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111.
The crystal structure of a new complex Ti-Cr oxide phase, K0.82Mg1.68(Cr2.84Fe0.84Ti2.11Zr0.08)O12, synthesized at 13 GPa and 1400 °C, has been determined with single-crystal X-ray diffraction. It has a hexagonal symmetry with the space group P63/m and unit-cell parameters a=9.1763(13) and , , Z=1. The structure is characterized by the hollandite-type double chains of edge-shared M2 octahedra occupied by trivalent and tetravalent cations (Ti+Cr+Fe+Zr); these double chains are linked to one another through shared octahedral apexes to form a framework structure containing two types of tunnels running parallel to the c-axis. One type of tunnels has a hexagonal cross-section and is occupied by large K+, whereas the other has a triangular cross-section and is occupied by Mg2+. The K+ cation is disordered between two crystallographically equivalent (2a) sites in the tunnels and displays a U33 displacement parameter that is significantly greater than U11. The new high-pressure phase reported in this study possesses many structural features similar to those for the hollandite compounds, making it a candidate for the 1-D fast ionic conductors. 相似文献
112.
Numerical results for the ground state of the HN
2
+
and HCO+ molecular ions at their near equilibrium geometry, obtained by the complex molecular orbitals (CMO) method in the extended basis set, are reported. The CMO wavefunction of the HN
2
+
ion is compared with the CI wavefunction obtained in the same basis set. This reveals the nature of approximations inherent in the CMO method. A peculiar feature of the occupation numbers of the CMO natural orbitals is also explained.Alexander von Humboldt Fellow. On leave from the Institute Rudjer Bokovi, Zagreb, Croatia, Yugoslavia. 相似文献
113.
Thecurrentsurgeofinterestinthefield0fnon-linearoptics(NL0)isderivedbothfromaquestforafundamentalunderstanding0fthenon-linearprocess,anditSimPortanceinthetechn0logyofphotonics.Amongnon-linearphen0mena,thethird-ordernon-linearophcsoccuPyanimPortantp0sihonbecauseitprovidesthemechanicsforophcalswitching,ophcallogic,andreal-hmeholograPhy"'.0rganicmaterialwithextendednconjugahonsandlargeRdelocalizahonsarewellknownastheimPortantmaterialsofachievinglargethird-ordernonlinearihes3.ForexamPle,thiosen… 相似文献
114.
115.
钴(Ⅱ)与5-(5-硝基-2-吡啶偶氮)-2,4-二氨基甲苯络合物吸附波及其应用 总被引:4,自引:1,他引:4
钴 (Ⅱ )在NH3·H2O -NH2OH·HCl-5_(5_硝基_2_吡啶偶氮)_2,4_二氨基甲苯体系中有一灵敏的极谱波 ,其峰电位Vp 为 -1.20V(vsSCE) ,钴质量浓度在0.25~25μg/L范围内与峰电流Ip′有良好的线性关系 ,检出限为0.12μg/L;经多种电化学方法证明该波为络合物吸附波 ,其电极过程为不可逆过程 ,电子转移数为2 ,此外还试验了多种离子对峰电流Ip′的影响;所拟方法已用于维生素B12 和模拟样中痕量钴的测定 相似文献
116.
Thorsteinn Loftsson Dagný Hreinsdóttir Már Másson 《Journal of inclusion phenomena and macrocyclic chemistry》2007,57(1-4):545-552
Studies have shown that cyclodextrins form both inclusion and non-inclusion complexes and that several different types of
complexes can coexist in aqueous solutions. In addition, both cyclodextrins and cyclodextrin complexes are known to form aggregates
and it is thought that these aggregates are able to solubilize drugs through micellar-type mechanism. Thus, stability constants
determined from phase-solubility profiles are rarely true stability constants for of some specific drug/cyclodextrin complexes.
A more precise method for evaluation of the solubilizing effects of cyclodextrins is to determine their complexation efficiency
(CE). CE can be determined by measuring the solubility of a given drug at 2–3 cyclodextrin concentrations in pure water or
a medium constituting the pharmaceutical formulation such as parenteral solution or aqueous eye drop formulation. Based on
the CE value the drug:cyclodextrin ratio in the complexation medium can be determined as well as the increase in the formulation
bulk in a solid dosage form. Determination of CE is a simple method for quick evaluating the solubilizing effects of different
cyclodextrins and/or the effects of excipients on the solubilization. Here we report the CE of 43 different drugs with mainly
2-hydroxypropyl-β-cyclodextrin but also with randomly methylated β-cyclodextrin as well as few other cyclodextrins. Calculation of CE, drug:cyclodextrin molar ratio and the increase in the
formulation bulk is discussed, as well as the influence of the intrinsic solubility and drug lipophilicity on the CE. 相似文献
117.
