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171.
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173.
A measure of intensity due to the superposition of diffracted X-rays from elementary regions in the line of X-ray path has been calculated on the basis of Gaussian distribution of intensity from every element. This gives the optimum thickness for maximum intensity implicitly by the relation. Μt0=α?′(αt0)/?(αt0) where ? is the error integral and α is a characteristic of the liquid which determines the Gaussian distribution form for the particular liquid. Good agreement between the theoretical relations and the experimental values have been observed. 相似文献
174.
Biren Gohain Bornali Boruah Palash M. Saikia Robin K. Dutta 《Journal of Physical Organic Chemistry》2010,23(3):211-219
The premicellar and micelle formation behaviors of four cationic triphenylmethane dyes, viz, Pararosaniline (RN), Crystal violet (CV), Ethyl violet (EV), and Malachite green (MG), in aqueous anionic surfactant solutions of sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS), and sodium dodecyl sulfonate (SDSN) have been studied by spectral and surface tension measurements. The study was carried out within a pH range where the dyes are stable in their quinoid forms. The dyes have been found to form dye–surfactant ion pairs (DSIPs) with the surfactants, at the surfactant concentrations well below their critical micelle concentration, CMC*. The DSIPs behave like nonionic surfactants and form an air–water interfacial monolayer. The DSIPs have a lower critical micelle concentration (CMCIP), greater efficiency, and lower effectiveness than the corresponding pure surfactants. As the surfactant concentration is increased below the CMC*, the DSIPs start forming micelles of their own where the dye gets protonated and exists as a protonated dye–surfactant ion pair (PDSIP) in the ion pair micelles. As the concentration of the surfactant exceeds the CMC* of the pure surfactant, the protonation reverses gradually with the dye remaining in the micelles in solubilized form and the DSIPs in the air–water interfacial monolayer are replaced by pure surfactants. The distorted helical isomeric form (isomer B) of the dyes is favored in the PDSIPs. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
175.
D. Sen J. S. Melo J. Bahadur S. Mazumder S. Bhattacharya G. Ghosh D. Dutta S. F. D’Souza 《The European physical journal. E, Soft matter》2010,31(4):393-402
Morphological transformation during evaporation-induced self-assembly of a mixed colloidal suspension in micrometric droplets
has been investigated. It has been demonstrated that a buckling-driven shape transition of drying droplets of mixed colloidal
suspension takes place during evaporation-induced self-assembly. Further, it is also shown that the distortion modulations
get significantly amplified with enhancement in volume fraction of anisotropic soft colloidal component of the mixed colloids.
It has been argued that the reduction in elastic modulus of formed shell, at the boundary of a drying droplet, and the anisotropic
nature of one of the colloidal components facilitate the deformation process. Hierarchical structures of these assembled colloidal
grains have been probed using electron microscopy and scattering techniques. 相似文献
176.
Laser flash photolysis and an external magnetic field have been used for the study of the interaction of 4-nitroquinoline-1-oxide (4NQO) with some indole derivatives, amino acids, tyrosine and tryptophan, and model proteins, lysozyme and bovine serum albumin. In an aprotic medium, photoinduced electron transfer (PET) from indoles to 4NQO is accompanied by proton transfer from the indole moieties irrespective of the substitution at the N-1 position. For 1,2-dimethylindole, however, proton abstraction is hindered possibly due to steric effects. In a protic medium, obviously proton transfer is possible from the medium and is the dominating reaction following PET. The effect of an external magnetic field is very small for all the systems studied. This is attributed to a competition between geminate proton abstraction by the 4NQO radical anion from the partner radical cation and escape of the 4NQO radical anion to the medium followed by proton transfer. The latter process is more predominant, and the former one, which produces a small population of geminate spin-correlated radical pairs, leads to a minor field effect. Another interesting observation is the affinity of 4NQO toward the tryptophan residues in a protein environment. It is seen that PET takes place preferably from the tryptophan residues rather than from the tyrosine residues. 相似文献
177.
