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111.
A new simple isocratic chiral RP-LC method has been developed for the separation and quantification of the enantiomer of (R,R)-tadalafil in bulk drugs and dosage forms with an elution time of about 20 min. Chromatographic separation of (R,R)-tadalafil and its enantiomer was achieved on a bonded macro cyclic glycopeptide stationary phase. The method resolves the
(R,R)-tadalafil and its enantiomer with a resolution (R
s) greater than 2.4 in the developed chiral RP-LC. The mobile phase used for the separation and quantification of (R,R)-tadalafil and its enantiomer involves a simple mixture of reverse phase solvents and the cost of analysis was drastically
decreased. The test concentration is 0.4 mg mL−1 in the mobile phase. This method is capable of detecting the enantiomer of (R,R)-tadalafil up to 0.0048 μg wrt test concentration 400 μg mL−1 for a 20 μL injection volume. The drug was subjected to stress conditions of hydrolysis, oxidation, photolysis and thermal
degradation. There was no interference of degradants with (R,R)-tadalafil and its enantiomer in the developed method. The developed chiral RP-LC method was validated with respect to linearity,
accuracy, precision and robustness. The percentage recovery for the enantiomer of (R,R)-tadalafil in bulk drug samples and in dosage forms ranged from 97.0 to 102.5%. The test solution was found to be stable
in the mobile phase for 48 h after preparation. 相似文献
112.
Chandrasekhar S Reddy MS Babu BN Jagadeesh B Prabhakar A Jagannadh B 《Journal of the American Chemical Society》2005,127(27):9664-9665
Tendencies of forming stable helices of heterooligomers composed of alternating rigid cis-beta-sugar amino acid and flexible beta-hGly motifs have been investigated, using a combination of molecular mechanics, CD, FT-IR, and NMR techniques. The results show that the solution structures of these oligomers exist as robust right-handed 14-helices. Here, we examine the role of conformationally rigid cis-beta-sugar amino acid in preorganizing the conformation of beta-hGly to form the 14-helix. Our findings also show that a right-handed 14-helix can be formed with as few as four properly sequenced heterogeneous residues. These results represent the expansion of the conformational pool of sugar amino acid in the design of well-folded 14-helices, which can be used to develop beta-peptides endowed with biological activity. 相似文献
113.
114.
The hyperfine splitting for the 133Cs isotope for the 6s 2S1/2 → 9s 2S1/2 transition has been measured using Doppler-free two-photon fluorescence spectroscopy in a gas cell for the first time to our knowledge. The hyperfine splitting between the two components was measured to be 8754 (1) MHz and the magnetic dipole coupling constant (A) for the excited 9s 2S1/2 level was determined to be 109.7 (3) MHz for the 133Cs isotope. The measured values are in good agreement with the earlier reported results. 相似文献
115.
V. R. Ganatra N. Kumar S. Suryanarayana Y. R. Bamankar N. Reghu V. N. Vaidya S. K. Mukerjee 《Journal of Radioanalytical and Nuclear Chemistry》2008,275(3):515-522
This paper describes Jet Entrainment Technique (JET) developed at Bhabha Atomic Research Centre (BARC) for the preparation
of small microspheres of UO2 in the size range of 100±20 μm diameter. The UO2 microspheres were prepared by Internal Gelation Process (IGP) using selected feed solution compositions. Equipment development
and the optimized process operations for obtaining more than 90% of high density UO2 microspheres in the desired size range are described. 相似文献
116.
117.
K. V. Sharma K. V. Suryanarayana P. K. Sarma V. Dharma Rao T. Subramanyam 《Heat and Mass Transfer》2010,46(6):665-673
Deaerator is used to remove oxygen from boiler feed-water. Experiments with deaerator indicate that the droplet diameter decreases
with increasing the mass flow rate of water and the increasing deaerator pressure leads to increase in heat and mass transfer
coefficients. The mass transfer coefficients are found to increase with increasing the deaerator pressure, the independent
of length and the oxygen concentration in inlet water. 相似文献
118.
