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991.
Sanae Abrakhi Sébastien Péralta Sophie Cantin Odile Fichet Dominique Teyssié 《Colloid and polymer science》2012,290(5):423-434
The photochemical behavior of photosensitive materials obtained by spin-coating or network synthesis of a cellulosic polymer
bearing photo-cross-linkable cinnamate groups was investigated. First, cinnamate groups were grafted on a cellulose acetate
butyrate polymer, with different grafting densities. The photochemical properties of the polymers were studied in solution
by UV–visible and 1H NMR spectroscopy. Then spin-coated films and networks were prepared and characterized as a function of the number of cinnamate
groups per cellulosic unit. The water-wetting properties of both surfaces were studied by dynamic contact angle measurements,
before and after photoirradiation, and subsequent heating. The surfaces obtained by the two methods have significantly different
behaviors that can be assigned to the distinct photochemical pathways of the cinnamate groups upon irradiation depending on
the sample preparation. Indeed, dimerization reaction is evidenced as the main process in the spin-coated films while the
expected isomerization is predominant at the surface of the polymer networks. 相似文献
992.
Sedimentation equilibria of ferrofluids: I. Analytical centrifugation in ultrathin glass capillaries
Analytical centrifugation is used for the first time to measure sedimentation equilibrium concentration profiles of a ferrofluid, a concentrated colloidal dispersion of strongly absorbing magnetic nanoparticles. To keep the optical absorbance from becoming too strong, the optical path length is restricted to 50 μm by placing the dispersion in a flat glass capillary. The concentration profile is kept from becoming too steep, despite the relatively high buoyant mass of the nanoparticles, by making novel use of a low-velocity analytical centrifuge that was not designed to measure equilibrium profiles. The experimental approach is validated by comparison with profiles obtained using an analytical ultracentrifuge. At concentrations of a few hundred grams per liter, the osmotic pressures calculated from the equilibrium profiles are lower than expected for hard spheres or non-interacting particles, due to magnetic dipolar interactions. By following the presented experimental approach, it will now also be possible to characterize the interparticle interactions of other strongly absorbing colloidal particles not studied before by analytical centrifugation. 相似文献
993.
Andriy Fedorov Reinhard Beichel Jayashree Kalpathy-Cramer Julien Finet Jean-Christophe Fillion-Robin Sonia Pujol Christian Bauer Dominique Jennings Fiona Fennessy Milan Sonka John Buatti Stephen Aylward James V. Miller Steve Pieper Ron Kikinis 《Magnetic resonance imaging》2012
Quantitative analysis has tremendous but mostly unrealized potential in healthcare to support objective and accurate interpretation of the clinical imaging. In 2008, the National Cancer Institute began building the Quantitative Imaging Network (QIN) initiative with the goal of advancing quantitative imaging in the context of personalized therapy and evaluation of treatment response. Computerized analysis is an important component contributing to reproducibility and efficiency of the quantitative imaging techniques. The success of quantitative imaging is contingent on robust analysis methods and software tools to bring these methods from bench to bedside. 相似文献
994.
The aim of our study was to validate a Pediatric Voice Symptom Questionnaire (PVSQ) presenting with a parallel form for children and their parents. The items of the questionnaire were elaborated from the results of structured interviews with dysphonic children (DP) and normophonic children (NP) and their mothers and were tested for feasibility in a pilot study involving 42 normophonic children aged 5-13 years. The items were then administered in a test-retest mode to 333 children and their parents (154 boys and 179 girls with a mean age of 9 years, standard deviation: 1.8); 45 consulting DP, 34 nonconsulting dysphonics (NcDP), 163 NP, and 91 others. Classical statistical analyses and an item response modeling approach were used to analyze the results. High internal consistency and good test-retest stability were found. Significant differences between total score of the NP, DP, and NcDP groups were observed both in the children and the parents and also between parental and child score for the NP and NcDP groups (P<0.001-P=0.014). Correlations between child and parental scores were found only in the DP groups (r=0.478; P<0.001). Based on our results, the PVSQ is a valid and reliable instrument for the autoevaluation of dysphonia in the child population. 相似文献
995.
Cottineau T Albrecht A Janowska I Macher N Bégin D Ledoux MJ Pronkin S Savinova E Keller N Keller V Pham-Huu C 《Chemical communications (Cambridge, England)》2012,48(9):1224-1226
Novel transparent 1D-TiO(2)/few-layer graphene electrodes are realised by the anodic growth of vertically aligned TiO(2) nano-tubes on a few-layer graphene film coated on a glass substrate. 相似文献
996.
