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991.
Roelf J Cruz-Rizzolo Miguel AX De Lima Edilson Ervolino José A de Oliveira Claudio A Casatti 《BMC neuroscience》2011,12(1):6
Background
According to several lines of evidence, the great expansion observed in the primate prefrontal cortex (PfC) was accompanied by the emergence of new cortical areas during phylogenetic development. As a consequence, the structural heterogeneity noted in this region of the primate frontal lobe has been associated with diverse behavioral and cognitive functions described in human and non-human primates. A substantial part of this evidence was obtained using Old World monkeys as experimental model; while the PfC of New World monkeys has been poorly studied. 相似文献992.
Nowadays, the synthetic dyes (as erythrosine, ponceau and tartrazina) and natural colourants (as annatto, paprika, curcuma and anthocyanin) are indispensable in the food, pharmaceutical and cosmetics applications. However, the use of natural colourant has been considered safer for human consumption then synthetic dye. For practical applications of the coloring, optical properties are important for the understanding of the characteristics of them. In this work, we presented the absorption and fluorescence spectroscopic characterizations of annatto extracts obtained from the seeds of the tropical shrub Bixa orellana L. solutions and commercial colourant. The measurements were performed in annatto extracts with acetone and chloroform in different concentrations range (3.5-52.5) μg/mL. The main carotenoids detected in annatto seeds is bixin. The numerical calculus of the absorbance spectra for cis- and trans-bixin conformation is presented. In addition, for commercial colourant, the measurements were performed for six different brands and five lots each one. Modifications in the shape of the colorific fluorescence spectra were observed and it can be an indicative of differences in the industrial methods applied for obtaining annatto pigments powders and/or the possibility of the presence of other impurities added in the commercial powders. 相似文献
993.
Tozoni JR Teles J Auccaise R Oliveira-Silva R Rivera-Ascona C Vidoto EL Guimarães AP Oliveira IS Bonagamba TJ 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2011,212(2):265-273
In this paper we present a series of high-resolution zero-field NMR spectra of the polycrystalline intermetallic compound GdAl2. The spectra were obtained with the sample at 4.2 K in the ordered magnetic state and in the absence of an external static magnetic field. Using a sequence composed of two RF pulses, we obtained up to five multi-quantum echoes for the 27Al nuclei, which were used to construct the zero-field NMR spectra. The spectra obtained from the FID observed after the second pulse and the even echoes exhibited higher resolution than the odd ones. In order to explain such behavior, we propose a model in which there are two regions inside the sample with different inhomogeneous spectral-line broadenings. Moreover, with the enhanced resolution from the FID signal, we were able to determine quadrupolar couplings with great precision directly from the respective spectra. These results were compared with those obtained from the quadrupolar oscillations of the echo signals, and showed good agreement. Similar data were also obtained from 155Gd and 157Gd nuclei. 相似文献
994.
da Silva ER de Oliveira EA Février A Nallet F Navailles L 《The European physical journal. E, Soft matter》2011,34(8):83
The structure of a complex between hydrated DNA and a non-cationic lipid is studied, including its phase diagram. The complex
is spontaneously formed by adding DNA fragments (ca. 150 base pairs in length) to non-cationic lipids and water. The self-assembly
process often leads to highly ordered structures. The structures were studied by combining X-ray scattering, fluorescence
and polarized microscopy, as well as freeze-fracture experiments with transmission electron microscopy. We observe a significant
increase of the smectic order as DNA is incorporated into the water layers of the lamellar host phase, and stabilization of
single phase domains for large amounts of DNA. The effect of confinement on DNA ordering is investigated by varying the water
content, following three dilution lines. A rich polymorphism is found, ranging from weakly correlated DNA-DNA in-plane organizations
to highly ordered structures, where transmembrane correlations lead to the formation of columnar rectangular and columnar
hexagonal superlattices of nucleotides embedded between lipid lamellae. From these observations, we suggest that addition
of DNA to the lamellar phase significantly restricts membrane fluctuations above a certain concentration and helps the formation
of the lipoplex. The alteration of membrane steric interactions, together with the appearance of interfacial interactions
between membranes and DNA molecules may be a relevant mechanism for the emergence of highly ordered structures in the concentrated
regime. 相似文献
995.
Luísa Durães Orlando Oliveira Benilde F.O. Costa António Portugal 《Journal of Physics and Chemistry of Solids》2011,72(6):678-684
Iron(III) oxyhydroxide xerogels were prepared through sol-gel technology, using iron(III) nitrate nonahydrate as precursor, ethanol as solvent and ammonium hydroxide as gelation agent. This base is used for propylene oxide substitution, which was the gelation agent in previous works. Synthesis of a gel using NH4OH as a gelation agent is an innovative result with this type of precursor, since with metal salts the addition of a strong base commonly results in precipitation of the solid. The gel synthesis was achieved by controlling the base addition time. The dried material has a residual amount of organic impurities, in contrast with the significant amount detected in xerogels prepared using propylene oxide. The iron phase prevailing in the produced xerogels can be defined as γ-FeO(OH) (lepidocrocite), according to FTIR and Mössbauer analyses. The xerogels are formed by large clusters of well connected nanocrystallites of this phase. XRD revealed a crystalline phase retained inside the iron oxyhydroxide amorphous structure, which corresponds to NH4NO3 and results from the combination of NO3− and NH4+ ions in solution. The produced xerogel has a promising composition to be an oxidizing composite for the energetic materials area. 相似文献
996.
