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941.
Coordination reactions of copper(II) ions and their effect on non-covalent interactions in uridine (Urd) or uridine 5′-monophosphate (UMP) systems with nucleosides (Ado, Cyd, Thd) and nucleotides (AMP and CMP) in aqueous solutions have been studied. At high pH the effective coordination centers are deprotonated N(3) atoms from Urd and Thd, whereas at low pH, the N(3) atoms of pyrimidine nucleosides are blocked for coordination and the metallation sites are endocyclic
nitrogen atoms from Ado, Cyd, AMP and CMP. Moreover, at low pH, the main reaction center in nucleotide solutions is the phosphate group. The NMR study has proven the
occurrence of non-covalent ion-dipole interactions and stacking interactions in the systems considered. Introduction of a
copper ion in the majority of systems causes the disappearance of weak interactions between ligands. The structures of the
complexes in solution have been inferred from the equilibrium study: an analysis of the pH range of their occurrence with
respect to the pH range of deprotonation of particular groups in the compounds studied, using Vis, EPR and 13C as well as 31P NMR spectral analysis. 相似文献
942.
We present a method for computing classical Newtonian trajectories that minimize the path length or transit time from reactant
to product. Our approach is based on a generalization of the fast-marching method, which allows us to construct the solution
of the Hamilton-Jacobi equation for the action that optimizes the desired quantity. The resulting “reactive paths” can be
interpreted as reaction coordinates but, unlike more conventional choices, they contain dynamical information about the chemical
system of interest. 相似文献
943.
A rapid, simple, and sensitive high-performance liquid chromatographic method for quantification of curcumin in dog plasma has been developed and validated. After addition of the internal standard (berberine), plasma was acidified and extracted with ethyl acetate. Analysis was performed on a C18 column. The mobile phase was acetonitrile–5% acetic acid, 52:48 (v/v) and the flow rate 1.0 mL min?1. The eluent was monitored at 425 nm. Chromatographic separation was achieved in less than 7 min and the calibration plot was linear over the concentration range 2–128 ng mL?1. Intra- and inter-assay variability were less than 7.3%. The accuracy ranged from 98.7 to 105.0%. The method was successfully applied to a pharmacokinetic study of curcumin in dogs. 相似文献
944.
Yun‐Yu Liu Guang‐Shan Zhu Guo‐Zhen Fan Shi‐Lun Qiu 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(4):m159-m160
In the title compound, poly[μ5‐pyrazine‐2,3‐dicarboxylato‐cadmium(II)], [Cd(C6H2N2O4)]n or [Cd(pdc)]n, where pdc is the pyrazine‐2,3‐dicarboxylate anion, the CdII atom is six‐coordinated by five carboxylate O atoms and one N atom from five different pdc ligands in a distorted octahedral CdO5N coordination geometry. Two CdII atoms are bridged by carboxylate groups of the pdc ligands to create a dimeric unit. The dimeric units are further connected by the pdc ligands to generate an interesting two‐dimensional structure. 相似文献
945.
Denifl S Ptasińska S Sonnweber B Scheier P Liu D Hagelberg F Mack J Scott LT Märk TD 《The Journal of chemical physics》2005,123(10):104308
Electron attachment to the polyaromatic hydrocarbons coronene and corannulene is studied in the electron energy range of about 0-14 eV using a high-resolution crossed electron-neutral beam setup. The major anions observed are the parent anions peaking at about 0 eV with cross sections of 3.8 x 10(-20) and 1 x 10(-19) m(2), respectively. The only fragment anions formed in coronene and corannulene are the dehydrogenated coronene and corannulene anions. Other anions observed in the negative mass spectra at about 0 eV can be ascribed to impurities of the sample. High-level quantum-mechanical studies are carried out for the determination of electron affinities, hydrogen binding energies, and structures of both molecules. The behavior of coronene and corannulene upon electron attachment is compared with that of other polyaromatic hydrocarbons studied previously. 相似文献
946.
This paper reports the first example of diruthenium phosphonate with kagomé structure, namely, [NH3(CH2)4NH3][Ru2(hedpH(0.5))2].2H2O (hedp = 1-hydroxyethylidenediphosphonate). The compound contains kagomé layers that are linked by very strong hydrogen bonds into a nanoscale kagomé structure. Ferromagnetic interactions are mediated between the paramagnetic diruthenium units. 相似文献
947.
Guang‐Fei Liu Lin‐Lin Li Yong Zhang Jian‐Ping Lang Seik Weng Ng 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(1):m1-m3
The title compound, [Cu(ClO4)2(C4H9N3O2)2][Cu(C4H9N3O2)2(CH4O)2](ClO4)2·2CH3OH, comprises two independent CuII species lying on different inversion sites. In the Cu complexes, a distorted octahedral geometry arises (from basic square‐planar N4 coordination) from the weak coordination of two perchlorate ions (as Cu—O) in one species and two methanol molecules in the other (also as Cu—O). Interactions between the O atoms of the perchlorate anions or methanol groups and the imide or amine NH groups afford an extensive intermolecular hydrogen‐bonding network. 相似文献
948.
Xiang‐Gao Meng Chun‐Shan Zhou Li Wang Chang‐Lin Liu 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(11):o667-o670
5‐Sulfosalicylic acid (5‐SSA) and 3‐aminopyridine (3‐APy) crystallize in the same solvent system, resulting in two kinds of 1:1 proton‐transfer organic adduct, namely 3‐aminopyridinium 3‐carboxy‐4‐hydroxybenzenesulfonate monohydrate, C5H7N2+·C7H5O6S−·H2O or 3‐APy·5‐SSA·H2O, (I), and the anhydrous adduct, C5H7N2+·C7H5O6S− or 3‐APy·5‐SSA, (II). Both compounds have extensively hydrogen‐bonded three‐dimensional layered polymer structures, with interlayer homo‐ and heterogeneous π–π interactions in (I) and (II), respectively. 相似文献
949.
熔融碳酸盐燃料电池阳极材料表面改性 总被引:1,自引:0,他引:1
选择铌作为合金化元素,通过氟化物熔盐电化学表面合金化的方法对熔融碳酸盐燃料电池阳极材料镍进行表面改性,改性后的阳极材料的耐蚀性能与电催化性能均得到明显的改善。 相似文献
950.
杂多配合物抗流感病毒活性 总被引:8,自引:1,他引:8
杂多配合物抗流感病毒活性刘杰王丽君**周云山王恩波*(东北师范大学化学系长春130024;**吉林医学院吉林)关键词杂多化合物,流感病毒,活性1997-07-09收稿,1997-09-01修回国家自然科学基金资助课题杂多化合物的药物化学已被广泛关注[... 相似文献