全文获取类型
收费全文 | 334篇 |
免费 | 4篇 |
国内免费 | 1篇 |
专业分类
化学 | 188篇 |
晶体学 | 1篇 |
力学 | 17篇 |
数学 | 69篇 |
物理学 | 64篇 |
出版年
2021年 | 4篇 |
2020年 | 6篇 |
2019年 | 4篇 |
2018年 | 5篇 |
2017年 | 3篇 |
2016年 | 12篇 |
2015年 | 7篇 |
2014年 | 12篇 |
2013年 | 14篇 |
2012年 | 34篇 |
2011年 | 33篇 |
2010年 | 22篇 |
2009年 | 13篇 |
2008年 | 25篇 |
2007年 | 36篇 |
2006年 | 26篇 |
2005年 | 12篇 |
2004年 | 11篇 |
2003年 | 13篇 |
2002年 | 20篇 |
2001年 | 4篇 |
1999年 | 2篇 |
1998年 | 2篇 |
1997年 | 3篇 |
1995年 | 1篇 |
1994年 | 5篇 |
1993年 | 1篇 |
1987年 | 3篇 |
1985年 | 3篇 |
1980年 | 1篇 |
1978年 | 1篇 |
1977年 | 1篇 |
排序方式: 共有339条查询结果,搜索用时 31 毫秒
81.
Hélène Vallette Gérard Coquerel Jean-Christophe Plaquevent 《Tetrahedron letters》2004,45(8):1617-1619
We demonstrate that chemical peptide coupling using modern coupling agents is efficient in rt ionic liquids. This new approach presents some advantages, especially in the case of hindered amino acids, which are not easy to couple under standard conditions, since high purities for the crude peptides were observed with respect to coupling in classical solvents. 相似文献
82.
Chiche L Heitz A Gelly JC Gracy J Chau PT Ha PT Hernandez JF Le-Nguyen D 《Current protein & peptide science》2004,5(5):341-349
In this article, we will first introduce the squash inhibitor, a well established family of highly potent canonical serine proteinase inhibitors isolated from Cucurbitaceae. The squash inhibitors were among the first discovered proteins with the typical knottin fold shared by numerous peptides extracted from plants, animals and fungi. Knottins contain three knotted disulfide bridges, two of them arranged as a Cystine-Stabilized Beta-sheet motif. In contrast to cyclotides for which no natural linear homolog is known, most squash inhibitors are linear. However, Momordica cochinchinensis Trypsin Inhibitor-I and (MCoTI-I and -II), 34-residue squash inhibitors isolated from seeds of a common Cucurbitaceae from Vietnam, were recently shown to be macrocyclic. In these circular squash inhibitors, a short peptide linker connects residues that correspond to the N- and C-termini in homologous linear squash inhibitors. In this review we present the isolation, characterization, chemical synthesis, and activity of these macrocyclic knottins. The solution structure of MCoTI-II will be compared with topologically similar cyclotides, homologous linear squash inhibitors and other knottins, and potential applications of such scaffolds will be discussed. 相似文献
83.
Current efforts devoted to the synthesis of Bafilomycin A(1) led us to investigate a synthetic route through a spiroketal intermediate for the construction of the C15-C25 subunit. Preliminary studies for the diastereoselective installation of the methyl-16 cis with respect to the vicinal OH-15 group through radical opening of either siloxafuran intermediate 7 or cyclopropyl compounds 9 and 13 have been carried out using model compounds derived from commercial Indalone 6. In each case the expected "cis" diastereoisomer was obtained in good to excellent yield. Application of these results to Bafilomycin A(1) synthon led to the opposite "trans" stereoselectivity when alpha-carboxy- or alpha-keto-substituted spiroketals 4 or 19 were used. However, the expected potential intermediate has been obtained from the alpha-hydroxymethyl cyclopropanated synthon 21. A Barton-Motherwell xanthate radical deoxygenation-cylopropane opening methodology, followed by a hydroboration-oxidation of the exovinylic intermediate, delivered the expected product 22cis in high yield and excellent stereoselectivity. 相似文献
84.
