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671.
Jian Ming Yu Dominique Teyssie Sylvie Boileau 《Journal of polymer science. Part A, Polymer chemistry》1993,31(9):2373-2381
Hydrosilylation of allyl carbamates by poly(methylhydrosiloxane) (PMHS) catalyzed by platinum- or rhodium-based complexes was investigated. About 10% of the carbamate molecules decompose during the hydrosilylation reaction through the cleavage of the carbamate bond. A redistribution process also takes place among the polysiloxane chains resulting in the formation of branched polymers but no crosslinking occurs. A mechanism for this side-reaction is proposed. © 1993 John Wiley & Sons, Inc. 相似文献
672.
P. Genard 《Magnetic resonance in chemistry : MRC》1979,12(7):396-398
Hydroxylation of saturated steroids such as androstane and pregnane results in appreciable aromatic solvent shifts for the 18- and 19-methyl protons. Solvent shifts associated with hydroxyl and/or carbonyl groups are in general approximately additive. 相似文献
673.
Tatiana E. Itina Karine Gouriet Sylvie Noël Marc Sentis 《Applied Surface Science》2007,253(19):7656-7661
The mechanisms involved into the formation of clusters by pulsed laser ablation are studied both numerically and experimentally. To facilitate the model validation by comparison with experimental results, the time and length scales of the simulation are considerably increased. This increase is achieved by using a combination of molecular dynamics (MD) and the direct simulation Monte Carlo (DSMC) methods. The combined MD-DSMC model is then used to compare the relative contribution of the two channels of the cluster production by laser ablation: (i) direct cluster ejection upon the laser-material interaction, and (ii) collisional sticking and aggregation in the ablated gas flow. Calculation results demonstrate that both of these mechanisms play a role. The initial cluster ejection provides cluster precursors thus eliminating the three-body collision bottleneck in the cluster growth process. The presence of clusters thus facilitates the following collisional condensation and evaporation processes. The rates of these processes become considerable, leading to the modification of not only the plume cluster composition, but also the dynamics of the plume expansion. Calculation results explain several recent experimental findings. 相似文献
674.
Electrical behaviour of catalytic nanostructured CeO2/CuOx composites under air-methane gas impulses
Sébastien Saitzek Sylvie Villain Jean Raymond Gavarri 《Applied Surface Science》2007,253(18):7490-7496
Nanostructured composites based on copper oxide and cerium dioxide phases [CuO-CeO2] were elaborated from sol-gel route, with weight fractions of CuO phase ranging between 0 and 0.4. They are interesting potential catalysts allowing conversion of CH4 and CO into CO2 and H2O and might be used in miniaturized gas sensors. An electrical study of this nanostructured system was carried out to determine catalytic behaviours under air-methane impulses at 350 °C. The electrical analysis was based on a specific homemade electronic device. Time dependent interactions between gas pulses and solid catalyst (CuO/CeO2) were analyzed from a frequency modification of the electronic device. Kinetic parameters were determined from a model describing adsorption and desorption of gases adapted to short interaction time between gas and solid. These time dependent electrical behaviours were then correlated with infrared spectroscopy analyses allowing time dependent analysis of methane conversion into CO2 gas, for long interaction time between gas and solid. 相似文献
675.
We provide local expressions for Chern–Weil type forms built from superconnections associated with families of Dirac operators previously investigated in [S. Scott, Zeta–Chern forms and the local family index theorem, Trans. Amer. Math. Soc. (in press). arXiv: math.DG/0406294] and later in [S. Paycha, S. Scott, Chern–Weil forms associated with superconnections, in: B. Booss-Bavnbeck, S. Klimek, M. Lesch, W. Zhang (Eds.), Analysis, Geometry and Topology of Elliptic Operators, World Scientific, 2006]. 相似文献
676.
