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551.
AbstractA new and practical method has been developed for the synthesis of 2,4-disubstituted quinolines via one-pot three-component reaction of o-amino arylketones, aldehydes and ammonium acetate in high yields by using DDQ in CH3CN under mild conditions. Neutral conditions, atom economy, easy work-up procedures and compatible with different functional groups are the salient features of this protocol. 相似文献
552.
Dr. Vijayakumar Govindaraj Harinarayana Ungati Surendar R. Jakka Sritama Bose Prof. Dr. Govindasamy Mugesh 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(48):11180-11192
The plasma membrane regulates the transport of molecules into the cell. Small hydrophobic molecules can diffuse directly across the lipid bilayer. However, larger molecules require specific transporters for their entry into the cell. Regulating the cellular entry of small molecules and proteins is a challenging task. The introduction of halogen, particularly iodine, to small molecules and proteins is emerging to be a promising strategy to improve the cellular uptake. Recent studies reveal that a simple substitution of hydrogen atom with iodine not only increases the cellular uptake, but also regulates the membrane transport. The strong halogen-bond-forming ability of iodine atoms plays a crucial role in the transport and the introduction of iodine may provide an efficient strategy for studying membrane activity and cellular functions and improving the delivery of therapeutic agents. This Concept article does not provide a comprehensive picture of membrane transport but highlights halogen-substitution as a novel strategy for understanding and regulating the cell-membrane traffic. 相似文献
553.
Agglomeration is an issue of major concern for unmodified multi‐walled carbon nanotubes (MWNTs)‐aided polymeric composites. To overcome the above‐mentioned problem, multi‐walled carbon nanotubes (MWNTs) are modified by polycarbosilane (PCS)‐derived Silicone carbide (SiC). Acrylonitrile Butadiene Styrene (ABS)/Liquid Crystalline polymer (LCP)/MWCNT nanocomposites are prepared through melt blending in a twin screw extruder. X‐Ray Diffraction (XRD) studies authenticate the creation of ß‐SiC particles. Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM) studies reveal the formation of core–shell morphology involving MWNT as the core and SiC‐coated MWNT as the shell. The degree of dispersion of MWNT is far better when it has been coated with SiC. As viewed from Thermo‐gravimetric analysis (TGA), the thermal stability is substantially increased in SiC‐aided nanocomposite in comparison to ABS/LCP/unmodified CNT blend. Glass transition temperature as well as mechanical properties are improved significantly (in the presence of SiC‐coated MWNT) as a result of homogeneous dispersion exhibited by MWNT. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
554.
Rajeswari Yogamalar Vellusamy Mahendran Ramasamy Srinivasan Dr. Ali Beitollahi R. Pradeep Kumar Dr. Arumugam Chandra Bose Dr. Ajayan Vinu 《化学:亚洲杂志》2010,5(11):2379-2385
The preparation of needle‐shaped SnO2 nanocrystals doped with different concentration of nickel by a simple sol–gel chemical precipitation method is demonstrated. By varying the Ni‐dopant concentration from 0 to 5 wt %, the phase purity and morphology of the SnO2 nanocrystals are significantly changed. Powder XRD results reveal that the SnO2 doped with a nickel concentration of up to 1 wt % shows a single crystalline tetragonal rutile phase, whereas a slight change in the crystallite structure is observed for samples with nickel above 1 wt %. High resolution scanning electron microscopy (HRSEM) results reveal the change in morphology of the materials from spherical, for SnO2, to very fine needle‐like nanocrystals, for Ni‐doped SnO2, annealed at different temperatures. The gas sensing properties of the SnO2 nanocrystals are significantly enhanced after the nickel doping. 相似文献
555.
We propose a mechanism where high entanglement between very distant boundary spins is generated by suddenly connecting two long Kondo spin chains. We show that this procedure provides an efficient way to route entanglement between multiple distant sites. We observe that the key features of the entanglement dynamics of the composite spin chain are well described by a simple model of two singlets, each formed by two spins. The proposed routing mechanism is a footprint of the emergence of a Kondo cloud in a Kondo system and can be engineered and observed in varied physical settings. 相似文献
556.
