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11.
Anna Bernardi Silvia Cardani Cesare Gennari Giovanni Poli Carlo Scolastico 《Tetrahedron letters》1985,26(52):6509-6512
MgBr2 mediated addition of Methyl α-methylthio propionate silylketene acetal to α and α,β-alkoxy aldehydes is highly 3,4 -selective (18:1). -α- methylene-β- hydroxy-?-alkoxy esters (6) and (8) are synthesized. 相似文献
12.
The thermal behaviour of a series of Ni-P alloys obtained by electroless plating from chloride-glycollate solutions at different pH values was studied by means of DSC analysis and X-ray diffraction.Alloys of composition up to Ni78P22 are microcrystalline or partially amorphous, depending on the P content; on heating up to 773 K, the amorphous phase is transformed into an equilibrium mixture of Ni and Ni3P crystals.Most of the alloys crystallize in two exothermic stages, these occurring ever closer to each other as the P concentration approaches the eutectic value; the alloys with near-eutectic compositions are the only ones crystallizing in one stage.The first thermal effect in hypo-eutectic alloys is due to the separation of Ni crystallites from the primary amorphous phase and/or to the growth of pre-existing solid-solution crystals; the second one is due to the crystallization of intermediate amorphous phase into Ni3P plus Ni. The first stage of crystallization in hyper-eutectic alloys corresponds to the formation of randomly-oriented Ni3P crystals, while in the second one the residual amorphous phase yields the eutectic mixture.
The authors wish to thank Professor P. Lanza and Mr. A. Garulli for their valuable assistance in the analytical studies. 相似文献
Zusammenfassung Das thermische Verhalten einer Reihe von durch stromlose Platierung mit Chlorid-Clykollat-Lösungen bei verschiedenen pH-Werten erhaltenen Ni-P-Legierungen wurde mittels DSC und Röntgendiffraktion untersucht. Legierungen mit einer Zusammensetzung bis Ni78P22 sind abhängig vom P-Gehalt, kristallin oder teilweise amorph. Beim Erhitzen auf 773 K wird die amorphe Phase in ein Gleichgewichtsgemisch von Ni- und Ni3P-Kristallen überführt. Die meisten Legierungen kristallisieren in zwei exothermen Schritten, die sich einander umso mehr nähern, je mehr sich die P-Konzentration dem eutektischen Wert nähert. Als einzige kristallisieren die in der Zusammensetzung dem Eutektikum nahekommenden Legierungen in einem Schritt. Bei hypoeutektischen Legierungen ist der erste thermische Effekt der Ausscheidung von Ni-Kristallen aus der primären amorphen Phase und/oder dem Wachstum von bereits in der festen Lösung vorliegenden Kristallen, der zweite der Kristallization von Ni3P und Ni aus der intermediären amorphen Phase zuzuschreiben. Bei hypereutektischen Legierungen entspricht der erste Schritt der Kristallisation der Bildung von random-orientierten Ni3P-Kristallen, während des zweiten wird dagegen die verbleibende amorphe Phase in das eutektische Gemisch überführt.
Ni-P , - pH. Ni78P22 , , . 773 Ni Ni3P . , . . - . Ni3P . - Ni3P, .
The authors wish to thank Professor P. Lanza and Mr. A. Garulli for their valuable assistance in the analytical studies. 相似文献
13.
Andreoli R Manini P Poli D Bergamaschi E Mutti A Niessen WM 《Analytical and bioanalytical chemistry》2004,378(4):987-994
A new and simple method for the determination of fat-soluble vitamins (retinol, alpha-tocopherol, and beta-carotene) in human serum was developed and validated by using liquid chromatography-tandem mass spectrometry with atmospheric pressure chemical ionization (LC-APCI-MS-MS). Different solvent mixtures were tested to obtain deproteinization and extraction of the analytes from the matrix. As a result, a volume of 240 microL of a 1:1 (v/v) ethanol/ethyl acetate mixture added to 60 microL of serum was found to be suitable for both protein precipitation and antioxidants solubilization, giving the best recovery for all three analytes. Deproteinized samples (20 microL) were injected after dilution, without the need for concentration or evaporation to dryness and reconstruction of the sample. Vitamins were separated on a C-8 column using a 95:5 (v/v) methanol/dichloromethane mixture and ionized in the positive-ion mode; detection was performed in the selected-reaction monitoring mode. Linearity of the LC-APCI-MS-MS method was established over 5 orders of magnitude for retinol and alpha-tocopherol, whereas in the case of beta-carotene it was limited to 4 orders. Lower limits of quantitation were 1.7, 2.3, and 4.1 nM for retinol, alpha-tocopherol, and beta-carotene, respectively. Serum concentrations of retinol, alpha-tocopherol, and alpha+beta-carotene determined in a group of healthy volunteers were 2.48, 38.07, and 0.50 microM, respectively, in samples collected in winter ( n=122) and 2.69, 45.88, and 0.90 microM during summer ( n=66). 相似文献
14.
15.
Giovanni Poli 《Tetrahedron letters》1989,30(52):7385-7388
The osmylation of several 3-substituted cyclopentenes has been studied. A preference for OsO4 addition syn to an allylic CHR2 substituent is observed. By contrast, bulkier substituents of type CMeR2 give rise to a striking reversal of selectivity. These results are interpreted in terms of the stereodivergent nature of the two differently reactive envelope conformations. 相似文献
16.
