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101.
102.
Eli M. Espinoza Duoduo Bao Maciej Krzeszewski Daniel T. Gryko Valentine I. Vullev 《国际化学动力学杂志》2019,51(9):657-668
Attaining long-lived charge-transfer (CT) states is of the utmost importance for energy science, photocatalysis, and materials engineering. When charge separation (CS) is slower than consequent charge recombination (CR), formation of a CT state is not apparent, yet the CT process provides parallel pathways for deactivation of electronically excited systems. The nuclear, or Franck-Condon (FC), contributions to the CT kinetics, as implemented by various formalisms based on the Marcus transition-state theory, provide an excellent platform for designing systems that produce long-lived CT states. Such approaches, however, tend to underestimate the complexity of alternative parameters that govern CT kinetics. Here we show a comparative analysis of two systems that have quite similar FC CT characteristics but manifest distinctly different CT kinetics. A decrease in the donor-acceptor electronic coupling during the charge-separation step provides an alternative route for slowing down undesired charge recombination. These examples suggest that, while infrequently reported and discussed, cases where CR is faster than CS are not necessarily rare occurrences. 相似文献
103.
Treatment of the Grignard reagent derived from the bromo-compound (III) with dimethyl formamide affords the corresponding aldehyde (IV) which undergoes ready condensation with nitroethane to give the nitropropene (V). Reduction of compound (V) with an excess of lithium aluminium hydride gives the amphetamine (VI) in reasonable yield. 相似文献
104.
105.
The trafficking of titanium(IV) by human serum transferrin (HsTf) has been implicated in the physiology of this hydrolysis-prone metal. The current work broadens to include the further interactions of Ti(IV) in serum that bear on this model. Ti2HsTf (2 equiv) binds the transferrin receptor TfR1 with Kd1 = 6.3 +/- 0.4 nM and Kd2 = 410 +/- 150 nM, values that are the tightest yet measured for a metal other than iron but weaker than the corresponding ones for Fe2HsTf due to both slightly slower on rates and slightly faster off rates. Comparing the affinities of metals for HsTf with the affinities of the resulting M2HsTf species for TfR1, we speculate that the formation of an M2HsTf complex of high affinity may predict a lobe-closed conformation that leads to a favorable interaction with TfR1. Human serum albumin (HSA), an important serum competitor for metal binding, can bind up to 20 equiv of Ti(IV) supplied in several forms. With some ligands, Ti(IV) may bind to the N-terminal metal binding site of albumin, forming a ternary complex. However, the dominant type of HSA binding is via Ti(IV) in complex form, probably at surface sites. Notably, HSA greatly stabilizes the titanocene moiety of the drug candidate Cp2TiCl2 with respect to hydrolysis and precipitation. HSA binds Ti(IV) citrate supplied as a hydrolyzed or unhydrolyzed source, with 1 equiv of citrate remaining bound. Titanium(IV) monocitrate neither competes with the binding of reporter molecules known to dock at canonical drug sites I or II nor binds at the N-terminus. HsTf outcompetes HSA for soluble Ti(IV) in a direct competition, but once bound to albumin, the transfer of Ti(IV) from HSA to HsTf is quite slow. Each of these findings has implications for the metabolism of Ti(IV) in human serum. 相似文献
106.
Hong C Bao D Thomas MS Clift JM Vullev VI 《Langmuir : the ACS journal of surfaces and colloids》2008,24(16):8439-8442
We describe a facile and expedient approach for the fabrication of arrays of microelectrodes on smooth substrates. A sequence of print-and-peel procedures allowed for the microfabrication of capacitance microsensors using office equipment and relatively simple wet chemistry. Microfluidic assemblies with reversibly adhered elastomer components allowed for the transfer of patterns of metallic silver, deposited via Tollens' reaction, onto the substrate surfaces. Electroplating of the silver patterns produced an array of micrometer-thick copper electrodes. Capacitance sensors were assembled by placing nonlithographically fabricated flow chambers over the microelectrode arrays. Triangular-waveform current-voltage (I/V) measurements showed a linear correlation between the capacitance of the print-and-peel fabricated devices and the dielectric constant of the samples injected into their flow chambers. 相似文献
107.
