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排序方式: 共有195条查询结果,搜索用时 15 毫秒
91.
92.
Annemieke van Dam Janina C. V. Schwarz Judith de Vos Dr. Maria Siebes Dr. Titia Sijen Prof. Ton G. van Leeuwen Prof. Maurice C. G. Aalders Dr. Saskia A. G. Lambrechts 《Angewandte Chemie (International ed. in English)》2014,53(24):6272-6275
No forensic method exists that can reliably estimate the age of fingermarks found at a crime scene. Information on time passed since fingermark deposition is desired as it can be used to distinguish between crime related and unrelated fingermarks and to support or refute statements made by the fingermark donors. We introduce a non‐contact method that can estimate the age of fingermarks. Fingermarks were approached as protein–lipid mixtures and an age‐estimation model was build based on the expected protein and lipid oxidation reactions. Two measures of oxidation are required from the fingermark to estimate its age: 1) the relative amount of fluorescent oxidation products 2) the rate at which these products are formed. Fluorescence spectroscopy was used to obtain these measures. We tested the method on 44 fingermarks and were able to estimate the age of 55 % of the male fingermarks, up to three weeks old with an uncertainty of 1.9 days. 相似文献
93.
Quoc Cuong Ton Michael Bolte Ernst Egert 《Acta Crystallographica. Section C, Structural Chemistry》2014,70(9):912-919
The crystal structures of eight benzoylhydrazones with different substituents have been investigated, namely 1‐benzoyl‐2‐(propan‐2‐ylidene)hydrazone, C10H12N2O, (I), 1‐benzoyl‐2‐(1‐cyclohexylethylidene)hydrazone, C15H20N2O, (II), 1‐benzoyl‐2‐[1‐(naphthalen‐2‐yl)ethylidene]hydrazone, C19H16N2O, (III), 1‐benzoyl‐2‐(1‐cyclohexylbenzylidene)hydrazone, C20H22N2O, (IV), 1‐benzoyl‐2‐(1‐phenylbenzylidene)hydrazone, C20H16N2O, (V), 1‐benzoyl‐2‐[1‐(4‐chlorophenyl)benzylidene]hydrazone, C20H15ClN2O, (VI), 1‐benzoyl‐2‐(4‐hydroxybenzylidene)hydrazone methanol monosolvate, C14H12N2O2·CH3OH, (VII), and 1‐benzoyl‐2‐(1,1‐diphenylpropan‐2‐ylidene)hydrazone, C22H20N2O, (VIII). The ten molecules in the eight crystal structures [there are two independent molecules in the structures of (V) and (VI)] show similar conformations and hydrogen‐bonding patterns. The C=N—NH—C=O group is planar, but the plane of the phenyl ring of the benzoyl group is rotated by about 30° with respect to that of the keto group [except for (IV), where the groups are coplanar]. Only in the amide group of (VIII) is the N—H group syn to the C=O bond, whereas the seven other compounds exhibit the anti conformation. Unless prevented by steric hindrance, N—H...O hydrogen bonds help to stabilize the crystal structure, which leads to infinite chains or dimers depending upon the molecular conformation. The molecular packing is supported by intermolecular C—H...O interactions. In the crystal structure of (VII), the methanol solvent molecule participates in two strong hydrogen bonds and two weak C—H...O interactions, thus acting as a link between the molecular chains. 相似文献
94.
Sigrid Pieters Wouter Saeys Tom Van den Kerkhof Mohammad Goodarzi Mario Hellings Thomas De Beer Yvan Vander Heyden 《Analytica chimica acta》2013
Owing to spectral variations from other sources than the component of interest, large investments in the NIR model development may be required to obtain satisfactory and robust prediction performance. To make the NIR model development for routine active pharmaceutical ingredient (API) prediction in tablets more cost-effective, alternative modelling strategies were proposed. They used a massive amount of prior spectral information on intra- and inter-batch variation and the pure component spectra to define a clutter, i.e., the detrimental spectral information. This was subsequently used for artificial data augmentation and/or orthogonal projections. The model performance improved statistically significantly, with a 34–40% reduction in RMSEP while needing fewer model latent variables, by applying the following procedure before PLS regression: (1) augmentation of the calibration spectra with the spectral shapes from the clutter, and (2) net analyte pre-processing (NAP). The improved prediction performance was not compromised when reducing the variability in the calibration set, making exhaustive calibration unnecessary. Strong water content variations in the tablets caused frequency shifts of the API absorption signals that could not be included in the clutter. Updating the model for this kind of variation demonstrated that the completeness of the clutter is critical for the performance of these models and that the model will only be more robust for spectral variation that is not co-linear with the one from the property of interest. 相似文献
95.
Joyce Wei Wei Chang Thi My Uyen Ton Philip Wai Hong Chan 《Chemical record (New York, N.Y.)》2011,11(6):331-357
Catalytic insertion or addition of a metal‐imido/nitrene species, generated from reaction of a transition‐metal catalyst with iminoiodanes, to C? H and C?C bonds offers a convenient and atom economical method for the synthesis of nitrogen‐containing compounds. Following this groundbreaking discovery during the second half of the last century, the field has received an immense amount of attention with a myriad of impressive metal‐mediated methods for the synthesis of amines and aziridines having been developed. This review will cover the significant progress made in improving the efficiency, versatility and stereocontrol of this important reaction. This will include the various iminoiodanes, their in situ formation, and metal catalysts that could be employed and new ligands, both chiral and non‐chiral, which have been designed, as well as the application of this functional group transformation to natural product synthesis and the preparation of bioactive compounds of current therapeutic interest. DOI 10.1002/tcr.201100018 相似文献
96.
Nguyen VD Akca BI Wörhoff K de Ridder RM Pollnau M van Leeuwen TG Kalkman J 《Optics letters》2011,36(7):1293-1295
We designed and fabricated an arrayed-waveguide grating (AWG) in silicon oxynitride as a spectrometer for spectral domain optical coherence tomography (SD-OCT). The AWG has a footprint of only 3.0 cm × 2.5 cm, operates at a center wavelength of 1300 nm, and has 78 nm free spectral range. OCT measurements are performed that demonstrate imaging up to a maximum depth of 1 mm with an axial resolution of 19 μm, both in agreement with the AWG design parameters. Using the AWG spectrometer combined with a fiber-based SD-OCT system, we demonstrate cross-sectional OCT imaging of a multilayered scattering phantom. 相似文献
97.
98.
In memoriam: N.G. de Bruijn. 相似文献
99.
Bui An Ton 《Numerical Functional Analysis & Optimization》2013,34(9-10):983-1001
The existence of a closed loop control problem for quasi-variational inequalities is established. Feedback laws are given. 相似文献
100.
In studying methods for the ab-initio calculation of Van der Waals interactions which can be extended to larger molecules, we have tested the Valence Bond scheme on the He2 system. This method looks promising, as it appears to yield in one consistent formalism both the attractive dipole—dipole terms and the repulsive exchange terms with reasonable accuracy, using only a simple orbital basis and a very small number of VB structures. 相似文献