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321.
Chemiexcitation Efficiency of Intermolecular Electron‐transfer Catalyzed Peroxide Decomposition Shows Low Sensitivity to Solvent‐cavity Effects 下载免费PDF全文
Muhammad Khalid Sergio P. de Souza Jr. Fernando H. Bartoloni Felipe A. Augusto Wilhelm J. Baader 《Photochemistry and photobiology》2016,92(4):537-545
Intermolecular chemically initiated electron exchange luminescence (CIEEL) systems are known to possess low chemiluminescence efficiency; whereas, the corresponding intramolecular transformations are highly efficient. As the reasons for this discrepancy are not known, we report in this work our studies of the solvent‐cavity effect on the efficiency of two intermolecular CIEEL systems, the catalyzed decomposition of diphenoyl peroxide and of a relatively stable 1,2‐dioxetanone derivative, spiro‐adamantyl‐1,2‐dioxetanone. The results indicate a very low medium viscosity effect on the quantum yields of these systems, a priori not compatible with these bimolecular transformations, showing also that their low efficiency cannot be due to solvent‐cavity escape of intermediate radical ion pairs. In addition, the solvent‐cage effect on the CIEEL efficiency, after the occurrence of the initial electron transfer, proved also to be very low, indicating the intrinsic low viscosity effect on the chemiexcitation step. Therefore, it is concluded that the low efficiency of these systems is intrinsic to the chemiexcitation step and cannot be improved by medium viscosity effects, being possibly due to sterical hindrance on charge‐transfer complex formation in the initial step of the CIEEL. 相似文献
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323.
Josiney A. Souza Carlos J. Braga Barros Victor H. L. Rocha 《Mathematische Nachrichten》2016,289(10):1272-1287
The present paper is dedicated to the study of various aspects of attraction and stability for semigroup actions on topological spaces. The main purpose is to present the connections among the distinct notions of attractors and stable sets. The concept of Conley attractor is also investigated and related to the other notions of attractors. All the results are applied to the theory of control systems. 相似文献
324.
De Souza D de Toledo RA Galli A Salazar-Banda GR Silva MR Garbellini GS Mazo LH Avaca LA Machado SA 《Analytical and bioanalytical chemistry》2007,387(6):2245-2253
The use of a copper solid amalgam electrode (CuSAE) for the analytical determination of triazine herbicides (atrazine and
ametryne) instead of the conventional hanging mercury drop electrode (HMDE) is reported. The results obtained using electroanalytical
methods utilizing each of these electrodes were also compared with those provided by the HPLC technique. The results indicated
that the CuSAE electrode can be used to detect the herbicides studied, since the detection limits reached using the electrode
(3.06 μg L−1 and 3.78 μg L−1 for atrazine and ametryne, respectively) are lower than the maximum values permitted by CONAMA (Brazilian National Council
for the Environment) for wastewaters (50 μg L−1) and by the US EPA (Environmental Protection Agency of the United States) in natural water samples (10.00 μg L−1). An electroanalytical methodology employing CuSAE and square wave voltammetry (SWV) was successfully applied to the determination
of atrazine and ametryne in natural water samples, yielding good recoveries (70.30%–79.40%). This indicates that the CuSAE
provides a convenient substitute for the HMDE, particularly since the CuSAE minimizes the toxic waste residues produced by
the use of mercury in HDME-based analyses. 相似文献
325.
Pilling S Lago AF Coutinho LH de Castilho RB de Souza GG de Brito AN 《Rapid communications in mass spectrometry : RCM》2007,21(22):3646-3652
We present results on the valence level excitation, ionization and dissociation of adenine, using time-of-flight mass spectrometry and synchrotron radiation, in the vacuum ultraviolet (VUV) range of 12-21 eV. The measurements were performed using a gas-phase (Ne) harmonics filter in order to eliminate contributions from higher-order harmonics. Mass spectra were obtained using the photoelectron-photoion coincidence technique (PEPICO). The relative abundances for each ionic fragment and their mean kinetic energy release have been determined from the analysis of the corresponding peak shapes in the mass spectra. Comparison with the available photoelectron spectra and previous measurements allowed the assignment of the main features in the spectra. A discussion on the dissociative photoionization channels of this molecule has also been included. Due to our harmonics-free incident photon beam we were able to propose new appearance energy (AE) for the most important ionic channels in this energy range. The precursor ion, C(5)H(5)N(5)+, is the most abundant species (40% at 15 eV and 20% at 20 eV), which confirms the high stability of adenine upon absorption of VUV photons. We have observed other intense fragment ions such as: C(4)H(4)N(4)+, C(3)H(3)N(3) (+), C(2)H(2)N(2)+ and HCNH+. The production of the neutral HCN fragment represents up to 40% of the dissociative channels for this molecule as induced by VUV photons. 相似文献
326.
Filho NL Costa RM Marangoni F Pereira DS 《Journal of colloid and interface science》2007,316(2):250-259
Nanoparticles of octakis[3-(3-amino-1,2,4-triazole)propyl]octasilsesquioxane (ATZ-SSQ) were tested as ligands for transition-metal ions in aqueous solution with a special attention to sorption isotherms, ligand-metal interaction, and determination of metal ions in natural waters. The adsorption potential of the material ATZ-SSQ was compared with related [3(3-amino-1,2,4-triazole)propyl]silica gel (ATZ-SG). The adsorption was performed using a batchwise process and both organofunctionalized surfaces showed the ability to adsorb the metal ions from aqueous solution. The Langmuir model was used to simulate the sorption isotherms. The results suggest that the sorption of these metals on ATZ-SSQ and ATZ-SG occurs mainly by surface complexation. The equilibrium condition is reached at time lower than 3 min for ATZ-SSQ, while for ATZ-SG is only reached at time of 25 min. The maximum metal ion uptake values for ATZ-SSQ were higher than the corresponding values achieved with the ATZ-SG. In order to obtain more information on the ligand-metal interaction of the complexes on the surface of the ATZ-SSQ nanomaterial, ESR study with various degrees of copper loadings was carried out. The ATZ-SSQ was tested for the determination (in flow using a column technique) of the metal ions present in natural waters. 相似文献
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328.
G. R. dos Santos M. C. Pereira M. Olzon-Dionysio S. D. de Souza M. R. Morelli 《Hyperfine Interactions》2014,224(1-3):137-142
Synthetic flow is proposed as a modifier agent of color firing in tile ceramic mass during the sinterization process, turning the red color firing into whiteness. Therefore, the 57Fe Mössbauer spectroscopy was used to understand how the interaction of the iron element in the mechanism of color firing mass occurs in this system. The results suggest that the change of color firing can be alternatively due to two main factors: (i) diluting the hematite content in the sample because of the use of synthetic flow and (ii) part of the hematite is converted in other uncolored crystal structures, which makes the final color firing lighter. 相似文献
329.
Josepha Yohanna de Jesus Eliane Santos de Carvalho Dantas Mairim Russo Serafini Paula dos Passos Menezes Juliana Cordeiro Cardoso Ricardo Luiz Cavalcanti Albuquerque-Jr Jivaldo do Rosário Matos Juliana Ferreira de Oliveira Irwin Rose Alencar de Menezes Francilene Amaral da Silva Adriano Antunes de Souza Araújo 《Journal of Thermal Analysis and Calorimetry》2016,123(3):2003-2012
330.