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141.
Tapan Kumar Lal John F. Richardson Mark S. Mashuta Robert M. Buchanan Rabindranath Mukherjee 《Polyhedron》1997,16(24):1248-4336
Synthesis and characterization of a nitrite-bound copper(II) compound [CuL4)2(ONO)]ClO4 have been achieved (L4 = 2-(3,5-dimethylpyrazol-1-ylmethyl)pyridine]. The bidentate ligand L4 provides a pyridine and a pyrazole donor site; however, they are separated by a methylene spacer. The complex has been structurally characterized and it belongs to only a handful of complexes having nitrito-bound mononuclear copper(II) centre. The metal atom has a distorted square pyramidal geometry with the copper atom displaced from the equatorial plane by 0.25 Å. In MeCN solution the green complex exhibits a broad ligand-field transition at 655 nm with a shoulder at 675 nm and in dichloromethane-toluene glass (80 K) it exhibits an EPR spectral feature characteristic of the unpaired electron in the dx2−y2 orbital. Variable-temperature (80–300 K) magnetic susceptibility measurements in the solid state as well as room temperature measurement in MeCN solution reveal mononuclear magnetically dilute copper(II) centre. When examined by cyclic voltammetry (MeCN solution) it displays electrochemically irreversible CuII---CuI response [cathodic peak potential, Epc (V vs saturated calomel electrode (SCE)): −0.32]. An oxidative response is observed at 1.14 V, probably due to bound-nitrite oxidation and is partially removed to generate a solvated complex at the electrode surface. The latter species gives rise to reversible CuII---CuI redox response [
]. 相似文献
142.
R. Lefbvre 《Chemical physics letters》1980,70(3):430-433
The complex rotation method is applied to the determination of widths and shifts of an harmonic oscillator predissociated by a linear potential, for when exact analytical formulas are available in the limit of small interchannel coupling. Excellent agreement is obtained. 相似文献
143.
Optimisation of accurate rutile TiO<Subscript>2</Subscript> (110), (100), (101) and (001) surface models from periodic DFT calculations 总被引:1,自引:0,他引:1
H. Perron C. Domain J. Roques R. Drot E. Simoni H. Catalette 《Theoretical chemistry accounts》2007,117(4):565-574
In this paper, geometric bulk parameters, bulk moduli, energy gaps and relative stabilities of the TiO2 anatase and rutile phases were determined from periodic DFT calculations. Then, for the rutile phase, structures, relaxations
and surface energies of the (110), (100), (101) and (001) faces were computed. The calculated surface energies are consistent
with the natural rutile powder composition, even if a dependence on the number of layers of the slab used to model the surface
was identified. Internal constraints, consisting in freezing some internal layers of the slab to atomic bulk positions, were
thus added to mimic the bulk hardness in order to stabilise the computed surface energies for thinner systems. In parallel,
the influence of pseudopotentials was studied and it appears that four valence electrons for titanium atoms are sufficient.
The aim of this study was to optimise accurate rutile TiO2 surface models that will be used in further calculations to investigate water and uranyl ion sorption mechanisms. 相似文献
144.
Otto P. Strausz Cornelia Kozmutza Ede Kapuy Michael A. Robb Giannoula Theodorakopoulos Imre G. Csizmadia 《Theoretical chemistry accounts》1978,48(3):215-221
Vertical proton affinities were calculated with closed and open shell direct SCF-MO methods for the ground, excited triplet and ionized doublet states of CH2O and CH2OH+.The computed gas phase basicity of CH2O follows the order: CH2O(1
A
1) > CH2O*(3
A
1 or 3
A
2) > CH2O+(2
B
2 or 2
B
1). 相似文献
145.