Traditional quantitative structure-activity relationship (QSAR) models aim to capture global structure-activity trends present in a data set. In many situations, there may be groups of molecules which exhibit a specific set of features which relate to their activity or inactivity. Such a group of features can be said to represent a local structure-activity relationship. Traditional QSAR models may not recognize such local relationships. In this work, we investigate the use of local lazy regression (LLR), which obtains a prediction for a query molecule using its local neighborhood, rather than considering the whole data set. This modeling approach is especially useful for very large data sets because no a priori model need be built. We applied the technique to three biological data sets. In the first case, the root-mean-square error (RMSE) for an external prediction set was 0.94 log units versus 0.92 log units for the global model. However, LLR was able to characterize a specific group of anomalous molecules with much better accuracy (0.64 log units versus 0.70 log units for the global model). For the second data set, the LLR technique resulted in a decrease in RMSE from 0.36 log units to 0.31 log units for the external prediction set. In the third case, we obtained an RMSE of 2.01 log units versus 2.16 log units for the global model. In all cases, LLR led to a few observations being poorly predicted compared to the global model. We present an analysis of why this was observed and possible improvements to the local regression approach. 相似文献
178.
The advanced glycation end products (AGEs) of DNA nucleobases have received little attention, perhaps due to the fact that
adenine, guanine, cytosine and thymine do not dissolve under mild pH conditions. To maintain nucleobases in solution, alkaline
pH conditions are typically required. The objectives of this investigation were twofold: to study the susceptibility of DNA
nucleobases to nonenzymatic attack by different sugars, and to evaluate the factors that influence the formation of nucleobase
AGEs at pH 12, i.e., in an alkaline environment that promotes the aldo–keto isomerization and epimerization of sugars. Varying
concentrations of adenine, guanine, thymine and cytosine were incubated over time with constant concentrations of D-glucose, D-galactose or D/L-glyceraldehyde under different conditions of temperature and ionic strength. Incubation of the nucleobases with the sugars
resulted in a heterogeneous assembly of AGEs whose formation was monitored by UV/fluorescence spectroscopy. Capillary electrophoresis
and HPLC were used to resolve the AGEs of the DNA adducts and provided a powerful tool for following the extent of glycation
in each of the DNA nucleobases. Mass spectrometry studies of DNA adducts of guanine established that glycation at pH 12 proceeded
through an Amadori intermediate. 相似文献
179.
We have studied CPT violation in neutrino oscillation considering three flavor framework with matter effect. We have constructed a new way to find the oscillation probability incorporating CPT violating terms without any approximation. Then CPT violation with atmospheric neutrinos for a magnetized iron calorimeter detector considering the muons (directly measurable with high resolution) of the charge current events has been studied for zero and nonzero θ13 values. It is found that a potential bound of δb32?6×10−24 GeV at 99% CL can be obtained with 1 Mton.year exposure of this detector; and unlike neutrino beam experiments, there is no possibility to generate ‘fake’ CPT violation due to matter effect with atmospheric neutrinos. The advantages of atmospheric neutrinos to discriminate CPT violation from CP violation and nonstandard interactions are also discussed. 相似文献
180.
In this paper we theoretically study the broadband mid-IR supercontinuum generation (SCG) in a lead-silicate microstructured fiber (the glass for simulation is SF57). The total dispersion of the fiber can be tailored by changing the core diameter of the fiber so that dispersion profiles with two zero dispersion wavelengths (ZDWs) can be obtained. Numerical simulations of the SCG process in a 4 cm long SF57 fiber/fiber taper seeded by femto-second pulses at telecommunications wavelength of 1.55 µm are presented. The results show that a fiber taper features a continuous shift of the longer zero dispersion wavelength. This extends the generated continuum to a longer wavelength region compared to fibers with fixed ZDWs. The phase-matching condition (PMC) is continuously modified in the fiber taper and the bandwidth of the generated dispersive waves (DWs) is significantly broadened. 相似文献