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91.
Hong SJ Ryu JY Lee JY Kim C Kim SJ Kim Y 《Dalton transactions (Cambridge, England : 2003)》2004,(17):2697-2701
The structures of new polymeric compounds containing Cu(II) ions and btp (2,6-bis(N'-1,2,4-triazolyl)pyridine) ligands have been determined. The btp ligands bridge Cu(II) ions to form double zigzag chains, [Cu(ClO4)2(btp)2] 3 with perchlorate anions, and form single zigzag chains, [Cu(btp)(H2O)4](SO4).2H2O 4 with sulfate anions. The polymeric compound 3 was found to effectively catalyze the epoxide ring-opening reaction with methanol, while polymeric compound 4 was almost inactive with epoxides under the same conditions. The polymeric compound 3 showed an efficient catalytic activity and regioselective reactivity in the ring opening of epoxides and allowed reuse without a significant loss of activity through three runs with epoxides. 相似文献
92.
A three-step one-pot synthesis of fenestranes from a readily available enyne and an alkyne diester has been carried out with cobalt nanoparticles and palladium(II) as catalysts. 相似文献
93.
94.
Crucial role of three-center hydrogen bonding in a challenging chiral molecular recognition 总被引:1,自引:0,他引:1
Kim SG Kim KH Kim YK Shin SK Ahn KH 《Journal of the American Chemical Society》2003,125(45):13819-13824
The enantio-discrimination of beta-chiral primary ammonium ions is achieved by a rational approach that utilizes three-center (bifurcated) hydrogen bonding. The extraction experiments on various selected guests reveal that the bifurcated H-bonding plays a crucial role for the chiral discrimination. The X-ray data obtained for an inclusion complex substantiate such interactions. Using the bifurcated H-bonding, the chiral molecular recognition with our C(3)-symmetric tripodal oxazoline receptors is extended generally toward ammonium ions of alpha-, beta-, and alpha,beta-chiral amines. Simple molecular models, evoking the bifurcated H-bonding, explain the chiral discrimination modes. 相似文献
95.
Jeong JO Byun J Jeon ES Gwon HC Lim YS Park J Yeo SJ Lee YJ Kim S Kim DK 《Experimental & molecular medicine》2002,34(4):278-284
Direct injection of the vascular endothelial growth factor (VEGF) gene plasmid DNA into the myocardium was shown to induce development of new blood vessels to increase the circulation in the heart of patients with coronary artery diseases. However, such angiogenic gene therapy (via naked DNA) was limited by low level of gene expression. Furthermore, the temporal and spatial characteristics of VEGF gene transfer in the heart are not known. In this study, we demonstrated that a plasmid vector, containing the human cytomegalovirus immediate early (HCMV IE) promoter and enhancer, induces greater expression of gene in the rat heart monitored by gene fused to the chloramphenicol acetyl transferase (CAT) reporter, than four different viral and cellular promoters. Interestingly, expression of VEGF121 protein showed an earlier peak, a shorter duration, and a wider distribution than that of CAT only. Therefore, a plasmid vector with an HCMV IE promoter/enhancer provides clear advantages over other previously developed plasmids. Furthermore, expression profile of VEGF121 gene may provide useful information in the design of angiogenic gene therapy in the heart. 相似文献
96.
George R. Newkome Gregory R. Baker James K. Young James G. Traynham 《Journal of polymer science. Part A, Polymer chemistry》1993,31(3):641-651
Cascade (dendritic) polymers are discrete, highly branched, monodisperse polymers that possess branching patterns described by a mathematical progression. A systematic nomenclature that accurately represents these molecules is described. © 1993 John Wiley & Sons, Inc. 相似文献
97.
Byeong Hyo Kim Rongbi HanFengyu Piao Young Moo JunWoonphil Baik Byung Min Lee 《Tetrahedron letters》2003,44(1):77-79
N-Arylacetamides were prepared in excellent yields from nitroarenes in the presence of acetic anhydride, acetic acid and indium by a one-pot procedure. 相似文献
98.
An efficient method for the oxidation of benzylic alcohols with [hydroxy(tosyloxy)iodo]benzene under solvent-free microwave irradiation conditions is described. 相似文献
99.
Buckart S Ganteför G Kim YD Jena P 《Journal of the American Chemical Society》2003,125(46):14205-14209
The change in the electronic structure of Au(n)- clusters induced by the exchange of an Au atom by hydrogen is studied using photoelectron spectroscopy. Au anion clusters react with one hydrogen atom but not with molecular hydrogen. The spectra of Au(n)- and Au(n-1)H- clusters show almost identical features for n > 2 suggesting that hydrogen behaves as a protonated species by contributing one electron to the valence pool of the Au(n)- cluster. This behavior is in sharp contrast to that of the commonly understood electronic structure of hydrogen in metals; namely, it attracts an electron from the conduction band of the metal and remains in an "anionic" form or forms covalent bonding. We discuss the influence of the unique electronic structure of H on the unusual catalytic behavior of Au clusters. 相似文献
100.
Vinogradov M. G. Gorshkova L. S. Chel"tsova G. V. Pavlov V. A. Razmanov I. V. Ferapontov V. A. Malyshev O. R. Heise G. L. 《Russian Chemical Bulletin》2003,52(2):471-479
Prochiral substrates (alkyl aryl ketones, cyclopropyl methyl ketone, 1-indanone, 1-tetralone, ethyl 2-oxo-4-phenylbutyrate, and N-(diphenylphosphinyl)acetophenoneimine) were subjected to asymmetric reduction with aluminum hydride reagents, which were prepared by modifications of NaAlH4 or AlH3 with chiral ,,","-tetraaryl-1,3-dioxolane-4,5-dimethanols (TADDOL). The effects of the nature of the substituents in TADDOL, the structure of the prochiral substrate, and the reaction conditions on the stereochemistry of reduction were investigated. The highest enantioselectivity (70—90% ee) was achieved upon reduction of alkyl aryl ketones and N-(diphenylphosphinyl)acetophenoneimine with NaAl(TADDOLate)H2 in THF or diglyme at a temperature from –70 to –20 °C. The mechanism of asymmetric induction in the reduction reactions of ketones with aluminum hydride reagents is discussed. The stereochemical results of reduction were explained by comparing three-dimensional models of the most probable transition states. 相似文献