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51.
The air quality in the Aragón valley, in the central Pyrenees, has been assessed by evaluation of lichen biodiversity and
mapped by elaboration of the Index of Air Purity (IAP) based on observations of the presence and abundance of eight kinds
of lichen with different sensitivity to air pollution. The IAP values obtained have been compared with quantitative analytical
measures of 16 PAHs in the lichen Evernia prunastri, because this species was associated with a wide range of traffic exposure and levels of urbanization. Analyses of PAHs were
carried out by the DSASE method followed by an SPE clean-up step and GC–MS analysis. The concentration of total PAHs found
in lichen samples from the Aragón valley ranged from 692 to 6420 ng g−1 and the PAHs profile showed predominance of compounds with three aromatic rings. The influence of the road traffic in the
area has been shown because values over the median concentration of PAHs (>1092 ng g−1), percentage of combustion PAHs (>50%), and equivalent toxicity (>169) were found in lichens collected at places exposed
to the influence of traffic. The combination of both methods suggests IAP as a general method for evaluating the air pollution
referenced to PAHs because it can be correlated with the content of combustion PAHs and poor lichen biodiversity can be partly
explained by the air pollution caused by specific PAHs.
Figure Map of the air pollution level in the Aragón valley (Pyrenees) based on the Index of Air Purity (IAP) calculation (lichen
biodiversity) 相似文献
52.
[reaction: see text] A stereocontrolled, convergent synthesis of the alkaloid australine, a glycosidase inhibitor of the pyrrolizidine class, is described. The chiral starting materials were ketone 3, derived from L-erythrulose, and alpha-alkoxy aldehyde 4, prepared from L-malic acid. A key step of the synthesis was the highly stereoselective aldol reaction between 4 and a Z boron enolate derived from 3. Another key step was the one-pot construction of the bicyclic pyrrolizidine system by means of a three-step sequence of SN2 displacements induced by benzylamine on a trimesylate precursor. 相似文献
53.
Mohammed K. Abdel-Hamid Jonathan Coates Celia Miländer Brian W. Skelton Anthony C. Willis 《Tetrahedron letters》2009,50(50):6947-8550
The allylation of indigo results in the one-step synthesis of two unique complex heterocyclic systems: a spiroindoline-pyridoindolone arising from the addition of three allyl moieties and a fused pyridoindolo-azepinoindolone generated from the addition and subsequent cyclisation of two allyl moieties. The structures of these novel heterocycles are assigned unambiguously using extensive NMR experiments and by X-ray crystallographic analysis. The distribution of the products is influenced by the use of thermal versus microwave heating. 相似文献
54.
Patricia Lara Margarita Paneque Prof. Dr. Manuel L. Poveda Prof. Dr. Laura L. Santos Dr. José E. V. Valpuesta Verónica Salazar Dr. Ernesto Carmona Prof. Dr. Salvador Moncho Gregori Ujaque Dr. Agustí Lledós Prof. Dr. Celia Maya Dr. Kurt Mereiter Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(36):9046-9057
Experimental and theoretical studies on equilibria between iridium hydride alkylidene structures, [(TpMe2)Ir(H){?C(CH2R)ArO }] (TpMe2=hydrotris(3,5‐dimethylpyrazolyl)borate; R=H, Me; Ar=substituted C6H4 group), and their corresponding hydride olefin isomers, [(TpMe2)Ir(H){R(H)C? C(H)OAr}], have been carried out. Compounds of these types are obtained either by reaction of the unsaturated fragment [(TpMe2)Ir(C6H5)2] with o‐C6H4(OH)CH2R, or with the substituted anisoles 2,6‐Me2C6H3OMe, 2,4,6‐Me3C6H2OMe, and 4‐Br‐2,6‐Me2C6H2OMe. The reactions with the substituted anisoles require not only multiple C? H bond activation but also cleavage of the Me? OAr bond and the reversible formation of a C? C bond (as revealed by 13C labeling studies). Equilibria between the two tautomeric structures of these complexes were achieved by prolonged heating at temperatures between 100 and 140 °C, with interconversion of isomeric complexes requiring inversion of the metal configuration, as well as the expected migratory insertion and hydrogen‐elimination reactions. This proposal is supported by a detailed computational exploration of the mechanism at the quantum mechanics (QM) level in the real system. For all compounds investigated, the equilibria favor the alkylidene structure over the olefinic isomer by a factor of between approximately 1 and 25. Calculations demonstrate that the main reason for this preference is the strong Ir–carbene interactions in the carbene isomers, rather than steric destabilization of the olefinic tautomers. 相似文献
55.
