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21.
Density functional theory (DFT) calculations are employed to compare the mechanism of the *OH attacks at all carbon atoms in quinoline. The computational analysis of the energy surface for the reaction of *OH with quinoline reveals that the formation of OH adducts proceeds through exothermic formation of pi-complexes/H-bonded complexes. The gas-phase reactions have activation energies ranging from <1.3 kcal/mol for the attack at positions C3 through C8 to 8.6 kcal/mol for the attack at the C2 position. Solvation, as described by the CPCM cavity model, lowers these activation barriers so that the attack at all carbon atoms except C2 is effectively barrierless. The *OH attack at C2 in solution is significantly different than at all other quinoline positions because it involves the only transition structure with energy higher than that of the starting materials and with an energetic barrier of 5.1 kcal/mol. The specific solvation approach also corroborates this finding because the attack at C2 was shown to have an energy barrier of 2.3 kcal/mol compared to the barrierless attack at C5. These results are in agreement with our recent experimental studies but differ from literature reports on the degradation of quinoline using the photo-Fenton reaction. 相似文献
22.
Synthesis, Crystal Structure and Spectroscopic Characterization of [Au12(PPh)2(P2Ph2)2(dppm)4Cl2]Cl2 The reaction of [(AuCl)2dppm] (dppm = Ph2PCH2PPh2) with P(Ph)(SiMe3)2 in CHCl3 results in the formation of [Au12(PPh)2(P2Ph2)2(dppm)4Cl2]Cl2 ( 1 ), the crystal structure of which was determined by single crystal X‐ray analysis (space group P21/c, a = 1425.3(3) pm, b = 2803.7(6) pm, c = 2255.0(5) pm, β = 95.00(3)°, V = 8977(3)·106 pm3, Z = 2). The dication in 1 consists of two Au6P3 units built by highly distorted Au3P and Au2P2 heterotetrahedra, connected via four bidentate phosphine ligands. Additionally, the compound was characterized by IR‐, UV‐ and NMR spectroscopy. The 31P{1H} NMR spectrum is discussed in detail. 相似文献
23.
Dirk Steinborn Olaf Gravenhorst Clemens Bruhn Dusan Miklo Michal Dunaj-Jur
o Alfred Kolbe 《无机化学与普通化学杂志》1997,623(12):1954-1958
Synthesis and Characterization of Aquapentachloroplatinates(IV) – Structure of [K(18-crown-6)][PtCl5(H2O)] The crown ether complex of the aquapentachloroplatinic acid of the composition [H13O6][PtCl5(H4O2)] · 2(18-cr-6) ( 2 ) reacts with K2CO3 and [NnBu4]OH in aqueous solution to give [K(18-cr-6)][PtCl5(H2O)] ( 5 a ) and [NnBu4][PtCl5(H2O)] · 1/2 (18-cr-6) · H2O ( 5 b ), respectively. Both compounds were characterized by microanalysis, vibrational (IR, Raman) and NMR (1H, 13C, 195Pt) spectroscopy. The X-ray structure analysis of 5 a (orthorhombic, pnma; a = 16,550(4), b = 18,044(3), c = 7,415(1) Å; Z = 4; R1 = 0,0183; wR2 = 0,0414) reveals that the crystal is threaded by chains built up of [PtCl5(H2O)]? and [K(18-cr-6)]+ units. There are tight K …? Cl contacts (d(K? Cl1)) = 3,0881(9) Å and OW? H? Ocr hydrogen bridges (d(O1 …? O2) = 2,806(3) Å) between these units. The coordination polyhedron [PtCl5O] has approximately C4v symmetry. 相似文献
24.
Olaf Evers Erich Hdicke Gregor Ley 《Colloids and surfaces. A, Physicochemical and engineering aspects》1994,90(2-3):135-147
The self-consistent mean field model of Scheutjens and Fleer is used to model spherical aggregates of homopolymers and monomer—polymer particles in solution. For homopolymer aggregates we found that the chain ends are preferentially located at the exterior side of the polymer/solvent interface. The distribution of the end segments may be an important parameter in latex film formation. For monomer—polymer particles a “core-shell” structure is found with an extended core containing a monomer—polymer mixture and a thin shell a few nanometres thick strongly enriched with monomer. The monomer-enriched shell seems to function as a solvating envelope for the dangling chain ends. These results are compared with other simulations based on a single chain in a spherical-cavity model. 相似文献
25.
