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11.
12.
Ionel I Mangalagiu Geanina C MangalagiuCalin Deleanu Gabi DrochioiuMagda Ghe Petrovanu 《Tetrahedron》2003,59(1):111-114
The ability of 4-methylpyrimidinium ylides (as 1,3-dipoles) to react with activated non-symmetrical substituted dipolarophiles (alkenes and alkynes) is presented. 4-Methylpyrimidinium ylides did not react with alkenes. With alkynes the reactions are regiospecific, a single regioisomer being obtained. A possible mechanism for the reaction pathway is proposed. For the first time in the pyrimidinium ylides series both isomers resulting from bonding to the 2-and 6-positions of the heterocycle ring were obtained. The appropriate conditions in order to increase the selectivity of one of the isomers were determined. 相似文献
13.
Single-molecule studies that allow to compute pKa values, proton affinities (gas-phase acidity/basicity) and the electrostatic energy of solvation have been performed for a heterogeneous set of 26 organic compounds. Quantum mechanical density functional theory (DFT) using the Becke-half&half and B3LYP functionals on optimized molecular geometries have been carried out to investigate the energetics of gas-phase protonation. The electrostatic contribution to the solvation energies of protonated and deprotonated compounds were calculated by solving the Poisson equation using atomic charges generated by fitting the electrostatic potential derived from the molecular wave functions in vacuum. The combination of gas-phase and electrostatic solvation energies by means of the thermodynamic cycle enabled us to compute pKa values for the 26 compounds, which cover six distinct chemical groups (carboxylic acids, benzoic acids, phenols, imides, pyridines and imidazoles). The computational procedure for determining pKa values is accurate and transferable with a root-mean-square deviation of 0.53 and 0.57 pKa units and a maximum error of 1.0 pKa and 1.3 pKa units for Becke-half&half and B3LYP DFT functionals, respectively. 相似文献
14.
The primary amino group of 3-(2-aminoethyl)-3-(4-chlorophenyl)-2,3-dihydro-1H-isoindol-1-one ( 1 ) was acylated with acetyl chloride, benzoyl chloride and phenyl acetyl chloride to form the amides 2a -c, respectively. These were cyclized in phosphorus oxychloride to give the 1-substituted-4a-(4-chlorophenyl)-4,4a-dihydropyrimido [6,1-a]isoindol-9(3H)-ones 3a-c . Heating of 1 in formic acid lead to the formation of 4a-(4-chlorophenyl)-4,4a-dihydropyrimido[6,1-a]isoindol-9(3H) -one (3d) . Heating of 1 in the presence of phosgene lead to the formation of 4a-(4-chlorophenyl)-2,3,4,4a-tetrahydropyrimido[6,1-a]isoindole-1, 9-dione (4). 相似文献
15.
Henri-Edouard Audier Marcel Fetizon Yannik Henry Thierry Prange 《Journal of mass spectrometry : JMS》1976,11(10):1047-1055
The fragmentation mechanisms of oxazole have been studied in detail on using various experimental techniques (refocusing of metastable ions, deuteration, AP measurements) and by theoretical calculations. 相似文献
16.
The temperature dependence of the 35Cl nuclear quadrupole resonance spectra of tetrachloro-o-benzoquinone (TOB) is reported. An analysis of the change in line multiplicities suggests that TOB undergoes three phase changes in going from 77 to 330 K. The transition temperatures have been determined. 相似文献
17.
Mohamed Boumerzoug Marcel Boudreau Peter Mascher 《Plasma Chemistry and Plasma Processing》1997,17(2):181-192
Real-time optical emission spectroscopy (OES) was used to monitor the deposition of TiN both from mixtures of tetrakis(dimethylamino)titanium
(TDMATi)-N2 and TiCl4-H2-N2 in an electron cyclotron resonance chemical vapor deposition system. The accurate control of the ratio of the emission intensities
of ionized nitrogen at 391.4 nm and molecular nitrogen at 357.7 nm (N
2
+
/N2) led to low temperature deposition of stoichiometric TiN (Ti/N ≈ 1) and very low resistivity in both cases. It was found
that high ion density plasmas are crucial for a considerable reduction of the deposition temperature while maintaining good
film quality. OES shows that the abundance of certain excited plasma species is not only dependent on the gas mixture and
the deposition parameters, such as total pressure and microwave power, but also is strongly affected by the magnetic field
configuration. The deposition rate and the film resistivity can be related to the emission intensity ratio, I(N
2
+
)/I(N2). Finally, the two processes are compared in terms of the quality of as-deposited and heat-treated films. The comparison
shows that the films obtained with TDMATi exhibit lower resistivity and are thermally more stable than with TiCl4. 相似文献
18.
José M. Bartoloméa Jesús AlcázarJ.Ignacio Andrés Marcel De BruynJavier Fernández Encarna MatesanzKristof Van Emelen 《Tetrahedron letters》2003,44(47):8545-8548
The synthesis of a series of novel analogues of the 3-substituted-2,3-dihydro-1,4-dioxino[2,3-b]pyridine core, modified in the non-aromatic ring, is described. Due to the presence of a versatile hydroxymethyl group in their structure, these novel scaffolds are attractive intermediates for the preparation of potential new therapeutic agents. 相似文献
19.
M. Ştefănescu M. Stoia O. Ştefănescu A. Popa M. Simon C. Ionescu 《Journal of Thermal Analysis and Calorimetry》2007,88(1):19-26
Hybrid organic-inorganic materials,
silica – polyols (ethylene-glycol – EG; 1,2 propane diol –
1,2PG; 1,3 propane diol – 1,3PG and glycerol – GL), were prepared
by a sol-gel process starting from tetraethylorthosilicate (TEOS) and polyols,
in acid catalysis. The resulting materials were studied by thermal analysis
(in air and nitrogen), FTIR and solid state 29Si-NMR
spectroscopy. These techniques evidenced the presence of polyols in the silica
matrix both hydrogen bounded and chemically bounded in the silica network.
The thermal analysis proves to be the most appropriate technique to evidence
the organic chains linked in the matrix network and to follow the thermal
evolution of the gels to the SiO2 matrix. 相似文献
20.
Organotin derivatives of dimethyldithioarsinic (dithocacodylic) acid have been obtained from the appropriate organotin chloride and the sodium salt of the latter. Tin(IV) chloride and NaS2AsMe2 · 2 H2O yielded only two products, namely Cl2Sn(S2AsMe2)2 and Sn (S2AsMe2)4, regardless of the reagent ratio. Spectroscopic characterization of the compounds (infrared and1H NMR) provides structural information suggesting that the dimethyldithioarsinato group behaves as monodentate (or anisobidentate) ligand in Me2Sn(S2AsMe2)2, Bu2Sn-(S2AsMe2)2 and Cy3Sn(S2AsMe2), as bidentate in Ph2Sn(S2AsMe2)2, Ph3Sn(S2AsMe2) and Cl2As(S2AsMe2)2, whereas Sn(S2AsMe2)4 contains both mono- and bidentate ligands, presumably in a six-coordinate structure. 相似文献