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71.
R. Zeleny S. Voorspoels M. Ricci R. Becker C. Jung W. Bremser M. Sittidech N. Panyawathanakit W. F. Wong S. M. Choi K. C. Lo W. Y. Yeung D. H. Kim J. Han J. Ryu S. Mingwu W. Chao M. M. Schantz K. A. Lippa S. Matsuyama 《Analytical and bioanalytical chemistry》2010,396(4):1501-1511
An international intercomparison involving eight national metrology institutes (NMIs) was conducted to establish their current measurement capabilities for determining five selected congeners from the brominated flame retardant classes polybrominated diphenyl ethers and polybrominated biphenyls. A candidate reference material consisting of polypropylene fortified with technical mixtures of penta-, octa- and decabromo diphenyl ether and decabromo biphenyl, which was thoroughly assessed for material homogeneity and stability, was used as study material. The analytical procedures applied by the participants differed with regard to sample pre-treatment, extraction, clean-up, employed calibrants and type of calibration procedure as well as regarding analytical methods used for separation, identification and quantification of the flame retardant congeners (gas chromatography coupled to an electron capture detector (GC-ECD), gas chromatography-mass spectrometry in the electron ionisation mode (GC-EI-MS), gas chromatography-mass spectrometry in the electron capture negative ionisation mode (GC-ECNI-MS), and liquid chromatography-inductive coupled plasma-mass spectrometry (LC-ICP-MS)). The laboratory means agreed well with relative standard deviations of the mean of means of 1.9%, 4.8%, 5.5% and 5.4% for brominated diphenyl ether (BDE) 47, 183 and 209 and for the brominated biphenyl (BB) congener 209, respectively. For BDE 206, a relative standard deviation of 28.5% was obtained. For all five congeners, within-laboratory relative standard deviations of six measurements obtained under intermediate precision conditions were between 1% and 10%, and reported expanded measurements uncertainties typically ranged from 4% to 10% (8% to 14% for BDE 206). Furthermore, the results are in good agreement with those obtained in the characterization exercise for determining certified values for the flame retardant congeners in the same material. The results demonstrate the state-of-the-art measurement capabilities of NMIs for quantifying representative BDE congeners and BB 209 in a polymer. The outcome of this intercomparison (pilot study) in conjunction with possible improvements for employing exclusively calibrants with thoroughly assessed purity suggests that a key comparison aiming at underpinning calibration and measurement capability (CMC) claims of NMIs can be conducted. Figure
Mass fraction of deca-brominated diphenyl ether (BDE 209) in the polypropylene study material analysed in the international intercomparison CCQM-P114 相似文献
72.
Yasunao Inoue Tomoki Omodani Ryotaro Shiratake Fuminori Sato 《Tetrahedron: Asymmetry》2010,21(15):1855-1860
We have successfully synthesized chiral β-amino trifluoromethyl alcohol (2S,3S)-7a, which is a key intermediate in the production of AE-3763, by stereoselective reduction of N-Cbz-protected 5-hydroxy-5-(trifluoromethyl)-1,3-oxazolidine 4 prepared from L-valine in 3 steps followed by alkaline hydrolysis. This new method can be applied to the industrial-scale synthesis of AE-3763. 相似文献
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74.
A novel flow-coulometric detector integrating an immobilized uricase reactor and an electrolytic cell was fabricated and used for the determination of uric acid in human urine. The procedure is based on the measurement of the total charge with and without passing the sample through an enzyme reactor which allows the complete conversion of the electro-active uric acid in electro-inactive products. The amount of uric acid is linearly related to the difference between the two total charges. The current efficiencies for 1 × 10?4-1 × 10?3 M uric acid were found to be nearly 100% (r.s.d. < 1%). 相似文献
75.
Kazuo Matsuyama Takeshi Komai Katsukiyo Ito 《Journal of polymer science. Part A, Polymer chemistry》1986,24(10):2425-2432
T-butylperoxy phenylcarbonate (BPPC) was prepared. Its decomposition rate constant in cumene is given by kd = 2.39 × 1015 exp(?17,300/T), where T is the absolute temperature. When BPPC decomposes to polymerize styrene at 100°C, it produces 12% phenoxy radical to total primary radicals. The phenoxy radical hardly adds to styrene and reacts the other primary radicals and polymer radical. Thus it retards the rate of polymerization. 相似文献
76.
