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71.
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
72.
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
73.
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
74.
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
75.
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
76.
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
77.
Bourgeois P Sato Y Shaw J Alarcon R Bernstein AM Bertozzi W Botto T Calarco J Casagrande F Distler MO Dow K Farkondeh M Georgakopoulos S Gilad S Hicks R Holtrop M Hotta A Jiang X Karabarbounis A Kirkpatrick J Kowalski S Milner R Miskimen R Nakagawa I Papanicolas CN Sarty AJ Sirca S Six E Sparveris NF Stave S Stiliaris E Tamae T Tsentalovich G Tschalaer C Turchinetz W Zhou ZL Zwart T 《Physical review letters》2006,97(21):212001
The mean square polarizability radii of the proton have been measured for the first time in a virtual-Compton-scattering experiment performed at the MIT-Bates out-of-plane scattering facility. Response functions and polarizabilities obtained from a dispersion analysis of the data at Q2 = 0.057 GeV2/c2 are in agreement with O(p3) heavy baryon chiral perturbation theory. The data support the dominance of mesonic effects in the polarizabilities. 相似文献
78.
Mackinnon AJ Patel PK Borghesi M Clarke RC Freeman RR Habara H Hatchett SP Hey D Hicks DG Kar S Key MH King JA Lancaster K Neely D Nikkro A Norreys PA Notley MM Phillips TW Romagnani L Snavely RA Stephens RB Town RP 《Physical review letters》2006,97(4):045001
Protons accelerated by a picosecond laser pulse have been used to radiograph a 500 microm diameter capsule, imploded with 300 J of laser light in 6 symmetrically incident beams of wavelength 1.054 microm and pulse length 1 ns. Point projection proton backlighting was used to characterize the density gradients at discrete times through the implosion. Asymmetries were diagnosed both during the early and stagnation stages of the implosion. Comparison with analytic scattering theory and simple Monte Carlo simulations were consistent with a 3+/-1 g/cm3 core with diameter 85+/-10 microm. Scaling simulations show that protons>50 MeV are required to diagnose asymmetry in ignition scale conditions. 相似文献
79.
Niccolai S Mirazita M Rossi P Baltzell NA Carman DS Hicks K McKinnon B Mibe T Stepanyan S Tedeschi DJ Adams G Ambrozewicz P Anefalos Pereira S Anghinolfi M Asryan G Avakian H Bagdasaryan H Baillie N Ball JP Batourine V Battaglieri M Bedlinskiy I Bektasoglu M Bellis M Benmouna N Berman BL Biselli AS Boiarinov S Bouchigny S Bradford R Branford D Briscoe WJ Brooks WK Bültmann S Burkert VD Butuceanu C Calarco JR Careccia SL Carnahan B Chen S Cole PL Collins P Coltharp P Crabb D Crannell H Crede V 《Physical review letters》2006,97(3):032001
For the first time, the reaction gammad-->DeltanK+ has been analyzed in order to search for the exotic pentaquark baryon Theta+(1540). The data were taken at Jefferson Laboratory, using the Hall-B tagged-photon beam of energy between 0.8 and 3.6 GeV and the CEBAF Large Acceptance Spectrometer (CLAS). No statistically significant structures were observed in the nK+ invariant-mass distribution. The upper limit on the gammad-->DeltaTheta+ integrated cross section has been calculated and found to be between 5 and 25 nb, depending on the production model assumed. The upper limit on the differential cross section is also reported. 相似文献
80.