Pedrosa R Andrés C Arias R Mendiguchía P Nieto J 《The Journal of organic chemistry》2006,71(6):2424-2428
Regio- and diastereoselective methoxyselenenylations of double bonds attached to the N,O-ketalic carbon of chiral perhydrobenzoxazines occur in high yields by reaction with benzeneselenenyl chloride in dichloromethane-methanol. The diastereoselection is dependent on the reaction conditions and the structure of the starting compounds and can be rationalized by accepting the coordination of the selenium to the oxygen atom of the heterocycle. 相似文献
56.
Fernández-Navarro JJ Ruiz-Ángel MJ García-Álvarez-Coque MC 《Journal of separation science》2012,35(10-11):1303-1309
The chromatographic behavior of seven tricyclic antidepressants (amitryptiline, clomipramine, doxepin, imipramine, maprotiline, nortryptiline, and trimipramine) was examined with micellar mobile phases containing the nonionic surfactant Brij-35. Acetonitrile-water mixtures were also used for comparison purposes. Tricyclic antidepressants are moderately polar basic drugs, which are positively charged in the usual working pH. This gives rise to a strong association with the alkyl chains and residual ionized silanols in silica-based stationary phases, which is translated in a high consumption of organic solvent to get appropriate retention times. Brij-35 modifies the surface of the stationary phases creating a neutral bilayer that masks silanols and reduces the polarity. Consequently, the retention times are decreased. A simple chromatographic procedure for the control of tricyclic antidepressants in pharmaceutical formulations was developed, using 0.02 M Brij-35 at pH 3 and UV detection. Satisfactory recoveries were achieved, with intra- and inter-day relative standard deviations usually below 1 and 2%, respectively. The preparation of the samples was simple and only required solubilization and filtration steps previous to injection. The proposed procedure has the advantage of not using an organic solvent in the mobile phase, and the biodegradable character of Brij-35. This makes an example of "green" liquid chromatographic analysis. 相似文献
57.
Dr. Jose E. V. Valpuesta Dr. Eleuterio Álvarez Dr. Joaquín López‐Serrano Dr. Celia Maya Prof. Ernesto Carmona 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(41):13149-13159
The double C? H bond activation of a series of linear and cyclic ethers by the iridium complex [Tptol′Ir(C6H5)(N2)] ( 2? N2), which features a cyclometalated hydrotris(3‐p‐tolylpyrazol‐1‐yl)borate ligand (Tptol′) coordinated in a κ4‐N,N′,N′′,C manner, has been studied. Two methyl ethers, namely, Me2O and MeOtBu, along with diethyl ether and the cyclic ethers tetrahydrofuran, tetrahydropyran (THP), and 1,4‐dioxane have been investigated with formation in every case of the corresponding hydride carbene complexes 3 – 8 , which are stabilized by κ4‐coordination of the ancillary Tptol′ ligand. Five of the compounds have been structurally authenticated by X‐ray crystallography. A remarkable feature of these rearrangements is the reversibility of the double C? H bond activation of Me2O, MeOtBu, Et2O, and THP. This has permitted catalytic deuterium incorporation into the methyl groups of the two methyl ethers, although in a rather inefficient manner (for synthetic purposes). Although possible in all cases, C? C coupling by migratory insertion of the carbene into the Ir? C σ bond of the metalated linkage has only been observed for complex 8 that contains a cyclic carbene that results from α,α‐C? H activation of 1,4‐dioxane. Computational studies on the formation of iridium carbenes are also reported, which show a role for metalated Tp ligands in the double C? H activation and account for the reversibility of the reaction in terms of the relative stability of the reagents and the products of the reaction. 相似文献
58.
