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121.
Antje Meltzer Roberta Cargnelutti Adelheid Hagenbach Ernesto Schulz Lang Ulrich Abram 《无机化学与普通化学杂志》2015,641(15):2617-2623
Reactions of (NEt4)2[Re(CO)3Br3] with N‐heterocyclic thiols such as 2‐mercaptobenzimidazole (H2Sbenzim), 2‐mercaptothiazoline (HSthiaz), or 5‐mercapto‐1‐methyltetrazole (HSmetetraz) give rhenium(I) complexes of various compositions: (NEt4)[Re(CO)3Br2(H2Sbenzim)], [Re(CO)3(HSthiaz)3]Br, and (NEt4)[Re2(CO)6(μ‐S‐Smetetraz‐κS)(μ‐N,S‐Smetetraz‐κS,N)2]. Corresponding reactions with 2‐mercaptopyridine (HSpy) and bis(2‐pyridine)diselenide [(Sepy)2] did not give defined products in reasonable yields, whereas [Re(CO)5Br] reacts with HSpy and (Sepy)2 with formation of [Re(CO)3(HSpy)3]Br and [Re2(CO)6(Sepy)2], respectively. All reactions were performed without the addition of a supporting base and the sulfur‐containing organic ligands are coordinated in their thione forms with the exception of Smetetraz– in its μS‐bridging coordination mode in (NEt4)[Re2(CO)6(μ‐S‐Smetetraz‐κS)(μ‐N,S‐Smetetraz‐κS,N)2], which can be regarded as thiolate. The bonding mode of the selenium containing ligands in the dimeric compound [Re2(CO)6(Sepy)2] (C–Se distance: 1.93 Å) can also best be described as selenolate. The products are stable on air at an ambient temperature. They were studied spectroscopically and by X‐ray diffraction. 相似文献
122.
Yan Liu Viorica Lopez-Avila Marcela Alcaraz Werner F. Beckert 《Journal of separation science》1993,16(2):106-112
The extraction of six tetraalkyltin and seven ionic organotin compounds from spiked topsoil samples with supercritical carbon dioxide and carbon dioxide modified with 5 percent methanol was investigated. Analysis of the soil extracts was performed by gas chromatography with atomic emission detection. Retention times, minimum detectable concentrations, and detector linear ranges are included for nine organotin compounds (seven of the nine compounds were derivatized with n-pentylmagnesium bromide prior to gas chromatographic analysis). A 23 factorial experimental design was used to study the effect of three variables (pressure, temperature, and extraction time) on compound recovery. The results indicate that the tetraalkyltin compounds are extracted from topsoil samples with recoveries ranging from 90 to 110 percent. Recoveries for the ionic organotin compounds ranged from 50 to 75 percent for trimethyltin chloride, triethyltin bromide, and tributyltin iodide; they were below 20 percent for dimethyltin dichloride, dibutyltin dichloride, diphenyltin dichloride, and butyltin trichloride. When sodium diethyldithiocarbamate was added to the soil samples prior to extraction, followed by extraction with carbon dioxide modified with 5 percent methanol, recoveries ranged from 70 to 90 percent for trimethyltin chloride, triethyltin bromide, dimethyltin dichloride, tributyltin iodide, and dibutyltin dichloride; recoveries were approximately 40 percent for butyltin trichloride and diphenyltin dichloride. 相似文献
123.
Călinescu O Badea IA Vlădescu L Meltzer V Pincu E 《Journal of chromatographic science》2012,50(4):335-342
Determination of acetaminophen and its main impurities: 4-nitrophenol, 4'-chloroacetanilide, as well as 4-aminophenol and its degradation products, p-benzoquinone and hydroquinone has been developed and validated by a new high-performance liquid chromatography method. Chromatographic separation has been obtained on a Hypersil Duet C18/SCX column, using gradient elution, with a mixture of phosphate buffer (pH = 4.88) and methanol as a mobile phase. Analysis time did not exceed 14.5 min and good resolutions, peak shapes and asymmetries have resulted. The linearity of the method has been tested in the range of 5.0-60 μg/mL for acetaminophen and 0.5-6 μg/mL for the other compounds. The limits of detection and quantification have been also established to be lower than 0.1 μg/mL and 0.5 μg/mL, respectively. The method has been successfully applied for the analysis of commercial acetaminophen preparations. 相似文献
124.
The excitation energies from ground state for 63 fine structure levels of the terms belonging to 1 s2, 1snl, 2lnl′ (n = 2,3), 3l3l′ (l ≠ ≠ l′) configurations of Au77+, as well as oscillator strengths for electric-dipole-allowed and intercombination transitions among the fine-structure levels were theoretically evaluated. The important relativistic effects in intermediate coupling are incorporated by means of the Breit–Pauli Hamiltonian. Extensive comparisons are performed with several approximations and previous data sets in order to size up contributing effects and to estimate accuracy ratings. The atomic excitation is obtained by electron impact in close coupling approach. For optically allowed transitions, the electron-impact collision strengths at collision energy up to 80 keV are reported. The results are relevant to the laboratory and astrophysical plasmas. 相似文献
125.
