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71.
The investigation reports preparation of two new adsorbent materials, SiPOLHET and SiPOLHOM, by attachment of linear poly(amido amine) (PAA) to silica surface by adopting heterogeneous and homogeneous modification procedures, respectively. Their structures were characterized by FTIR, 13C and 29Si NMR spectroscopy. Surface morphologies and corresponding elemental composition were determined by using SEM and EDS techniques. The metal binding characteristics of the adsorbents towards Cu2+ and Ni2+ were studied in dilute aqueous solution which presents an interesting aspect of increasing trend. 相似文献
72.
DC magnetization, neutron depolarization and neutron diffraction (with both polarized and unpolarized neutrons) measurements
have been reported for the Co1.1−x
Zn
x
Ge0.1Fe1.2O1 spinels with x=0.5, 0.6 and 0.7. Neutron depolarization and neutron diffraction measurements confirm the presence of a long range ferrimagnetic
ordering of the local canted spins in these ferrite samples. The observed features of low field magnetization have been explained
under the framework of thermally activated domain wall movement of ferrimagnetic arrangement of local canted spins. An important
role of magnetic anisotropy (due to the presence of Co2+ ions) in establishing the magnetic ordering and domain kinetics in these ferrites has been observed. 相似文献
73.
M G Clarkson I U Swain R K Clifton K Cohen 《The Journal of the Acoustical Society of America》1991,89(5):2411-2420
Four experiments assessed the importance of stimulus number, repetition rate, and duration for newborns' head orientation toward brief sounds and related those parameters to the critical ones found for adults. Infants' responses to various trains of repeated 14-ms rattle sounds were compared with those to a 10-s rattle sound, known to elicit head orientation. Directional responses did not differ from the standard when rattle bursts were repeated at a rate of 20 per second for 1 s (experiment 1). Responding did differ from the standard and deteriorated to chance levels when either the number of moderately paced (6/s) stimulus bursts was decreased to six or fewer (experiments 2 and 3) or the duration of rapidly repeated (24/s) bursts was shortened to 500 ms (experiments 4A and 4B). These results suggest that newborns' head orientation depends, in part, upon the number of stimulus bursts and stimulus duration. 相似文献
74.
The level of endogenous norepinephrine (NE) in several tissue types was determined by CE with amperometric detection. We report herein on the method validation by HPLC using both amperometric and coulometric detection (CD). Keys to the method were the use of a diamond microelectrode for detection and off-line SPE for sample preparation. The run buffer was a 250 mM borate solution adjusted to pH 8.8 with potassium hydroxide. The diamond microelectrode exhibited a low and stable background current, and a low peak-to-peak noise < or =0.65 pA at the detection potential of +0.86 V versus Ag/AgCl. For standard solutions, the detector signal (i.e., oxidation current) changed linearly with the NE concentration (r(2) = 0.999) between 60 and 1000 nmol/L with an estimated LOD of 51 nmol/L (S/N = 3) and a response variability of 4.5% (RSD, n = 5). An Oasis MCX sorbent was used for SPE and the procedure produced an NE recovery of 95.1 +/- 5.6% (n = 6) from tissue homogenates. NE levels in the spleen, small intestine, and heart of a normotensive rat were found to be in the range of 0.77-0.97, 0.22-0.32, and 0.29-0.45 microg/g tissue (n = 3), respectively. 相似文献
75.
Ethan Zars Lisa Pick Dr. Abinash Swain Dr. Mrinal Bhunia Dr. Patrick J. Carroll Prof. Dr. Dominik Munz Prof. Dr. Karsten Meyer Prof. Dr. Daniel J. Mindiola 《Angewandte Chemie (International ed. in English)》2023,62(51):e202311749
Here we report the use of a base metal complex [(tBupyrpyrr2)Fe(OEt2)] ( 1 -OEt2) (tBupyrpyrr22−=3,5-tBu2-bis(pyrrolyl)pyridine) as a catalyst for intermolecular amination of Csp3−H bonds of 9,10-dihydroanthracene ( 2 a ) using 2,4,6-trimethyl phenyl azide ( 3 a ) as the nitrene source. The reaction is complete within one hour at 80 °C using as low as 2 mol % 1 -OEt2 with control in selectivity for single C−H amination versus double C−H amination. Catalytic C−H amination reactions can be extended to other substrates such as cyclohexadiene and xanthene derivatives and can tolerate a variety of aryl azides having methyl groups in both ortho positions. Under stoichiometric conditions the imido radical species [(tBupyrpyrr2)Fe{=N(2,6-Me2-4-tBu-C6H2)] ( 1 -imido) can be isolated in 56 % yield, and spectroscopic, magnetometric, and computational studies confirmed it to be an S = 1 FeIV complex. Complex 1 -imido reacts with 2 a to produce the ferrous aniline adduct [(tBupyrpyrr2)Fe{NH(2,6-Me2-4-tBu-C6H2)(C14H11)}] ( 1 -aniline) in 45 % yield. Lastly, it was found that complexes 1 -imido and 1 -aniline are both competent intermediates in catalytic intermolecular C−H amination. 相似文献
76.
