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71.
72.
Noushine Shahidzadeh Mohamed M. Chehimi Farzaneh Arefi-Khonsari Jacques Amouroux Michel Delamar 《Plasmas and Polymers》1996,1(1):27-45
Acid-base properties of ammonia plasma-treated polypropylene (APTPP) were characterized by X-ray photoelectron spectroscopy
(XPS) in conjunction with the molecular probe technique and using chloroform (TCM) as a reference Lewis acid. It is shown
that TCM is retained by the basic surfaces of APTPP but not by the untreated PP. The retention of TCM is shown to be entirely
due to the formation of TCM:APTPP acid-base complexes. This is supported by the C12p3/2 binding energy (BE) and the shape of the Cl2p peak from the adsorbed TCM. ΔHAB, the heat of TCM:APTPP acid-base interaction was found to be in the range of 3.1–4.3 kcal/mol using a published Cl2p3/2 BE−ΔHAB correlation. This ΔHAB compares remarkably well with the values of 4.3–4.9 kcal/mol determined for TCM:amine complexes, and shows indeed that TCM
is complexed by nitrogen containing basic groups grafted at the surface. However, the TCM/N ratio has an optimal value up
to 1 second of plasma treatment and then decreases sharply, showing that less specific interaction sites are accessible at
the surface for longer treatment times. This parallels previous findings about the metallization of APTPP by aluminium which
was found to be optimal for treatment times lower than 1 second in our experimental conditions. This work shows that XPS can
now indeed be used to quantitatively assess the acid-base properties of modified polymer surfaces. 相似文献
73.
Saeed Dehghanpour Rhett Kempe Sreenivas Balireddi Lida Fotouhi Farzaneh Tabasia Fresia Mojahed Samaneh Salek 《无机化学与普通化学杂志》2006,632(14):2321-2325
A novel ligand, N,N′‐Bis‐[3‐(2‐nitrophenyl)‐allylidene]‐ethane‐1,2‐diamine (nca2en), and their corresponding copper(I) complexes, [Cu(ncaen)2]ClO4 ( 1 ), and [Cu(nca2en)(PPh3)2]BPh4 ( 2 ), have been synthesized and characterized by CHN analyses, 1H and 13C‐NMR, IR, and UV‐Vis spectroscopy. The crystal and molecular structures of [Cu(ncaen)2]ClO4 ( 1 ), and [Cu(nca2en)(PPh3)2]BPh4 ( 2 ), were determined by X‐ray crystallography from single‐crystal data. The coordination polyhedron about the copper(I) atom in the two complexes is best described as a distorted tetrahedron. A quasireversible redox behavior is observed for complex 1 and 2 (E1/2 = 0.55 and 0.95 V, respectively). 相似文献
74.
Development of a cloud point extraction and preconcentration method for silver prior to flame atomic absorption spectrometry 总被引:1,自引:0,他引:1
The possibility was investigated of using 2-mercaptobenzothiazole (MBT) for Ag(I) concentration by micellar extraction at
cloud point (CP) temperature and subsequent determination by flame atomic absorption spectrometry (FAAS). The method is based
on the complexation of Ag(I) with 2-mercaptobenzothiazole (MBT) in the presence of non-ionic micelles of Triton X-114. The
effect of experimental conditions such as pH, concentration of chelating agent and surfactant, equilibration temperature and
time on cloud point extraction was studied. Under the optimum conditions, the preconcentration of 10 mL of water sample in
the presence of 0.1% Triton X-114 and 2 × 10−4 mol L−1 2-mercaptobenzothiazole permitted the detection of 2.2 ng mL−1 silver. The calibration graph was linear in the range of 10–200 ng mL−1, and the recovery of more than 99% was achieved. The proposed method was used in FAAS determination of Ag(I) in water samples. 相似文献
75.
Physical and thermodynamic properties have been calculated and analyzed for the best and optimized geometries of the 3‐D clusters with N = 3 to N = 10 atoms and unit cells of three types of crystalline systems using ab initio RHF/6–31G** method. Dependence of the lattice binding energy on the cluster parameter, R, has been studied. Similar behavior observed for the binding energies for all clusters shows that probabilities of their existence in the condensed phase are more or less the same. In the next step, thermodynamic properties have been calculated and analyzed for He27 3‐D helium clusters with simple cubic, body centered cubic (bcc), trigonal and hexagonal (hcp) configurations. The results show that the hexagonal cluster is more favored over other clusters. It is found that these clusters are electronically stable over a limited range of the values for the lattice parameter. ΔfH is constant in this stability region and thus the ΔfG exactly follows the variations of TΔfS. Surface effects have been investigated by comparing the square and hexagonal He9 2‐D lattices with the cubic and hexagonal He27 3‐D lattices, respectively. The lattice parameters, densities and molar volumes calculated for the clusters with hcp and bcc configurations have satisfactory agreement with the available experimental values. Properties of the He13, He34 and He104 hcp clusters have also been calculated and analyzed. 相似文献
76.
We analyze the network of cross-border bank lending connections among countries from 1977 to 2018. The network includes core countries that lend money and peripheral countries that borrow money from core countries. In nowadays highly connected banking network, financial crisis that start from a country can spread to other countries very fast and cause global affects. We use principal component analysis (PCA) to find the influential lending (core) countries in this network over the years and clusters of borrowing (peripheral) countries related to these impactful core countries. We find three clusters of peripheral countries, with some constant and some changing members over time. This can be a sign of changes in the financial or political interactions among countries. The changes in the role of core countries and how these roles get affected by the important financial crisis in the past decades is investigated. Among 31 of core countries, 7 countries have a partially or constantly important role in the network including France, United Kingdom, United States, Japan, Germany, Chinese Taipei and Switzerland. 相似文献
77.
Majid Masteri-Farahani Faezeh Farzaneh Mehdi Ghandi 《Reaction Kinetics and Catalysis Letters》2008,95(2):379-384
The sythesis, characterization and catalytic activity of WO2pypr [N,N′-bis (2-pyrrolmethlidenaminopropyl) amine] complexed to MCM-41 surface in the epoxidation of some alkenes with excellent
selectivity toward the corresponding epoxides is described in this presentation. 相似文献
78.
79.
80.
Novel derivatives of pyrido-[2,3-d] pyrimidines were synthesized via an efficient and catalyst- free, one-pot, three-component reaction of 3-(1-methyl-1H-pyrrol-2-yl)-3-oxopropanenitrile, 6-amino-(ethylthio)pyrimidine-4(3H)-one, and arylaldehydes under ultrasonic irradiations. This practical method furnished the desired pyridopyrimidines in high yields (79–89%) and short reaction times (25–40 min). 相似文献