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41.
Animesh Roy Maximilian A. Silvestri Robert A. Hall Salvatore D. Lepore 《Tetrahedron letters》2017,58(1):106-108
In the attempt to synthesize substituted allenyl esters through a metathesis coupling of unsubstituted allenyl esters and alkenes using a variety of ruthenium catalysts, it was discovered that allenyl esters themselves cleanly arrested the activity of the catalysts. Further studies suggests possible utility of allene esters as general quenching agents for metathesis reactions. To explore this idea, several representative olefin metathesis reactions, including ring closing, were successfully terminated by the addition of simple allenyl esters for more convenient purification. 相似文献
42.
We present a complex multiconfigurational self‐consistent field (CMCSCF)‐based approach to investigate electron‐atom scattering resonances. It is made possible by the use of second quantization algebra adapted for biorthogonal spin orbitals, which has been applied to develop a quadratically convergent CMCSCF method. To control the convergence to the correct CMCSCF stationary point, a modified step‐length control algorithm is introduced. Convergence to a tolerance of 1.0 × 10?10 a.u. for the energy gradient is found to be typically within 10 iterations or less. A method involving the first block of the M matrix defined in the multiconfigurational spin tensor electron propagator method (MCSTEP) based on the CMCSCF reference state has been implemented to investigate 2P Be? shape resonances. The position and width of these resonances have been calculated for different complete active space choices. The wide distribution of the position and width of the resonance reported in the literature is explained by the existence of two distinct resonances which are close in energy. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 相似文献
43.
Densities and viscosities of urea in (1.0, 2.5, and 5.0) mass% of aqueous glucose solutions have been measured at T = (298.15, 303.15, 308.15, and 313.15) K, respectively. Apparent molar volumes, limiting partial molar volume, and relative viscosity have been obtained from the density and viscosity data. Limiting partial molar expansibilities have also been calculated from the temperature dependence of limiting partial molar volumes. The viscosity data has been analyzed using the Jones–Dole equation. The results are used to establish the nature of solute–solute and solute–solvent interactions. The activation parameters of viscous flow have also been calculated on the basis of transition state treatment of the relative viscosity. Result shows that the solute acts as water structure breaker and posses’ weak solute–solvent interaction. 相似文献
44.
Anuva Samanta Bijan Kumar Paul Sankar Jana Nikhil Guchhait 《Photochemistry and photobiology》2010,86(5):1022-1029
The photophysical properties of 5-(4-fluorophenyl)-2-hydroxypyridine (FP2HP) at different pH and its fluorescence response toward different transition metal ions have been studied by steady-state absorption and emission spectroscopy in combination with quantum chemical calculations. Although keto-enol tautomerization is observed in the excited state, the molecule is weakly fluorescent due to the presence of electron-rich nitrogen atom and relatively electron-deficient fluorine atom, which may lead to photoinduced electron transfer process. In the presence of the transition metal ions, such as Zn2+, Cd2+, Hg2+, etc., the studied molecule exhibits changes in its absorption and emission properties. The present system shows fluorescence enhancement instead of usual quenching in presence of the transition metal ions, such as Fe2+ and Cu2+. Spectral observation leads to the interpretation that this structurally simple molecule can be effectively utilized as a chelation-enhanced fluorescence-based chemosensor for the detection of transition metal ions. The experimental findings corroborate well with theoretical calculations at Hartree–Fock level using 6-31G** and lanl2dz basis sets. 相似文献
45.
Stable, high-power, second-harmonic-generation (SHG) of a compact CW Ytterbium (Yb) fiber laser at 1064 nm into the green
and its use as a pump source for CW singly-resonant optical parametric oscillator (SRO) is demonstrated. Using a simple single-pass
SHG configuration in MgO:sPPLT, as much as 9.6 W of single-frequency green radiation at 532 nm is generated from 30 W of fundamental
power at a conversion efficiency of 32.7% in a Gaussian spatial profile with a beam quality factor of M
2 < 1.3. Thermal effects have been investigated at different fundamental power levels and various thermal management schemes
are employed to maximize the second-harmonic power. The green source is successfully deployed to pump a CW SRO tunable over
855–1408 nm, generating up to 2.1 W of idler at 1168 nm. The peak-to-peak idler power stability is better than 10.7% over
40 min, with beam quality factor M
2 < 1.26 for the idler and M
2 < 1.52 for the signal. 相似文献
46.
