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排序方式: 共有281条查询结果,搜索用时 15 毫秒
31.
Designing Excited States: Theory‐Guided Access to Efficient Photosensitizers for Photodynamic Action
32.
Nezaket ParlakMesut Gür Vedat Ar?Hasan Küçük Tahsin Engin 《Experimental Thermal and Fluid Science》2011,35(1):60-67
In the study, a second law analysis for a steady-laminar flow of water in adiabatic microtubes has been conducted. Smooth microtubes with the diameters between 50 and 150 μm made of fused silica were used in the experiments. Considerable temperature rises due to viscous dissipation and relatively high pressure losses of flow were observed in experiments. To identify irreversibility of flow, rate of entropy generation from the experiments have been determined in the laminar flow range of Re = 20-2200. The second law of thermodynamics was applied to predict the entropy generation. The results of model taken from the literature, proposed to predict the temperature rise caused by viscous heating, correspond well with the experimental data. The second law analysis results showed that the flow characteristics in the smooth microtubes distinguish substantially from the conventional theory for flow in the larger tubes with respect to viscous heating/dissipation (temperature rise of flow) total entropy generation rate and lost work. 相似文献
33.
The replacement of a point dipole and a point quadrupole by a corresponding linear arrangement of two point charges (+q, ?q) and accordingly three point charges (+q, ?2q, +q) is studied with respect to vapour–liquid equilibria. The dependence of saturated liquid density, vapour pressure and heat of vaporization on the choice of the distance d between the charges in the point charge arrangement is analysed. For the studied dipolar two-centre Lennard-Jones (2CLJD) and quadrupolar two-centre Lennard-Jones (2CLJQ) models, d/σ between 1/15 and 1/20 is a reasonable compromise between numerical and physical accuracy, where σ is the Lennard-Jones size parameter. The results are used to derive validated partial charge based models of 59 real fluids from previously published point dipole and point quadrupole based models. 相似文献
34.
Spori DM Venkataraman NV Tosatti SG Durmaz F Spencer ND Zürcher S 《Langmuir : the ACS journal of surfaces and colloids》2007,23(15):8053-8060
A series of alkyl phosphates with alkyl chain lengths ranging from C10 to C18 have been synthesized. Self-assembled monolayers (SAMs) of these molecules were prepared on titanium oxide surfaces by immersion of the substrates in alkyl phosphate solutions of 0.5 mM concentration in n-heptane/isopropanol. The SAMs were characterized by means of dynamic water contact angle (dCA) measurements, variable-angle spectroscopic ellipsometry (VASE), X-ray photoelectron spectroscopy (XPS), and polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS). A higher degree of order and packing density within the monolayers was found for alkyl phosphates with alkyl chain lengths exceeding 15 carbon atoms. This is reflected in a lower dCA hysteresis, as well as a film thickness measured by VASE and XPS close to the expected values for SAMs with an average alkyl chain tilt angle of 30 degrees to the surface normal. Additionally a shift of the symmetric and antisymmetric C-H stretching modes in the PM-IRRAS spectra to lower wave numbers was observed. These findings imply a higher two-dimensional crystallinity of the films derived from alkyl phosphates with a longer alkyl chain length. 相似文献
35.
The in situ prepared three‐component system Pd(OAc)2–1,3‐dialkylbenzimidazolium chlorides ( 2a – f ) and Cs2CO3 catalyses, quantitatively, the Suzuki cross‐coupling of deactivated aryl chlorides and Heck coupling reactions of aryl bromide and iodide substrates. The 1,3‐dialkylbenzimidazolium salts ( 2a – f ) were characterized by conventional spectroscopic methods and elemental analysis. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
36.
Neslihan Saki Engin U. Akkaya 《Journal of inclusion phenomena and macrocyclic chemistry》2005,53(3):269-273
A novel dimeric calixpyrrole has been synthesized. The dimer forms stable complexes with p-nitrophenolate ion with a concomitant reduction in extinction coefficient. The chromogenic anion is displaced by the addition of various anions like fluoride and acetate. Effective optical sensing of these anions is accomplished using the calixpyrrole dimer. 相似文献
37.
Kadriye Ertekin Ozlem Oter Mustafa Ture Serpil Denizalti Engin Cetinkaya 《Journal of fluorescence》2010,20(2):533-540
In this study, a very sensitive and highly selective irreversible optical chemical sensor (optode) for mercury ions was described.
The sensing scheme was based on the interaction of Hg (II) with a newly synthesized fluoroionophore; chloro phenyl imino propenyl
aniline (CPIPA) in plasticized PVC membrane. The sensor membranes were tested for the determination of mercury ion in aqueous
solutions by batch and flow-through methods. The optodes allow determination of Hg (II) in the working range of 1.0 × 10−9–1.0 × 10−5 M with a detection limit of 4.3 ppb. The sensor exhibited excellent selectivity for Hg (II) with respect to several common
alkali, alkaline earth and transition metal ions. The association constant of the 1:1 complex formation for Hg (II) was found
to be Ka = 1.86 × 105 M−1. The CPIPA exhibited high fluorescence quantum yield, long excitation and emission wavelength and high Stokes’ shift values
in the solid matrix which makes it compatible with solid state optics. 相似文献
38.
In this article, we find elements of the Lucas polynomials by using two matrices. We extend the study to the n-step Lucas polynomials. Then the Lucas polynomials and their relationship are generalized in the paper. Furthermore, we give relationships between the Fibonacci polynomials and the Lucas polynomials. 相似文献
39.
İzzet Amour Morkan Ayşe Uztetik Morkan Çiğdem Tuç Engin Kendi 《Journal of chemical crystallography》2008,38(7):541-545
Abstract Pentacarbonyl(4-methylpyridine)chromium(0) complex was isolated from n-hexane solution as yellow plate-like crystals and characterized by using X-ray crystallography. It crystallizes in the orthorhombic
system with the space group Cmcm and Z = 4. The unit cell parameters are a = 11.737(1) ?, b = 12.857(2) ?, c = 8.465(1) ?. The single crystal X-ray structure of the complex shows that the coordination sphere around the chromium central
atom is slightly distorted octahedron, involving the 4-methylpyridine (4-mp), ligand as a monodentate N-donor ligand and five
carbonyl groups. The four equatorial CO groups in the complex, with the Cr–C2 distance of 1.886 Ǻ, are slightly bent away
from the 4-methylpyridine ligand with the N–Cr–C2 angle of 91.69°. The pyridine ring plane makes an angle of 135.17° with
the Cr–N–CO bond axis. The thermal analysis (differential thermal analysis and thermal gravimetry) and IR spectra of the complex
indicated that the compound undergoes complete decomposition to form the Cr2O3 as the final decomposition product.
Index Abstract The crystal structure of pentacarbonyl(4-methylpyridine)chromium(0) complex has been determined and its thermal behavior has
also been studied.
相似文献
40.
Paul T. Beurskens M. Kolenbrander J. H. Noordik V. Parthasarathi Engin Kendi 《Journal of chemical crystallography》1986,16(4):459-465
The structure of the title compound C21H22O3, was determined by X-rays.Minr=322.4, monoclinic, space groupP21/a,a=11.960(2),b=14.275(3),c=10.858(2) Å,=103.20(2)°,V
c
=1804.8 Å3,Z=4,D
x
=1.223 Mg m–3. CuK radiation (graphite crystal monochromator,=1.54184 Å),(CuK)=6.53 cm–1,F(000)=688, T=290 K. Final conventionalR factor=0.050,R
w
=0.069 for 1679 unique reflections and 284 variables. The structure was solved usingMultan. 相似文献