When an acoustic wave excites a phase-shifted fiber Bragg grating (PSFBG) several properties of the transmission/reflection spectrum, such as transmission notch depth and spectral bandwidth are influenced. In this work, a study on the effect of acoustic waves in PSFBGs is presented. The results are supported by theoretical simulation and experimental work. The technique can be used for different applications, such as in a fast tunable optical notch filter. 相似文献
997.
An experimental and theoretical study of magnetization curves of Fe/Cr nanometric magnetic films grown with the structure of the quasiperiodic Fibonacci sequence is presented. Fe ferromagnetic films with interfilm exchange coupling provided by intervening Cr non-ferromagnetic layers were grown on MgO (100) by dc magnetron sputtering at 300 °C. The magnetization curves were investigated using the magneto-optical Kerr effect with the external field applied along the easy axis. The theoretical approach for this system is based on a realistic phenomenological model that includes the following contributions to free magnetic energy: Zeeman, cubic magneto-crystalline anisotropy, as well as bilinear and biquadratic exchange energies. Our numerical results are in very good agreement with the experimental data. 相似文献
998.
Garcia CC Angeli JP Freitas FP Gomes OF de Oliveira TF Loureiro AP Di Mascio P Medeiros MH 《Journal of the American Chemical Society》2011,133(24):9140-9143
Acetaldehyde is an environmentally widespread genotoxic aldehyde present in tobacco smoke, vehicle exhaust and several food products. Endogenously, acetaldehyde is produced by the metabolic oxidation of ethanol by hepatic NAD-dependent alcohol dehydrogenase and during threonine catabolism. The formation of DNA adducts has been regarded as a critical factor in the mechanisms of acetaldehyde mutagenicity and carcinogenesis. Acetaldehyde reacts with 2'-deoxyguanosine in DNA to form primarily N(2)-ethylidene-2'-deoxyguanosine. The subsequent reaction of N(2)-ethylidenedGuo with another molecule of acetaldehyde gives rise to 1,N(2)-propano-2'-deoxyguanosine (1,N(2)-propanodGuo), an adduct also found as a product of the crotonaldehyde reaction with dGuo. However, adducts resulting from the reaction of more than one molecule of acetaldehyde in vivo are still controversial. In this study, the unequivocal formation of 1,N(2)-propanodGuo by acetaldehyde was assessed in human cells via treatment with [(13)C(2)]-acetaldehyde. Detection of labeled 1,N(2)-propanodGuo was performed by HPLC/MS/MS. Upon acetaldehyde exposure (703 μM), increased levels of both 1,N(2)-etheno-2'-deoxyguanosine (1,N(2)-εdGuo), which is produced from α,β-unsaturated aldehydes formed during the lipid peroxidation process, and 1,N(2)-propanodGuo were observed. The unequivocal formation of 1,N(2)-propanodGuo in cells exposed to this aldehyde can be used to elucidate the mechanisms associated with acetaldehyde exposure and cancer risk. 相似文献
999.
Diego F.M. Oliveira Jürgen Vollmer Edson D. Leonel 《Physica D: Nonlinear Phenomena》2011,240(4-5):389-396
Some dynamical properties for a Lorentz gas were studied considering both static and time-dependent boundaries. For the static case, it was confirmed that the system has a chaotic component characterized with a positive Lyapunov exponent. For the time-dependent perturbation, the model was described using a four-dimensional nonlinear map. The behaviour of the average velocity is considered in two different situations: (i) non-dissipative and (ii) dissipative dynamics. Our results confirm that unlimited energy growth is observed for the non-dissipative case. However, and totally new for this model, when dissipation via inelastic collisions is introduced, the scenario changes and the unlimited energy growth is suppressed, thus leading to a phase transition from unlimited to limited energy growth. The behaviour of the average velocity is described using scaling arguments. 相似文献
1000.
C.M. Chaves A.L. de OliveiraN.A. de Oliveira A. Troper 《Journal of magnetism and magnetic materials》2011,323(6):881-884
Recent experimental results for the magnetic hyperfine field Bhf at the nuclei of s-p impurities such as 119Sn in intermetallic Laves phases RM2 (R=Gd, Tb, Dy, Ho, Er; M=Fe, Co) and 111Cd in R Co2, the impurity occupying a R site indicate that the ratio Bhf/μ3d exhibits different behavior when one goes from RFe2 to RCo2. In this work, we calculate these local moments and the magnetic hyperfine fields. In our model, Bhf has two contributions: one arising from the R ions, and the other arising from magnetic 3d-elements; these separate contributions allow the identification of the origin of different behavior of the ratio mentioned above. For 111Cd in RCo2 we present also the contributions for Bhf in the light rare earth Pr, Nd, Pm, Sm compounds. For the sake of comparison we apply also the model to 111Cd diluted in R Ni2. Our self-consistent magnetic hyperfine field results are in good agreement with those recent experimental data. 相似文献