G.?A.?Mun I.?K.?Nam R.?R.?SarsengalievEmail author Z.?S.?Nurkeeva P.?I.?Urkimbaeva K.?Park 《Colloid and polymer science》2004,282(10):1111-1117
Amphiphilic hydrogels of copolymers of the vinyl ether of ethylene glycol and vinyl isobutyl ether were synthesized by -radiation-induced free radical polymerization. Hydrogels with certain copolymer compositions showed thermo-sensitive behavior in aqueous solutions. The swelling behavior of the hydrogels in cetylpyridinium bromide aqueous solution was studied. Increased swelling of the hydrogels was observed in the surfactant solutions. The increased swelling was more prominent for the hydrogels with a higher content of hydrophobic moiety in the copolymer composition, and with higher surfactant concentration. The reason for this phenomenon is discussed. Treatment of some hydrogels in the surfactant solutions resulted in higher swelling ability in distilled water with distinct thermo-induced contraction over a narrow temperature interval. 相似文献
118.
119.
Alternative Ligands. XXXII [1]. Novel Tetraphosphane Nickel Complexes with Tripod-Ligands of the Type XM′(OCH2PMe2)n(CH2CH2PR2)3 – n (M′ = Si, Ge; n = 0 – 3) Tripod Ligands of the type XM′(OCH2PMe2)n(CH2CH2PMe23 – n (M′ = Si, Ge; n = 0 – 3) ( 1 – 6 , Table 1) have been used together with PPh3 or PMe3 for the preparation of novel tetraphosphane complexes of Nickel. The representatives LNiPPh3 ( 7 – 12 ) are obtained by reaction of Ni(COD)2 (COD = 1,5-cyclooctadiene) with the corresponding ligands and PPh3 in toluene in moderate yields. The synthesis of the derivatives LNiPMe3 ( 13 – 18 ) is partly ( 16 – 18 ) accomplished in analogy to the Ph3P-complexes; compounds 13 – 16 are obtained in higher yields by reaction of Ni(PMe3)4 with the respective ligand. As a rule, 13 – 18 cannot be separated from by-products. The trinuclear complex FSi(CH2CH2PMe2)3[Ni(PMe2CH2CH2)3SiF]3 ( 19 ) is formed together with 18 in the reaction of Ni(COD)2 with 6 and PMe3. The new compounds have been characterized (if possible) by analytical (C, H), but in general by spectroscopic investigations (IR; 1H-, 13C-, 19F-, 31P-NMR; MS). A weak, but significant Ni → Si interaction through the cage is indicated by the following results: (i) Large low-field shifts δδF of 35.2 ppm ( 12 ), 38.3 ppm ( 18 ) and 37.7 ppm ( 19 ); (ii) 6J(PF) coupling constants [or 3J(PNiSiF) through the cage] of 6.0 Hz ( 12 ) and 7.6 Hz ( 18 ) together with a low-field shift δδSi of 12.8 ppm ( 12 ); (iii) NiSi distances of 3.95 Å in 7 and 3.92 Å in 12 , accompanied by a compression of the cage along the Ni ··· Si axis. An additional release from the high charge density on Ni results from π-backbonding to the phosphane ligands. 相似文献
120.
《Electroanalysis》2006,18(22):2243-2250
This work is focused on the voltammetric examination of the ion exchange properties of a smectite type clay, before and after its modification by the replacement of its native interlamellar cations (Na+, K+, Ca2+) by hexadecyltrimethylammonium cations (HDTMA+). The raw clay and its organically modified form were first characterized by X‐ray diffraction (XRD) and N2 adsorption–desorption isotherms (BET method) that confirmed the modification via an intercalation process. These materials were subsequently coated onto glassy carbon surfaces, and the resulting modified electrodes were evaluated for the uptake of [Ru(NH3)6]3+ and [Fe(CN)6]3? ions used as redox probes. Some experimental parameters affecting the incorporation of the probes within the film, including the ionic strength, the surfactant loading and the solution pH are thoroughly examined, in order to highlight the mechanism of the process. The possibility of using the surfactant‐intercalated clay modified electrode as an electrochemical sensor for [Fe(CN)6]3? is also evaluated. 相似文献