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911.
Existence and nature of C–H?F, C–H?O interactions in 2-(2-nitrophenyl)-3-pentafluorophenyl-oxirane (1) and 2-pentafluorophenyl-3-phenyl-1-(p-tosyl)-aziridine (2) are discussed. In compound 1 with a linear molecule, C–H?F, C–H?O hydrogen bonds assemble adjacent molecules into the two-dimensional layers, F?F, O?F interactions connect adjacent layers into three-dimensional supramolecular networks. Owing to the inductive effect of nitro group, the C–H acidity of nitrophenyl increases and the numbers of C–H?F, C–H?O hydrogen bonds also increase, C–H?F, C–H?O interactions become stronger and more important. 1D ribbons of compound 2 are stabilized by C–H?F, C–H?O intermolecular interactions. Nonplanar tritopic molecule would demand the formation of a π?π packing interactions between benzene rings and pentafluorobenzene rings in 2. 相似文献
912.
913.
电流变智能流体在外电场刺激下能快速可逆地改变自身流变性能,具有重要技术应用价值.传统的基于微米颗粒的电流变流体易于沉降并且电致屈服强度不高限制了技术应用,最近基于纳米颗粒的非传统电流变材料研究受到重视,特别是具有各向异性形貌的纳米颗粒悬浮液被发现具有明显增强的电/磁流变效应.本文介绍了最近基于石墨烯的二维纳米复合电流变材料的研究进展,主要包括石墨烯/半导聚合物、石墨烯/极性聚合物、石墨烯/碳等几种典型的电流变材料的制备、结构和电流变行为.研究表明利用石墨烯独特的二维纳米结构、优异的电学和热学性质可能为制备新颖的高性能纳米电流变材料提供途径。 相似文献
914.
X. H. Liu M. Sun J. J. Yue Y. X. Yin X. L. Liu F. M. Miao 《Journal of Molecular Structure》2003,620(2-3):227-230
In this paper, we carried out a theoretical study on the active site structures of the Mn-SOD with ab initio Hartree–Fock SCF method, and analyzed the molecular orbital energies, charges and atomic orbital contribution to the frontier molecular orbital. 相似文献
915.
Summary Three -Cyclodextrin derivatives (-CDs) were synthesized by substituting the 2,6-OH groups of -CD with allyl groups and the 3-OH groups with three different acyl groups (valeryl, heptanonyl, octanoyl). The chromatographic properties of these -CDs as stationary phases for capillary gas chromatography (CGC) were studied. The test results showed that the three -CDs possessed good coating properties and that the capillary columns coated with them exhibited high column efficiency. These -CDs can separate not only the disubstituted benzene isomers but also some racemic compounds. 相似文献
916.
An efficient palladium-catalyzed amination of aromatic bromides with hindered N-alkyl-substituted anilines is described, either using the combination of Pd(OAc)(2) and P(t-Bu)(3) or a palladium(I) tri-tert-butylphosphine bromide dimer, [Pd(mu-Br)(t-Bu(3)P)](2), a new, commercially available, and easily handled catalyst. 相似文献
917.
918.
Samuel K Yin W Stearns RA Tang YS Chaudhary AG Jewell JP Lanza T Lin LS Hagmann WK Evans DC Kumar S 《Journal of mass spectrometry : JMS》2003,38(2):211-221
Metabolic activation of drug candidates to electrophilic reactive metabolites that can covalently modify cellular macromolecules may result in acute and/or idiosyncratic immune system-mediated toxicities in humans. This presents a significant potential liability for the future development of these compounds as safe therapeutic agents. We present here an example of an approach where sites of metabolic activation within a new drug candidate series were rapidly identified using online liquid chromatography/multi-stage mass spectrometry on an ion trap mass spectrometer. This was accomplished by trapping the reactive intermediates formed upon incubation of compounds with rat and human liver microsomes as their corresponding glutathione conjugates and mass spectral characterization of these thiol adducts. Based on the structures of the GSH adducts identified, potential sites and mechanisms of bioactivation within the chemical structure were proposed. These metabolism studies were interfaced with iterative structural modifications of the chemical series in order to block these bioactivation sites within the molecule. This strategy led to a significant reduction in the propensity of the compounds to undergo metabolic activation as evidenced by reductions in the irreversible binding of radioactivity to liver microsomal material upon incubation of tritium-labeled compounds with this in vitro system. With the efficiency and throughput achievable with such an approach, it appears feasible to identify and address the metabolic activation potential of new drug leads during routine metabolite identification studies in an early drug discovery setting. 相似文献
919.
920.