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81.
M. Assunta Girasolo Patrizia Portanova Giuseppe Ruisi 《Journal of organometallic chemistry》2010,695(4):609-3579
Novel diorganotin(IV) derivatives of l-Arginine (HArg), Nα-(tert-Butoxycarbonyl)-l-Arginine (Boc-Arg-OH) and l-Ala-l-Arg (H2Ala-Arg), H2NC(NH)NH(CH2)3CH(NHR′)CO2H, where R′ = H in HArg, R′ = C(O)OC(CH3)3 in Boc-Arg-OH, R′ = H2NCH(CH3)CO in H2Ala-Arg and triorganotin(IV) derivatives of Boc-Arg-OH have been synthesized and structurally characterized. The complexes were investigated by FT-IR and 119Sn Mössbauer in the solid state and by 1H, 13C, 119Sn and 1H-1H COSY NMR spectroscopy, in solution. The spectroscopic characterization leading to the proposed molecular structures was accomplished on the basis of these experiments. l-Arginine appears to behave as a chelating ligand through carboxylate and -NH2 groups in Me2Sn(Arg)2, while in Nα-t-Boc-l-Arginine complex, the Nα-protected amino group being exempted from coordination, only the carboxylate groups are effectors of bonding to the organometallic moieties. FT-IR spectra give a clear indication that guanidino groups in all the complexes are not involved in coordination, since ν(CN-H) frequency of the terminal guanidino group is fairly constant and unshifted relative to the free ligand. The biological activity of organotin(IV)-complexes was also investigated by use of human HT29 colorectal carcinoma cells. The cytotoxic activity of the compounds was determined by the MTT quantitative colorimetric assay, capable of detecting viable cells in comparison with that exerted by cisplatin. A marked cytotoxic activity for nearly all complexes, is evident being higher than that exerted by cisplatin, while no significant improvement of activity was observed for Me2Sn(Arg)2 and Me2Sn(Ala-Arg), which was confirmed by IC50 values. Then, we assessed whether the cytotoxicity induced by organotin(IV) complexes was associated with the induction of apoptosis. Light microscopy analysis, performed to study the morphological changes induced in HT29 cells, confirmed the results obtained with MTT test. No significant morphological alterations were observed in HT29 cells after treatment with Me2Sn(Ala-Arg) and Me2Sn(l-Arg)2. Cells treated with nBu2Sn(Boc-Arg)2, nBu2Sn(Ala-Arg), nBu3Sn(Boc-Arg) and Me3Sn(Boc-Arg), appeared rounded, isolated and detached from culture substrate, indicating the commitment to apoptotic cell death. 相似文献
82.
Mahelet Aweke Tadesse Carlo Galli Patrizia Gentili 《Journal of Physical Organic Chemistry》2011,24(7):529-538
The aminoxyl radical 6‐trifluoromethyl‐benzotriazol‐N‐oxyl (TFNO) has been generated from the parent hydroxylamine 6‐CF3‐1‐hydroxy‐benzotriazole (TFBT) by one‐electron oxidation with a CeIV salt and characterized by spectrophotometry and cyclic voltammetry (CV). Rate constants of H‐abstraction (kH) by TFNO from a number of H‐donor benzylic substrates have been determined spectrophotometrically in MeCN solution at 25 °C. A radical H‐atom transfer (HAT) route of oxidation is substantiated for TFNO by several pieces of evidence. The kinetic data also testify the relevance of stereoelectronic effects upon the HAT reactivity of TFNO. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
83.
Kanishka Perera Patrizia Pucci Csaba Varga 《NoDEA : Nonlinear Differential Equations and Applications》2014,21(3):441-451
We consider a nonlinear eigenvalue problem under Robin boundary conditions in a domain with (possibly noncompact) smooth boundary. The problem involves a weighted p–Laplacian operator and subcritical nonlinearities satisfying Ambrosetti–Rabinowitz type conditions. Using Morse theory and a cohomological local splitting as in Degiovanni et al. (Commun Contemp Math 12:475–486, 2010), we prove the existence of a nontrivial weak solution for all (real) values of the eigenvalue parameter. Our result is new even in the semilinear case p = 2 and complements some recent results obtained in Autuori et al. (Adv Anal Equ 18:1–48, 2013). 相似文献
84.
