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排序方式: 共有271条查询结果,搜索用时 218 毫秒
101.
Madhavan?Jaccob Gopalan?RajaramanEmail author Federico?TottiEmail author 《Theoretical chemistry accounts》2012,131(3):1150
Abounding potential technological applications is one of the many reasons why adsorption of aliphatic thiols on gold surface
is a subject of intense research by many research groups. Understanding and exploring the nature of adsorbed species, the
site of adsorption and the nature of interaction between adsorbed species and the gold surface using experimental and theoretical
investigations is an active area of pursuit. However, despite a large number of investigations to understand the atomistic
structures of thiols on Au(111), some of the basic issues are still unaddressed. For instance, there is still no clear information
about the mechanism of adsorption of alkylthiol on gold surface. Furthermore, the reactivity and mechanism of adsorption of
alkylthiol is likely to differ when gold adatoms and/or vacancies in the gold layers are considered. In this work, we have
tackled these issues by computing the stationary states involved in the thiols adsorption in order to shed light on the kinetics
aspects of adsorption process. In this respect, we have considered a variety of thiols into consideration such as methylthiol,
dimethylsulfide, dimethyldisulfide, thioacetates, and thiocyanates. We have also considered the cleavage mechanism in the
clean and the reconstructed surface scenario and the structure, energetics and spin densities have been computed using electronic
structure calculations. For all the studied cases, an homolytic cleavage of CH3S–X (X = H, CH3, SCH3, CN, and COCH3) bond has been found to occur upon adsorption on the gold surface. 相似文献
102.
S Sinhababu RK Siwatch G Mukherjee G Rajaraman S Nagendran 《Inorganic chemistry》2012,51(17):9240-9248
Fluorination of aminotroponiminate (ATI) ligand-stabilized germylene monochloride [(t-Bu)(2)ATI]GeCl (1) with CsF gave the aminotroponiminatogermylene monofluoride [(t-Bu)(2)ATI]GeF (2). Oxidative addition reaction of compound 2 with elemental sulfur and selenium led to isolation of the corresponding germathioacid fluoride [(t-Bu)(2)ATI]Ge(S)F (3) and germaselenoacid fluoride [(t-Bu)(2)ATI]Ge(Se)F (4), respectively. Similarly, reaction of aminotroponiminatogermylene monochloride [(i-Bu)(2)ATI]GeCl (9) with elemental sulfur and selenium gave the aminotroponiminatogermathioacid chloride [(i-Bu)(2)ATI]Ge(S)Cl (11) and aminotroponiminatogermaselenoacid chloride [(i-Bu)(2)ATI]Ge(Se)Cl (12), respectively. Compound 9 has been prepared through a multistep synthetic route starting from 2-(tosyloxy)tropone 5. All compounds (2-4 and 6-12) were characterized through the multinuclear NMR spectroscopy, and single-crystal X-ray diffraction studies were performed on compounds 2, 4, and 8-12. The germaselenoacid halide complexes 4 and 12 showed doublet (-142.37 ppm) and singlet (-213.13 ppm) resonances in their (77)Se NMR spectra, respectively. Germylene monohalide complexes 2 and 9 have a germanium center in distorted trigonal pyramidal geometry, whereas a distorted tetrahedral geometry is seen around the germanium center in germaacid halide complexes 4, 11, and 12. The length of the Ge═E bond in germathioacid chloride (11) and germaselenoacid halide (4 and 12) complexes is 2.065(1) and 2.194(av) ?, respectively. Theoretical studies (based on the DFT methods) on complexes 4, 11, and 12 reveal the nature of the Ge═E multiple bond in these germaacid halide complexes with computed Wiberg bond indices (WBI) being 1.480, 1.508, and 1.541, respectively. 相似文献
103.
Chung CY Wen TC Gopalan A 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2004,60(3):585-593
Poly(1-napthylamine) (PNPA) was modified by incorporation of diphenylamine (DPA) to result copolymer film on the indium tin oxide (ITO) coated glass electrode using cyclic voltammetry. Detailed static and dynamic UV-Vis spectroelectrochemical studies were performed on the copolymer films to identify the electrochromic sites corresponding to individual DPA and NPA units. Absorbance-wavelength-potential (AWP) profiles were constructed from the dynamic spectroelectrochemical results to infer the electrochromic sites. The advantages of using AWP profile in the analysis of electrochromic sites are discussed. 相似文献
104.
This paper deals with the costn–benefit analysis of a cold standby system composed of n identical repairable units, subject to slow switch. Two models of system functioning are studied in this paper. In model 1, the repair time of a unit is assumed to follow exponential distribution and the other time distributions as arbitrary, while in model 2, the repair time of a unit is assumed to be arbitrarily distributed and the other time distributions follow exponential law. For both the models, the system characteristics, namely (i) the expected upn–time of the system during the period (O,t] (ii) the expected busyn–period of the repair facility during the period (0,t] and (iii) the expected time the units spend in the switchover/installation state during the period (O,t] are studied by identifying the system a t suitable regeneration epochs. The cost-benefit analysis is carried out using these characteristics 相似文献
105.
Harish Gopalan 《International Journal of Computational Fluid Dynamics》2013,27(3):285-290
‘Stream function as a coordinate approach’ (SFC) combined with compact high-order finite difference schemes has been developed and applied to aeroacoustics and unsteady aerodynamics problems. Straightforward implementation of SFC creates coarse grids at the vicinity of stagnation points that smears high-order numerical computations. Grid clustering is employed to resolve coarse grid near stagnations points. The agreement between numerical results and particle image velocimetry (PIV) measurements for flapping airfoil shows the robustness of the current approach for performing high-order computations. 相似文献
106.
