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91.
Scarpellini M Gätjens J Martin OJ Kampf JW Sherman SE Pecoraro VL 《Inorganic chemistry》2008,47(9):3584-3593
In view of the biological and commercial interest in models for Oxalate Decarboxylases (OxDC) and Oxalate Oxidases (OxOx), we have synthesized and characterized three new Mn (II) complexes ( 1- 3) employing N3O-donor amino-carboxylate ligands (TCMA, 1,4,7-triazacyclononane- N-acetic acid; K (i) Pr 2TCMA, potassium 1,4-diisopropyl-1,4,7-triazacyclononane- N-acetate; and KBPZG, potassium N,N-bis(3,5-dimethylpyrazolyl methyl)glycinate). These complexes were characterized by several techniques including X-ray crystallographic analysis, X-band electron paramagnetic resonance (EPR), electrospray ionization mass spectrometry (ESI-MS), and cyclic voltammetry. The crystal structures of 1 and 3 revealed that both form infinite polymeric chains of Mn (II) complexes linked by the pendant carboxylate arms of the TCMA (-) and the BPZG (-) ligands in a syn-antipattern. Complex 2 crystallizes as a mononuclear Mn (II) cation, six-coordinate in a distorted octahedral geometry. Although complexes 1 and 3 crystallize as polymeric chains, all compounds present the same N3O-donor set atoms around the metal center as observed in the crystallographically characterized OxDC and OxOx. Moreover, complex 2 also contains two water molecules coordinated to the Mn center as observed in the active site of OxDC and OxOx. ESI-MS spectrometry, combined with EPR, were useful techniques to establish that complexes 1- 3 are present as mononuclear Mn (II) species in solution. Finally, complexes 1- 3 are able to model the resting state active sites, with special attention focused on complex 2 which provides the first exact first coordination sphere ligand structural model for the resting states of both OxDC and OxOx. 相似文献
92.
Disinfection and Mechanistic Insights of Escherichia coli in Water by Bismuth Oxyhalide Photocatalysis 下载免费PDF全文
Ilana Sherman Yoram Gerchman Yoel Sasson Hani Gnayem Hadas Mamane 《Photochemistry and photobiology》2016,92(6):826-834
This study demonstrates the potential of a new BiOCl0.875Br0.125 photocatalyst to disinfect Escherichia coli in water under simulated solar irradiation. Photocatalytic efficiency was examined for different photocatalyst loadings, solar wavelengths, exposure times, photocatalyst concentration × contact time (Ct) concept and with the use of scavengers. To elucidate the inactivation mechanism, we examined DNA damage, membrane damage, lipid peroxidation and protein release. Both photolysis and photocatalysis were negligible under visible irradiation, but enhanced photocatalytic activity was observed under solar UVA (λ > 320 nm) and UVB (λ > 280 nm), with 1.5 and 3.6 log inactivation, respectively, after 40 min of irradiation. The log inactivation vs Ct curve for E. coli by UVA/BiOCl0.875Br0.125 was fairly linear, with Ct = 10 g L?1 × min, resulting in 2 log inactivation. Photocatalytic treatment led to membrane damage, but without lipid peroxidation. Accordingly, protein was released from the cells after UVA or UVA/BiOCl0.875Br0.125 treatment. Photocatalysis also increased endonuclease‐sensitive sites vs photolysis alone, by an unknown mechanism. Finally, E. coli inactivation was not influenced by the addition of tert‐butanol or l ‐histidine, implying that neither hydroxyl radicals nor singlet oxygen reactive species are involved in the inactivation process. 相似文献
93.
94.
An approach to the assessment of the limit of detection and the limit of quantitation using uncertainty calculation is discussed.
The approach is based on the known evaluation of the limits of detection and quantitation as concentrations of the analyte
equal to three and ten standard deviations of the blank response, respectively. It is shown that these values can be calculated
as the analyte concentrations, for which relative expanded uncertainty achieves 66% and 20% of possible results of the analyte
determination, correspondingly. For example, the calculation is performed for the validation of a new method for water determination
in the presence of ene-diols or thiols, developed for analysis of chemical products, drugs or other materials which are unsuitable
for direct Karl Fischer titration. A good conformity between calculated values and experimental validation data is observed.