Weakly bound linear and bent dimers, FH—X (where X = CO, OC, CNH, NCH, N2O and ON2), are investigated using the DFT B3LYP and ab initio MP2 methods with the same basis sets (6–311++G(3df,2pd)). The strengths of the H—C or H—N H‐bonds in dimers FH—CO, FH—CNH, and FH—N2O are compared with those of the H—O or H—N H‐bonds in dimers FH—OC, FH—NCH, and FH—ON2. The results obtained for the H‐bond distances, the elongation effect of the HF bond, the red shift of the HF stretching frequency, and the energy difference between the dimer and the charge transfer reveal that the H‐bonds of the first group of dimers are stronger than those of the second. The Gibbs energies calculated for the six dimer formations indicate that the weakly bound dimers are unstable at room temperature (T = 298 K) (FH—X's → FH + X's, ΔG < 0). 相似文献
146.
A new PVC membrane electrode for Zn2+ ions based on tetra(2-aminophenyl) porphyrin (TAPP) as membrane carrier is prepared. The sensor exhibits a linear stable response over a wide concentration range (5.0×10−5 to 1.0×10−1 M) with a slope of 26.5 mV/decade and a limit of detection 3.0×10−5 M (1.96 ppm). It has a response time of about l0 s and can be used for at least 8 months without any divergence in potential. The propose membrane sensor revealed good selectivities for Zn2+ over a wide variety of other metal ions and can be used in pH range of 3.0–6.0. It was successfully applied to the direct determination of zinc in a pharmaceutical sample and also as an indicator electrode in potentiometric titration of Zn2+ ions. 相似文献
147.
Copolymerization of an excess of methyl methacrylate (MMA) relative to 2-hydroxyethyl methacrylate (HEMA) was carried out in toluene at 80 °C according to both conventional and controlled Ni-mediated radical polymerizations. Reactivity ratios were derived from the copolymerization kinetics using the Jaacks method for MMA and integrated conversion equation for HEMA (rMMA = 0.62 ± 0.04; rHEMA = 2.03 ± 0.74). Poly(ethylene glycol) α-methyl ether, ω-methacrylate (PEGMA, Mn = 475 g mol−1) was substituted for HEMA in the copolymerization experiments and reactivity ratios were also determined (rMMA = 0.75 ± 0.07; rPEGMA ∼ 1.33). Both the functionalized comonomers were consumed more rapidly than MMA indicating the preferred formation of heterogeneous bottle-brush copolymer structures with bristles constituted by the hydrophilic (macro)monomers. Reactivity ratios for nickel-mediated living radical polymerization were comparable with those obtained by conventional free radical copolymerization. Interactions between functional monomers and the catalyst (NiBr2(PPh3)2) were observed by 1H NMR spectroscopy. 相似文献
148.
The structures of B32 and B32H2–32 with Ih symmetry have been investigated by means of ab initio calculations at STO-3G level. The relationship between molecular orbitals of them has been analyzed and their bonding properties have been discussed. Then the possibility of their existence, as well as the similarity and difference between B32 (B32H2–32) and C60 (C60H60) have been inferred. 相似文献
149.
PRODUCTION OF LIGHTOLEFINS FROM CO_2 HYDROGENATION OVER Fe/SILICALITE-2 CATALYST Ⅱ. PROMOTION EFFECT OF MnO PROMOTER 下载免费PDF全文
IntroductionItilasbeenshot'-nthattileadditionofMnOpromotertoFocatal}stcanresultinaremarkableimprovementinthesclectivit}'to11ghtalkenesforCOh}!drogenationll'l.Ho-c'cvcr.thecadetofMnOonCH4formationandCOconversionisvery'ambigUouslltolMoreover.MnOpromotergrca… 相似文献
150.
Colloidal silica and titanium dioxide were surface-modified by chemisorption of octadecyl dimethylmethoxy silane. The surface density of these alkyl silane groups was adjusted to less than 7% of the available surface hydroxyls, leaving the adsorbents hydrophilic and electrically charged in aqueous solution.Ionic surfactants (tetradecylpyridinium chloride and sodium lauryl sulfate) are adsorbed onto the surface-modified silica and titanium dioxide from aqueous solution, even in the case where the surface of the adsorbents exhibits the same sign of electrical charge as the surfactant ionic head groups. According to the adsorption model of Gu the chemiadsorbed alkyl chains are supposed to serve as anchors for small surface aggregates of the ionic surfactants. 相似文献