Highly chemoselective hydrogenolysis of iodoarenes 总被引:1,自引:0,他引:1
Faucher N Ambroise Y Cintrat JC Doris E Pillon F Rousseau B 《The Journal of organic chemistry》2002,67(3):932-934
The catalytic hydrodehalogenation reaction using molecular hydrogen and Pd/C has been revisited. It is shown that the speed of removal of halogen increases with increasing electronegativity I < Br < Cl. Nevertheless, selective dehydrohalogenation in compounds containing other reducible functions can be achieved only with iodine and not with bromine or chlorine. Selective deiodination of iodobenzophenone could be accomplished without reducing the carbonyl group. Hydrogenolysis of azidoiodoaromatic compounds to the corresponding azido compounds is high yielding. This selectivity was exploited for the labeling of benzophenone- and azido-containing compounds by deuterium and tritium. 相似文献
85.
Fontaine O Ghilane J Martin P Lacroix JC Randriamahazaka H 《Langmuir : the ACS journal of surfaces and colloids》2010,26(23):18542-18549
The electrochemical reduction of 4-nitrophenyl diazonium, NPD, in different ionic liquids presenting different viscosities has been investigated. The electrochemical studies show that the reduction of diazonium leading to the formation of its corresponding radical occurs whatever the viscosity of the grafting media. Following that, the presence of an organic layer attached to the electrode after electrochemical treatment was evidenced by cyclic voltammetry (CV) in acidic media thanks to the presence of nitro groups. Moreover, infrared spectroscopy (IR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) confirm the presence of a nitrophenyl (NP) layer attached to the electrode material. Next, the examination of the electrochemical data through the measurement of the charge, corresponding to the reduction of the attached nitrophenyl (NP) moieties, shows that the surface concentration of NP, Γ(NP), decreases when the viscosity, η, of the grafting media increases. Additionally, in the case of the more viscous ionic liquid, N-tributyl-N-methylammonium bis(trifluoromethylsulfonyl)imide [Bu(3)MeN] [NTf(2)], a cosolvent has been added leading to fine decrease of the viscosity. The IR and CV investigations of the modified electrodes demonstrate the decrease of the amount of the attached molecules when the viscosity of the grafting media increases. In addition, a correlation between Γ(NP) as function of 1/η was observed. Finally, XPS and AFM experiments lead to an estimate of the thickness of the attached layer. As a result, both methods are in perfect agreement and thicknesses of 4 and 1 nm are measured after grafting in acetonitrile and in pure ionic liquid [Bu(3)MeN] [NTf(2)], respectively. By comparison with classical solvent, the use of viscous ionic liquid for the grafting leads to a decrease in the amount of the attached molecules and conduce to the formation of thinner or less dense layer. 相似文献
86.
Florent Hivert Jean-Christophe Novelli Lenny Tevlin Jean-Yves Thibon 《Selecta Mathematica, New Series》2009,15(1):105-119
We prove conjectures of the third author [L. Tevlin, Proc. FPSAC’07, Tianjin] on two new bases of noncommutative symmetric
functions: the transition matrices from the ribbon basis have nonnegative integral coefficients. This is done by means of
two composition-valued statistics on permutations and packed words, which generalize the combinatorics of Genocchi numbers.
相似文献
87.
Binet C Bourrier D Dilhan M Estève D Ferrère S Garrigue JC Granier H Lattes A Gué AM Mauzac M Mingotaud AF 《Talanta》2006,69(3):757-762
Liquid crystalline thin films elastomers that are able to bind pesticides have been developed. The synthesis involves grafting mesogen and crosslinkable groups on a polysiloxane chain in the presence of a template molecule. The molecular imprinted material is obtained after thin film deposition, UV crosslinking and washing. Experiments of readsorption of pesticide are presented. Development of a multisensor platform based on thermal and capacitive sensors is described and tests of deposition of the polymer film are presented. 相似文献
88.
Florent Hivert Jean-Christophe Novelli Jean-Yves Thibon 《European Journal of Combinatorics》2010,31(1):29-33
We give a combinatorial formula for the inverses of the alternating sums of free quasi-symmetric functions of the form where I runs over compositions with parts in a prescribed set C. This proves in particular three special cases (no restriction, even parts, and all parts equal to 2) which were conjectured by B.C.V. Ung in [B.C.V. Ung, Combinatorial identities for series of quasi-symmetric functions, in: Proc. FPSAC’08, Toronto, 2008]. 相似文献
89.
Jean-Christophe Breton 《Journal of Theoretical Probability》2010,23(1):21-38
We investigate the regularity of shot noise series and of Poisson integrals. We give conditions for the absolute continuity
of their law with respect to the Lebesgue measure and for their continuity in total-variation norm. In particular, the case
of truncated series in addressed. Our method relies on a disintegration of the probability space based on a mere conditioning
by the first jumps of the underlying Poisson process. 相似文献
90.