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981.
Quintana JB Rodil R López-Mahía P Muniategui-Lorenzo S Prada-Rodríguez D 《Analytical and bioanalytical chemistry》2007,388(5-6):1283-1293
A selective analytical method for the determination of nine organophosphate triesters and triphenylphosphine oxide (TPPO)
in outdoor particulate matter is presented. It involves a fully automated pressurised liquid extraction (PLE) step, integrating
an alumina clean-up process, and subsequent determination by large-volume injection gas chromatography–positive chemical ionisation–tandem
mass spectrometry (LVI-GC–PCI–MS/MS). The extraction variables (solvent, amount of adsorbent, temperature, time and number
of cycles) were optimised using a multicriteria strategy which implements a desirability function that maximises both extraction
and clean-up efficiencies while searching for the best-compromise PLE conditions. The final method affords quantification
limits of between 0.01 and 0.3 μg g−1 and recoveries of >80%, with the exceptions of the most polar analytes, TCEP and TPPO (~65%) for both urban dust and PM10
samples. Moreover, the method permitted the levels of these compounds in dust deposited outdoors (between LOD and 0.5 μg g−1 for TEHP) and PM10 samples (between LOD and 2.4 μg m−3 for TiBP) to be measured and reported for the first time.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
982.
Reactions catalyzed by supported enzymes present important advantages when compared with those in aqueous media or organic
solvents: separation of enzymes from substrate is easily accomplished, enzyme stability may be improved, and control of the
reaction products is more accurate. We present the experimental results of the kinetic study of ethyl acetate hydrolysis in
gaseous phase catalyzed by a commercial immobilized lipase (Lipozyme IM; Novo Nordisk). The hydrolysis reaction was studied
as a function of ethyl ester and water partial pressure at a constant temperature of 318 K. The amount of biocatalyst used
was varied between 100 and 300 mg, and the reaction was studied in a flow-through glass microreactor. Under the conditions
used, water was an important parameter in the gas-phase reaction. Activation energy was 24.8 kJ/mol and the overall order
of reaction was one. Finally a Bi-Bi reaction mechanism is proposed. 相似文献
983.
Company A Jee JE Ribas X Lopez-Valbuena JM Gómez L Corbella M Llobet A Mahía J Benet-Buchholz J Costas M van Eldik R 《Inorganic chemistry》2007,46(22):9098-9110
A study of the reversible CO2 fixation by a series of macrocyclic dicopper complexes is described. The dicopper macrocyclic complexes [Cu2(OH)2(Me2p)](CF3SO3)2, 1(CF3SO3)2, and [Cu2(mu-OH)2(Me2m)](CF3SO3)2, 2(CF3SO3)2, (Scheme 1) containing terminally bound and bridging hydroxide ligands, respectively, promote reversible inter- and intramolecular CO2 fixation that results in the formation of the carbonate complexes [{Cu2(Me2p)}2(mu-CO3)2](CF3SO3)4, 4(CF3SO3)4, and [Cu2(mu-CO3)(Me2m)](CF3SO3)2, 5(CF3SO3)2. Under a N2 atmosphere the complexes evolve CO2 and revert to the starting hydroxo complexes 1(CF3SO3)2 and 2(CF3SO3)2, a reaction the rate of which linearly depends on [H2O]. In the presence of water, attempts to crystallize 5(CF3SO3)2 afford [{Cu2(Me2m)(H2O)}2(mu-CO3)2](CF3SO3)4, 6(CF3SO3)4, which appears to rapidly convert to 5(CF3SO3)2 in acetonitrile solution. [Cu2(OH)2(H3m)]2+, 7, which contains a larger macrocyclic ligand, irreversibly reacts with atmospheric CO2 to generate cagelike [{Cu2(H3m)}2(mu-CO3)2](ClO4)4, 8(ClO4)4. However, addition of 1 equiv of HClO4 per Cu generates [Cu2(H3m)(CH3CN)4]4+ (3), and subsequent addition of Et3N under air reassembles 8. The carbonate complexes 4(CF3SO3)4, 5(CF3SO3)2, 6(CF3SO3)4, and 8(ClO4)4 have been characterized in the solid state by X-ray crystallography. This analysis reveals that 4(CF3SO3)4, 6(CF3SO3)4, and 8(ClO4)4 consist of self-assembled molecular boxes containing two macrocyclic dicopper complexes, bridged by CO32- ligands. The bridging mode of the carbonate ligand is anti-anti-mu-eta1:eta1 in 4(CF3SO3)4, anti-anti-mu-eta2:eta1 in 6(CF3SO3)4 and anti-anti-mu-eta2:eta2 in 5(CF3SO3)2 and 8(ClO4)4. Magnetic susceptibility measurements on 4(CF3SO3)4, 6(CF3SO3)4, and 8(ClO4)4 indicate that the carbonate ligands mediate antiferromagnetic coupling between each pair of bridged CuII ions (J = -23.1, -108.3, and -163.4 cm-1, respectively, H = -JS1S2). Detailed kinetic analyses of the reaction between carbon dioxide and the macrocyclic complexes 1(CF3SO3)2 and 2(CF3SO3)2 suggest that it is actually hydrogen carbonate formed in aqueous solution on dissolving CO2 that is responsible for the observed formation of the different carbonate complexes controlled by the binding mode of the hydroxy ligands. This study shows that CO2 fixation can be used as an on/off switch for the reversible self-assembly of supramolecular structures based on macrocyclic dicopper complexes. 相似文献
984.
