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61.
Vasyl' I. Zaremba Dariusz Kaczorowski Galyna P. Nychyporuk Ute Ch. Rodewald Birgit Heying Rainer Pttgen 《无机化学与普通化学杂志》2006,632(6):975-980
New indides Ce3Ge0.66In4.34 and Ce11Ge4.74In5.26 were synthesized from the elements by arc‐melting and subsequent annealing at 870 K. Single crystals were grown through special annealing procedures in sealed tantalum tubes in a high‐frequency furnace. Both compounds were investigated on the basis of X‐ray powder and single crystal data: I4/mcm, La3GeIn4 type, a = 848.8(1), c = 1192.0(2) pm, Z = 4, wR2 = 0.0453, 499 F2 values, 17 variables for Ce3Ge0.66In4.34 and I4/mmm, Sm11Ge4In6 type (ordered version of the Ho11Ge10 type), a = 1199.3(2), c = 1662.0(3) pm, wR2 = 0.0507, 1217 F2 values, 41 variables for Ce11Ge4.74In5.26. The Ce3Ge0.66In4.34 structure shows a mixed Ge/In occupancy on the 4c Wyckoff position. This site is octahedrally coordinated by cerium atoms. These octahedra share all edges, leading to a three‐dimensional network. The latter is penetrated by a two‐dimensional indium substructure which consists of flattened tetrahedra at In–In distances of 291 and 300 pm. The Ce11Ge4.74In5.26 structure contains three crystallographically independent germanium sites. The latter are coordinated by eight or nine cerium neighbors. These CN8 and CN9 polyhedra are condensed to a complex network which is penetrated by a three‐dimensional indium network with In–In distances of 301–314 pm. The 16m site shows a mixed In/Ge occupancy. Chemical bonding in both compounds is dominated by the p elements. Both ternaries studied exhibit localized magnetism due to the presence of Ce3+ ions. The compound Ce3GeIn4 remains paramagnetic down to 1.72 K, whereas Ce11Ge4In6 orders ferromagnetically at TC = 7.5 K. 相似文献
62.
Bogusawa Czarnik-Matusewicz Sylwia Pilorz Dariusz Bieko Danuta Michalska 《Vibrational Spectroscopy》2008,47(1):44-52
Comprehensive studies of the molecular structures, vibrational frequencies and infrared intensities of the antiperiplanar (ap) and synclinal (sc) conformers of 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) have been performed by the density functional (B3LYP) method using the extended 6-311++G(df,pd) basis set. The detailed natural bond orbital (NBO) analysis has revealed the nature of the hyperconjugative interactions, which stabilize each conformer, in the gas phase. The mid-infrared spectra of HFIP in carbon tetrachloride solution were measured, and the experimental intensities of each conformer were obtained by the curve–resolution procedure. The relative abundance of the two conformers, calculated from the relative intensities, shows nearly equimolar ratio (Nsc/Nap ≈ 1), in this solution. The DFT-predicted frequencies show very good agreement with the experimental data. The clear-cut vibrational assignment for each conformer is reported on the basis of the calculated potential energy distributions. Several controversies in an earlier assignment of HFIP have been elucidated. 相似文献
63.
Martiskainen O Sztanke K Matosiuk D Pihlaja K 《Rapid communications in mass spectrometry : RCM》2006,20(17):2548-2552
The electron ionization mass spectra of the title compounds (1: a R = H, b 2-CH(3), c 4-CH(3), d 2,3-diMe, e 2-OCH(3), f 4-OCH(3), g 2-Cl, h 3-Cl, i 4-Cl, j 3,4-diCl) were recorded at 70 eV to determine the effects of substituents and the possible keto-enol tautomerism. The compounds showed several common fragment ions but also fragment ions which divided them into three classes, namely 1a-1d (parent compound and Me-substituted derivatives), 1e and 1f (MeO-substituted derivatives), and 1g-1j (Cl-substituted derivatives). The presence of the HOCN(+.) ion as well as the exponential dependence of its total ion current in the case of p- and also 3-Cl-substituted compounds (1a, c, f, h-j) on the Hammett sigma constants and the loss of CHO or one or two HOCN moieties can be somewhat easier explained by the presence of the enol form but as a whole the results support the predominance of the keto form, in parallel to the situation in solution. 相似文献
64.
