetraamine and octaamine dendrimers. Translational diffusion coefficients of the hybrid compounds were measured in DMSO-d
6 by the stimulated echo diffusion (STE) NMR technique. Molecular radii were derived from the diffusion coefficients by the Stokes–Einstein equation and appeared to be incorrect because of fast exchange on the NMR time scale of the counter cation in the solution, which led to an averaging of the NMR signal and high diffusion coefficients. An effective hydrodynamic diameter of the [PSn(Cl)W11O39]4−–polypropylenimine octaamine hybrid adduct was measured in a light scattering experiment. 相似文献
318.
Tugarinov V Muhandiram R Ayed A Kay LE 《Journal of the American Chemical Society》2002,124(34):10025-10035
A four-dimensional (4-D) NMR study of Escherichia coli malate synthase G (MSG), a 723-residue monomeric enzyme (81.4 kDa), is described. Virtually complete backbone (1)HN, (15)N, (13)C, and (13)C(beta) chemical shift assignments of this largely alpha-helical protein are reported. The assignment strategy follows from our previously described approach based on TROSY triple resonance 4-D NMR spectroscopy [Yang, D.; Kay, L. E. J. Am. Chem. Soc. 1999, 121, 2571-2575. Konrat, R; Yang, D; Kay, L. E. J. Biomol. NMR 1999, 15, 309-313] with a number of modifications necessitated by the large size of the protein. A protocol for refolding deuterated MSG in vitro was developed to protonate the amides deeply buried in the protein core. Of interest, during the course of the assignment, an isoaspartyl linkage in the protein sequence was unambiguously identified. Chemical shift assignments of this system are a first step in the study of how the domains of the protein change in response to ligand binding and for characterizing the dynamical properties of the enzyme that are likely important for function. 相似文献
319.
320.