Leydier F Chizallet C Costa D Raybaud P 《Chemical communications (Cambridge, England)》2012,48(34):4076-4078
The adsorption of CO on amorphous silica-alumina (ASA) was calculated by DFT. CO appears as a probe of the electrostatic field induced by the whole surface, at the origin of a so-called vibrational Stark effect responsible for the CO frequency shifts. Br?nsted acidity of the ASA sites does not directly correlate CO frequency shifts. 相似文献
997.
While the crucial role of intrinsically disordered proteins (IDPs) in the cell cycle is now recognized, deciphering their molecular mode of action at the structural level still remains highly challenging and requires a combination of many biophysical approaches. Among them, small angle X-ray scattering (SAXS) has been extremely successful in the last decade and has become an indispensable technique for addressing many of the fundamental questions regarding the activities of IDPs. After introducing some experimental issues specific to IDPs and in relation to the latest technical developments, this article presents the interest of the theory of polymer physics to evaluate the flexibility of fully disordered proteins. The different strategies to obtain 3-dimensional models of IDPs, free in solution and associated in a complex, are then reviewed. Indeed, recent computational advances have made it possible to readily extract maximum information from the scattering curve with a special emphasis on highly flexible systems, such as multidomain proteins and IDPs. Furthermore, integrated computational approaches now enable the generation of ensembles of conformers to translate the unique flexible characteristics of IDPs by taking into consideration the constraints of more and more various complementary experiment. In particular, a combination of SAXS with high-resolution techniques, such as x-ray crystallography and NMR, allows us to provide reliable models and to gain unique structural insights about the protein over multiple structural scales. The latest neutron scattering experiments also promise new advances in the study of the conformational changes of macromolecules involving more complex systems. 相似文献
998.
Moura do Carmo DF Amaral AC Machado GM Leon LL Silva JR 《Molecules (Basel, Switzerland)》2012,17(2):1819-1829
The essential oils obtained from leaves of Piper duckei and Piper demeraranum by hydrodistillation were analyzed by gas chromatography-mass spectrometry. The main constituents found in P. demeraranum oil were limonene (19.3%) and β-elemene (33.1%) and in P. duckei oil the major components found were germacrene D (14.7%) and trans-caryophyllene (27.1%). P. demeraranum and P. duckei oils exhibited biological activity, with IC(50) values between 15 to 76 μg mL(-1) against two Leishmania species, P. duckei oil being the most active. The cytotoxicity of the essential oils on mice peritoneal macrophage cells was insignificant, compared with the toxicity of pentamidine. The main mono- and sesquiterpene, limonene (IC(50) = 278 μM) and caryophyllene (IC(50) = 96 μM), were tested against the strains of Leishmania amazonensis, and the IC(50) values of these compounds were lower than those found for the essential oils of the Piper species. The HET-CAM test was used to evaluate the irritation potential of these oils as topical products, showing that these oils can be used as auxiliary medication in cases of cutaneous leishmaniasis, with less side effects and lower costs. 相似文献
999.
Lateral profiles of the electron probe of scanning transmission electron microscopy (STEM) were simulated at different vertical positions in a micrometers-thick carbon sample. The simulations were carried out using the Monte Carlo method in CASINO software. A model was developed to fit the probe profiles. The model consisted of the sum of a Gaussian function describing the central peak of the profile and two exponential decay functions describing the tail of the profile. Calculations were performed to investigate the fraction of unscattered electrons as a function of the vertical position of the probe in the sample. Line scans were also simulated over gold nanoparticles at the bottom of a carbon film to calculate the achievable resolution as a function of the sample thickness and the number of electrons. The resolution was shown to be noise limited for film thicknesses less than 1 μm. Probe broadening limited the resolution for thicker films. The validity of the simulation method was verified by comparing simulated data with experimental data. The simulation method can be used as quantitative method to predict STEM performance or to interpret STEM images of thick specimens. 相似文献
1000.
Davide Valenti Giovanni Denaro Dominique Persano Adorno Nicola Pizzolato Salvatore Zammito Bernardo Spagnolo 《Central European Journal of Physics》2012,10(3):560-567
Polymer translocation through the nanochannel is studied by means of a Monte Carlo approach, in the presence of a static or
oscillating external electric voltage. The polymer is described as a chain molecule according to the two-dimensional “bond
fluctuation model”. It moves through a piecewise linear channel, which mimics a nanopore in a biological membrane. The monomers
of the chain interact with the walls of the channel, modelled as a reflecting barrier. We analyze the polymer dynamics, concentrating
on the translocation time through the channel, when an external electric field is applied. By introducing a source of coloured
noise, we analyze the effect of correlated random fluctuations on the polymer translocation dynamics. 相似文献