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311.
Kazumi Ohya Yasuhiko Yotsui Kenichi Yamazaki Mitsuji Sano 《Journal of mass spectrometry : JMS》1983,18(1):27-33
The pyrolysis reaction of carpronium chloride and its structurally related compounds, which were trimethyl-aminoalkyl acid alkyl esters involving two, three or four skeletal methylene groups, have been investigated by pyrolysis gas chromatography mass spectrometry. The results indicated that the reaction modes of these ammonium compounds were essentially dependent on the number of skeletal methylene groups, and secondarily on the length of the carbon chain of the ester group. These phenomena have been interpreted in terms of electronic and steric contributions for the ionic elimination reaction. The electronic and steric effects on the orientation of the reaction are discussed on the basis of the atomic population calculated by the CNDO/2 method. 相似文献
312.
Orita A Nakano T An DL Tanikawa K Wakamatsu K Otera J 《Journal of the American Chemical Society》2004,126(33):10389-10396
Pyridine-containing arylene ethynylene strands were connected to the 2- and 2'-positions of (R)- and (S)-1,1'-binaphthyl templates. The arylene ethynylene moieties underwent intramolecular coordination with Ag(I) or Cu(I) ion to afford enantiopure double helicates. The double-helical structure was elucidated on the basis of circular dichroic (CD) spectra. The importance of intramolecular complexation of the double strands for the helicate formation was confirmed by comparison with a ligand bearing a single strand. Connection of the strands through an ether linkage enabled a sorting out of the Cotton effect induced by double-helical arylene ethynylene moieties. The CD exciton chirality method unambiguously proved that the termini of the strands approach each other upon complexation and that the sense of the induced helicity is the same as predicted by molecular modeling. 相似文献
313.
Chen R Tagawa M Hoshi N Ogura T Okamoto H Danjo K 《Chemical & pharmaceutical bulletin》2004,52(9):1066-1070
A solid dispersion of the drug can be made using a polymer carrier to improve solubility. Generally, drugs become amorphized when solid dispersion is formed using a polymer carrier. In such high energy conditions, the solubility of the drug molecule is increased. We previously prepared solid dispersion using a spray-drying technique and reported its solubility and crystallinity. In this study, hydroxypropylmethylcellulose (HPMC) was used as the carrier, and tolubutamide was the model drug, which is water-insoluble. Solubility was evaluated by preparing a solid dispersion using a newly developed 4-fluid nozzle spray dryer. Observation of particle morphology by scanning electron microscopy (SEM) revealed that the particles from the spray drying were atomized to several microns, and they had also become spherical. Assessment of the crystallinity of the spray-dried particles by powder X-ray diffraction and differential scanning calorimetry demonstrated that the tolbutamide had been amorphized, forming a solid dispersion. The apparent release rate constant K of the drug from the spray-dried particles was 4 to 6 times faster than the original drug in pH 1.2, and it was also 1.5 to 1.9 times faster than the original drug in pH 6.8. The 70% release time (T(70)) of the drug from the spray-dried particles was 20 to 30 times faster than the original drug in pH 1.2 solution as well as 2 to 3 times faster than the original drug in pH 6.8 solution. Pharmaceutical preparations prepared in this way using the 4-fluid nozzle system spray dryer formed composite particles, resulting in a remarkably improved dissolution rates of the drug. 相似文献
314.
Kazuyuki Suzuki Kaori Nishizawa Takeshi Miki Kazumi Kato 《Journal of Sol-Gel Science and Technology》2007,42(3):251-256
(Y,Yb)MnO3 and HfO2 films were prepared using alkoxy-derived precursor solutions, and (Y,Yb)MnO3/HfO2/Si structures were fabricated. The thickness, surface uniformity and crystallinity of the HfO2 film affect the crystallization of Y0.5Yb0.5MnO3 films. The degree of c-axis orientation and crystallinity of the Y0.5Yb0.5MnO3 films were changed with preparation conditions of HfO2 films. It was difficult to obtain Y0.5Yb0.5MnO3 films with high crystallinity and high degree of c-axis orientation on the HfO2 films thinner than 10 nm. The degree of c-axis orientation and crystallinity of the Y0.5Yb0.5MnO3 films on HfO2 films were improved by using diluted HfO2 precursor solution in the case of 10 nm-thick HfO2 film. Following this, the capacitance-voltage (C-V) characteristics were improved. 相似文献
315.
Kuniko Kimura Kei Kobayashi Toshihisa Horiuchi Kazumi Matsushige 《European Polymer Journal》2004,40(5):933-938
We have developed an orientation control technique for polymer molecules utilizing contact-mode atomic force microscopy (AFM). In this technique, the molecular chains were directly modified by scanning an AFM cantilever tip in contact with the film surface at the temperature just below its melting point. We call this process “modification scan”. Here, we applied this technique to poly(vinylidenefluoride-trifluoroethylene) (P(VDF-TrFE)) thin films on graphite and glass. We prepared a 75-nm thick copolymer crystalline film on graphite whose lamellar plane was perpendicular to the substrate (edge-on), and also prepared a film of the same thickness on glass whose lamellar plane was parallel to the substrate (flat-on). After applying this technique on both films, molecular chains were stretched and aligned to the modification scan direction, and new edge-on crystals were obtained, whose lamellar planes were well-aligned perpendicular to the modification scan direction. 相似文献
316.
317.
Boron nitride (BN) nanolayers encapsulating iron (Fe) fine particles and BN nanotubes were synthesized by annealing mixture powders of hematite, boron and carbon (C) at 1473 K for 2 h in a nitrogen atmosphere. The particles exhibited good soft magnetic properties. The thickness of BN nanolayers increased in the range of 10-100 nm with increasing C content in the mixture powders, which results in providing improvement of oxidation resistance of the particles. In the BN layers, no C was detected. BN nanotubes with diameters of ∼100 nm were also synthesized, and they had cup-stacked and bamboo-like structures. 相似文献
318.
319.
Two new analogs of the human lethal toxin polycavernoside A, polycavernoside C and C2 (0.1-0.2 mg for each), were isolated from the red alga, Gracilaria edulis. The relative stereostructure of polycavernoside C and the absolute structure of polycavernoside C2 were determined by spectroscopic analysis and synthesis of the model of their aglycon. 相似文献
320.
Young-Jong Kim Jiwon Han Kyung-Hwang Lee Takashi Ichii Kazumi Matsushige 《Applied Surface Science》2009,256(5):1507-1513
A xenon excimer lamp which irradiates vacuum ultra-violet (VUV) light at 172 nm in wavelength was applied to the photochemical surface conversion of n-octadecyltrimethoxysilane self-assembled monolayer (ODS-SAM) in the presence of atmospheric oxygen and subsequent multilayer fabrication. The terminal functional groups of ODS-SAM, -CH3 groups, were converted into polar functional groups, like -COOH, by the reaction with atomic oxygen species generated photochemically through VUV excitation of atmospheric oxygen molecules. The structure of the resulting organosilane multilayer with different numbers of superimposed monolayers (from 1 to 11), prepared on a smooth and hydrophilic silicon substrate by the layer-by-layer (LbL) approach, was examined in terms of molecular organization as well as the intra- or interlayer binding modes in such novel films. Ellipsometry and grazing angle X-ray reflectivity measurements revealed that multilayer films of up to 11 discrete monolayers were successfully obtained, indicating that the self-assembly is a viable technique for the construction of relatively thick (16 nm and above) multilayer films. 相似文献