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101.
102.
J. Oueslati A. Rayes C. Ben Nasr F. Lefebvre 《Phosphorus, sulfur, and silicon and the related elements》2013,188(3):693-705
The synthesis and structures of two new compounds with the general formula N(C2H4NH3)3(H2TO4)(HTO4)·2H2O (T = P, As) are reported. They crystallize with triclinic unit cells and are isotropic. We determined the structure of phosphate salt. The following unit cell parameters were found: a = 9.886(4), b = 9.308(2), c = 10.140(3) Å, α = 109.38(2), β = 108.83(3), γ = 74.40(3)°, V = 819.2(5) Å3, and ρcal. = 1.537 g · cm?3. The crystal structure was solved with a final R = 0.042 for 3748 with I > 3σ I). The space group is P-1 and Z = 2. The atomic arrangement can be described as a three-dimensional network of hydrogen bonds made up from HnPO4 3?n (n = 1, 2) anions and H 2 O molecules between which are trapped the tris(2-ammoniumethyl)amine cations. Solid-state 13C and 31P MAS-NMR spectroscopies are in agreement with X-ray structure. Ab initio calculations allow the attribution of the phosphorus signals to the independent crystallographic sites. 相似文献
103.
Sutanjay Saxena 《高分子科学杂志,A辑:纯化学与应用化学》2013,50(5):387-393
The dynamic release of drug propranolol HCl from the propranolol HCl–resin complex (PRC) loaded calcium alginate beads has been studied in the buffer media of pH 1.2 at the physiological temperature 37°C. The PRC encapsulated beads demonstrated nearly 58.04% release while naked PRC particles released 98.00% drug in 24 h in the gastric fluid. The amount of drug released was found to increase with and decrease in the amount of sodium alginate in the beads. Similarly, with the increase in the amount of entrapped PRC particles within the beads, the quantity of drug released was also observed to increase. The degree of crosslinking of beads also affected the release kinetics. Interestingly, the release from naked PRC particles followed ‘first‐order’ kinetics while PRC particles, entrapped in calcium–alginate beads, exhibited ‘diffusion controlled’ release behavior as indicated by liner nature of fractional release vs. √t plot. 相似文献
104.
Yvon Pointud Anne-Gaelle Valade Christelle Pointon Georges Jeminet Jose-Luis Beltran 《Supramolecular chemistry》2013,25(4):261-269
The binding abilities of a new class of 14-membered ring ligands bearing diketal dilactam functions were explored by UV-visible spectrophotometry. Their formation constants, determined in THF solution, showed appreciable complexation with divalent cations (stability order: Sr2+≥Ca2+>Zn2+≥Mg2+>Ba2+) whereas no association was observed with monovalent cations. The stoichiometry of the complexes formed was essentially 1:1 although sometimes a low percentage (<10%) of 1:2 (cation–ligand) species was detected. The corresponding formation constants determined by computation (STAR program) were in the range 1.5<log?β 11<4.8 and 4.4<log?β 12<7.1. They depend significantly on the nature of the substituents. In addition, solvent extractions carried out in a water–chloroform system showed the highest constants (log K ex) for the most substituted macrocycles 7b and 7c (norephedrine series) with a lipophilic skeleton. 相似文献
105.
o-Dihyroxy-3-phenylchromenone derivatives, namely, 6,7-dihydroxy-3-(3′,4′-dimethoxyphenyl)chromenone and 6,7-dimethoxy-3-(3′,4′-dihydroxyphenyl)chromenone, were obtained from 2,4,5-trihydroxybenzaldehyde/3,4-dimethoxyphenylacetic acid and 2-hydroxy-4,5-dimethoxybenzaldehyde/3,4-dihydroxyphenylacetic acid, respectively, in the presence of acetic anhydride and sodium acetate under an inert atmosphere, after treatment with MeOH/HCl(aq). The chromenone-crown ethers were prepared from cyclic condensation of o-dihydroxy-3-phenylchromenones with poly(ethylene glycol) ditosylates in the presence of CH3CN/alkali metal carbonates. The chromatographically purified novel chromenone-crown ethers were identified by 1H NMR, MALDI-TOF mass spectrometry and elemental analysis. The fluorescence and UV–vis spectroscopic properties of the obtained chromenone-crown ethers and their complexes with Li+, Na+ and K+ perchlorate salts were estimated in acetonitrile. The quantum yields of novel chromenone-crown ethers were determined by the comparative method. 相似文献
106.
