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991.
Dharminder Sharma Sandeep Kumar Arun K. Shil Nitul Ranjan Guha Pralay Das 《Tetrahedron letters》2012,53(52):7044-7051
Solid supported palladium nano/microparticles were found to be active catalysts to perform mono- and β,β-double-Heck reactions. Different β-unsubstituted and substituted alkenes including acrylate, methacrylate, crotonate, styrene, acrylonitrile, and acrylamide were investigated successfully for mono- and β,β-double-Heck reactions with aryl iodide under milder reaction condition. One-pot β,β-double-Heck reaction of aryl iodides with α,β-unsaturated ester, amide, nitrile, and styrene derivatives were also performed under standard reaction conditions. Wide functional group tolerance, easy catalyst recovery, and recyclability up to twelve times without significant loss of catalytic activity added extra importance to the present process. 相似文献
992.
993.
We study a generalization of K-contact and (k, μ)-contact manifolds, and show that if such manifolds of dimensions ≥ 5 are conformally flat, then they have constant curvature +1. We also show under certain conditions that such manifolds admitting a non-homothetic closed conformal vector field are isometric to a unit sphere. Finally, we show that such manifolds with parallel Ricci tensor are either Einstein, or of zero ${\xi}$ -sectional curvature. 相似文献
994.
M. S. Raghu K. Basavaiah P. J. Ramesh Sameer A. M. Abdulrahman K. B. Vinay 《Journal of Applied Spectroscopy》2012,79(1):131-138
A sensitive, precise, and cost-effective UV-spectrophotometric method is described for the determination of pheniramine maleate
(PAM) in bulk drug and tablets. The method is based on the measurement of absorbance of a PAM solution in 0.1 N HCl at 264 nm.
As per the International Conference on Harmonization (ICH) guidelines, the method was validated for linearity, accuracy, precision,
limits of detection (LOD) and quantification (LOQ), and robustness and ruggedness. A linear relationship between absorbance
and concentration of PAM in the range of 2–40 μg/ml with a correlation coefficient (r) of 0.9998 was obtained. The LOD and
LOQ values were found to be 0.18 and 0.39 μg/ml PAM, respectively. The precision of the method was satisfactory: the value
of relative standard deviation (RSD) did not exceed 3.47%. The proposed method was applied successfully to the determination
of PAM in tablets with good accuracy and precision. Percentages of the label claims ranged from 101.8 to 102.01% with the
standard deviation (SD) from 0.64 to 0.72%. The accuracy of the method was further ascertained by recovery studies via a standard
addition procedure. In addition, the forced degradation of PAM was conducted in accordance with the ICH guidelines. Acidic
and basic hydrolysis, thermal stress, peroxide, and photolytic degradation were used to assess the stability-indicating power
of the method. A substantial degradation was observed during oxidative and alkaline degradations. No degradation was observed
under other stress conditions. 相似文献
995.
M. Chandrasekhar D.V. Sunitha N. Dhananjaya H. Nagabhushana S.C. Sharma B.M. Nagabhushana C. Shivakumara R.P.S. Chakradhar 《Journal of luminescence》2012,132(7):1798-1806
Low temperature solution combustion method was employed to synthesize Dy2O3 nanophosphors using two different fuels (sugar and oxalyl dihydrazine (ODH)). Powder X-ray diffraction confirm pure cubic phase and the estimated particle size from Scherrer's method in sugar and ODH fuel was found to be 26 and 78 nm, respectively, and are in close agreement with those obtained using TEM and W–H plot analysis. SEM micrographs reveal porous, irregular shaped particles with large agglomeration in both the fuels. An optical band gap of 5.24 eV and 5.46 eV was observed for Dy2O3 for sugar and ODH fuels, respectively. The blueshift observed in sugar fuel is attributed to the particles size effect. Thermoluminescence (TL) response of cubic Dy2O3 nanophosphors prepared by both fuels was examined using gamma and UV radiations. The thermoluminescence of sugar used samples shows a single glow peak at 377 °C for 1–4 kGy gamma irradiations. When dose is increased to 5 kGy, two more shouldered peaks were observed at 245 and 310 °C. However, in TL of ODH used samples, a single glow peak at 376 °C was observed. It is observed that TL intensity is found to be more in sugar used samples. In UV irradiated samples a single glow peak at 365 °C was recorded in both the fuels with a little variation in TL intensity. The trapping parameters were estimated by different methods and the results are discussed. 相似文献
996.
Theoretical and experimental study of the surface plasmon–polariton and guided wave plasmon polariton modes is presented for the Sapphire/Ag/Polycarbonate/Air structure. Theoretical results are obtained by solving complex multilayer eigenvalue equations as well as the reflectivity equation for this structure. It is proposed that the mode attenuation can be significantly reduced by inserting a low index dielectric buffer between the metal and the guiding dielectric layer. The dispersion and attenuation curves are generated. Both the surface plasmon and guided wave plasmon polariton modes are studied experimentally. The experimental values of the effective refractive indices agree well with the theoretical values. The electric field profiles are generated and used to examine the nature of modes. After optimization of various parameters the condition for low loss single mode guiding is obtained for the proposed structure. Effect of metal thickness on surface plasmon mode is also discussed. It is inferred that in a properly optimized plasmonic waveguide, the losses can be reduced by a factor of 4. 相似文献
997.