Dr. Natalia Busto Jesús Valladolid Cristina Aliende Prof. Félix A. Jalón Prof. Blanca R. Manzano Dr. Ana M. Rodríguez Prof. Jorge F. Gaspar Celia Martins Dr. Tarita Biver Dr. Gustavo Espino Prof. José María Leal Prof. Begoña García 《化学:亚洲杂志》2012,7(4):788-801
The reactions of two diaminotriazine ligands 2,4‐diamino‐6‐(2‐pyridyl)‐1,3,5‐triazine (2‐pydaT) and 6‐phenyl‐2,4‐diamino‐1,3,5‐triazine (PhdaT) with ruthenium–arene precursors led to a new family of ruthenium(II) compounds that were spectroscopically characterized. Four of the complexes were cationic, with the general formula [(η6‐arene)Ru(κ2‐N,N‐2‐pydaT)Cl]X (X=BF4, TsO; arene=p‐cymene: 1.BF4 , 1.TsO arene=benzene: 2.BF4 , 2.TsO ). The neutral cyclometalated complex [(η6‐p‐cymene)Ru(κ2‐C,N‐PhdaT*)Cl] ( 3 ) was also isolated. The structures of complexes 2.BF4 and 3.H2O were determined by X‐ray diffraction. Complex 1.BF4 underwent a partial reversible‐aquation process in water. UV/Vis and NMR spectroscopic measurements showed that the reaction was hindered by the addition of NaCl and was pH‐controlled in acidic solution. At pH 7.0 (sodium cacodylate) Ru–Cl complex 1.BF4 was the only species present in solution, even at low ionic strength. However, in alkaline medium (KOH), complex 1.BF4 underwent basic hydrolysis to afford a Ru–OH complex ( 5 ). Fluorimetric studies revealed that the interaction of complex 1.BF4 with DNA was not straightforward; instead, its main features were closely linked to ionic strength and to the [DNA]/complex ratio. The bifunctional complex 1.BF4 was capable of interacting concurrently through both its p‐cymene and 2‐pydaT groups. Cytotoxicity and genotoxicity studies showed that, contrary to the expected behavior, the complex species was biologically inactive; the formation of a Ru–OH complex could be responsible for such behavior. 相似文献
59.
Ilaria Bonaduce Leslie Carlyle Maria Perla Colombini Celia Duce Carlo Ferrari Erika Ribechini Paola Selleri Maria Rosaria Tiné 《Journal of Thermal Analysis and Calorimetry》2012,107(3):1055-1066
This article presents a multi-analytical approach to investigating the drying, polymerisation and oxidative degradation of
linseed oil, which had undergone various treatments known to be undertaken during the nineteenth century in preparation for
painting. The oil was mechanically extracted from the same seed lot then processed by different methods: water washing, heat
treatments, and the addition of driers, with and without heat. The oil was prepared in 1999 within the framework of the MOLART
project. We compared thermogravimetric analysis (TG), which yields macromolecular information, with gas-chromatography mass-spectrometry
(GC/MS) and direct exposure mass spectrometry (DE-MS), which provide molecular information. This comparison enabled us to
elucidate the role of pre-treatment on the composition of the oil. TG and oxygen uptake curves registered at a constant temperature
helped us to identify the different physical behaviour of the oil samples, thus highlighting the presence of hydrolysed, oxidised
and crosslinked fractions, as a consequence of the different pre-treatments. GC/MS was used to characterise the soluble and
non-polymeric fraction of the oil, to calculate the ratios of palmitic to stearic acid (P/S), and azelaic to palmitic acid
(A/P), and to further evaluate the effects of oil pre-treatments. DE-MS using chemical ionisation with CH4, enabled us to establish the chemical composition of the oil in different stages of ageing. DE-MS proved to be a useful tool
for a simultaneous semi-quantitative characterisation of the free fatty acids, monoglycerids, diglycerides and triglycerides
present in each sample. The combination of thermal analysis with GC/MS and DE-MS enabled a model to be developed, which unravelled
how oil pre-treatments produce binders with different physical–chemical qualities. 相似文献
60.
Hernández-Reyes CX Angeles-Beltrán D Lomas-Romero L González-Zamora E Gaviño R Cárdenas J Morales-Serna JA Negrón-Silva GE 《Molecules (Basel, Switzerland)》2012,17(3):3359-3369
New azanucleosides were obtained using sulphated zirconia (ZS) as catalyst in the nucleophilic oxirane ring opening reaction of 1-allyl-3-(oxiran-2-ylmethyl) pyrimidine-2,4(1H,3H)-dione and 1-allyl-5-methyl-3-(oxiran-2-ylmethyl)-pyrimidine-2,4(1H,3H)-dione, with (S)-prolinol. The new templates were obtained with good yields following a route which exploits the reactivity of epoxides in the presence of sulphated zirconia as catalyst. The key step was carried out using microwave and solvent-free conditions and proceeds with high selectivity. 相似文献