A simple electrochemical process has been implemented to fabricated fractal structured leaf-like metallic zinc. The fabricated material was structurally characterized using X-ray diffraction that reveals the hexagonal unit cell structure. Also the growth of the structure is anisotropic. Field emission scanning electron microscopic images revealed clearly the leaf-like morphology of the fabricated material is fern like and ∼500 μm in length, ∼50-60 μm wide and the platelets thickness is ∼5 μm. The growth of this structure is diffusion controlled and locally accomplished with the oriented attachment. Raman shift measurement revealed the existence of surface optical phonon modes which is very significant for surface defects. 相似文献
47.
It is a well-known fact that the degree distribution (DD) of the nodes in a partition of a bipartite network influences the DD of its one-mode projection on that partition. However, there are no studies exploring the effect of the DD of the other partition on the one-mode projection. In this article, we show that the DD of the other partition, in fact, has a very strong influence on the DD of the one-mode projection. We establish this fact by deriving the exact or approximate closed-forms of the DD of the one-mode projection through the application of generating function formalism followed by the method of iterative convolution. The results are cross-validated through appropriate simulations. 相似文献
48.
Sukanta Kumar DashAmar Nath Samanta Syamalendu S. Bandyopadhyay 《Fluid Phase Equilibria》2011,307(2):166-174
In this work, new experimental results of the vapour-liquid equilibrium (VLE) of CO2 in aqueous 2-amino-2-methyl-1-propanol (AMP) and piperazine (PZ) have been presented in the temperature range of 298-328 K and PZ concentration range of 2-8 mass%, keeping the total amine concentration in the solution at 30 mass%. The partial pressures of CO2 were in the range of 0.1-1450 kPa. A thermodynamic model was developed to correlate and predict the VLE of CO2 in aqueous AMP + PZ. The electrolyte nonrandom two liquid (ENRTL) theory has been used to develop the VLE model for the quaternary system (CO2 + AMP + PZ + H2O) to describe the equilibrium behaviour of the solution. The experimental data from this work and data available in the literature were used to regress the ENRTL interaction parameters. The model predictions are in good agreement with the experimental data of CO2 solubility in aqueous blends of this work as well as those reported in the literature. The current model can also predict speciation, heat of absorption, pH of the CO2 loaded solution, and amine volatility. 相似文献
49.
Densities and viscosities of glucose in (1.0, 2.5, and 5.0) mass% aqueous urea solutions have been measured at T = (298.15, 303.15, 308.15, and 313.15) K, respectively. Apparent molar volumes, limiting partial molar volume, and relative viscosity have been obtained from the density and viscosity results. Limiting partial molar expansibilities have also been calculated from the temperature dependence of limiting partial molar volumes. The viscosity data have been analyzed by using the modified Jones–Dole equation. The results are used to establish the nature of solute–solute and solute–solvent interactions. Transition state treatment of the relative viscosity was also used for the calculation of activation parameters of viscous flow. Pour findings show that the solute acts as a water structure former and provides strong solute–solvent interaction. 相似文献
50.
The interfacial and thermodynamic properties of a non-ionic surfactant, poly[oxyethylene(10)] lauryl ether, [C12H25(OCH2CH2)10OH], in aqueous solution in the presence of amino acids have been investigated. Critical micelle concentrations (cmcs) were determined by surface tension measurements at different additive concentrations and temperatures using a du Nouy tensiometer. From the surface tension data, the surface excess concentration (F), the minimum area per molecule (Amin), and the surface pressure at the cmc(?cmc) were evaluated. Thermodynamic parameters of adsorption and micellization were evaluated and discussed. The other solution properties of this surfactant like the cloud point viscosity, and foaming have been determined in the presence of different concentrations of alanine and glycine. 相似文献