Fettinger JC Gordon JC Mattamana SP O'Connor CJ Poli R Salem G 《Inorganic chemistry》1996,35(25):7404-7412
By interaction of MoX(3)(THF)(3) with [Cat]X in THF, the salts [Cat][MoX(4)(THF)(2)] have been synthesized [X = I, Cat = PPh(4), NBu(4), NPr(4), (Ph(3)P)(2)N; X = Br, Cat = NBu(4), PPh(4) (Ph(3)P)(2)N]. Mixed-halide species [MoX(3)Y(THF)(2)](-) (X, Y = Cl, Br, I) have also been generated in solution and investigated by (1)H-NMR. When the tetraiodo, tetrabromo, and mixed bromoiodo salts are dissolved in CH(2)Cl(2), clean loss of all coordinated THF is observed by (1)H-NMR. On the other hand, [MoCl(4)(THF)(2)](-) loses only 1.5 THF/Mo. The salts [Cat](3)[Mo(3)X(12)] (X = Br, I) have been isolated from [Cat][MoX(4)(THF)(2)] or by running the reaction between MoX(3)(THF)(3) and [Cat]X directly in CH(2)Cl(2). The crystal structure of [PPh(4)](3)[Mo(3)I(12)] exhibits a linear face-sharing trioctahedron for the trianion: triclinic, space group P&onemacr;; a = 11.385(2), b = 12.697(3), c = 16.849(2) ?; alpha = 76.65(2), beta = 71.967(12), gamma = 84.56(2) degrees; Z = 1; 431 parameters and 3957 data with I > 2sigma(I). The metal-metal distance is 3.258(2) ?. Structural and magnetic data are consistent with the presence of a metal-metal sigma bond order of (1)/(2) and with the remaining 7 electrons being located in 7 substantially nonbonding orbitals. The ground state of the molecule is predicted to be subject to a Jahn-Teller distortion, which is experimentally apparent from the nature of the thermal ellipsoid of the central Mo atom. The [Mo(3)X(12)](3)(-) ions reacts with phosphines (PMe(3), dppe) to form products of lower nuclearity by rupture of the bridging Mo-X bonds. 相似文献
17.
Wolfgang Oppolzer Giovanni Poli Arend J. Kingma Christian Starkemann Grald Bernardinelli 《Helvetica chimica acta》1987,70(8):2201-2214
The 1,4-addition of alkylmagnesium chlorides to conjugated N-enoylsultams and subsequent ‘enolate trapping’ with aq. NH4Cl or MeI/hexamethylphosphoric triamide generated centers of asymmetry at C(β) and/or at C(α) with good to excellent π-face defferentiation as demonstrated by the conversions 1 → 2 , 1 → 4 , and 8 → 9 . This holds also for the regioselective 1,4-addition of EtMgC1 to a dienoylsultam ( 15 → 16 ). Reactive conformations 1 ≠, 8 ≠, 13 , and 14 are postulated in agreement with X-ray evidence which also served for the structure determination of the product 9j . 相似文献
18.
The title compounds, new chirally masked α,β unsaturated aldehydes, undergo diastereoselective dihydroxylation reactions with 45–60% diastereisomeric excesses; chromatographic purification of the major diols, di-O-protection and auxiliary removal afford optically pure α,β dialkoxy aldehydes. 相似文献
19.
Bruno P Caselli M de Gennaro G De Rienzo M Ielpo P Manigrassi D 《Annali di chimica》2002,92(9):815-824
In this paper an application of new procedures for atmospheric particulate analysis is illustrated. PM10, PAHs (benzo[a]anthracene (BaA), benzo[b]fluoranthene (BbF), benzo[j]fluoranthene (BjF), benzo[k]fluoranthene (BkF), benzo[a]pyrene (BaP), indeno[1, 2, 3-cd]pyrene (Ip), dibenzo[a, h]anthracene (DbA)) and heavy metals (Cu, Ni, Zn, Co, Mn, Cd, Fe and Pb) were investigated. PM10 determination was performed by gravimetric method, PAHs were measured by GC-MS, and heavy metals by HPIC. An air quality monitoring campaign on the territory of Bari municipality has been organised, and its results are shown. 相似文献
20.
Polycyclic aromatic hydrocarbons in the atmosphere: monitoring, sources, sinks and fate. II: Sinks and fate 总被引:1,自引:0,他引:1
Vione D Barra S De Gennaro G De Rienzo M Gilardoni S Perrone MG Pozzoli L 《Annali di chimica》2004,94(4):257-268
This paper reviews the transformation processes that polycyclic aromatic hydrocarbons (PAHs) undergo in the atmosphere. These processes can take place both in the gas phase and in the particulate/aerosol one. Among the gas-phase processes, the most important ones are the daytime reaction with *OH and the nighttime reaction with *NO3. The relative importance of the two processes depends on the particular PAH molecule. For instance, gaseous naphthalene is mainly removed from the atmosphere upon reaction with *OH, while gaseous phenanthrene is mainly removed by reaction with *NO3. Oxy-, hydroxy-, and nitro-PAHs are the main transformation intermediates. Reaction with ozone and photolysis play a secondary role in the transformation of gaseous PAHs. The particle-associated processes are usually slower than the gas-phase ones, thus the gas-phase PAHs usually have shorter atmospheric lifetimes than those found on particulate. Due to the higher residence time on particulate when compared with the gas phase, direct or assisted photolysis plays a relevant role in the transformation of particle-associated PAHs. Among the other processes taking place in the condensed phase, nitration plays a very important role due to the health impact of nitro-PAHs, some of them being the most powerful mutagens found so far in atmospheric particulate extracts. 相似文献