E. Veena Gopalan K.A. Malini D. Sakthi Kumar M.R. Anantharaman 《Journal of magnetism and magnetic materials》2009,321(8):1092-1099
Mn1−xZnxFe2O4 nanoparticles (x=0-1) were synthesized by wet chemical co-precipitation techniques. X-ray diffraction, transmission electron microscopy and high-resolution transmission electron microscopy were effectively utilized to investigate the different structural parameters. The elemental analysis was conducted using energy-dispersive spectrum and inductively coupled plasma analysis. The magnetic properties such as magnetization and coercivity were measured using vibrating sample magnetometer. The observed magnetization values of the nanoparticles were found to be lower compared to the bulk counterpart. The magnetization showed a gradual decrease with zinc substitution except for a small increase from x=0.2 to 0.3. The Curie temperature was found to be enhanced in the case of ferrites in the nanoregime. The variation in lattice constant, reduced magnetization values, variation of magnetization with zinc substitution, the presence of a net magnetic moment for the zinc ferrite and the enhancement in Curie temperature in Mn1−xZnxFe2O4 all provide evidence to the existence of a metastable cation distribution together with possible surface effects at the nanoregime. 相似文献
107.
Mohammad Asadikiya Yuexing Zhu Srikanth Gopalan Yu-cheng Chuang Ping-chun Tsai Ralph Nicolai Nasara Shih-kang Lin Yu Zhong 《Ionics》2018,24(3):707-713
The Li4Ti5O12 is applied in lithium ion batteries as anode material, which can be synthesized by various synthesis techniques. In this study, the molten salt synthesis technique at low temperatures, i.e. 350 °C, was applied to synthesize Li4Ti5O12. Surprisingly, the Li4Ti5O12 was not formed according to XRD analysis, which raised question about the stability range of Li4Ti5O12. To investigate the stability of Li4Ti5O12 at low temperatures, the high-temperature calcined Li4Ti5O12 powder was equilibrated in the LiCl-KCl eutectic salt at 350 °C. The result of experiment revealed that the Li4Ti5O12 is not decomposed. Results of ab initio calculations also indicated that the Li4Ti5O12 phase is a stable phase at 0 K. The products of molten salt synthesis technique were then annealed at 900 °C, which resulted in the Li4Ti5O12 formation. It was concluded that the Li4Ti5O12 is a stable phase at low temperatures and the reasons for not forming the Li4Ti5O12 by molten salt technique at low temperature are possibly related to activation energy and kinetic barriers. The Li4Ti5O12 formation energy is also very small, due to the results of ab initio calculations. 相似文献
108.
Thangaraj Arasakumar Sadasivam Mathusalini Athar Ata Ramasamy Shankar Subashini Gopalan Krishnasamy Lakshmi Pandiyarajan Sakthivel Palathurai Subramaniam Mohan 《Molecular diversity》2017,21(1):37-52
A series of 4-quinolone-3-carboxylic acid-containing spirooxindole-pyrrolidine derivatives was synthesized via multicomponent 1,3-dipolar cycloaddition reactions of azomethine ylides with new (E)-4-oxo-6-(3-phenyl-acryloyl)-1,4-dihydroquinoline-3-carboxylic acids in good yields with high regioselectivity. The cycloadducts were characterized by analytical and spectral data including \(^{1}\hbox {H}\), \(^{13}\hbox {C}\), 2D NMR and mass spectroscopy. The structure of one of the compounds (8a) was investigated theoretically by computational techniques. DFT studies support the proposed mechanism for this cycloaddition reaction. Furthermore, antibacterial activities of the new compounds were evaluated against Gram-positive and Gram-negative bacterial strains. Compounds 8f, 8m and 8p showed potent inhibition activities against selected bacteria. The in vitro cytotoxicity of spirooxindole derivatives (8a–r) was evaluated against MCF-7 breast cancer cell line. Among the various compounds tested, compound 8f \((\hbox {IC}_{50} = 18.35~\upmu \hbox {M})\) showed significant cytotoxic activity compared to the standard drug doxorubicin \((\hbox {IC}_{50 }= 15.00~\upmu \hbox {M})\). 相似文献
109.
A. K. Bandyopadhyay P. C. Ray V. Gopalan 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,65(4):525-531
Ferroelectric materials, such as lithium niobate, show interesting non-linear hysteresis behavior that can be explained by
a dynamical system analysis. By using variational principle, a non-linear Klein-Gordon (K-G) equation is derived for lithium
niobate type of uniaxial ferroelectrics involving various types of energy, which was not considered previously to construct
the Hamiltonian. This leads to soliton solutions under different conditions of soliton velocity. The critical value of the
(dimensional) effective electric field has been estimated to be 54–58 kV/cm for lithium niobate depending on the impurity
content in these type inhomogeneous ferroelectrics. Beyond this critical field, there is no existence of solitons. This critical
field is related to a break-up mechanism of Landau-Ginzburg two-well potential to a single well, as the driving force is increased. 相似文献
110.
Part A.—Steady viscous incompressible flow in a rotating coaxial cylindrical annulus with suction and injection is studied. The unsteady flow is also considered. Part B.—An exact solution for temperature distribution at different constant wall temperatures is obtained. It is assumed that the rate of injection at the inner wall equals the rate of suction at the outer wall. 相似文献