Ccile Martias Nadine Baroukh Sylvie Mavel Hlne Blasco Antoine Lefvre La Roch Frdric Montigny Julie Gatien Laurent Schibler Diane Dufour-Rainfray Lydie Nadal-Desbarats Patrick Emond 《Molecules (Basel, Switzerland)》2021,26(14)
Currently, most clinical studies in metabolomics only consider a single type of sample such as urine, plasma, or feces and use a single analytical platform, either NMR or MS. Although some studies have already investigated metabolomics data from multiple fluids, the information is limited to a unique analytical platform. On the other hand, clinical studies investigating the human metabolome that combine multi-analytical platforms have focused on a single biofluid. Combining data from multiple sample types for one patient using a multimodal analytical approach (NMR and MS) should extend the metabolome coverage. Pre-analytical and analytical phases are time consuming. These steps need to be improved in order to move into clinical studies that deal with a large number of patient samples. Our study describes a standard operating procedure for biological specimens (urine, blood, saliva, and feces) using multiple platforms (1H-NMR, RP-UHPLC-MS, and HILIC-UHPLC-MS). Each sample type follows a unique sample preparation procedure for analysis on a multi-platform basis. Our method was evaluated for its robustness and was able to generate a representative metabolic map. 相似文献
677.
Shuffle Relations for Regularised Integrals of Symbols 总被引:1,自引:1,他引:0
We prove shuffle relations which relate a product of regularised integrals of classical symbols to regularised nested iterated integrals:
where Σ
k
is the group of permutations over k elements. We show that these shuffle relations hold if all the symbols σ
i
have vanishing residue; this is true of non-integer order symbols on which the regularised integrals have all the expected
properties such as Stokes’ property [MMP]. In general the shuffle relations hold up to finite parts of corrective terms arising
from a renormalisation on tensor products of classical symbols, a procedure adapted from renormalisation methods to compute
Feynman diagrams familiar to physicists. We relate the shuffle relations for regularised integrals of symbols with shuffle
relations for multiple zeta functions adapting the above constructions to the case of a symbol on the unit circle. 相似文献
678.
The title compounds were synthesized by radical cyclization of the corresponding stilbenes intermediates. The latter ones arose from a Wittig reaction in a stereoselective manner (Z isomer is either the only one or the major one). Confusarin (1) was prepared in 13 steps from gallic acid. Its regioisomer (2) was obtained in five steps from syringaldehyde. 相似文献
679.
Chevolleau S Jacques C Canlet C Tulliez J Debrauwer L 《Journal of chromatography. A》2007,1167(2):125-134
The determination of biomarkers of acrylamide exposure in humans from general French population by measurement of hemoglobin adduct levels of acrylamide (AA) and glycidamide (GA) is presented. The analytical procedure included modified Edman degradation and LC-ESI-MS/MS analysis of the final derivatives using deuterated internal standards. Method performances were evaluated in terms of linearity, precision, accuracy, and sensitivity. The method was firstly assessed on rat blood samples and then applied to the study of background adducts levels of AA and GA in 68 human hemoglobin samples, showing mean levels of 33 and 23 pmol/g globin for AA and GA adducts, respectively. 相似文献
680.
A Bayesian network (BN) is a knowledge representation formalism that has proven to be a promising tool for analyzing gene expression data. Several problems still restrict its successful applications. Typical gene expression databases contain measurements for thousands of genes and no more than several hundred samples, but most existing BNs learning algorithms do not scale more than a few hundred variables. Current methods result in poor quality BNs when applied in such high-dimensional datasets. We propose a hybrid constraint-based scored-searching method that is effective for learning gene networks from DNA microarray data. In the first phase of this method, a novel algorithm is used to generate a skeleton BN based on dependency analysis. Then the resulting BN structure is searched by a scoring metric combined with the knowledge learned from the first phase. Computational tests have shown that the proposed method achieves more accurate results than state-of-the-art methods. This method can also be scaled beyond datasets with several hundreds of variables. 相似文献