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81.
82.
C. J. McDonald P. B. Smith J. A. Roper D. I. Lee J. G. Galloway 《Colloid and polymer science》1991,269(3):227-241
Polymer structure developed in latex particles has been investigated by measuring the temperature dependence of the carbon magnetic resonance (CMR) peak linewidths. Interpenetrating polymer networks (IPN) were formed by a continuous-addition emulsion polymerization process, in which a crosslinked seed particle was the site for formation of a linear second-stage polymer. Morphology was controlled by the level of crosslinking in the seed stage. The two polymers of the composite particle differ in their glass-transition temperatures by 100°C. By heating the particles to 50°C above the glass-transition temperature of the softer polymer, which formed the continuous network phase of this composite, it was possible to observe its CMR spectrum independently of the other polymer. The temperature dependence of the linewidth varied with the structure of the network. This was characterized by limiting linewidth behavior at both low and high temperature, which systematically varied as a function of the degree of mixing the two phases. Differential scanning calorimetry and electron microscopy corroborated the morphology change observed with the linewidth data. The influence of a diluent, present during formation of the network stage, was also examined with this CMR approach. 相似文献
83.
The complexes OsHX(CS)L(PPh3)2 (X Cl, Br; L CO and X Cl; L CN-p-tolyl), which contain mutually cis hydrido and thiocarbonyl ligands, undergo transfer of the hydrido ligand to CS when treated with CO to give blue complexes containing the thioformyl ligand [OsCHS]. OsCl(CHS)(CO)2(PPh3)2 reacts with borohydride to give the first metal complex of the thioformaldehyde monomer, viz. Os(η2-CH2S)(CO)2(PPh3)2, which reacts rapidly with HCl to give OsCl(SCH3)(CO)2(PPh3)2 and then, by a slower reaction, OsCl2(CO)2(PPh3)2 and CH3SH. The ligands produced in this stepwise reduction have possible relevance as models for postulated intermediates in the Fischer—Tropsch synthesis. Synthetic routes to formyl [OsCHO], iminoformyl [OsCHNMe] and secondary carbene complexes [OsCHSMe, OsCHNMe2, OsCHOMe] are also demonstrated. 相似文献
84.
85.
W.R. Roper G.E. Taylor J.M. Waters L.J. Wright 《Journal of organometallic chemistry》1979,182(3):C46-C48
Reaction between Ru(CO)2(PPh3)3 and MeHgI yields Ru[η2-C(O)CH3]I(CO)(PPh3)2 which in solution exists mainly as RuCH3I(CO)2(PPh3)2 and crystal structure determination of Ru[η2-C(O)CH3]I(CO)(PPh3)2 and previously described Ru[η2-C(O)p-tolyl]I(CO) (PPh3)2 confirms that in the solid state both molecules contain dihapto-acyl ligands. 相似文献
86.
Direct observation of thiolate displacement reactions on Au(111): the role of physisorbed disulfides
Line-of-sight mass spectroscopy (LOSMS) has been used to study the displacement reaction of ( radical3x radical3)R30 degrees methylthiolate on Au(111) by butylthiolate. The reaction was carried out at room temperature and constant saturation coverage, by exposing the methylthiolate-covered surface to dibutyl disulfide gas. The adsorbed methylthiolate was desorbed as dimethyl disulfide and the cross product methylbutyl disulfide, both identified by LOSMS. This shows that reaction occurs between adsorbed thiolates of different chain length at room temperature, while the kinetics indicate that a rapid equilibrium is established between immobile, chemisorbed thiolates, and highly mobile, physisorbed disulfides. 相似文献
87.
Detailed procedures for the syntheses of Os(CO)2(PPh3)3, Os(CO)(CNR)-(PPh3)3 (R = p-tolyl), Os(CO)(CS)(PPh3)3 and Os(CS)(CNR)(PPh3)3, together with the derived complexes Os(CO)2(CS)(PPh3)2, Os(CO)(CS)(CNR)(PPh3)2, Os(η2-C2H4)(CO)(CNR)(PPh3)2, Os(η2-C2H4)(CO)(CS)(PPh3)2, Os(η2CS2)(CO)2-(PPh3)2, Os(η2CS2)(CO)(CS)(PPh3)2, Os(η2-CS2)(CO)(CNR)(PPh3)2, Os(η2PhC2Ph)(CO)2(PPh3)2 and OsH(C2Ph)(CO)2(PPh3)2 are described. 相似文献
88.
K.W.Michael Siu Christopher M. Roper Louis Ramaley Walter A. Aue 《Journal of chromatography. A》1981,210(3)
An electronic control mode has been developed for operating a d.c. electron-capture detector at constant-current levels by means of a feed-back circuit. A linear range of 1·104 and a detection limit of 100 fg have been observed with aldrin. 相似文献
89.
We demonstrate, for what is the first time to our knowledge, long-term stable, continuously tunable operation of a doubly resonant optical parametric oscillator (OPO) pumped by a single-stripe diode laser without the use of an external semiconductor amplifier. The OPO is based on periodically poled lithium niobate and is pumped by a 150-mW distributed Bragg grating diode laser. 18-mW total output power is generated at 1.3- and 2.3-mum wavelengths. A cavity-length servo system allows continuous signal tuning of 17 GHz and idler tuning of 10 GHz, limited only by the range of a piezoelectric cavity mirror mount. OPO tuning is demonstrated from 1.1 to 1.4 mum and from 2.2 to 3.7 mum. 相似文献
90.
In response to a growing interest in the use of smaller, faster microchip (mu-chip) methods for the separation of proteins, advancements are proposed that employ the asymmetric squarylium dye Red-1c as a noncovalent label in mu-chip CE separations. This work compares on-column and precolumn labeling methods for the proteins BSA, beta-lactoglobulin B (beta-LB), and alpha-lactalbumin (alpha-LA). Nonequilibrium CE of equilibrium mixtures (NECEEM) represents an efficient method to determine equilibrium parameters associated with the formation of intermolecular complexes, such as those formed between the dye and proteins in this work, and it allows for the use of weak affinity probes in protein quantitation. In particular, nonequilibrium methods employing both mu-chip and conventional CE systems were implemented to determine association constants governing the formation of noncovalent complexes of the red luminescent squarylium dye Red-1c with BSA and beta-LB. By our mu-chip NECEEM method, the association constants K(assoc) for beta-LB and BSA complexes with Red-1c were found to be 3.53 x 10(3) and 1.65 x 10(5) M(-1), respectively, whereas association constants found by our conventional CE-LIF NECEEM method for these same protein-dye systems were some ten times higher. Despite discrepancies between the two methods, both confirmed the preferential interaction of Red-1c with BSA. In addition, the effect of protein concentration on measured association constant was assessed by conventional CE methods. Although a small decrease in K(assoc) was observed with the increase in protein concentration, our studies indicate that absolute protein concentration may affect the equilibrium determination less than the relative concentration of protein-to-dye. 相似文献