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131.
Chovelon JM Grabchev I 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2007,67(1):87-91
A newly synthesized bis-1,8-naphthalimide aimed to increase its fluorescence intensity in the presence of protons or metal cations has been investigated. Its spectral photophysical characteristics in acetonitrile and chloroform solutions are described. The influence of metal cations (Zn(2+), Ni(2+), Ce(3+), Co(2+), Cu(2+) and Ag(+)) and protons on the fluorescence intensity has been investigate with regard to obtain fluorescence sensors for this ions in the environment. 相似文献
132.
Hodgson DM Chung YK Nuzzo I Freixas G Kulikiewicz KK Cleator E Paris JM 《Journal of the American Chemical Society》2007,129(14):4456-4462
Lithium 2,2,6,6-tetramethylpiperidide (LTMP)-induced intramolecular cyclopropanation of unsaturated terminal epoxides provides an efficient and completely stereoselective entry to bicyclo[3.1.0]hexan-2-ols and bicyclo[4.1.0]heptan-2-ols. Further elaboration of C-5 and C-6 stannyl-substituted bicyclo[3.1.0]hexan-2-ols via Sn-Li exchange/electrophile trapping or Stille coupling generates a range of substituted bicyclic cyclopropanes. An alternative straightforward cyclopropanation protocol using a catalytic amount of 2,2,6,6-tetramethylpiperidine (TMP) allows for a convenient (1 g-7.5 kg) synthesis of bicyclo[3.1.0]hexan-2-ol and other bicyclic adducts. The synthetic utility of this chemistry has been demonstrated in a concise asymmetric synthesis of (+)-beta-cuparenone. The related unsaturated chlorohydrins also undergo intramolecular cyclopropanation via in situ epoxide formation. 相似文献
133.
This communication presents an instrumental development based on the printed circuit board (PCB) technology to integrate electrochemiluminescence (ECL) analysis in microfluidic systems. PCB gold macro- (10 mm2) and micro- (0.09 mm2) electrodes and two ECL microfluidic devices are designed, fabricated and tested via luminol ECL detection. Potential modulation is performed between 0.7 and 0 V vs. Ag/AgCl for luminol oxidation, thus giving rise to on/off ECL responses in the presence of hydrogen peroxide. Synchronous detection is adopted to allow weak ECL signal recovery at a very low signal-to-noise ratio (SNR). The detection limit obtained with the two ECL microfluidic devices is 50 nM and 100 nM H2O2 for macroelectrodes and microelectrodes, respectively. 相似文献
134.
Strong ion-exchange centrifugal partition chromatography as an efficient method for the large-scale purification of glucosinolates 总被引:1,自引:0,他引:1
The glucosinolates sinalbin and glucoraphanin were purified by strong ion-exchange displacement centrifugal partition chromatography (SIXCPC). The optimized conditions involved the biphasic solvent system ethyl acetate/n-butanol/water (3:2:5, v/v), the lipophilic anion-exchanger Aliquat 336 (trioctylmethylammonium chloride, 160 and 408 mM) and a sodium iodide solution (80 and 272 mM) as displacer. Amounts as high as 2.4 g of sinalbin and 2.6g of glucoraphanin were obtained in one step in 2.5 and 3.5h respectively, starting from 12 and 25 g of mustard and broccoli seed aqueous extracts, using a laboratory scale CPC column (200 mL inner volume). 相似文献
135.
Crystalle Chardet Corinne Payrastre Batrice Gerland Jean-Marc Escudier 《Molecules (Basel, Switzerland)》2021,26(19)
Many strategies have been developed to modulate the biological or biotechnical properties of oligonucleotides by introducing new chemical functionalities or by enhancing their affinity and specificity while restricting their conformational space. Among them, we review our approach consisting of modifications of the 5’-C-position of the nucleoside sugar. This allows the introduction of an additional chemical handle at any position on the nucleotide chain without disturbing the Watson–Crick base-pairing. We show that 5’-C bromo or propargyl convertible nucleotides (CvN) are accessible in pure diastereoisomeric form, either for nucleophilic displacement or for CuAAC conjugation. Alternatively, the 5’-carbon can be connected in a stereo-controlled manner to the phosphate moiety of the nucleotide chain to generate conformationally constrained nucleotides (CNA). These allow the precise control of the sugar/phosphate backbone torsional angles. The consequent modulation of the nucleic acid shape induces outstanding stabilization properties of duplex or hairpin structures in accordance with the preorganization concept. Some biological applications of these distorted oligonucleotides are also described. Effectively, the convertible and the constrained approaches have been merged to create constrained and convertible nucleotides (C2NA) providing unique tools to functionalize and stabilize nucleic acids. 相似文献
136.
