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201.
Festus A. Adedeji Joseph A. Connor Christopher P. Demain Jose A. Martinho-Simoes Henry A. Skinner Mohamed T. Zafarani Moattar 《Journal of organometallic chemistry》1978,149(3):333-343
Microcalorimetric measurements at elevated temperatures of the heats of thermal decomposition and of iodination of a number of [M(CO)nL6-n] complexes (M = Cr, Mo, W; n = 3, 4; L = py, MeCN) have led to values for the standard enthalpies of formation of the following crystalline compounds (values given in kJ mol?) at 25°C: fac-[Mo(CO)3py3](275 ± 12), fac-[Mo(CO)3(NCCH3)3] (410 ± 12), fac-[W(CO)3py3](250 ± 12), fac-[W(CO)3(NCCH3)3](405 ± 12) and cis-[Cr(CO)4py2](505 ± 20). From these and other data, including estimated heats of sublimation, the bond enthalpy contributions of the various metalligand bonds in the gaseous metal complexes were evaluated as follows (values in kJ mol?): D(Crpy) 102, D(Mopy) 146, DWPy) 173, D(Mo7z.sbnd;NCMe) 135 and D(WNCMe) 169. For a given metal the bond enthalpy contribution decreased in the order D(MCO) > D(Mpy) > D(Mz.sbnd;NCMe). This order is related to the σ- and π-bonding character of the ligand. 相似文献
202.
D. Lalage S. Brown Joseph A. Connor Henry A. Skinner 《Journal of organometallic chemistry》1974,81(3):403-409
From measurements of the heats of iodination of CH3Mn(CO)5 and CH3Re(CO)5 at elevated temperatures using the ‘drop’ microcalorimeter method, values were determined for the standard enthalpies of formation at 25° of the crystalline compounds: ΔHof[CH3Mn(CO)5, c] = ?189.0 ± 2 kcal mol?1 (?790.8 ± 8 kJ mol?1), ΔHof[Ch3Re(CO)5,c] = ?198.0 ± kcal mol?1 (?828.4 ± 8 kJ mo?1). In conjunction with available enthalpies of sublimation, and with literature values for the dissociation energies of MnMn and ReRe bonds in Mn2(CO)10 and Re2(CO)10, values are derived for the dissociation energies: D(CH3Mn(CO)5) = 27.9 ± 2.3 or 30.9 ± 2.3 kcal mol?1 and D(CH3Re(CO)5) = 53.2 ± 2.5 kcal mol?1. In general, irrespective of the value accepted for D(MM) in M2(CO)10, the present results require that, D(CH3Mn) = D(MnMn) + 18.5 kcal mol?1 and D(CH3Re) = D(ReRe) + 30.8 kcal mol?1. 相似文献
203.
Joseph A. Connor Nabila I. El-Saied Jose A. Martinho-Simoes Henry A. Skinner 《Journal of organometallic chemistry》1981,212(3):405-410
Microcalorimetric measurements at 520–523 K of the heats of thermal decomposition and of iodination of bis-(benzene)molybdenum and of bis-(toluene)tungsten have led to the values (kJ mol?): ΔHof[Mo(η-C6H6)2, c] = (235.3 ± 8) and ΔHof[W(η6-C7H8)2, c] = (242.2 ± 8) for the standard enthalpies of formation at 25°C. The corresponding ΔHof(g) values, using available and estimated enthalpies of sublimation, are (329.9 ± 11) and 352.2 ± 11) respectively, from which the metalligand mean bond-dissociation enthalpies, (Mo—benzene) = (247.0 ± 6) and (W—toluene) = (304.0 ± 6) kJ mol?1, are derived. 相似文献
204.