This paper deals with the problem of scenario tree reduction for stochastic programming problems. In particular, a reduction method based on cluster analysis is proposed and tested on a portfolio optimization problem. Extensive computational experiments were carried out to evaluate the performance of the proposed approach, both in terms of computational efficiency and efficacy. The analysis of the results shows that the clustering approach exhibits good performance also when compared with other reduction approaches. 相似文献
85.
86.
Patrizia Ferraboschi Maria De Mieri Fiorella Galimberti 《Tetrahedron: Asymmetry》2010,21(17):2136-2141
The (S)-2-chlorophenylglycine moiety is well recognized in the structure of (S)-clopidogrel, a known antithrombotic drug. We prepared an enantiomerically pure chiral building block via an enzyme-catalyzed resolution of (RS)-N-Boc-2-chlorophenylglycine methylester. The best results were obtained by means of an immobilized subtilisin, the cross-linked enzyme aggregate (Alcalase-CLEA®). The high enantiomeric excess of the synthon obtained remained the same over the course of clopidogrel synthesis; the simplicity of the process makes this pathway suitable for large-scale preparation. 相似文献
87.
A classical system for the preparation of carbonyl compounds from alkenes relies upon ozonolysis of the double bond, followed by reductive cleavage of the ozonide so formed. Among the reagents of choice for such a reduction, triphenylphosphine certainly has enjoyed a widespread use.1 However, in spite of the simplicity of the method, often one can face problems in the purification of the carbonyl compound from unreacted triphenylphosphine, especially if the polarities of both products are very similar. We have encountered such a problem during the preparation of the (20 S)-6β -ethoxy-3 α, 5-cyclo-5α -pregnane-20-carbaldehyde 4 from the suitably protected stigmasterol32. In this case, when triphenylphosphine was used for reduction of ozonide we never could isolate the aldehyde 2 uncontaninated by tripherylphosphine. 相似文献
88.
Margherita Bernardeschi Patrizia Guidi Vittoria Scarcelli Giada Frenzilli Marco Nigro 《Analytical and bioanalytical chemistry》2010,396(2):619-623
Titanium dioxide is extensively used in a variety of products, including industrial materials and cosmetics. Studies mainly
performed on human cell lines and in vivo exposure on experimental animals have raised concern about the toxic effects of
ultrafine titanium dioxide; however, scarce information is available about its impact on aquatic life. The aim of this article
was to assess the genotoxic potential of TiO2 (anatase and rutile) on bottlenose dolphin leukocytes. Blood samples were obtained from four male and one female specimens
reared at the Adriatic SeaWorld “Oltremare” (Riccione, Italy). Leukocytes were isolated by the lyses procedure and in vitro
exposed to TiO2 in RPMI. Experimental solutions were sonicated immediately before dosing the cells. Three exposure times (4, 24 and 48 h)
and three doses (20, 50 and 100 μg/ml) were tested. Genotoxicity was detected by the single-cell gel electrophoresis (or comet
assay) at pH ≥ 13, assessing single/double-strand breaks and alkali-labile sites. Cytotoxicity was also detected by the Trypan
blue exclusion method. Results showed that both the crystalline forms of TiO2 were genotoxic for bottlenose dolphin leukocytes, with a statistically significant increase of DNA fragmentation after exposure
to 50 and 100 μg/ml for 24 and 48 h. Although preliminary, these are the first data regarding the genetic susceptibility of
toothed cetaceans toward an “emerging” pollutant, such as TiO2 particles. 相似文献
89.
Patrizia Di Gennaro Silvana Bernasconi Fulvia Orsini Erika Corretto Guido Sello 《Tetrahedron: Asymmetry》2010,21(15):1885-1889
The use of two oxidoreductases (an aldoketo reductase from Escherichia coli JM109 and an alcohol dehydrogenase from Lactobacillus brevis) has demonstrated that it is possible to prepare enatiomerically pure diols in a one-pot operation. The reactions were applied to the synthesis of (1R)-1-[3-(hydroxymethyl)phenyl]ethanol and (1S)-1-phenylethane-1,2-diol, using a two-step procedure. The yield is nearly quantitative and the enantiomeric purity is greater than 95%. A third step has been introduced by adding a cell biocatalyst showing dihydrodiol dehydrogenase activity from Pseudomonas fluorescens N3. This allows for the preparation of 3-[(1R)-1-hydroxyethyl]benzoic acid and (2S)-hydroxy(phenyl)ethanoic acid. 相似文献
90.