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871.
Dominique Fasseur Pascal Cauliez Daniel Couturier Benoît Rigo Sebastien Defretin 《Journal of heterocyclic chemistry》1994,31(4):829-835
In the pyroglutamic acid series, β-enaminoesters 3 were formed in the 2-position by opening of the corresponding Meldrum's derivative 6 , and β-enaminonitriles 4 were obtained by treating carbamate vinylogous 5 by trimethytsilyl iodide. Alkylation and acylation of β-enaminoester 3a was briefly examined. 相似文献
872.
Let ℱ be a holomorphic foliation ofCP(n). If ℱ has a leaf L, the closure L of which is disjoint from the singular set of the foliation, we prove that there exists
a loop in a leaf contained in L with contracting hyperbolic holonomy.
Chargé de recherche au C.N.R.S. 相似文献
Chargé de recherche au C.N.R.S. 相似文献
873.
Idrissi H Turner S Mitsuhara M Wang B Hata S Coulombier M Raskin JP Pardoen T Van Tendeloo G Schryvers D 《Microscopy and microanalysis》2011,17(6):983-990
Focused ion beam (FIB) induced damage in nanocrystalline Al thin films has been characterized using advanced transmission electron microscopy techniques. Electron tomography was used to analyze the three-dimensional distribution of point defect clusters induced by FIB milling, as well as their interaction with preexisting dislocations generated by internal stresses in the Al films. The atomic structure of interstitial Frank loops induced by irradiation, as well as the core structure of Frank dislocations, has been resolved with aberration-corrected high-resolution annular dark-field scanning TEM. The combination of both techniques constitutes a powerful tool for the study of the intrinsic structural properties of point defect clusters as well as the interaction of these defects with preexisting or deformation dislocations in irradiated bulk or nanostructured materials. 相似文献
874.
875.
Pierry C Cahard D Couve-Bonnaire S Pannecoucke X 《Organic & biomolecular chemistry》2011,9(7):2378-2386
The addition reaction of organometallic reagents to N-(tert-butanesulfinyl)-α-fluoroenimines was studied. Depending of the nature of the organometallic species (Grignard reagents or zincate complexes), we were able to control the configuration of the newly created stereogenic centers in high yields with good to high diastereomeric ratios. The chiral β-fluoro allylamines are key synthons toward the synthesis of fluorinated pseudopeptides bearing a fluoroolefin moiety as a peptide bond mimic. 相似文献
876.
A strategy for the stepwise annulation of pyrrolic rings of a porphyrin to imidazole rings is presented. Mono(imidazole), Janus and corner bis(imidazole), T-shaped tris(imidazole), and tetrakis(imidazole) porphyrins have been synthesized and characterized. 相似文献
877.
Analytical pyrolysis with thermally assisted hydrolysis and methylation was employed to investigate ancient ointments collected
from Spanish vessels coming from the sixteenth century pharmacies. The ointments were reproduced on the basis of historical
recipes and characterization was made in comparison with real samples. Characteristic markers indicate the presence of beeswax,
of animal and plant lipids, and of natural resins. Analyses of old samples are consistent with the modern reproductions and
with the analysis of raw materials. Multivariate data analysis was used to discriminate between the different types of lipidic
materials, also in connection with their relative amount in the samples. 相似文献
878.
879.
Reinholdt M Croissant J Di Carlo L Granier D Gaveau P Bégu S Devoisselle JM Mutin PH Smith ME Bonhomme C Gervais C van der Lee A Laurencin D 《Inorganic chemistry》2011,50(16):7802-7810
We describe the preparation of the first crystalline compounds based on arylboronate ligands PhB(OH)(3)(-) coordinated to metal cations: [Ca(PhB(OH)(3))(2)], [Sr(PhB(OH)(3))(2)]·H(2)O, and [Ba(PhB(OH)(3))(2)]. The calcium and strontium structures were solved using powder and single-crystal X-ray diffraction, respectively. In both cases, the structures are composed of chains of cations connected through phenylboronate ligands, which interact one with each other to form a 2D lamellar structure. The temperature and pH conditions necessary for the formation of phase-pure compounds were investigated: changes in temperature were found to mainly affect the morphology of the crystallites, whereas strong variations in pH were found to affect the formation of pure phases. All three compounds were characterized using a wide range of analytical techniques (TGA, IR, Raman, XRD, and high resolution (1)H, (11)B, and (13)C solid-state NMR), and the different coordination modes of phenylboronate ligands were analyzed. Two different kinds of hydroxyl groups were identified in the structures: those involved in hydrogen bonds, and those that are effectively "free" and not involved in hydrogen bonds of any significant strength. To position precisely the OH protons within the structures, an NMR-crystallography approach was used: the comparison of experimental and calculated NMR parameters (determined using the Gauge Including Projector Augmented Wave method, GIPAW) allowed the most accurate positions to be identified. In the case of the calcium compound, it was found that it is the (43)Ca NMR data that are critical to help identify the best model of the structure. 相似文献
880.
Dominique Armspach Dominique Matt Laurent PoortersRafael Gramage-Doria Peter JonesLoïc Toupet 《Polyhedron》2011,30(4):573-578
The X-ray crystal structures of trigonal silver(I) cyclodextrin complexes of introverted bidentate sulfur (1) and phosphorus (2) ligands give a clear indication on how a cyclodextrin-included ligand may bind in a ditopic fashion both the encapsulated metal ion and the cyclodextrin inner wall. In the solid state, the silver-coordinated water molecule of complex [Ag(H2O)(1)]BF4 induces a major distortion of the macrocyclic structure, along with dramatic conformational changes in the two opposite glucose units with which it is hydrogen bonded. In complex [AgBr(2)], the included bulky bromide anion, which lacks hydrogen bonding capability, does not affect the overall circular shape of the cyclodextrin receptor. A 1H-19F HOESY experiment conducted on the silver(I) complex of 1 in CDCl3 showed that in this solvent, the water molecule is displaced by the BF4 counterion at the metal coordination site, the cavity being here no longer distorted. 相似文献