985.
Perruchas S Flores S Jousselme B Lobkovsky E Abruña H Disalvo FJ 《Inorganic chemistry》2007,46(21):8976-8987
The functionalization of octahedral [W(6)S(8)] clusters with a family of phosphino-thiophene ligands has been investigated with the goal of synthesizing extended networks of [W(6)S(8)] units covalently linked to one another through thiophene-conjugated bridges. In addition to new phosphino-thiophene ligands, eight clusters were synthesized and characterized by (1)H and (31)P NMR spectroscopies, elemental analysis, and UV-vis absorption. These clusters are formulated [W(6)S(8)(T-PPh(2))6] (1a), [W(6)S(8)(T-PEt(2))(6)] (1b), [W(6)S(8)(2T-PPh(2))(6)] (2a), [W(6)S(8)(2T-PEt(2))(6)] (2b), [W(6)S(8)(3T-PPh(2))(6)] (3a), [W(6)S(8)(3T-PEt(2))(6)] (3b), [W(6)S(8)((2T)(3)P)(6)] (4), and [W(6)S(8)(2EDOT-PEt(2))(6)] (5) (T = thiophene and EDOT = 3,4-ethylenedioxythiophene). The molecular structure of six of them has been obtained by single-crystal X-ray diffraction analysis. All of them crystallize in the P1 triclinic space group except 3b, which has the P2(1)/c monoclinic symmetry. The redox behavior of both the ligands and the corresponding functionalized clusters has been investigated by cyclic voltammetry. An attempt to electropolymerize these species is also reported. 相似文献
986.
Santiago-Rivas S Moreda-Piñeiro A Bermejo-Barrera P Moreda-Piñeiro J Alonso-Rodríguez E Muniategui-Lorenzo S López-Mahía P Prada-Rodríguez D 《Analytica chimica acta》2007,603(1):36-43
The possibilities of pressurized liquid extraction (PLE) have been novelty tested to assist the cytosol preparation from wet mussel soft tissue before the determination of metals bound to metallothionein-like proteins (MLPs). Results obtained after PLE were compared with those obtained after a classical blending procedure for mussel cytosolic preparation. Isoforms MLP-1 (retention time of 4.1 min) and MLP-2 (retention time of 7.4 min) were separated by anion exchange high-performance liquid chromatography (HPLC) and the concentrations of Ba, Cu, Mn, Sr and Zn bound to MLP isoforms were directly measured by inductively coupled plasma-atomic emission spectrometry (ICP-OES) as a multi-element detector. The optimized PLE-assisted mussel cytosol preparation has consisted of one extraction cycle at room temperature and 1500 psi for 2 min. Since separation between the solid mussel residue and the extract (cytosol) is performed by the PLE system, the cytosol preparation method is faster than conventional cytosol preparation methods by cutting/blending using Ultraturrax or Stomacher devices. 相似文献
987.
Gonzalez-García N Gonzalez-Lafont A Lluch JM 《The journal of physical chemistry. A》2007,111(32):7825-7832
The mechanism for the atmospheric oxidation of methanesulfinic acid (MSIA) has been studied. This is the first theoretical study of the reaction between MSIA and the OH radical. All the possible channels in this reaction have been studied theoretically, and their corresponding rate constants have been evaluated under the variational transition-state theory (VTST) formalism. Two different products can be formed: the CH3S(O)2 radical (which had been experimentally proposed as the only one), and sulfurous acid (H2SO3). The CH3S(O)2 radical can be formed directly or can form via an intermediate adduct, which yields to the radical through the elimination of a water molecule. For the first time, it is theoretically demonstrated that SO2 is formed in the addition channel of the DMS + OH reaction. The consequences of this result in the interpretation of the T-dependence of the SO4(2-)/MSA (methanesulfonic acid) quocient are analyzed. The competition between the unimolecular dissociation of the CH3S(O)2 radical and OH-addition to yield MSA is proposed as one of the possible multiple branching points (along the DMS + OH degradation scheme) influencing the T-dependence of the SO4(2-)/MSA relation. 相似文献
988.
989.