Niedzwiedzki DM Sullivan JO Polívka T Birge RR Frank HA 《The journal of physical chemistry. B》2006,110(45):22872-22885
Xanthophylls are a major class of photosynthetic pigments that participate in an adaptation mechanism by which higher plants protect themselves from high light stress. In the present work, an ultrafast time-resolved spectroscopic investigation of all the major xanthophyll pigments from spinach has been performed. The molecules are zeaxanthin, lutein, violaxanthin, and neoxanthin. beta-Carotene was also studied. The experimental data reveal the inherent spectral properties and ultrafast dynamics including the S(1) state lifetimes of each of the pigments. In conjunction with quantum mechanical computations the results address the molecular features of xanthophylls that control the formation and decay of the S* state in solution. The findings provide compelling evidence that S* is an excited state with a conformational geometry twisted relative to the ground state. The data indicate that S* is formed via a branched pathway from higher excited singlet states and that its yield depends critically on the presence of beta-ionylidene rings in the polyene system of pi-electron conjugated double bonds. The data are expected to be beneficial to researchers employing ultrafast time-resolved spectroscopic methods to investigate the mechanisms of both energy transfer and nonphotochemical quenching in higher plant preparations. 相似文献
65.
Emilia Styczeń Zygmunt Warnke Dariusz Wyrzykowski Julia K?ak Jerzy Mroziński Artur Sikorski 《Structural chemistry》2010,21(1):269-276
The crystal structures of tetrabromocobaltate(II) and tetrabromomanganate(II) salts of general formula [(C2H5)4N]2[CoBr4] (1) and [(C4H9)4N]2[MnBr4] (2) were determined. The manganese and cobalt cations are four-coordinated by bromide anions and they adopt a slightly distorted
tetrahedral coordination. In the structure of both compounds there are neither hydrogen bonds nor any unusual short-range intermolecular interactions. Magnetic measurements of the powdered samples gave negative values of the Weiss constants
equal to −4.9 and −1.1 K for (1) and (2), respectively, which suggest antiferromagnetic interactions to be transferred within the crystal lattice. 相似文献
66.
Nataliya Chumalo Galyna P. Nychyporuk Rainer Pöttgen Dariusz Kaczorowski 《Journal of solid state chemistry》2010,183(12):2963-2967
The indides Ce7Ni5±xGe3±xIn6 and Pr7Ni5±xGe3±xIn6 were synthesized from the elements by arc-melting of the components. Single crystals were grown via special annealing sequences. Both structures were solved from X-ray single crystal diffraction data: new structure type, P6/m, Z=1, a=11.385(2), c=4.212(1) Å, wR2=0.0640, 634F2 values, 25 variables for Ce7Ni4.73Ge3.27In6 and a=11.355(6), c=4.183(2) Å, wR2=0.0539, 563F2 values, 25 variables for Pr7Ni4.96Ge3.04In6. Both indides show homogeneity ranges through Ni/Ge mixing (M sites). This new structure type can be derived from the AlB2 structure type by a substitution of the Al and B atoms by CeM12 and NiIn6Ce3 polyhedra (tricapped trigonal prism). Magnetic susceptibility measurements on a polycrystalline sample of Ce7Ni5Ge3In6 indicated Curie-Weiss like paramagnetic behavior down to 1.71 K with the effective magnetic moment slightly reduced in relation to the value expected for trivalent cerium ions. No magnetic ordering is evident. 相似文献
67.
A GC/tandem quadrupole MS/MS method was developed and validated for the determination of the residues of 140 pesticides in fruits and vegetables. Pesticides were extracted from samples by using a miniaturized acetonitrile-based extraction technique known as the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method. Validation studies were carried out on carrots, tomatoes, and strawberries. In order to reduce systematic errors due to a matrix-induced effect, quantification was carried out using matrix-matched standard calibration curves. The recovery and precision results satisfied the European Union criteria (i.e., average recoveries were in the range 70-120% with RSDs < or = 20%) for 125 of the 140 pesticides at a spiking level of 0.01 mg/kg. At the higher spiking levels, there were just two instances of overall average recovery < 70% (chlorothalonil and captan). The measurement uncertainty was estimated following a "top down" approach as being 21 and 35%, on average, based on validation and ongoing recovery data, respectively (coverage factor k = 2, confidence level 95%). Practical application to 541 samples of apples, tomatoes, strawberries, cucumbers, currants, mushrooms, carrots, peppers, pears, onions, and gooseberries under strict QC conditions demonstrated the ruggedness of the total procedure. 相似文献
68.
Romuald Bartnik Dariusz Cal 《Phosphorus, sulfur, and silicon and the related elements》2013,188(9):1858-1861
The regioselective synthesis of 3-diethoxyphosphonopyrazoles has been accomplished through the addition of aryl or alkyl hydrazines to (3-ethoxyacryloyl)phosphonic acid diethyl ester. An example of hydrolysis of the pyrazolephosphonic ester to the corresponding acid is described. 相似文献
69.
Steed JW Goeta AE Lipkowski J Swierczynski D Panteleon V Handa S 《Chemical communications (Cambridge, England)》2007,(8):813-815
Templation of a daughter phase by a parent crystal results from an equilibrating mixture of two very different copper(ii) N,N',N'-trimethyltriazacyclononane complexes. 相似文献
70.