Received: 27 July 1998 · Accepted: 29 November 1998 相似文献
95.
A method proposed for determining water and enediols or thiols is based on consecutive titration of the enediols or thiols by a novel reagent and of water by the conventional Karl Fischer reagent in the same cell. The time for both titrations is 8-20 min. The novel reagent consists of iodine, sodium acetate as a base, and potassium iodide in a nonaqueous solvent system. The method is applicable for quality control of chemical products and drugs during their production and trade. 相似文献
96.
A study of the condensation of a metal vapor in an inert carrier gas is made. Superheated zinc vapor is generated in a hot
shot wind tunnel in a helium carrier gas and expanded in a converging-diverging nozzle. Static pressure measurements along
the length of the nozzle are made to determine the location of the onset of condensation. A conical nominal Mach 5 (helium)
nozzle is employed. The amount of supercooling before the onset of condensation is found to be approximately 430 K, measured
along the isentrope over a range of initial zinc mass fractions of .35 to .70 for saturation partial pressures of zinc between
10 psia and 70 psia. The measurements are compared with results of an analysis based on the classical liquid drop model of
nucleation. The computed results agree reasonably well with the measurements. 相似文献
97.
Novel polyisobutylene/poly(dimethylsiloxane) bicomponent networks. I. Synthesis and characterization
Melissa A. Sherman Joseph P. Kennedy 《Journal of polymer science. Part A, Polymer chemistry》1998,36(11):1891-1899
The synthesis of novel polyisobutylene (PIB)/poly(dimethylsiloxane) (PDMS) bicomponent networks is described. The synthesis strategy (see Figure 1) was to prepare well-defined and -characterized allyl-tritelechelic polyisobutylenes [ϕ(PIB—C—C=C)3] and SiH-ditelechelic poly(dimethylsiloxanes) (HSi–PDMS–SiH) and then crosslink these moieties by hydrosilation. The ϕ(PIB—C—C=C)3 was prepared by living isobutylene polymerization followed by end-quenching with allyltrimethylsilane, whereas the HSi–PDMS–SiH was obtained by equilibrium polymerization of octamethylcyclotetrasiloxane and tetramethyldisiloxane. The detailed structures of the starting polymers were characterized by GPC and 1H-NMR spectroscopy. A series of PIB/PDMS bicomponent networks of varying compositions and average molecular weights between crosslinks (M c) of ∼ 20,000 g/mol were assembled. Optimum crosslinking conditions were defined in terms of H2PtCl6 catalyst concentration, nature of solvent, time, temperature, and stoichiometry of ∼ CH2CH=CH2/∼SiH groups, allowing for the convenient synthesis of well-defined model bicomponent networks. Swelling studies and elemental analysis confirm the correctness of the synthetic strategy. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1891–1899, 1998 相似文献
98.
V. I. Medvedev A. A. Vasiliev K. N. Ermakov V. P. Koptev L. M. Kochenda V. I. Poromov O. V. Rogachevsky V. V. Sarantsev V. A. Trofimov S. G. Sherman 《Physics of Atomic Nuclei》2009,72(9):1475-1478
The energy spectrum of a neutron beam produced in a thin-wall liquid-deuterium target by a proton beam of energy 1 GeV was
measured in a hydrogen bubble chamber by detecting events of the reaction np → ppπ
−. 相似文献
99.
100.
K. N. Ermakov V. I. Medvedev V. A. Nikonov O. V. Rogachevsky A. V. Sarantsev V. V. Sarantsev S. G. Sherman 《The European Physical Journal A - Hadrons and Nuclei》2014,50(6):1-6
The new data on the elastic pp and single-pion production reaction pp → pnπ + taken at the incident proton momentum 1581 MeV/c are presented. To extract contributions of the leading partial waves the single-pion production data are analyzed in the framework of the event-by-event maximum-likelihood method together with pp → ppπ + data measured earlier and the pp → pnπ + data taken at 1628 MeV/c. The analysis shows that at 1581 MeV/c the largest contributions stem from the 3 P 2, 3 P 1, 3 P 0 and 3 F 2 initial partial waves. From these partial waves we also deduce contributions for the production of the Δ(1232) and N(1440) states. 相似文献