Sodium, potassium, rubidium, caesium, ammonium and tetramethylammonium tetraphenylborates were studied by both positive and negative ion electrospray mass spectrometry. An affinity order of Cs+ > Rb+ > K+ ~ Na+ was obtained. The results obtained were compared with both calculations and solid-state structures, where available. The previously reported high affinity of caesium for tetraphenylborate concluded from NMR experiments was confirmed for the gas phase. The affinity does not appear to result from steric effects and a cation–pi interaction seems likely. In the positive ion mode, a unique acetonitrile complex of NaBPh4 was observed. 相似文献
107.
p-tert-Butyloctahomotetraoxacalix[8]arene (LH8) reacts with uranyl nitrate hexahydrate in the presence of rubidium hydroxide to give a mixed complex that can be viewed as a tetrauranate dimer [(UO2)4(LH4)2(OH)4] containing four disordered rubidium ions and water molecules. Two uranyl ions are complexed in an “external” fashion by each macrocycle, each of them bound to two phenoxide groups and one ether group, as well as to two bridging hydroxide ions. The latter ensure the formation of a dimeric capsule that contains the disordered set of alkali metal ions. Apart from water molecules, the Rb+ ions are bound to the uranyl oxo groups directed towards the inner cavity, and to phenol and ether oxygen atoms from the macrocycle. The resulting octanuclear complex presents an unprecedented geometry evidencing the assembling potential of uranyl ions. p-tert-Butyloctahomotetraoxacalix[8]arene (LH8) reacts with uranyl nitrate hexahydrate in the presence of rubidium hydroxide to give a mixed complex that can be viewed as a tetrauranate dimer [(UO2)4(LH4)2(OH)4] containing four disordered rubidium ions and water molecules. Two uranyl ions are complexed in an “external” fashion by each macrocycle, each of them bound to two phenoxide groups and one ether group, as well as to two bridging hydroxide ions. The latter ensure the formation of a dimeric capsule that contains the disordered set of alkali metal ions. Apart from water molecules, the Rb+| ions are bound to the uranyl oxo groups directed towards the inner cavity, and to phenol and ether oxygen atoms from the macrocycle. The resulting octanuclear complex presents an unprecedented geometry evidencing the assembling potential of uranyl ions. 相似文献
108.
摘要: 以优化的两步一锅反应法合成了生物金属有机化合物Fe(C5H4-CH2-Trp-OMe)2(FcL),通过NMR、HRMS及IR等对其结构进行了表征,利用X射线单晶衍射测定了分子结构。循环伏安法研究表明FcL在0.00~0.90 V电位范围内,给出一稳定的、形态良好的氧化还原峰,这归于化合物中Fc/Fc+电对的氧化还原过程。电化学金属离子识别研究显示FcL在过渡金属离子Zn2+和Cu2+的存在下,导致了配体Fc/Fc+式量电位的显著阳极移动,其△E0''对Zn2+和Cu2+分别为342和335 mV,表明了FcL对Zn2+和Cu2+具有良好的识别能力。 相似文献
109.
110.
Leonardo M. da Costa Stanislav R. Stoyanov Raimundo N. Damasceno José Walkimar de M. Carneiro 《International journal of quantum chemistry》2013,113(24):2621-2628
Density Functional Theory (UB3LYP/6‐311++G(d,p)) calculations of the affinity of the pentaaqua nickel(II) complex for a set of phosphoryl [O?P(H)(CH3)(PhR)], imino [HN?C(CH3)(PhR)], thiocarbonyl [S?C(CH3)(PhR)] and carbonyl [O?C(CH3)(PhR)] ligands were performed, where R?NH2, OCH3, OH, CH3, H, Cl, CN, and NO2 is a substituent at the para‐position of a phenyl ring.The affinity of the pentaaqua nickel(II) complex for these ligands was analized and quantified in terms of interaction enthalpy (ΔH), Gibbs free energy (ΔG298), geometric and electronic parameters of the resultant octahedral complexes. The ΔH and ΔG298 results show that the ligand coordination strength increases in the following order: carbonyl < thiocarbonyl < imino < phosphoryl. This coordination strength order is also observed in the analysis of the metal‐ligand distances and charges on the ligand atom that interacts with the Ni(II) cation. The electronic character of the substituent R is the main parameter that affects the strength of the metal‐ligand coordination. Ligands containing electron‐donating groups (NH2, OCH3, OH) have more exothermic ΔH and ΔG298 than ligands with electron‐withdrawing groups (Cl, CN, NO2). The metal‐ligand interaction decomposed by means of the energy decomposition analysis (EDA) method shows that the electronic character of the ligand modulates all the components of the metal‐ligand interaction. The absolute softness of the free ligands is correlated with the covalent contribution to the instantaneous interaction energy calculated using the EDA method. © 2013 Wiley Periodicals, Inc. 相似文献