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131.
S. Fakhi J. M. Paulus S. Bouhlassa 《Journal of Radioanalytical and Nuclear Chemistry》1988,121(1):99-107
A method is described for the analysis of uranium by neutron activation. The sample is brought into solution and the neptunium present is reduced to oxidation state (IV); quantitative extraction of239Np in the acidified aqueous phase (0.4<pH<1) is performed with a solution of HTTA (0.2M) in benzene. The use of a low-power reactor (100 kWthermal) enables determination of uranium at a lower concentration limit of 33 ng for periods of irradiation. cooling and measurement of 3 hours, 24 hours and 900 seconds, respectively. 相似文献
132.
PdSCl, a Molecular Palladium(II) Disulfidechloride with Octanuclear Pd8(S2)4Cl8 Groups and with Tetra Metal-coordinated bridging Disulfide Groups Black crystals of PdSCl have been obtained by reaction of Pd with S2Cl2 in closed quartz ampoules at 200°C. The compound is to be formulated as a Palladium(II)-disulfidechloride consisting of Pd8(S2)4Cl8 molecules with approximately D4h symmetry. In the octanuclear complexes Pd atoms form a cube, where bridging disulfide groups are found in front of 4 faces and μ2?bridging Cl atoms on 8 edges. In the monoclinic crystal structure (a = 8.763(2) Å; b = 9.082(2) Å; c = 13.662(4) Å; β = 91.748(23)°; V = 1086.8 Å3; Z = 16 PdSCl; Space gr. P21/n) the molecules form a cubic closed arrangement. 相似文献
133.
The structure of (s)-1,1-bis(methylsulphinyl)-3-phthalimidopropane (2)2 was established by X-ray crystallography. Comparison of 1H and 13C NMR chemical shifts with structural parameters allowed the configurational assignment to non-cyclic gem-disulphoxides containing a centre of pseudoasymmetry. 相似文献
134.
Ernst Pittenauer Josè Carlos Quintela Erich R. Schmid Günter Allmaier Gerd Paulus Miguel A. de Pedro 《Journal of the American Society for Mass Spectrometry》1995,6(10):892-905
A strategy for the characterization of bacterial lipoprotein-in this case Braun’s lipoprotein (an outer membrane 7-ku lipoprotein) isolated from Escherichia coli—is described by time-of-flight mass spectrometric (TOF/MS) techniques [252Cf plasma desorption (PD) TOF/MS and matrix-assisted laser desorption-ionization (MALDI) TOF/MS]. Covalent linkage of lipid at the N-terminal cysteine (posttranslationally modified to a S-[2,3-bis(acyloxy)-propyl]-N-acylcysteine) and, therefore, strict insolubility in aqueous solution constitute common features for this class of proteins. Relative molecular mass determination of the major molecular species of Braun’s lipoprotein was obtained by selection of an appropriate mixture of organic solvents compatible with matrix/support materials useful for the mass spectrometric techniques applied. Minor components of this lipoprotein that differ only in the fatty acid composition of the lipid anchor were detected by PD TOF/MS after enzymatic release of the extremely hydrophobic N-terminal amino acid followed by selective extraction with chloroform. Part of the primary sequence of this lipoprotein was confirmed based on peptide fragment ions observed in the positive ion PD mass spectra of cyanogen bromide-generated peptide fragments that had been isolated previously by reverse phase high-performance liquid chromatography (HPLC). Peptidoglycan fragments that represent the attachment sites of lipoprotein to peptidoglycan were enzymatically released, separated by reverse phase HPLC, and finally characterized by time-of-flight mass spectrometric techniques (252Cf-PD TOF/MS, MALDI TOF/MS). The results obtained with both techniques differed only in the better sensitivity obtained with MALDI TOF/MS, which consumed a factor of 100 to 1000 less material than with PD TOF/MS. 相似文献
135.
The incremental scheme for obtaining the energetic properties of extended systems from wave-function-based ab initio calculations of small (embedded) building blocks, which has been applied to a variety of van der Waals-bound, ionic, and covalent solids in the past few years, is critically reviewed. Its accuracy is assessed by means of model calculations for finite systems, and the prospects for applying it to delocalized systems are given. 相似文献
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138.
Stolker AA Zoontjes PW Schwillens PL Kootstra PR van Ginkel LA Stephany RW Brinkman UA 《The Analyst》2002,127(6):748-754
Acetyl gestagenic steroids are isolated from animal tissues such as bovine kidney fat by automated supercritical fluid extraction (SFE). After the addition of internal standards and sample pretreatment, the analytes are extracted from the matrix by supercritical CO2 and trapped directly in-line on alumina placed in the extraction vessel. The samples are analysed by liquid chromatography combined with ion-trap mass selective detection (LC-MSn). For quantification, deuterated internal standards are added and single ions of the analytes and internal standards are monitored. For confirmation of the identity of the analytes, two transition ions (one MS2 and one MS3) were monitored and the ratios between the ions were calculated and compared with those of standards. The detection capability for the multi-analyte LC-MSn analysis of megestrol acetate (MA), medroxyprogesterone acetate (MPA), chlormadinone acetate (CMA) and melengestrol acetate (MGA) is 0.5 microg kg(-1). The mean within-laboratory reproducibility ranges from 16-19% (%RSD) at a concentration level of 0.5 microg kg(-1) (n = 9). Running the SFE procedure overnight allows the analysis of 24 samples of fat per day. 相似文献
139.
Helmut Paulus Karl Schlögl Walter Weissensteiner 《Monatshefte für Chemie / Chemical Monthly》1983,114(6-7):799-808
Starting from1-(dimethylaminomethyl)-2-iodo-ferrocene (3) [2.2](1,2)ferrocenophane (2) was prepared in an 8-step synthesis with 17% overall yield. Both from the oxoderivative12 and the ferrocenophane2 puretrans-isomers (12b and2b, resp.) were obtained; the former (12b) was reduced to a separable mixture ofexo andendo 1-hydroxy-ferrocenophanes13a andb, resp. (~ 3:7), the configurations of which were assigned by the LIS-method. X-ray crystal structure analysis of2b revealed a centrosymmetrical chair conformation. From1H- and13C-NMR spectra both for2b and for the hydroxyderivatives13 a rigidexo-exo chair conformation was deduced. 相似文献
140.
Preparation and Crystal Structure of a Potassium Imidenitridesilicate, K3Si6N5(NH)6 Crystals of K3Si6N5(NH)6 sufficient for an X-ray structure determination are formed when potassium and silicium react with supercritical ammonia under the following conditions K:Si = 1:1, P(NH)3 = 6 kbar, T = 500°C within 3 days in a temperature gradient within the autoclaves used. The compound crystallizes cubic with a = 10.789(4) Å, the space group is P4332 (with tests for enantiomorphous pairs) and the cell contains four formula units. The positions of H-atoms are determined. The following data characterize the structure determination: N(F) = 518 with 517 ≥ 3σ(F02) N(Variables) = 37, R = 0.019 resp. Rw = 0.017. The conditions for the synthesis of the compound and its structure are discussed with respect to Si3N4 and Si2N2(NH). 相似文献