Melanie Sieland Valentine Camus-Genot Prof. Igor Djerdj Prof. Bernd M. Smarsly 《ChemistryOpen》2021,10(2):181-188
The influence of the cation of imidazolium-derived ionic liquids (ILs) on a low-temperature solution-based synthesis of hexagonal tungsten bronze (HTB) type Ti(OH)OF ⋅ 0.66 H2O and bronze-type TiO2(B) is investigated. The IL (Cxmim BF4) acts as solvent and also as reaction partner with respect to the decomposition of [BF4]−, releasing F−. In the present study, the chain length of the alkyl chain side groups attached to the imidazolium ring was varied (C2mim BF4 to C10mim BF4), and the obtained solids were analyzed by Powder X-Ray diffraction (PXRD) followed by Rietveld refinement. As a main finding these analyses indicate a transformation of Ti(OH)OF ⋅ 0.66 H2O into TiO2(B), and upon prolonged reaction time finally also into anatase TiO2. Rietveld analysis suggests that when using ILs with longer alkyl chains, the conversion of Ti(OH)OF ⋅ 0.66 H2O is slower compared to syntheses performed with smaller alkyl chains. Hence, Ti(OH)OF ⋅ 0.66 H2O appears to be metastable and is stabilized by long-chain ILs serving as surfactant attached to the crystallites’ surface. In this view, the ILs shield the nanoparticles and thus slow down the conversion into the more stable compounds. This confirms previous findings that ILs act as both, solvent and reaction medium in this reaction, thus enabling the synthesis of peculiar Ti-oxides. 相似文献
108.
Jones G Yan D Hu J Wan J Xia B Vullev VI 《The journal of physical chemistry. B》2007,111(24):6921-6929
The photophysical properties of a series of 9-arylacridinium conjugates in solid glass matrices composed of sucrose octaacetate have been determined. The fluorescence of the charge-shift states is significantly enhanced because of the retardation of nonradiative pathways for back-electron transfer. Changes of more than 3 orders of magnitude in back-electron-transfer rates (sucrose octaacetate glass vs conventional solvents at room temperature) were observed. Transient spectra displayed long-lived charge-shift species in the microsecond time regime for thianthrene acridinium conjugates. The rate retardation is associated with slow solvation times for surrounding solvent layers in the solid matrix. The red-edge effect (excitation wavelength-dependent fluorescence) for the arylacridinium ions in solid glass confirms the microheterogeneity of the sucrose octaacetate medium. 相似文献
109.
We analyzed the functional MRI signal of 15 men and 15 women. All had been presented with a flashed and a reversing, radial checkerboard stimulus. We investigated both positive and negative blood oxygenation level-dependent (BOLD) responses. The extent of activation and the change in the neuronal activity were examined. The former, by counting the number of activated voxels, the latter by using deltaR2* as an indicator of the change in the local deoxyhemoglobin (HbR) concentration. We examined both the positive and the negative BOLD response. Positive BOLD response: The flashed checkerboard gave rise to a larger number of activated voxels than for the reversing checkerboard. The mean number of activated pixels did not differ between men and women. The peak deltaR2* was significantly larger to the flashed than the reversing checkerboard, but did not reveal a gender-related difference. We noted an attenuation of the BOLD signal amplitude with time. This attenuation was larger in women than in men. Negative BOLD response: The attenuation was also larger for the flashed than the reversing stimulus and more pronounced in the chromatic contrast compared to the luminance contrast stimulus. The extent of activation was larger for the flashed than the reversing checkerboard, but did not differ between the sexes. The deltaR2* for the chromatic contrast checkerboard was larger in men than in women. No other significant differences were found. We conclude that the difference in the extent of activation between men and women is the result of our ability to detect activated pixels using statistical methods and not the result of a difference in the processing between the sexes. 相似文献
110.
Valentine SJ Kurulugama RT Clemmer DE 《Journal of the American Society for Mass Spectrometry》2011,22(5):804-816
The origin of non-integer overtone peaks in overtone mobility spectrometry (OMS) spectra is investigated by ion trajectory
simulations. Simulations indicate that these OMS features arise from higher-order overtone series. An empirically-derived
formula is presented as a means of describing the positions of peaks. The new equation makes it possible to determine collision
cross sections from any OMS peak. Additionally, it is extended as a means of predicting the resolving power for any peak in
an OMS distribution. 相似文献