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21.
The paper discusses errors and error propagation in respect of graphic methods in quantitative in situ measurements in TLC. An error of 0.3% is possible by measuring only peak height if optimal conditions are chosen. This is in good agreement with analysis done practically which gives errors in the order of 0.3–0.6%. If the peak area is evaluated using the approximation peak height × half width, the error is in the order of 0.6%, but in real experiments only 1.5% had been found. Systematic errors in determining peak heights are introduced by the time constant of the amplifiers and the recorder. 相似文献
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This systematic review and meta-analysis examined recent articles that have used the 1995 Draw-A-Scientist Checklist (DAST-C). This study was focused on the current state of students' stereotypes of scientists and the appropriateness of the DAST-C as a tool to assess these perceptions. Articles included in the review were published between 2003 and 2018, resulting in n = 30 studies. Mean results across studies are presented to describe current stereotypes of scientists, and the current format of the DAST-C is evaluated. Findings suggest that students' perceptions of scientists have largely remained consistent across time: scientists are still perceived as Caucasian, middle-aged or elderly males who wear lab coats and work indoors. However, while the DAST-C is a generally appropriate measure to assess students' perceptions of scientists, recommended revisions to the DAST-C could assist in capturing more modern scientist stereotypes and culturally bound perceptions of scientists. 相似文献
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本文介绍了由本省省情构建的一套江西省社会发展评价指标体系,并用系统工程和计算机技术对全省11地市1988至1990年三年间的社会发展进行综合评述。 相似文献
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Xiuqiong Chen Qingmei Zhu Zhengyue Li Huiqiong Yan Qiang Lin 《Molecules (Basel, Switzerland)》2021,26(19)
On account of the rigid structure of alginate chains, the oxidation-reductive amination reaction was performed to synthesize the reductive amination of oxidized alginate derivative (RAOA) that was systematically characterized for the development of pharmaceutical formulations. The molecular structure and self-assembly behavior of the resultant RAOA was evaluated by an FT-IR spectrometer, a 1H NMR spectrometer, X-ray diffraction (XRD), thermal gravimetric analysis (TGA), a fluorescence spectrophotometer, rheology, a transmission electron microscope (TEM) and dynamic light scattering (DLS). In addition, the loading and in vitro release of ibuprofen for the RAOA microcapsules prepared by the high-speed shearing method, and the cytotoxicity of the RAOA microcapsules against the murine macrophage RAW264.7 cell were also studied. The experimental results indicated that the hydrophobic octylamine was successfully grafted onto the alginate backbone through the oxidation-reductive amination reaction, which destroyed the intramolecular hydrogen bond of the raw sodium alginate (SA), thereby enhancing its molecular flexibility to achieve the self-assembly performance of RAOA. Consequently, the synthesized RAOA displayed good amphiphilic properties with a critical aggregation concentration (CAC) of 0.43 g/L in NaCl solution, which was significantly lower than that of SA, and formed regular self-assembled micelles with an average hydrodynamic diameter of 277 nm (PDI = 0.19) and a zeta potential of about −69.8 mV. Meanwhile, the drug-loaded RAOA microcapsules had a relatively high encapsulation efficiency (EE) of 87.6 % and good sustained-release properties in comparison to the drug-loaded SA aggregates, indicating the good affinity of RAOA to hydrophobic ibuprofen. The swelling and degradation of RAOA microcapsules and the diffusion of the loaded drug jointly controlled the release rate of ibuprofen. Moreover, it also displayed low cytotoxicity against the RAW264.7 cell, similar to the SA aggregates. In view of the excellent advantages of RAOA, it is expected to become the ideal candidate for hydrophobic drug delivery in the biomedical field. 相似文献
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S. Alcaro F. Gasparrini O. Incani S. Mecucci D. Misiti M. Pierini C. Villani 《Journal of computational chemistry》2000,21(7):515-530
The main purpose of this work is the development and validation of a general scheme based on a systematic and automatic “quasi‐flexible” docking approach for studying stereoselective recognition mechanisms. To achieve our goals we explore the conformational and configurational space for small‐ or medium‐size flexible molecules in a systematic way, seeking a method that is both reasonably accurate and relatively fast from the computational point of view. In particular, we have developed a general computational protocol for the global molecular interaction evaluation (“Glob‐MolInE”) to efficiently explore the orientational and conformational space of flexible selectors and selectands used in modern chiral high‐performance liquid chromatography (HPLC); the enantioselective binding of the selector (S)‐N‐(3,5‐dinitrobenzoyl)‐leucine‐ n‐propylamide (S)‐ 1 towards the selectand N‐(2‐naphthyl)‐alanine methyl ester 2 has been studied; the global minimum obtained for the homochiral associate [S( 1 )/S( 2 )] (Pop. >99%) is very close (RMS≃0.20) to the crystallographically determined structure. © 2000 John Wiley & Sons, Inc. J Comput Chem 21: 515–530, 2000 相似文献
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H. Berger 《Crystal Research and Technology》2002,37(7):716-726
The reflection curves as measured by means of the “Ω‐Scan Method” have been simulated as exactly as possible and practicable. The contributions of the collimator function for different beam geometry and of the spectral distribution are considered. The influence of the dead time of the counting unit on the fluctuations of the used high intensities is described by computer modelling. By means of the simulated curves, the theoretical statistic errors of the method, employed to the orientation determination of quartz, can be estimated and compared to the measured ones. The statistic errors due to the intensity fluctuations were found to be dominating the measuring errors. From the simulated curves also the corrections to be applied to the measuring values of the peak positions are derived. Thus, the real physical values of the orientation coordinates can be determined. 相似文献
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Kasper Pedersen 《Random Structures and Algorithms》2009,35(1):15-41
We show that systematic scan for H‐colorings of the n‐vertex path mixes in O(log n) scans for any fixed H using block dynamics. For a restricted family of H we furthermore show that systematic scan mixes in O(log n) scans for any scan order. For completeness we show that a random update Markov chain mixes in O(nlog n) updates for any fixed H. © 2008 Wiley Periodicals, Inc. Random Struct. Alg., 2009 相似文献
30.
标定激光陀螺仪与g有关偏置可以进一步提高双轴旋转惯导的定位精度。在传统的六位置标定方法上增加四个倾斜的位置,形成一套十位置自标定算法。该算法不仅可以标定惯性器件的常值偏置,比例因数误差和失准角,还能标定陀螺仪的与g有关偏置。静态试验表明,在标定和补偿了陀螺仪与g有关偏置项后,经纬度误差(尤其是经度误差)随着时间的变化量明显减小。与传统的六位置法相比,经度误差随着时间发散速度明显降低。该自标定法在静态时至少可以提高50%的系统精度。 相似文献