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611.
N. Padmanabha Iyer T. Philip Gnanarajan Ganga Radhakrishnan 《Journal of polymer science. Part A, Polymer chemistry》2001,39(24):4236-4242
The catalysis of imidine formation between an amine‐blocked polyurethane prepolymer and bisphthalide was studied with a series of metal alkoxides, phenoxides, and organotin compounds and tertiary amines. The carbon dioxide released during the reaction was followed for monitoring of the reaction. The metal alkoxides and phenoxides catalyzed the imidine formation reaction but did not catalyze the deblocking reaction, whereas the organotin compounds and tertiary amines showed no catalytic activity in the reaction between isocyanate and phthalide. With tin catalysts, the imidine formation reaction depended on the deblocking of the blocked prepolymer, but it was independent of deblocking with amine catalysts. The resultant poly(urethane imidine) copolymers were characterized with Fourier transform infrared, 1H NMR, 13C NMR, gel permeation chromatography, and thermogravimetric analysis techniques. The thermal stability of polyurethane increased significantly with the incorporation of imidine groups. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4236–4242, 2001 相似文献
612.
Divya Tripathi 《Tetrahedron letters》2008,49(49):7012-7014
A versatile and efficient method for the enantioselective synthesis of 2,7-cis-disubstituted oxepane 1c, (+)-isolaurepan, using oxidative resolution of a secondary alcohol and highly diastereoselective Et3SiH/TMSOTf-promoted reductive cyclization of a hydroxy ketone is described. 相似文献
613.
Carbohydrate based fluorescent sensors S1 and S2 have been developed by fluorogenic dual click chemistry and are characterized by various spectroscopic techniques. Both the fluorescent probes displayed highly selective detection of Cu2+ ions by means of fluorescence quenching. The job plot experiment suggested 1:1 complexation of probes S1 and S2 with Cu2+ ions having detection limit of 6.99 μM and 7.30 μM, respectively. The binding constants for S1-Cu2+ and S2-Cu2+ complexation were evaluated to be 3.34 × 103 M−1 and 5.93 × 103 M−1, respectively. 相似文献
614.
Sathishkumar Munusamy Vivek Panyam Muralidharan Sathiyanarayanan Kulathu Iyer 《Tetrahedron letters》2017,58(6):520-523
This paper presents a methodology of oxidative cascade cyclisation of 2-aminobenzoic acids and arylaldehyde using I2 as a catalyst and an environmentally benign oxidant oxone. This method displays facile access to a diverse range of substituted aryl 4H-3,1-benzoxazin-4-ones. This synthetic methodology has many advantages such as: (1) easy availability of starting material, (2) transition metal-free condition (3) use of an environmentally benign oxidant. 相似文献
615.
Phani Motamarri Mrinal Iyer Jaroslaw Knap Vikram Gavini 《Journal of computational physics》2012,231(20):6596-6621
In the present work, we study various numerical aspects of higher-order finite-element discretizations of the non-linear saddle-point formulation of orbital-free density-functional theory. We first investigate the robustness of viable solution schemes by analyzing the solvability conditions of the discrete problem. We find that a staggered solution procedure where the potential fields are computed consistently for every trial electron-density is a robust solution procedure for higher-order finite-element discretizations. We next study the convergence properties of higher-order finite-element discretizations of orbital-free density functional theory by considering benchmark problems that include calculations involving both pseudopotential as well as Coulomb singular potential fields. Our numerical studies suggest close to optimal rates of convergence on all benchmark problems for various orders of finite-element approximations considered in the present study. We finally investigate the computational efficiency afforded by various higher-order finite-element discretizations, which constitutes the main aspect of the present work, by measuring the CPU time for the solution of discrete equations on benchmark problems that include large Aluminum clusters. In these studies, we use mesh coarse-graining rates that are derived from error estimates and an a priori knowledge of the asymptotic solution of the far-field electronic fields. Our studies reveal a significant 100–1000 fold computational savings afforded by the use of higher-order finite-element discretization, alongside providing the desired chemical accuracy. We consider this study as a step towards developing a robust and computationally efficient discretization of electronic structure calculations using the finite-element basis. 相似文献
616.
When listeners hear a target signal in the presence of competing sounds, they are quite good at extracting information at instances when the local signal-to-noise ratio of the target is most favorable. Previous research suggests that listeners can easily understand a periodically interrupted target when it is interleaved with noise. It is not clear if this ability extends to the case where an interrupted target is alternated with a speech masker rather than noise. This study examined speech intelligibility in the presence of noise or speech maskers, which were either continuous or interrupted at one of six rates between 4 and 128 Hz. Results indicated that with noise maskers, listeners performed significantly better with interrupted, rather than continuous maskers. With speech maskers, however, performance was better in continuous, rather than interrupted masker conditions. Presumably the listeners used continuity as a cue to distinguish the continuous masker from the interrupted target. Intelligibility in the interrupted masker condition was improved by introducing a pitch difference between the target and speech masker. These results highlight the role that target-masker differences in continuity and pitch play in the segregation of competing speech signals. 相似文献
617.
Akshay Ganesh Iyer Jeroen Adrianus van Oijen Johannes Hendrikas Maria ten Thije Boonkkamp Laurentius Phlippus Hendrika de Goey 《Combustion Theory and Modelling》2016,20(1):173-188
The mass-based stretch rate is used to study the response of premixed axisymmetric counterflow flames subject to an oscillating strain rate. Integral analysis is used to estimate the mass burning rate of the oscillating counterflow flames. From this study it can be concluded that the flame responds in a nonlinear manner. With an increase of the applied strain frequencies, it is found that unsteady stretch effects arising due to flame thickness variations become significant and the mass-based stretch rate is able to capture these nonlinear effects. The inclusion of these unsteady stretch effects in the mass-based stretch helps the integral analysis to predict the mass-burning rate of oscillating flames more accurately. 相似文献
618.
619.
Satish Sohal Chitral Rohan Kori Amitkumar Sharma Basantkumar Puttur Jayashree Khan Afreen A. Desle Deepali Raikuvar Kavita Korkegian Aaron Martis Elvis A. F. Iyer Krishna R. Coutinho Evans C. Parish Tanya Nandan Santosh 《Molecular diversity》2022,26(1):73-96
Molecular Diversity - N-furfuryl piperazine ureas disclosed by scientists at GSK Tres Cantos were chosen as antimycobacterial hits from a phenotypic whole-cell screen. Bioisosteric replacement of... 相似文献
620.
Crystallography Reports - Molybdenum oxide is one of the most important inorganic material, which exhibits several phases, such as MoO3, MoO2, Mo4O11, Mo5O14, etc. Among them, molybdenum trioxide... 相似文献