Low pressure CO oxidation was studied over small supported Pd particles by means of static secondary ion mass spectrometry (SSIMS). The SSIMS spectra of adsorbed layers on Pd particles with diameters below ~7nm contained, besides other species, Pd n X+ ions (X=C, O, CO;n=1–3). In experiments with Pd films, Pd n C+ species were much less abundant or even absent from the mass spectra. We conclude that CO decomposed in appreciable amounts only on Pd particles. No significant influence of the support material (mica, MgO,α-Al2O3) was seen and posthumous TEM analysis revealed well defined particle morphologies with largely (111) and (100) facets. At total pressures below 10?4 Pa, the relative carbidic intensities Pd n C+/Pd n + , which were taken as proportional to the carbon surface concentrations, first increased with increasing temperatures and then decreased after they passed a maximum at T=400–440 K. The smaller the particle size, the more intense were the maxima. For T ?440 K, carbon was removed from the surface via reaction with oxygen. Strong hysteresis effects in the Cad and COad concentrations occurred during temperature variation measurements. The Pd n C+/Pd n + ratios displayed maxima during heating but not during cooling. While the Pd n CO+/Pd n + ratios were always high at 300 K and always low at T>550 K, they were more intense in the medium temperature range when subjecting the samples to heating. These hysteresis effects are discussed in terms of asymmetric adsorption and reaction behaviour of CO/O2 mixtures, involving inhibition of CO2 formation by adsorbed carbon and carbon monoxide. 相似文献
26.
Wiest O Harrison CB Saettel NJ Cibulka R Sax M König B 《The Journal of organic chemistry》2004,69(24):8183-8185
Two new artificial photolyase models that recognize pyrimidine dimers in protic and aprotic organic solvents as well as in water through a combination of charge and hydrogen-bonding interactions and use a mimic of the flavine to achieve repair through reductive photoinduced electron transfer are presented. Fluorescence and NMR titration studies show that it forms a 1:1 complex with pyrimidine dimers with binding constants of approximately 10(3) M(-1) in acetonitrile or methanol, while binding constants in water at pH 7.2 are slightly lower. Excitation of the complex with visible light leads to clean and rapid cycloreversion of the pyrimidine dimer through photoinduced electron transfer catalysis. The reaction in water is significantly faster than in organic solvents. The reaction slows down at higher conversions due to product inhibition. 相似文献
27.
28.
Paloma Sevillano Sven Koenig Daniel Himmel Olaf Fuhr Dieter Fenske 《无机化学与普通化学杂志》2005,631(11):2236-2240
The reactions of [Co2(CO)8] with E(SiMe3)2 (E = Se, Te) in CH2Cl2 result in the formation of the compounds [Co4Se2(CO)10]> ( 1 ) and [Co4Te2(CO)11] ( 2 ), respectively. Both cluster complexes have similar molecular structures in which the cobalt atoms form four‐membered rings with μ4‐bridging chalcogen atoms (Se and Te) above and below the plane of the metal atoms and the carbonyl ligands as either terminal or μ2‐bridging ligands. DFT‐calculations for both compounds have been carried out in order to obtain some more information about their electronic distribution. In the presence of the phosphine Ph2PC≡CPPh2 (dppa), the reaction of [Co2(CO)8] with Se(SiMe3)2 leads to the formation of [Co8Se4(CO)16(μ‐dppa)2] ( 3 ). During the reaction two molecules of [Co2(CO)8] have been added to the acetylene groups of the dppa ligands, whilst the remaining cobalt atoms coordinate to the phosphorus atoms of the phosphine. In this compounds the selenium atoms act as μ3‐ligands, bridging the metal atoms bonded to the phosphorus with those bonded to the acetylene groups. 相似文献
29.
Karim Fahmy Olaf Weidlich Martin Engelhard Jörg Tittor Dieter Oesterhelt Friedrich Siebert † 《Photochemistry and photobiology》1992,56(6):1073-1083
Abstract— In order to assign the proton acceptor for Schiff base deprotonation in bacteriorhodopsin to a specific Asp residue, the photoreaction of the Asp85 → Glu mutant, as expressed in Halobacterium sp . GRB, was investigated by static low-temperature and time-resolved infrared difference spec-troscopy. Measurements were also performed on the mutant protein labeled with [4-13 C]Asp which allowed discrimination between Asp and Glu residues. 14,15-di13 C-retinal was incorporated to distinguish amide-II absorbance changes from changes of the ethylenic mode of the chromophore. In agreement with earlier UV-VIS measurements, our data show that from both the 540 and 610 nm species present in a pH-dependent equilibrium, intermediates similar to K and L can be formed. The 14 ms time-resolved spectrum of the 540 nm species shows that a glutamic acid becomes protonated in the M-like intermediate, whereas the comparable difference spectrum of the 610 nm species demonstrates that in the initial state a glutamic acid is already protonated. In conjunction with earlier observations of protonation of an Asp residue in wild-type M, the data provide direct evidence that the proton acceptor in the deprotonation reaction of the Schiff base is Asp85. 相似文献
30.
The title compound (1) was prepared by the reaction of 3,5-bis(CF3)C6H3P(i-C3H7)2 (L1) and Co2(CO)8. Its solubility in supercritical carbon dioxide was measured at varying temperatures and pressures using a modified analytical extraction device. Solubility data were determined in the temperature and pressure ranges between 40 and 70 °C and between 100 and 300 bar, respectively. The solubility of 1 is lower compared to (p-CF3C6H4)3P, but much higher than for transition metal complexes bearing phosphines without fluorinated substituents. 相似文献