G. Saravanan M. V. Suryanarayana N. Balaji N. Someswararao N. M. Sekhar 《Chromatographia》2008,67(1-2):179-182
This paper describes the development of a stability-indicating high-performance liquid chromatographic (HPLC) method for quantitative
determination of topotecan hydrochloride, a semi-synthetic derivative of camptothecin and anti-tumor drug with topoisomerase
I-inhibitory activity. Chromatographic separation was achieved on a C18 column with a mixture of phosphate buffer and acetonitrile as mobile phase. The method was validated for linearity, accuracy,
precision, and robustness. Forced degradation studies were performed by treating bulk samples of topotecan hydrochloride with
acid (0.5 M hydrochloric acid), base (0.5 M sodium hydroxide), oxidizing agent (10% v/v hydrogen peroxide), heat (60 °C), and UV light (254 nm). 相似文献
119.
Bindu KH Reddy IU Anjaneyulu Y Suryanarayana MV 《Journal of chromatographic science》2012,50(4):368-372
A simple, linear gradient, rapid, precise and stability-indicating analytical method was developed for the estimation of related substances and degradants of paliperidone API and tablets. The chromatographic separations were achieved using an Acquity ultra-performance liquid chromatograph (BEH 100 mm, 2.1 mm, 1.7 μm C-18 column) employing 0.01 M potassium dihydrogen phosphate buffer (pH 2.0) as mobile phase A and acetonitrile-water (9:1) as mobile phase B. A linear gradient (mobile phase A, mobile phase B in the ratio of 84:16) with a 0.45 mL/min flow rate was chosen. All six impurities were eluted within five minutes of run time. The column temperature was maintained at 25 °C and a detector wavelength of 238 nm was employed. Paliperidone was exposed to thermal, photolytic, hydrolytic and oxidative stress conditions. The stressed samples were analyzed by the proposed method. Considerable degradation of the analyte was observed when it was subjected to oxidative conditions and impurity F was found to be the major degradant. Peak homogeneity data of paliperidone obtained by photodiode array (PDA) detection demonstrated the specificity of the method in the presence of degradants. The method was validated with respect to linearity, precision, accuracy, ruggedness, robustness, limit of detection and limit of quantification. 相似文献
120.
Reddy DC Bapuji AT Rao VS Himabindu V Ravinder S 《Journal of chromatographic science》2012,50(6):538-546
A rapid and high sensitive liquid chromatography-tandem mass spectrometry (LC-MS-MS) method was developed and validated for the quantification of zolpidem in human EDTA plasma using ondansetron (IS) as an internal standard. The analyte and IS were extracted from human plasma using ethyl acetate and separated on a C18 column (Inertsil-ODS, 5 μm, 4.6 × 50 mm) interfaced with a triple quadrupole tandem mass spectrometer. The mobile phase, which consisted of a mixture of methanol and 20 mM ammonium formate (pH 5.00 ± 0.05; 75:25 v/v), was injected at a flow rate of 0.40 mL/min. The retention times of zolpidem and IS were approximately 1.76 and 1.22. The LC run time was 3 min. The electrospray ionization source was operated in positive ion mode. Multiple reaction monitoring used the [M + H](+) ions m/z 308.13 → 235.21 for zolpidem and m/z 294.02 → 170.09 for the ondansetron, respectively. Five freeze-thaw cycles was established at -20 and -70°C.The linearity of the response/concentration curve was established in human EDTA plasma over the concentration range 0.10-149.83 ng/mL. The lower detection limit [(signal-to-noise (S/N) > 3] was 0.04 ng/mL and the lower limit of quantification (S/N > 10) was 0.10 ng/mL. This LC-MS-MS method was validated with intra-batch and inter-batch precision of 0.52-8.66.The intra-batch and inter-batch accuracy was 96.66-106.11. Recovery of zolpidem in human plasma was 87.00% and IS recovery was 81.60%. The primary pharmacokinetic parameters were T(max) (h) = (1.25 ± 0.725), C(max) (ng/mL) (127.80 ± 34.081), AUC(0→t), = (665.37 ± 320.982) and AUC(0→∞), 686.03 ± 342.952, respectively. 相似文献