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101.
Serge Van Calenbergh Elfride Van Den Eeckhout Piet Herdewijn Andr De Bruyn Christophe Verlinde Wim Hol Mia Callens Arthur Van Aerschot Jef Rozenski 《Helvetica chimica acta》1994,77(3):631-644
A series of 2′-benzamido-2′-deoxyadenosine analogues were synthesized in an effort to find new lead structures for the treatment of sleeping sickness. The 2′-deoxy-2′-(3-methoxybenzamido)adenosine ( 1h ) was proved to be a selective inhibitor of the parasite glyceraldehyde 3-phosphate dehydrogenase which confirms the modeling studies. The solution-state conformation of 2′-(thiophene-2-carboxamido) analogue 1d demonstrates a 2′-endo conformation, an orientation of the thiophene ring under the ribose moiety, and the base part occupying a ‘syn’/‘anti’ equilibrium. 相似文献
102.
Supramolecular chemistry has grown into a major scientific field over the last thirty years and has fueled numerous developments at the interfaces with biology and physics, clearly demonstrating its potential at a multidisciplinary level. Simultaneously, organometallic chemistry and transition metal catalysis have matured in an incredible manner, broadening the pallet of tools available for chemical conversions. The interface between supramolecular chemistry and transition metal catalysis has received surprisingly little attention. It provides, however, novel and elegant strategies that could lead to new tools in the search for effective catalysts, as well as the possibility of novel conversions induced by metal centres that are in unusual environments. This perspective describes new approaches to transition metal catalyst development that evolve from a combination of supramolecular strategies and rational ligand design, which may offer transition metal catalysts for future applications. 相似文献
103.
G. Ren van der Hoff Robert A. Baumamn Piet van Zoonen Udo A. Th. Brinkman 《Journal of separation science》1997,20(4):222-226
Off-line normal-phase LC has been used for the clean-up of compounds in our laboratory for several years. On-line coupling of this LC system, which typically yields 12 ml fractions, is not possible due to its large fraction volume. The maximum transfer volume in on-line LC-GC/ECD is approx. 300 μl. Therefore down-scaling of the LC system was attempted in order to reach these low fraction volumes. Miniaturization resulted in a 240 μ1 LC fraction containing the analytes of interest, which is transferred to GC/ECD via an on-column interface. Sensitivity requires that a minimum amount equivalent to 1–2 mg of sample should reach the GC detector; the selectivity is determined by the separation between the matrix and the last eluting target analyte. For the analysis of fatty samples, limitations were observed in the separation of dieldrin from triglycerides. Other organochlorine compounds, e.g. polychlorobiphenyls (PCBs), the DDT group, HCB and the HCHs can be analyzed with RSDs of 2–4 % (n = 10) at concentration levels of sub-μ/kg in milk fat using a 3 μm Hypersil silica 50 × 1.0 mm i.d. LC column. 相似文献
104.
Edward N. Timofeev Sergey N. Mikhailov Andrei N. Zuev Ekaterina V. Efimtseva Piet Herdewijn Robert L. Somers Marc M. Lemaitre 《Helvetica chimica acta》2007,90(5):928-937
2′‐Deoxy‐1‐methyladenosine was incorporated into synthetic oligonucleotides by phosphoramidite chemistry. Chloroacetyl protecting group and controlled anhydrous deprotection conditions were used to avoid Dimroth rearrangement. Hybridization studies of intramolecular duplexes showed that introduction of a modified residue into the loop region of the oligonucleotide hairpin increases the melting temperature. It was shown that modified oligonucleotides may be easily transformed into oligonucleotides containing 2′‐deoxy‐N6‐methyladenosine. 相似文献
105.
106.
Mattheus Froeyen Berthold Wroblowski Robert Esnouf Hans DeWinter Brigitte Allart Eveline Lescrinier Piet Herdewijn 《Helvetica chimica acta》2000,83(9):2153-2182
The influence of the orientation of a 3′‐OH group on the conformation and stability of hexitol oligonucleotides in complexes with RNA and as single strands in aqueous solution was investigated by molecular‐dynamics (MD) simulations with AMBER 4.1. The particle mesh Ewald (PME) method was used for the treatment of long‐range electrostatic interactions. An equatorial orientation of the 3′‐OH group in the single‐stranded D ‐mannitol nucleic acid (MNA) m(GCGTAGCG) and in the complex with the RNA r(CGCAUCGC) has an unfavorable influence on the helical stability. Frequent H‐bonds between the 3′‐OH group and the O−C(6′) of the phosphate backbone of the following nucleotide explain the distorted conformation of the MNA⋅RNA complex as well as that of the single MNA strand. This is consistent with experimental results that show lowered hybridization potentials for MNA⋅RNA complexes. An axial orientation of the 3′‐OH group in the D ‐altritol nucleic acid (ANA) a(GCGTAGCG) leads to a stable complex with the complementary RNA r(CGCAUCGC), as well as to a more highly preorganized single‐stranded ANA chain. The averaged conformation of the ANA⋅RNA complex is similar to that of A‐RNA, with only minor changes in groove width, helical curvature, and H‐bonding pattern. The relative stabilities of ANA⋅RNA vs. HNA⋅RNA (HNA=D ‐hexitol nucleic acid without 3′‐OH group) can be explained by differences in restricted movements, H‐bonds, and solvation effects. 相似文献
107.
Lars A. van der Veen Paul C. J. Kamer Piet W. N. M. van Leeuwen 《Angewandte Chemie (International ed. in English)》1999,38(3):336-338
Unprecedented high activities and selectivities were observed in the hydroformylation of internal octenes to linear products using rhodium catalysts with rigid diphosphane ligands. Dibenzophosphole 1 and a phenoxaphosphane analogue with bite angles of 120 and 119°, respectively, are suited for this. 相似文献
108.
Dirk E. De Vos Stefaan de Wildeman Bert F. Sels Piet J. Grobet Pierre A. Jacobs 《Angewandte Chemie (International ed. in English)》1999,38(7):980-983
Covalent anchoring of 1,4-dimethyl-1,4,7-triazacyclononane on silica gel is the first step in the preparation of a heterogenized Mn catalyst. When H2O2 is used as the oxidant, this material can catalyze the vicinal cis-dihydroxylation of disubstituted olefins, as shown schematically here. Both enantiomers of the product are obtained. 相似文献
109.
110.