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131.
132.
Polysulfides as biologically active ingredients of garlic 总被引:2,自引:0,他引:2
Garlic has long been considered as a natural remedy against a range of human illnesses, including various bacterial, viral and fungal infections. This kind of antibiotic activity of garlic has mostly been associated with the thiosulfinate allicin. Even so, recent studies have pointed towards a significant biological activity of trisulfides and tetrasulfides found in various Allium species, including a wide range of antibiotic properties and the ability of polysulfides to cause the death of certain cancer cells. The chemistry underlying the biological activity of these polysulfides is currently emerging. It seems to include a combination of several distinct transformations, such as oxidation reactions, superoxide radical and peroxide generation, decomposition with release of highly electrophilic S(x) species, inhibition of metalloenzymes, disturbance of metal homeostasis and membrane integrity and interference with different cellular signalling pathways. Further research in this area is required to provide a better understanding of polysulfide reactions within a biochemical context. This knowledge may ultimately form the basis for the development of 'green' antibiotics, fungicides and possibly anticancer agents with dramatically reduced side effects in humans. 相似文献
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134.
Ute Henniges Elisabeth Kloser Anjan Patel Antje Potthast Paul Kosma Martin Fischer Klaus Fischer Thomas Rosenau 《Cellulose (London, England)》2007,14(5):497-511
The oxidative effect of carbanilation mixtures containing dimethylsulfoxide (DMSO) was demonstrated by means of alcohol model
substances in which competitive carbanilation was prevented due to steric hindrance of the hydroxyl function, rendering those
compounds specific probes for oxidation effects. Dimethylsulfonium ions and derived ylide species were shown to be the actually
oxidizing species according to trapping methodology using lipophilic olefins which were converted into the corresponding cyclopropane
and epoxide derivatives. The experimental data were in good agreement with DFT computations carried out on the B3LYP/6-311+G(d,p)
level of theory. The direct interaction of cellulose and sulfoxide solvent was proven by means of methyl-(2-naphthyl)sulfoxide
(MNSO) as a model for DMSO, which caused introduction of UV-detectable methylthionaphthyl ether moieties into the cellulose,
formed in Pummerer-type side reaction paralleling the chemical behavior of DMSO. A facile color test—responding to sulfoxide-derived
oxidizing species—was developed to assess the suitability of carbanilation conditions with regard to cellulose oxidation and
degradation. DMSO-based carbanilation systems have to be used with great caution for determination of molecular weight parameters
and for similar purposes which require complete maintenance of the cellulose integrity. Cellulose oxidation/degradation by
DMSO-derived intermediates upon carbanilation can be minimized but cannot be avoided completely. Thus, if cellulose integrity
is an issue as it is in cellulose analytics, it is recommended to replace DMSO by solvent components of similar solution behavior
but without the inherent danger of generating oxidants, such as pyridine or DMAc, whenever possible.
相似文献
Thomas RosenauEmail: |
135.
Natural product drug discovery: the times have never been better 总被引:1,自引:0,他引:1
The annual meeting of the Society for Industrial Microbiology (SIM) this year was held in Denver, Colorado, from July 29 to August 2, 2007. Nearly 200 oral and about 120 poster presentations kept the approximately 600 participants busy for more than 4 days. This report focuses on the 35 talks dedicated to natural products chemistry, biosynthesis, engineering, drug discovery and development, as well as neutraceuticals. 相似文献
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137.
The title compounds were synthesized from the elements by reactions at high temperature. They crystallize with a hexagonal structure which was determined from single‐crystal X‐ray data of Dy12Ni30As21: P63/m, Z = 1, a = 1698.5(5) pm, c = 387.7(1) pm, R = 0.053 for 797 F values and 69 variable parameters. It belongs to a large family of hexagonal structures with a metal to metalloid ratio of 2 : 1. In these hexagonal structures an ordered distribution of occupied atomic positions around the hexagonal 63 axis is possible only for refinements in space groups of lower symmetry. This is discussed for the present case and the very closely related structures reported for (La, Ce)12Rh30P21 and Nd3Ni7P5. 相似文献
138.