G Mukherjee P Singh C Ganguri S Sharma HB Singh N Goel UP Singh RJ Butcher 《Inorganic chemistry》2012,51(15):8128-8140
The synthesis and characterization of the complexes of Cu(I), Ag(I), Cu(II), and Co(II) ions with 1,2,5-selenadiazolopyridine (psd) is reported. The following complexes have been prepared: [Cu(2)(psd)(3)(CH(3)CN)(2)](2+)2(PF(6)(-)); [(CuCl)(2)(psd)(3)]; [Cu(2)(psd)(6)](2+)2(ClO(4))(-); [Ag(2)(psd)(2)](2+)2(NO(3))(-); [Ag(2)(psd)(2)](2+)2(CF(3)COO)(-); [Cu(psd)(2)(H(2)O)(3)](2+)2(ClO(4))(-)·(psd)(2); [Cu(psd)(4)(H(2)O)](2+)2(ClO(4))(-)·(CHCl(3)); [Cu(psd)(2)(H(2)O)(3)](2+)2(NO(3))(-)·(H(2)O)·(psd)(2), and [Co(psd)(2)(H(2)O)(4)](2+)2(ClO(4))(-)·(psd)(2). The electronic structure of ligand psd, in particular the bond order of Se-N bonds, has been probed by X-ray diffraction, (77)Se NMR, and computational studies. A detailed analysis of the crystal structures of the ligand and the complexes revealed interesting supramolecular assembly. The assembly was further facilitated by the presence of neutral ligands for some complexes (Cu(II) and Co(II)). The molecular structure of the ligand showed that it was present as a dimer in the solid state where the monomers were linked by strong secondary bonding Se···N interactions. The crystal structures of Cu(I) and Ag(I) complexes revealed the dinuclear nature with characteristic metallophilic interactions [M···M] (M = Cu, Ag), while the Cu(II) and Co(II) complexes were mononuclear. The presence of M···M interactions has been further probed by Atoms in Molecules (AIM) calculations. The paramagnetic Cu(II) and Co(II) complexes have been characterized by UV-vis, ESI spectroscopy, and room temperature magnetic measurements. 相似文献
998.
We extend the spin-adapted density matrix renormalization group (DMRG) algorithm of McCulloch and Gulacsi [Europhys. Lett. 57, 852 (2002)] to quantum chemical Hamiltonians. This involves using a quasi-density matrix, to ensure that the renormalized DMRG states are eigenfunctions of S?(2), and the Wigner-Eckart theorem, to reduce overall storage and computational costs. We argue that the spin-adapted DMRG algorithm is most advantageous for low spin states. Consequently, we also implement a singlet-embedding strategy due to Tatsuaki [Phys. Rev. E 61, 3199 (2000)] where we target high spin states as a component of a larger fictitious singlet system. Finally, we present an efficient algorithm to calculate one- and two-body reduced density matrices from the spin-adapted wavefunctions. We evaluate our developments with benchmark calculations on transition metal system active space models. These include the Fe(2)S(2), [Fe(2)S(2)(SCH(3))(4)](2-), and Cr(2) systems. In the case of Fe(2)S(2), the spin-ladder spacing is on the microHartree scale, and here we show that we can target such very closely spaced states. In [Fe(2)S(2)(SCH(3))(4)](2-), we calculate particle and spin correlation functions, to examine the role of sulfur bridging orbitals in the electronic structure. In Cr(2) we demonstrate that spin-adaptation with the Wigner-Eckart theorem and using singlet embedding can yield up to an order of magnitude increase in computational efficiency. Overall, these calculations demonstrate the potential of using spin-adaptation to extend the range of DMRG calculations in complex transition metal problems. 相似文献
999.
Seerat Fatima Anindra Sharma Rahul Sharma Rama P. Tripathi 《Journal of heterocyclic chemistry》2012,49(3):600-606
One‐pot economical and efficient synthesis of multifunctional 5H‐thiazolo[3,2‐a]pyrimidines by the reaction of 4‐aryl dihydrothiopyrimidines with propargyl bromide in the presence of inorganic base has been reported in very short time. 相似文献
1000.
A mild, efficient, and expeditious method has been developed for the synthesis of spiro-hexahydropyrimidine derivatives via a three-component, one-pot cyclocondensation reaction of aromatic amines, formaldehyde, and cyclic ketones in 4-6 h using In(OTf)3 as Lewis acid catalyst for the first time. The reaction involving creation of six new covalent bonds was efficiently promoted by 10 mol % In(OTf)3 and the catalyst could be recovered easily after the reaction and reused without any loss of its catalytic activity. The advantageous features of this methodology are high atom-economy, operational simplicity, shorter reaction time, and easy handling. 相似文献