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391.
Qiu Jin Takashi Yamashita Kazuyuki Horie Rikio Yokota Itaru Mita 《Journal of polymer science. Part A, Polymer chemistry》1993,31(9):2345-2351
The polyaddition reactions of alicyclic diamines such as 1,4-diaminocyclohexane (1,4-CHDA) or 4,4′-diaminodicyclohexylmethane (DCHM) and configurational isomers of 1,4-CHDA or DCHM with tetracarboxylic aromatic anhydrides in aprotic solvents were carried out to prepare high molecular weight poly(amic acid)s. Through the thermal imidization of poly(amic acid)s, several flexible polyimide films were prepared. Because of the stiffness of the alicyclic moieties in diamines, the resulting polyimides exhibit high glass transition temperatures (220–340°C) almost similar to those for corresponding aromatic polyimides which have phenylene groups in place of cyclohexyl groups, and show good thermal stability. The partial crystallization was observed for polyimides with trans-cyclohexyl moiety during the heating in differential scanning calorimetry and ascertained by wide-angle x-ray diffraction. Thus, the inhibition of the occurrence of charge transfer in polyimides is accomplished by introducing alicyclic diamines in place of aromatic diamines without reducing their thermal stability. © 1993 John Wiley & Sons, Inc. 相似文献
392.
393.
Measurement of infrared absorption spectra in amorphous chalcogenide films revealed changes which can be closely related with the reversible photostructural change. The changes came out in intensity of absorption peak situated near 650 cm-1 as well as definite change in infrared fundamental absorption peak. The absorption peak intensity near 650 cm-1 showed considerable decrease by annealing, while it recovered initial value after light exposure. The change was shown to be in close correspondence with the well known reversible optical absorption edge shift. 相似文献
394.
The central limit (or fluctuation) phenomena are discussed in the interacting diffusion system. The tightness in the Kolmogorov-Prokhorov sense is proved for a sequence of distribution valued processes arising from finite particle systems. Further, the stochastic differential equation for the limit process is derived by constructing an infinite dimensional Brownian motion. 相似文献
395.
Dedicated to Professor Haruo Suzuki on the occasion of his sixtieth birthday 相似文献
396.
The MM2 force field has been extended to alkyl radicals. The known structures and conformational energy relationships are well reproduced for many simple radicals, and predictions were made for 1-butyl, 2-butyl, cyclopentyl, cyclohexyl and others. Heats of formation were also studied. 相似文献
397.
Zhou SL Matsumoto S Tian HD Yamane H Ojida A Kiyonaka S Hamachi I 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(4):1130-1136
A pH-responsive volume-change function was successfully introduced into a supramolecular hydrogel that contained GalNAc-appended (GalNAc=N-acetylgalactosamine) glutamate ester 1 by the simple mixing of it with an appropriate amount of 2 a or 2 b amphiphilic carboxylic acid. In the 1:1 mixture (1:2), the hydrogel swelled under neutral pH conditions, but shrank to almost half of its original volume under acidic pH conditions. The structure and pH response of the mixed hydrogel were characterized by using X-ray diffraction (XRD), confocal laser scanning microscopy (CLSM), transmission or scanning electron microscopy (TEM, SEM), and Fourier transform IR (FTIR) spectroscopy. Well-developed fibers formed a stable hydrogel by self-assembly, and under acidic conditions the charge of the carboxylic acid terminal (from the carboxylate anion) was neutralized and then these fibers became densely packed. This macroscopic pH response was also applied to the pH-triggered release of bioactive substances. In this mixed supramolecular hydrogel, the hydrogelator 1 provides a stable hydrogel structure and the additive 2 acts as a commander that is sensitive to an environmental pH signal. The present supramolecular copolymerization strategy should be useful for the construction of novel, stimuli-responsive, soft materials. 相似文献
398.
A determination method of flomoxef (FMOX) concentration in serum by capillary electrophoresis is developed. Serum samples are extracted with acetonitrile. After pretreatment, they are separated in a fused-silica capillary tube with a 25 mM borate buffer (pH 10.0) as a running buffer that contains 50mM sodium dodecyl sulfate. The FMOX and acetaminophen (internal standard) are detected by UV absorbance at 200 nm. Linearity (0-200 mg/L) is good, and the minimum limit of detection is 1.0 mg/L (S/N = 3). The relative standard deviations of intra- and interassay variability are 1.60-4.78% and 2.10-3.31%, respectively, and the recovery rate is 84-98%. This method can be used for determination of FMOX concentration in serum. 相似文献
399.
Polymethylenes with different chain lengths and having a central primary amino group were prepared. Rates of the reaction of the amines with 1,5-naphthalenedisulphonyl dichloride, a bifunctional fluorescent reagent, were measured by fluorometry in dilute solution. The rate constants obtained are equivalent to those for the reaction of two chain molecules having a functional group at each centre. Rates of the reactions of the amines with 5-dimethylamino-1-naphthalenesulphonyl chloride (a monofunctional fluorescent reagent), i.e. the reactions between a low molecular weight species and a functional group at the centre of a chain molecule, were also measured. Effects of chain length on reactivity of the central functional group, e.g. “local solvent medium effect” and “kinetic excluded volume effect,” are discussed briefly. 相似文献
400.
Calorimetric investigation of polymerization reactions. III. Curing reaction of epoxides with amines
K. Horie H. Hiura M. Sawada I. Mita H. Kambe 《Journal of polymer science. Part A, Polymer chemistry》1970,8(6):1357-1372
The curing reactions of epoxy resin with aliphatic diamines and the reaction of phenyl glycidyl ether with butylamine as a model for the curing reactions were investigated with a differential scanning calorimeter (DSC) operated isothermally. The heat of reaction of phenyl glycidyl ether with butylamine is equal to 24.5 ± 0.6 kcal/mole. The rate of reaction was followed over the whole range of conversion for both model and curing reactions. The reactions are accelerated by the hydrogen-bond donor produced in the system. The rate constants based on the third-order kinetics were determined and discussed for the model reaction and for the chemically controlled region of curing reactions. The activation energies for these rate constants are 13-14 kcal/mole. At a later stage of conversion, the curing reactions become controlled by diffusion of functional groups. The final extent of conversion is short of completion for most isothermally cured and even for postcured samples because of crosslinking. It was quantitatively indicated that the final conversion of isothermal cure corresponds to the transition of the system from a viscous liquid to a glass on the basis of the theory of glass transition temperature of crosslinked polymer systems. 相似文献