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611.
Pair association in Ionic Liquids is an important quantity that affects many of their physical and chemical properties. However, the association constant is a complex function of the component ions as well as of the solvent environment, and no single theory can compute or predict it with quantitative accuracy. In this work we analyze infinite-dilution association data from a number of recent conductance measurements, and develop a linear model correlating the association constant with two relevant interaction energies, i.e., (1) the dielectrically screened Coulomb attraction and hydrogen bonding between ion-pairs, and (2) the ion solvation energy, which in turn takes into account solvent-specific interactions like hydrogen-bond acidity/basicity and hydrophobic/hydrophilic interactions. The results reveal the unique nature of water as a solvent in that it affects ionic association in ways qualitatively different from other common solvents. 相似文献
612.
A short and highly diastereoselective synthesis of the amphibian alkaloid pumiliotoxin C is described, based on the preparation of an octahydroquinoline derivative through a four-component reaction. The route proceeds in 66% overall yield from 1,3-cyclohexanedione and includes two hydrogenation steps, whose stereochemical outcome was controlled via nitrogen acylation. 相似文献
613.
Pandit P Gayen KS Khamarui S Chatterjee N Maiti DK 《Chemical communications (Cambridge, England)》2011,47(24):6933-6935
Activation of π-bond with organic Lewis acid and cationic surfactant mediated direct transfer of halides to alkyne and alkene are demonstrated to afford α,α-dihaloketones and other valuable synthons with outstanding selectivities. 相似文献
614.
Khamarui S Sarkar D Pandit P Maiti DK 《Chemical communications (Cambridge, England)》2011,47(47):12667-12669
A general strategy for fast decarboxylative difunctionalization to gem-dihalohydrin, gem-dihaloether, gem-dibromoester and cyclized bromo-1,4-dioxane synthons with outstanding regio- and stereoselectivity is demonstrated. 相似文献
615.
Kaustab Ghosh Moumita Maiti Susanta Lahiri 《Journal of Radioanalytical and Nuclear Chemistry》2013,298(2):1049-1054
The room temperature ionic liquid (RTIL), 1-butyl-3-methylimidazolium hexafluorophosphate [C4mim][PF6] has various applications in the separation of a range of metal ions replacing volatile and toxic traditional organic solvents in liquid–liquid extraction systems. In this study, the RTIL [C4mim][PF6] was used to separate no-carrier-added (NCA) 109Cd from α-particle irradiated Ag target. A natural Ag foil was bombarded by 30 MeV α-particles to produce 109Cd. After the decay of all co-produced short-lived products, NCA 109Cd was separated from the bulk Ag using [C4mim][PF6] as extractant from HNO3 medium. Ammoniumpyrrolidine dithiocarbamate (APDC) was used as a complexing agent. At the optimum condition, 3 M HNO3, 0.01 M APDC in presence of [C4mim][PF6], ~99 % bulk Ag was extracted to the IL phase, leaving NCA 109Cd in the aqueous phase. The amount of Ag became negligibly small after re-extraction in the same condition. The ionic liquid was recovered by washing it with 1 M HCl. 相似文献
616.
A.V. Narender Reddy Samarendra N. Maiti Inder Pal Singh Ronald G. Micetich 《合成通讯》2013,43(17):3021-3025
Reaction of chlorosulfonyl isocyanate with nitroketene aminals of imidazolidines afforded acyclic intermediates which on treatment with diisopropylamine were smoothly transformed into the corresponding 1-substituted-1,2,3,7-tetrahydro-8-nitroimidazo [1,2-a] [1,2,6] thiadiazine-7 (1H) one-5, 5-dioxides. 相似文献
617.
The copolymerization of isoprene, butadiene, and other conjugated dienes with maleic anhydride was readily initiated in polar solvents by conventional free radical catalysts, including peroxides, hydroperoxides, and azobisisobutyronitrile, at high concentrations or at temperatures at which the catalyst had a half-life of 1 hr or less and the total reaction time was 0.5-1 hr. Decreasing the reaction temperature or the rate of catalyst addition resulted in increased yields of Diels-Alder adduct and decreased yields of copolymer. The molecular weight decreased as the temperature increased. Dioxane and tetrahydrofuran peroxides, obtained by the passage of oxygen or UV irradiation in air, also initiated the copolymerization. The soluble diene-maleic anhydride copolymers were equimolar and alternating, had [n] 0.1-6 (cyclohexanone) and contained 75-95% 1,4 structure according to ozonolysis, titration with IC1 and NMR. The IR spectrum of the butadiene–maleic anhydride copolymer indicated 75-95% cis-1,4, 5-20% trans-1,4 and 0-5% 1,2-vinyl unsaturation. The proposed mechanism of polymerization involves a donor-acceptor (diene-dienophile) interaction generating a ground-state charge transfer complex which is readily converted to the cyclic adduct. Under the influence of radicals the ground-state complex is transformed into an excited complex which undergoes polymerization. High concentrations of radicals are necessary to generate polymerizable excited complexes in competition with adduct formation. 相似文献
618.