Jean-Marc Richard 《Few-Body Systems》2009,45(1):65-70
A new investigation is done of the possibility of binding the “dodecatoplet”, a system of six top quarks and six top antiquarks,
(t
6
t̄
6), using the Yukawa potential mediated by Higgs exchange. A simple variational method gives a upper bound close to that recently
estimated in a mean-field calculation. It is supplemented by a lower bound provided by identities among the Hamiltonians describing the system and its subsystems. 相似文献
137.
Amor Ben Ali Jean-Marc Grenche Marc Leblanc Vincent Maisonneuve 《Solid State Sciences》2009,11(9):1631-1638
The hydrothermal synthesis, using tris-(2-ethylamino)amine (tren) as a template, and the crystal structures of three new hybrid iron fluorides, (H3O)2·[H3tren]2·(FeF6)2·(FeF5(H2O))·2H2O (I), [H3tren]2·(FeF6)2·(FeF2(H2O)4)·8H2O (II) and [H3tren]2·(FeF6)·(F)3·H2O (III), are reported. I, II, and III are triclinic (P-1), monoclinic (P21/c) and orthorhombic (I222), respectively. The structure of I is built up from isolated FeF6 and FeF5(H2O) distorted octahedra separated by triprotonated [H3tren]3+ cations, disordered H3O+ cations and H2O molecules. In II, FeIIIF6 and neutral [FeIIF2(H2O)4] octahedra form, together with [H3tren]3+ cations, infinite (100) layers separated by extra water molecules. The structure of III consists of isolated and disordered FeF6 octahedra, fluoride anions F− connected to [H3tren]3+ cations and extra fluoride anions F− disordered with H2O molecules. All [H3tren]3+ cations have a “spider” type conformation. 57Fe Mössbauer characterization shows that +III valence state can only be considered for iron cations in I and III and preliminary Mössbauer results are consistent with the presence of both +II and +III valences for iron cations in II, in agreement with the crystallographic results. 相似文献
138.
We prove two related results. The first is an “earthquake theorem” for closed hyperbolic surfaces with cone singularities
where the total angle is less than π: any two such metrics in are connected by a unique left earthquake. The second result
is that the space of “globally hyperbolic” AdS manifolds with “particles” – cone singularities (of given angle) along time-like
lines – is parametrized by the product of two copies of the Teichmüller space with some marked points (corresponding to the
cone singularities). The two statements are proved together.
F.B. was partially supported by the A.N.R. project GEODYCOS. J.-M.S. was partially supported by the A.N.R. programs RepSurf,
2006-09, ANR-06-BLAN-0311, GeomEinstein, 2006-09, 06-BLAN-0154, and FOG, 2007-10, ANR-07-BLAN-0251-01. 相似文献
139.
The Central Limit Theorem for the random walk on a stationary random network of conductances has been studied by several authors. In one dimension, when conductances and resistances are integrable, and following a method of martingale introduced by S. Kozlov (1985), we can prove the Quenched Central Limit Theorem. In that case the variance of the limit law is not null. When resistances are not integrable, the Annealed Central Limit Theorem with null variance was established by Y. Derriennic and M. Lin (personal communication). The quenched version of this last theorem is proved here, by using a very simple method. The similar problem for the continuous diffusion is then considered. Finally our method allows us to prove an inequality for the quadratic mean of a diffusion. To cite this article: J. Depauw, J.-M. Derrien, C. R. Acad. Sci. Paris, Ser. I 347 (2009). 相似文献
140.
Emerenciano VP Alvarenga SA Scotti MT Ferreira MJ Stefani R Nuzillard JM 《Analytica chimica acta》2006,579(2):217-226
Feed-forward neural networks (FFNNs) were used to predict the skeletal type of molecules belonging to six classes of terpenoids. A database that contains the 13C NMR spectra of about 5000 compounds was used to train the FFNNs. An efficient representation of the spectra was designed and the constitution of the best FFNN input vector format resorted from an heuristic approach. The latter was derived from general considerations on terpenoid structures. 相似文献