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101.
We establish the optimality of structured replacement policies for a periodically inspected system that fails silently whenever the cumulative number of shocks, or the magnitude of a single shock it has received, exceeds a corresponding threshold. Shocks arrive according to a Markov-modulated Poisson process which represents the (controllable or uncontrollable) environment. 相似文献
102.
103.
We consider supplier diversification in an EOQ type inventory setting with multiple suppliers and binomial yields. We characterize the optimal policy for the model and show that, in this case, it does not pay to diversify, in contrast to previous results in the random yield literature. 相似文献
104.
Murat Durandurdu 《Journal of Physics and Chemistry of Solids》2008,69(11):2894-2897
An ab initio constant pressure technique is carried out to study the pressure-induced phase transition of the zinc blende AlN (aluminum nitride). A first order phase transformation into a rock salt structure is observed in the constant pressure simulations. The transformation is accompanied by an initial tetragonal distortion and a subsequent shearing, similar to that found in the other zinc blende structured materials. This phase transition should occur around 6.2 GPa based upon the enthalpy calculations. 相似文献
105.
Water-soluble Mo(0) tetracarbonyl complexes containing a α-diimine ligand have been prepared. All the complexes were characterized
by elemental, LC-MS (APCI), FT-IR, 1H-NMR, and 13C-NMR spectroscopy. The pH dependent phase transfer of these complexes was investigated. This pH dependent phase transfer
was accomplished over 10 times with no evidence of complex decomposition. Their catalytic activities on methyl methacrylate
polymerization were determined. 相似文献
106.
Aly Ashraf A. Hassan Alaa A. Mohamed Asmaa H. Osman Esraa M. Bräse Stefan Nieger Martin Ibrahim Mahmoud A. A. Mostafa Sara M. 《Molecular diversity》2021,25(1):461-471
Molecular Diversity - During formylation of 2-quinolones by DMF/Et3N mixture, the unexpected 3,3′-methylenebis(4-hydroxyquinolin-2(1H)-ones) were formed. The discussed mechanism was proved as... 相似文献
107.
Energetic and structural stability of Al2B2H2n (n = 0—6) clusters is investigated by DFT calculations and a stochastic search algorithm. 相似文献
108.
Eno E. Ebenso Taner Arslan Fatma Kandemi̇rlı Ian Love Cemi̇l Öğretır Murat Saracoğlu Savıour A. Umoren 《International journal of quantum chemistry》2010,110(14):2614-2636
Density functional theory (DFT) at the B3LYP/6‐31G (d,p) and BP86/CEP‐31G* basis set levels and ab initio calculations using the RHF/6‐31G (d,p) methods were performed on four sulfonamides (namely sulfaacetamide (SAM), sulfapyridine (SPY), sulfamerazine (SMR), and sulfathiazole (STI)) used as corrosion inhibitors for mild steel in acidic medium to determine the relationship between molecular structure and their inhibition efficiencies (%IE). The order of inhibition efficiency obtained was SMR > SPY > STI > SAM which corresponded with the order of most of the calculated quantum chemical parameters namely EHOMO (highest occupied molecular orbital energy), ELUMO (lowest unoccupied molecular orbital energy), the energy gap (ΔE), the Mulliken charges on the C, O, N, S atoms, hardness (η), softness (S), polarizability (α), dipole moment (μ), total energy change (ΔET), electrophilicity (ω), electron affinity (A), ionization potential (I), the absolute electronegativity (χ), and the fraction of electrons transferred (ΔN). Quantitative structure activity relationship (QSAR) approach has been used and a correlation of the composite index of some of the quantum chemical parameters was performed to characterize the inhibition performance of the sulfonamides studied. The results showed that the %IE of the sulfonamides was closely related to some of the quantum chemical parameters but with varying degrees/order. The calculated %IE of the sulfonamides studied was found to be close to their experimental corrosion inhibition efficiencies. The experimental data obtained fits the Langmuir adsorption isotherm. The negative sign of the EHOMO values and other thermodynamic parameters obtained indicates that the data obtained supports physical adsorption mechanism. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 相似文献
109.
Hydrogen transfer reduction processes are attracting increasing interest from synthetic chemists in view of their operational simplicity. For this aim, a series of novel Ru(II) complexes with the P-N-P ligands were synthesized starting from the complex [Ru(η6-p-cymene)(μ-Cl)Cl]2 or [RuCp*Cl(COD)]. The complexes were fully characterized by analytical and spectroscopic methods. 31P-{1H} NMR, DEPT, 1H-13C HETCOR or 1H-1H COSY correlation experiments were used to confirm the spectral assignments. Complexes 5, 6 and 7 catalyze the transfer hydrogenation of acetophenone derivatives to 1-phenylethanol derivatives in the presence of iso-PrOH as the hydrogen source. Catalytic studies showed that all complexes are excellent catalytic precursors for the transfer hydrogenation of acetophenone derivatives in 0.1 M iso-PrOH solution. Notably 5 acts as an excellent catalyst giving the corresponding alcohols in excellent conversions up to 99% (TOF ≤ 492 h−1). 相似文献
110.
In order to rationalize the effect of the size and coordinating ability of counteranions upon the structure of Ag(I)–dithioether coordination polymers, a series of such polymers has been synthesized by the combination of the 1,3-bis(methylthio)propane building block and AgX silver salts (X = ClO4− (1), BF4− (2), CF3SO3− (3), SbF6− (4), C6H5COO− (5), CF3COO− (6), CF3CF2CF2COO− (7) and −OOCCF2CF2COO− (8)). Except in two cases, all complexes form 1D-coordination polymers. 相似文献