Jorge Silva Jo?o M. Maia Rongzhi Huang Donald Meltzer Mark Cox Ricardo Andrade 《Rheologica Acta》2012,51(11-12):947-957
In this work, we report on the sensitivity of rheometrical techniques to the nature and size of the interface/interphase in coextruded thermoplastic urethanes (TPUs). In particular, the interphases developed during coextrusion of an amorphous glass (hard) TPU (Isoplast? ETPU 301) with one of two elastomeric (soft) TPUs (Estane? TPU 58277 and Estane? TPU X1175) were studied. Differences in the thickness and nature of the interphase of the two coextruded bilayer films were observed by atomic force microscopy. In one case, the interphase is thicker and rough, and in the other case, it is thinner and flat. Rheology was used in order to probe the type and characteristics of the interphases, with coextruded films having been tested in steady shear, small-amplitude oscillatory shear (SAOS), uniaxial extension, and stress relaxation after a step strain in shear. The results were compared with theoretical predictions assuming zero-thickness interfaces and no interfacial slip. For SAOS and stress relaxation experiments, expressions were deduced in order to enable such a prediction to be made. Of all four rheometrical tests, only stress relaxation after a step shear did not follow the theoretical predictions and, thus, was sensitive enough to detect the presence of the interphase. 相似文献
126.
Stephan A. Lehmann A. Donald Meltzer Hans Wolfgang Spiess 《Journal of Polymer Science.Polymer Physics》1998,36(4):693-703
The microphase separation (MPS) in polyureas based on methylene diphenyl diisocyanate (MDI) hard segment, diethyltoluenediamine chain extender, and amino-terminated polypropylene glycol soft segment prepared by reaction injection molding (RIM) was studied by advanced solid-state NMR spectroscopy. Incomplete microphase separation leads to the presence of mobilized hard segments dispersed in the soft segment domains as well as immobilized soft segments residing in the hard domains. This is detected by 1H-NMR spectra recorded under spinning at the magic angle (MAS) as well as two-dimensional wide-line separation (WISE) NMR spectra. The sizes of the various domains as well as the interfaces between them are quantified by spin diffusion measurements. In this way the impact of annealing, method of polymerization, and hard segment content on MPS is studied. Whereas annealing at temperatures up to 170°C results in improving the MPS, major changes are observed after annealing at higher temperatures (190°C), where the system changes from “soft-in-hard” to “hard-in-soft” behavior. The MPS decreases with increasing hard segment content. The highest MPS is observed for solution polymerized samples. The various NMR experiments clearly reveal the nonequilibrium nature of RIM systems. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 693–703, 1998 相似文献
127.
Viorica Lopez-Avila 《Journal of separation science》1980,3(11):545-550
Combination of various GC detectors by using a Varian effluent splitter with glass capillary columns has been found to be a rapid procedure for profiling organics extracted from sludges and river sediments. The selectivity and the increased sensitivity of the thermionic nitrogen-phosphorus detector (TSD), the electron capture detector (ECD), and the flame photometric detector (FPD) over the flame ionization detectors (FID) or mass spectrometers allow the detection of compounds present at trace levels without need for extensive sample cleanup. Furthermore, the combination of two selective detectors may supplement the information with regard to the chemical functionalities required for structure elucidation. 相似文献
128.
Adriana Popa Lavinia Macarie Ecaterina S. Dragan Viorica Parvulescu Gheorghe Ilia 《International Journal of Polymer Analysis and Characterization》2020,25(6):457-466
Abstract The chlorometylated styrene–divinylbenzene copolymer with different percent of divinylbenzene (code: S-6.7 DVB, S-12DVB, and S-15DVB) was functionalized with 3-hydroxybenzaldehyde for obtaining intermediated polymers. The aminotrimethoxysilanphosphonate groups were grafted by one-pot reactions in tetrahydrofuran using three components: polymers grafted with aldehyde groups (code: CHO-6.7, CHO-12, and CHO-15), 3-aminopropyltrimethoxysilane, diethylphosphite. The aminotrimethoxysilanphosphonate groups functionalized onto styrene-(6.7, 12, and 15%) divinylbenzene copolymer (code: PAF-6.7, PAF-12, and PAF-15) and evolution of the reaction were evidenced by FT-IR spectroscopy and porous structure by N2 adsorption-desorption, SEM microscopy. The thermal behavior of aldehydes and materials: PAF-6.7, PAF-12, and PAF-15 are different than initial polymer supports. 相似文献
129.
Stolze SC Meltzer M Ehrmann M Kaiser M 《Chemical communications (Cambridge, England)》2010,46(46):8857-8859
The solid phase total synthesis of the marine cyanobacterial Ahp-cyclodepsipeptide Symplocamide A is reported as a model for a general route for the synthesis of tailor-made non-covalent serine protease inhibitors. 相似文献
130.
H. Jensen O. Schales W. Zimmermann M. J. Schmulowitz H. B. Wylie G. Pincus G. Wheeler G. Young P. A. Zahl S. L. Cohen G. F. Marrian G. F. Castland R. K. Meyer L. C. Miller M. H. Ritz S. Goertz K. David R. Wagner J. P. Visscher D. E. Bowman C. Dolff E. Wiesener S. Aschheim B. Zondek B. Ostadal K. J. Anselmino Friedrich Hoffmann W. Kestraneck H. Molitor E. P. Pick I. A. Smorodinzew A. M. Feldt W. W. Palmer J. P. Leland A. B. Gutmann G. L. Foster V. Trevorrow G. J. Fashena J. Devine K. Bhagvat H. Blaschko D. Richter H. Schlossmann S. J. Meltzer C. M. Auer J. M. Rogoff 《Analytical and bioanalytical chemistry》1942,123(1-2):71-77