Abazov VM Abbott B Abolins M Acharya BS Adams M Adams T Alexeev GD Alkhazov G Alton A Alverson G Alves GA Ancu LS Aoki M Arnoud Y Arov M Askew A Asman B Atramentov O Avila C BackusMayes J Badaud F Bagby L Baldin B Bandurin DV Banerjee S Barberis E Baringer P Barreto J Bartlett JF Bassler U Beale S Bean A Begalli M Begel M Belanger-Champagne C Bellantoni L Benitez JA Beri SB Bernardi G Bernhard R Bertram I Besançon M Beuselinck R Bezzubov VA Bhat PC Bhatnagar V Blazey G Blessing S Bloom K 《Physical review letters》2010,105(19):191802
We report the results of a search for R parity violating (RPV) interactions leading to the production of supersymmetric sneutrinos decaying into eμ final states using 5.3 fb-1 of integrated luminosity collected by the D0 experiment at the Fermilab Tevatron Collider. Having observed no evidence for production of eμ resonances, we set direct bounds on the RPV couplings λ311' and λ312 as a function of sneutrino mass. 相似文献
557.
This study describes the use of chiral nature of synthetic self-assembled nanofibers for nucleation and growth of Cadmium
sulfide (CdS) nanocrystals with different sizes and shapes in room temperature. The templates are built by immobilizing a
peptide capping agent on the surface of synthetic self-assembled helical or nonhelical nanofibers and CdS nanocrystals were
allowed to grow on them. It is observed that there are differences in shapes and sizes of the nanocrystals depending on the
chiral nature of the nanofibers on which they were growing. Even the CdS nanocrystals grown on different chiral and achiral
nanofibers differ markedly in their photoluminescence properties. Thus, here we introduce a new way of using chirality of
nanofibers to nucleate and grow CdS nanocrystals of different shape, size, and optical property. 相似文献
558.
I. Bose A. K. Pal 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,77(1):139-146
The elementary excitation spectrum of the spin-
\frac12\frac{1}{2} antiferromagnetic (AFM)
Heisenberg chain is described in terms of a pair of freely propagating spinons. In the
case of the Ising-like Heisenberg Hamiltonian spinons can be interpreted as domain walls (DWs)
separating degenerate ground states. In dimension d > 1, the issue of spinons as elementary
excitations is still unsettled.
In this paper, we study two spin-
\frac12\frac{1}{2} AFM ladder models
in which the individual chains are described by the Ising-like Heisenberg
Hamiltonian. The rung exchange interactions are assumed to be pure Ising-type in
one case and Ising-like Heisenberg in the other. Using the low-energy
effective Hamiltonian approach in a perturbative formulation, we show
that the spinons are coupled in bound pairs. In the first model, the
bound pairs are delocalized due to a four-spin ring exchange term
in the effective Hamiltonian. The appropriate dynamic structure factor
is calculated and the associated lineshape is found to be almost symmetric
in contrast to the 1d case. In the case of the second model, the bound
pair of spinons lowers its kinetic energy by propagating between chains.
The results obtained are consistent with recent theoretical studies
and experimental observations on ladder-like materials. 相似文献
559.
Prediction of weld strength and seam width for laser transmission welding of thermoplastic using response surface methodology 总被引:1,自引:0,他引:1
Bappa Acherjee Dipten Misra Dipankar Bose K. Venkadeshwaran 《Optics & Laser Technology》2009,(8):956-967
In the present work, a study is made to investigate the effects of process parameters, namely, laser power, welding speed, size of the laser beam and clamp pressure, on the lap-shear strength and weld-seam width for laser transmission welding of acrylic (polymethyl methacrylate), using a diode laser system. Response surface methodology (RSM) is employed to develop mathematical relationships between the welding process parameters and the output variables of the weld joint to determine the welding input parameters that lead to the desired weld quality. In addition, using response surface plots, the interaction effects of process parameters on the responses are analyzed and discussed. The statistical software Design-Expert v7 is used to establish the design matrix and to obtain the regression equations. The developed mathematical models are tested by analysis-of-variance (ANOVA) method to check their adequacy. Finally, a comparison is made between measured and calculated results, which are in good agreement. This indicates that the developed models can predict the responses adequately within the limits of welding parameters being used. 相似文献
560.