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Three methods have been examined for evaluating the concentration of nitrogen atoms in the afterglow of a nonequilibrium, helium-stabilized, atmospheric pressure plasma. These are nitric oxide titration, absolute emission intensity of N2(B 3g) and temporal decay of the N2(B 3g) emission. To employ the second method, the rate constants for the recombination of N atoms into N2(B 3g), at different vibrational levels of the B state, were determined. The third newly developed method has three advantages over the other two techniques: (1) it can predict the N-atom density for the entire afterglow, (2) it does not require calibration of the N2(B 3g) emission intensity, and (3) it does not disturb the gas flow. According to these measurements, the atmospheric pressure plasma produced a high density of nitrogen atoms, exceeding 4.0×1015 cm–3 at the edge of the discharge for 10 Torr N2 in 745 Torr He at 375 K and 15.5 W/cm3. 相似文献
85.
R G Hicks M T Lemaire L Ohrstr?m J F Richardson L K Thompson Z Xu 《Journal of the American Chemical Society》2001,123(29):7154-7159
The X-ray crystal structure and magnetic properties of a molecular crystal consisting of 1,5-dimethyl-3-(2-pyridyl)-6-oxoverdazyl radical and hydroquinone (pyvd:hq) are presented. The structure contains a two-dimensional network of hydrogen bonds involving the hydroquinones and the pyridine ring of the pyvd radical. The radicals adopt an unusual head-over-tail (antiparallel) pi-stacked array perpendicular to the hydrogen-bonded planes. The variable-temperature magnetic susceptibility data can be modeled using a one-dimensional antiferromagnetic chain model, with J = -58 cm(-1). The strength of the magnetic coupling is very unusual because there are no close intermolecular radical-radical contacts to provide conventional pathways for magnetic interactions. A pathway for coupling is proposed involving the mediation of magnetic exchange interactions between radical centers by the pyridine rings. Density functional calculations on the pyvd radical, as well as aggregates thereof based on the X-ray structure, have been employed in attempts to understand the possible mechanisms by which the strong magnetic interactions are achieved. 相似文献
86.
W. B. Hicks R. C. Wells R. K. Bailey und J. G. Fairchild 《Fresenius' Journal of Analytical Chemistry》1925,67(7-8):312-313
Ohne Zusammenfassung 相似文献
87.
Dr. Alexa Caise Dr. Jamie Hicks Dr. M. Ángeles Fuentes Prof. Jose M. Goicoechea Prof. Simon Aldridge 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(6):2138-2148
A novel β-diketiminate stabilized gallium hydride, (DippL)Ga(Ad)H (where ( Dipp L)={HC(MeCDippN)2}, Dipp=2,6-diisopropylphenyl and Ad=1-adamantyl), has been synthesized and shown to undergo insertion of carbon dioxide into the Ga−H bond under mild conditions. In this case, treatment of the resulting κ1-formate complex with triethylsilane does not lead to regeneration of the hydride precursor. However, when combined with B(C6F5)3, (DippL)Ga(Ad)H catalyses the reductive hydrosilylation of CO2. Under stoichiometric conditions, the addition of one equivalent of B(C6F5)3 to (DippL)Ga(Ad)H leads to the formation of a 3-coordinate cationic gallane complex, partnered with a hydroborate anion, [(DippL)Ga(Ad)][HB(C6F5)3]. This complex rapidly hydrometallates carbon dioxide and catalyses the selective reduction of CO2 to the formaldehyde oxidation level at 60 °C in the presence of Et3SiH (yielding H2C(OSiEt3)2). When catalysis is undertaken in the presence of excess B(C6F5)3, appreciable enhancement of activity is observed, with a corresponding reduction in selectivity: the product distribution includes H2C(OSiEt3)2, CH4 and O(SiEt3)2. While this system represents proof-of-concept in CO2 hydrosilylation by a gallium hydride system, the TOF values obtained are relatively modest (max. 10 h−1). This is attributed to the strength of binding of the formatoborate anion to the gallium centre in the catalytic intermediate (DippL)Ga(Ad){OC(H)OB(C6F5)3}, and the correspondingly slow rate of the turnover-limiting hydrosilylation step. In turn, this strength of binding can be related to the relatively high Lewis acidity measured for the [(DippL)Ga(Ad)]+ cation (AN=69.8). 相似文献
88.
Three-phase displacement experiments for a water-benzyl alcohol-decane system are simulated. Literature experimental three-phase relative permeabilities for the system are used to describe the relative permeabilities in the three-phase region for different three-phase relative permeability models. Saturation trajectories and elliptical regions are mapped in the three-phase region. Simulations are performed to model displacement experiments including breakthrough and the formation of multiple shocks. The model can be used to predict the results for other displacements. In an experiment where significant gravity segregation is present, the displacement is more accurately modeled by assuming a uniform initial condition than by using the actual vertical saturation and assuming no cross flow. It is shown how different residual saturation values can be measured in the laboratory depending on the initial saturation conditions in the core. The experimental residual saturations can be significantly different than the ‘theoretical’ or model values. 相似文献
89.
The evolution of linear viscoelasticity during the vulcanization of polyethylene is studied through the gel point. The material in the vicinity of the gel point is described by two scaling laws: one characterizes the viscoelasticity at the critical point and a second characterizes the evolution of viscoelasticity near the gel point. Time Resolved Mechanical Spectroscopy is used to observe both scaling phenomena. The material at the gel point displays power law relaxation over five decades of time with a power-law relaxation exponent equal to 0.32. This study conforms with previous findings that this exponent is composition-dependent. The longest relaxation time diverges in the vicinity of the gel point as max |p
c - p| –1/, and we find = 0.2. This result conforms with previous reports that this exponent may be independent of composition. The Arrhenius flow activation energy for this material undergoes three-fold changes during crosslinking up to the gel point. A single-adjustable-parameter stretched-exponential-power law relaxation function is an inadequate representation of crosslinked materials over any significant range of extent of the reaction up to the gel point. 相似文献
90.
Nhuan P. Nghiem Kevin B. Hicks David B. Johnston 《Applied biochemistry and biotechnology》2010,162(7):1915-1928
Production of succinic acid from glucose by Escherichia coli strain AFP184 was studied in a batch fermentor. The bases used for pH control included NaOH, KOH, NH4OH, and Na2CO3. The yield of succinic acid without and with carbon dioxide supplied by an adjacent ethanol fermentor using either corn or
barley as feedstock was examined. The carbon dioxide gas from the ethanol fermentor was sparged directly into the liquid media
in the succinic acid fermentor without any pretreatment. Without the CO2 supplement, the highest succinic acid yield was observed with Na2CO3, followed by NH4OH, and lowest with the other two bases. When the CO2 produced in the ethanol fermentation was sparged into the media in the succinic acid fermentor, no improvement of succinic
acid yield was observed with Na2CO3. However, several-fold increases in succinic acid yield were observed with the other bases, with NH4OH giving the highest yield increase. The yield of succinic acid with CO2 supplement from the ethanol fermentor when NH4OH was used for pH control was equal to that obtained when Na2CO3 was used, with or without CO2 supplementation. The benefit of sparging CO2 from ethanol fermentation on the yield of succinic acid demonstrated the feasibility of integration of succinic acid fermentation
with ethanol fermentation in a biorefinery for production of fuels and industrial chemicals. 相似文献