Variable-temperature in situ crystallography on KHSO 4 shows that the pyrolysis of KHSO 4 to K 2S 2O 7 occurs via a three-step kinetic pathway monitored by crystal-to-crystal phase transitions while providing an explanation for the high proton conductivity to be due to the disordered hydrogen-bonding pattern. 相似文献
77.
This paper reports on preliminary tests of the performance of boron-doped diamond powder (BDDP) as a stationary phase in electrochemically modulated liquid chromatography (EMLC). EMLC manipulates retention through changes in the potential applied (E(appl)) to a conductive packing. Porous graphitic carbon (PGC) has routinely been utilized as a material in EMLC separations. Herein the utility of BDDP as a stationary phase in EMLC was investigated and its stability, both compositionally and microstructurally, relative to PGC was compared. The results show that BDDP is stable over a wide range of E(appl) values (i.e., -1.2 to +1.2V vs. Ag/AgCl, sat'd NaCl). The data also reveal that electrostatics play a key role in the adsorption of the aromatic sulfonates on the BDDP stationary phase, and that these analytes are more weakly retained in comparison to the PGC support. The potential for this methodology to provide a means to advance the understanding of molecular adsorption and retention mechanisms on carbonaceous materials is briefly discussed. 相似文献
78.
The objective of this research was to investigate nanoindentation-induced residual stresses in human enamel using Raman microspectroscopy
and establish if this approach can be used as a stress meter. Healthy human premolars and sintered hydroxyapatite samples
were embedded, cut, and the surfaces were polished finely with a 0.05 μm polishing paste before Berkovich and spherical indentations
were made with a force of 100 mN. Spectra were collected using a Renishaw Raman InVia reflex microscope equipped with an air-cooled
charge-coupled device (CCD) camera. Sample excitation was achieved using either an argon ion laser emitting at 514.5-nm or
a NIR diode laser emitting at 830-nm. The residual micro stresses within and surrounding the indentation impressions were
monitored by mapping the position of the ν1(PO4) band of (crystalline) hydroxyapatite. The Raman maps coincided well with the optical micrographs of the samples. Despite
the presence of a fluorescence background from the organic component of human enamel, spectra collected using 514.5-nm excitation
exhibited more significant shifts in the position of the ν1(PO4) band than spectra collected using 830-nm excitation. This implies that the former excitation may be a more appropriate excitation
for stress detection. It was concluded that Raman microspectroscopy provides a novel high-resolution and non-destructive method
for exploring the role of microstructure on the residual stress distribution within natural biocomposites.
Figure Stress maps of nanoindentation impressions on both human enamel and hydroxyapatite disk via Raman Microspectroscopy 相似文献
79.
Mathew W. C. Robinson Anthony C. Swain 《International Journal of Polymer Analysis and Characterization》2015,20(7):589-601
The influence of hexagonal boron nitride (h-BN) on the network structure and properties of poly(dimethylsiloxane) networks was investigated. A silane coupling reaction occurs during the preparation of materials to fix the filler to the network. The composite materials display a reduction in bulk network cross-linking and increase in hydrogen bonding interactions when compared to the unfilled material. Consequently, the tensile modulus is enhanced, the tan-delta decreases and compression set resistance diminishes. The in situ silane coupling reaction does not impact the expected thermal conductivity of the material and the inclusion of h-BN leads to materials with decreased coefficient of thermal expansion. 相似文献
80.
Trilochan Swain Prakash Mohanty 《Phosphorus, sulfur, and silicon and the related elements》2013,188(8):1702-1713
Abstract Substitution reactions of the complex [Pt(dien)H2O]2+ (where dien = diethylentriamine or 1,5-diamino-3-azapentane) with sulfur-containing L-cystine have been studied in a 1.0 × 10?1 mol dm?3 aqueous perchlorate medium at various temperatures (298–323 K) and 4.45 ≤ pH ≤ 2.15 using UV-vis spectroscopy. The products obtained have been characterized by their infrared and 1H NMR datasets at various pH levels and temperatures. From infrared and 1H NMR data, products have indicated that [Pt(dien)H2O]2+ reacted with L-cystine forming a Pt–S bond at low pH. At high pH, a product complex through the Pt–N bond has been formed. All rate constants have been evaluated from nonlinear double exponential plots. The activation parameters ΔH# and ΔS# have been determined using the Eyring equation. The products, SNi, and reversible rate constants have been evaluated. Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file. GRAPHICAL ABSTRACT 相似文献