Cefuroxime is a broad-spectrum second-generation bactericidal cephalosporin antibiotic active against β-lactamase-producing strains. Anti-cefuroxime, the geometric isomer of cefuroxime, might be present in cefuroxime dosage forms as a process-related impurity and possible degradation product. In the work discussed in this paper a precise and sensitive micellar liquid chromatographic (MLC) method for stability testing of cefuroxime axetil and anti-cefuroxime axetil in tablets, using benzoic acid as internal standard, was developed and validated. MLC was performed on an XTerra C18 reversed-phase column at 50 °C with 8:92 (v/v) acetonitrile–20 mM sodium dodecyl sulphate, pH 2.5, as mobile phase at a flow rate of 1.5 mL min?1. Detection was at 280 nm. Under these conditions the retention time and retention factor were of 6.65 min and 4.57, respectively, for cefuroxime axetil and 11.45 min and 8.59, respectively, for anti-cefuroxime axetil, indicating that the compounds were well separated. RSD values for quantification of cefuroxime axetil and anti-cefuroxime axetil were 0.39 and 1.7%, respectively, indicating the precision of the MLC method was good. The method is sensitive—LOD=0.5 μg mL?1 and LOQ=1.5 μg mL?1 for anti-cefuroxime axetil—and reproducible, with good recovery values. 相似文献
205.
A symbolic computer language SMP* is employed to analytically solve sets of first-order linear differential equations which occur in kinetic rate-reaction studies. The solutions studied are fully analytic functions of time and the rate constants. Two typical systems are studied: the first contains four species and four rate constants, corresponding to four parallel and consecutive first-order reactions; and the second contains four species and six rate constants, including two additional reverse reactions. These analytic functions allow insight into the mechanism, analytic expressions for the rate constants, and more rapid and precise solutions for the species concentrations than a completely numerical solution of the differential rate equations themselves. The results of the first system are applied to a recent experimental study of enzyme kinetics in which constituent amino acid residues of an enzyme are photooxidized and the corresponding catalytic activity measured with time. A second application of the SMP gives rise to a rapid semianalytic method for obtaining the values of the four and six exponentially nonlinear rate constants from the experimental data. 相似文献
206.
van den Brink HB Blok HP Bobeldijk I Bouwhuis M Dodge GE Harakeh MN Hesselink WH Ireland DG de Jager CW Jans E de Jonge N Kalantar-Nayestanaki N Kasdorp WJ Ketel TJ Konijn J Lapikás L van Leeuwe JJ van der Meer RL Nooren GJ Norum BE Passchier E Pellegrino AR Spaltro CM van der Steenhoven G Steijger JJ Templon JA Theunissen JA van Uden MA de Vries H de Vries R de Witt Huberts PK 《Physical review letters》1995,74(18):3561-3564
207.
208.
A. Stutzer John Sebel und F. F. Skinner 《Fresenius' Journal of Analytical Chemistry》1896,35(1):558-559
Ohne Zusammenfassung 相似文献
209.
Recently there has been substantial interest in optimising perovskite type ceramics as mixed ionic-electronic conductors (MIECs)
for use in ceramic oxygen generators and solid oxide fuel cells. However these materials suffer from thermomechanical deficiencies
and therefore there is a need to develop alternative materials.
Using the IEDP/SIMS technique the La2−xSrxNi1−yFeyO4+δ series of compounds has been investigated and the oxygen tracer diffusion and surface exchange coefficients determined. It
has been found that the oxide ion diffusivity of the x and y=0 material is very close to that of the fast oxide ion conducting
perovskites such as La1−xSrxCoO3 (LSC) but on acceptor doping with Sr a considerable decrease in the oxygen tracer diffusion coefficient was observed. Further
studies on the effects of B site doping, where y>0, indicate that this has very little effect on the transport properties.
Paper presented at the 6th Euroconference on Solid State Ionics, Cetraro, Calabria, Italy, Sept. 12–19, 1999. 相似文献
210.
M. Rohmer G. Rollin L. A. Youtz H. Causse H. W. Rowell J. v. Ferentzy J. A. Muller A. Fraenkel J. Fasal S. W. Young F. Ibbotson H. Brearley A. Gibb L. B. Skinner R. H. Hawley Th. Brown E. D. Campbell E. C. Champion J. S. C. Wells H. Angenot S. Burman Dinan A. G. Levy G. Lunge H. Mastbaum R. Job J. P. Pattinson H. S. Pattinson 《Analytical and bioanalytical chemistry》1907,46(10-11):722-737