Arpita Banerjee Averi Guha Pali Maiti Somen Goswami Tanmay Chattopadhyay Tapan Kumar Mondal Santanu Bhattacharya Ennio Zangrando Debasis Das 《Transition Metal Chemistry》2011,36(8):829-839
Three Ni(II) complexes of cresol-based Schiff-base ligands, namely [Ni2(L1)(NCS)3(H2O)2], (1) [Ni2(L2)(CH3COO)(NCS)2(H2O)] (2) and [Ni2(L3)(NCS)3] (3), (where L1 = 2,6-bis(N-ethylpyrrolidineiminomethyl)-4-methylphenolato, L2 = 2,6-bis(N-ethylpiperidineiminomethyl)-4-methylphenolato and L3 = 2,6-bis{N-ethyl-N-(3-hydroxypropyl iminomethyl)}-4-methylphenolato), have been synthesized and structurally characterized by X-ray single-crystal diffraction in addition to routine physicochemical techniques. Density functional theory calculations have been performed to understand the nature of the electronic spectra of the complexes. Complexes 1?C3 when reacted with 4-nitrophenyl phosphate in 50:50 acetonitrile?Cwater medium promote the cleavage of the O?CP bond to form p-nitrophenol and smoothly convert 3,5-di-tert-butylcatechol (3,5-DTBC) to 3,5-di-tert-butylquinone (3,5-DTBQ) either in MeOH or in MeCN medium. Phosphatase- and catecholase-like activities were monitored by UV?Cvis spectrophotometry and the Michaelis?CMenten equation was applied to rationalize all the kinetic parameters. Upon treatment with urea, complexes 1 and 2 give rise to [Ni2(L1)(NCS)2(NCO)(H2O)2] (1??) and [Ni2(L2)(CH3COO)(NCO)(NCS)(H2O)] (2??) derivatives, respectively, whereas 3 remains unaltered under same reaction conditions. 相似文献
619.
Moumita Maiti 《Journal of Radioanalytical and Nuclear Chemistry》2011,290(1):11-16
The crux of the present work is to explore the various channels leading to the production of proton rich rhenium radionuclides,
181–186Re, for different applications. The possible production routes encompass both light and heavy ion induced reactions up to
a maximum 100 MeV projectile energy starting from threshold. The nuclear reaction model codes ALICE91 and PACE-II were employed
in this endeavour. Excitation functions of the rhenium radionuclides have been calculated using the aforesaid nuclear reaction
model codes and compared with the measured data wherever available. The contributions of preequilibrium and equilibrium reaction
mechanisms to the total reaction cross section were analysed. For the first time, this study talks about the possibility of
light-heavy ion (6,7Li and 9Be) induced production of proton rich rhenium radionuclides. 相似文献
620.
We present herein a simple method for enhancing the emission of DNA intercalators in homogeneous nanobiohybrids of unlabeled oligonucleotides and unmodified gold nanoparticles (GNPs). Pristine single‐stranded DNA (ss‐DNA) has been wrapped around unmodified GNPs to induce metal‐enhanced fluorescence (MEF) of DNA intercalators, such as ethidium bromide and propidium iodide. The thickness of the ss‐DNA layer on the gold nanosurface determines the extent of MEF, since this depends on the position of the intercalator in relation to the metal surface. Presumably, at a suitable thickness of this DNA layer, more of the intercalator is localized at the optimum distance from the nanoparticle to give rise to MEF. Importantly, no external spacer or coating agent was needed to induce the MEF effect of the GNPs. The concentration ratios of Au to DNA in the nanohybrids, as well as the capping agents applied to the GNPs, play key roles in enhancing the emission of the intercalators. The dimensions of both components of the nanobiohybrids, that is, the size of the GNPs and the length of the oligonucleotide, have considerable influences on the emission enhancement of the intercalators. Emission intensity increased with increasing size of the GNPs and length of the oligonucleotide only when the DNA efficiently wrapped the nanoparticles. An almost 100 % increment in the quantum yield of ethidium bromide was achieved with the GNP–DNA nanobiohybrid compared with that with DNA alone (in the absence of GNP), and the fluorescence emission was enhanced by 50 % even at an oligonucleotide concentration of 2 nM . The plasmonic effect of the GNPs in the emission enhancement was also established by the use of similar nanobioconjugates of ss‐DNA with nonmetallic carbon nanoparticles and TiO2 nanoparticles, with which no increase in the fluorescence emission of ethidium bromide was observed. 相似文献