Makino K Nakajima T Shikamura M Ito F Ando S Kochi C Inagawa H Soma G Terada H 《Colloids and surfaces. B, Biointerfaces》2004,36(1):35-42
Monodispersed PLGA microspheres containing rifampicin (RFP) have been prepared by solvent evaporation method using a Shirasu porous glass (SPG) membrane. The microspheres were spherical and their average diameter was about 2 microm. The loading efficiency of rifampicin was dependent on the molecular weight of PLGA. The higher loading efficiency was obtained by the usage of PLGA with the lower molecular weight, which may be caused by the interaction of the amino groups of rifampicin with the terminal carboxyl groups of PLGA. PLGA with the monomer compositions of 50/50 and 75/25, of lactic acid/glycolic acid, were used in this study. From rifampicin-loaded PLGA microspheres formulated using PLGA with the molecular weight of 20,000, rifampicin was released with almost constant rate for 20 days after the lag phase was observed for the initial 7 days at pH 7.4. On the other hand, from rifampicin-loaded PLGA microspheres formulated using PLGA with the molecular weight of 5000 or 10,000, almost 90% of rifampicin-loaded in the microspheres was released in the initial 10 days. Highly effective delivery of rifampicin to alveolar macrophages was observed by the usage of rifampicin-loaded PLGA microspheres. Almost 19 times higher concentration of rifampicin was found to be incorporated in alveolar macrophages when rifampicin-loaded PLGA microspheres were added to the cell culture medium than when rifampicin solution was added. 相似文献
77.
Uchida T Miyanaga Y Tanaka H Wada K Kurosaki S Ohki T Yoshida M Matsuyama K 《Chemical & pharmaceutical bulletin》2000,48(11):1843-1845
The bitterness of 11 commercial medicines was evaluated both by a multichannel taste sensor and in human gustatory sensation tests with 15 volunteers. For basic drugs with amino groups in the molecule, such as quinine, there was a comparatively strong relative response electric potential (mV) of channels 1 or 2, those containing negatively charged membranes and the bitterness determined by human gustatory sensation tests. The suppression of the bitterness of quinine by sucrose and aspartame could be quantified using the artificial taste sensor and the results concurred with those from gustatory sensation tests. The usefulness of the sensor was thus confirmed for this type of compound. Anionic drugs, such as diclofenac sodium or salicylic acid gave rise in a negative response electric potential in channels 5 or 6, those containing positively charged membrane, seemed to be useful information even though their tastes are being sour rather than bitter. For drugs with both an amino (cationic) group and carboxylic acid (anionic) group in the molecule, such as theophylline, caffeine, and metronidazole, the relative response electric potential (mV) of channels containing negatively charged membranes was not increased, even though bitterness was observed in human gustatory sensation tests. Therefore, a different design of membrane component is required for more general evaluation of the bitterness of various medicines. 相似文献
78.
79.
80.
Xunyao Fu Tatsuo Maruyama Tomohiro Sotani Hideto Matsuyama 《Journal of membrane science》2008,320(1-2):483-491
A serious problem faced during the application of membrane filtration in water treatment is membrane fouling by natural organic matter (NOM). The hydrophilicity, zeta potential and morphology of membrane surface mainly influence membrane fouling. The aim of the present study is to reveal the correlation between membrane surface morphology and membrane fouling by use of humic acid solution and to investigate the efficiency of backwashing by water, which is applied to restore membrane flux. Cellulose acetate butyrate (CAB) hollow fiber membranes were used in the present study. To obtain the membranes with various surface structures, membranes were prepared via both thermally induced phase separation (TIPS) and nonsolvent-induced phase separation (NIPS) by changing the preparation conditions such as polymer concentration, air gap distance and coagulation bath composition. Since the membrane material is the same, the effects of hydrophilicity and zeta potential on membrane fouling can be ignored. More significant flux decline was observed in the membrane with lower humic acid rejection. For the membranes with similar water permeability, the lower the porosity at the outer surface, the more serious the membrane fouling. Furthermore, the effect of the membrane morphology on backwashing performance was discussed. 相似文献