Wolfgang Jeitschko Dieter H. Heumannskmper Ute Ch. Rodewald Marietta S. Schriewer‐Pttgen 《无机化学与普通化学杂志》2000,626(1):80-88
The crystal structure of the known compounds Ln5Re2O12 (Ln = Y, Gd, Dy–Lu) and the new isotypic terbium rhenate Tb5Re2O12 was determined from X‐ray data of a twinned crystal of Ho5Re2O12: B2/m, a = 1236.5(4) pm, b = 748.2(2) pm, c = 563.8(1) pm, γ = 107.73(3)°, Z = 2, R = 0.034 for 379 structure factors and 37 variable parameters. The rhenium atoms (oxidation number +4.5) have octahedral oxygen coordination. These ReO6 octahedra share edges, thus forming infinite strings with alternating short and long Re–Re distances: 243.6(2) and 320.1(2) pm. Of the three holmium positions two are surrounded by seven oxygen atoms and the third one has octahedral oxygen coordination. The crystal structure of Pr3ReO8 was refined from single‐crystal X‐ray data: P21/a, a = 1498.0(2) pm, b = 749.09(8) pm, c = 610.48(9) pm, γ = 110.39(1)°, R = 0.017 for 2082 F values and 110 variable parameters. It is isotypic with a structure first determined for Sm3ReO8. The new compounds Pr3Re2O10 and Pr4Re2O11 were prepared by reaction of elemental praseodymium with the metaperrhenate Pr(ReO4)3. They were characterized through their X‐ray powder diagrams. Pr3Re2O10 was found to be monoclinic: a = 778.47(9) pm, b = 773.62(9) pm, c = 706.10(8) pm, β = 114.77(1)°. It is isotypic with La3Os2O10 and La3Re2O10. Pr4Re2O11 crystallizes with Nd4Re2O11 type structure with the tetragonal lattice constants a = 1272.49(3) pm, c = 562.29(2) pm. The compounds Nd4Re2O11 and Sm4Re2O11 are confirmed. The magnetic properties of Ho5Re2O12, Tb5Re2O12, Pr3Re2O10, Pr4Re2O11, Nd4Re2O11, and Sm4Re2O11 were investigated with a Faraday balance. None of these compounds shows magnetic order above 200 K. 相似文献
139.
Pnictogenidostannates(IV) with Discrete Tetrahedral Anions: New Representatives (E1)4(E2)2[Sn(E15)4] (with E1 = Na, K; E2 = Ca, Sr, Ba; E15 = P, As, Sb, Bi) of the Na6[ZnO4] Type and the Superstructure Variant of K4Sr2[SnAs4] The silvery to dark metallic lustrous compounds (E1)4(E2)2[Sn(E15)4] (E1 = Na, K; E2 = Ca, Sr, Ba; E15 = P, As, Sb, Bi) were prepared from melts of stoichiometric mixtures of the elements. They crystallize in the Na6[ZnO4]‐type structure (hexagonal, space group: P63mc, Z = 2; Na4Ca2[SnP4]: a = 938.94(7), c = 710.09(8) pm; K4Sr2[SnAs4]: a = 1045.0(2), c = 767.0(1) pm; K4Ba2[SnP4]: a = 1029.1(6), c = 780.2(4) pm; K4Ba2[SnAs4]: a = 1051.3(1), c = 795.79(7) pm; K4Ba2[SnSb4]: a = 1116.9(2), c = 829.2(1) pm; K4Ba2[SnBi4]: a = 1139.5(2), c = 832.0(2) pm). The anionic partial structure consists of tetrahedra [Sn(E15)4]8– orientated all in the same direction along [001]. In the cationic partial structure one of the two cation positions is occupied statistically by alkali and alkaline earth metal atoms. Up to now only for K4Sr2[SnAs4] a second modification could be isolated, forming a superstructure type with three times the unit cell volume (hexagonal, space group: P63cm, Z = 6; a = 1801.3(2), c = 767.00(9) pm) and an ordered cationic partial structure. 相似文献
140.
Cyclic Phosphidostannate(III) Anions [Sn12P24]36– in Sr3[Sn2P4] The metallic lustrous, air sensitive compound Sr3[Sn2P4] was prepared from melts of mixtures of the elements. Sr3[Sn2P4] crystallizes in the orthorhombic system, space group Cmca (a = 2510,4(9), b = 1259,3(6), c = 1869,3(8), Z = 24). In the anionic partial structure six moieties [Sn2P6] isostructural to Si2Cl6 are linked by each four common P-ligands forming cyclic units [Sn12P24]36–. The strontium cations are octahedrally coordinated by P. The arrangement can be described as a distorted cubic close packing of P3– in which in an ordered manner 3/4 of the octahedral vacancies are occupied by Sr2+ and 1/4 by Sn2-dumbbells. 相似文献