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81.
Glansdorp FG Spandl RJ Swatton JE Loiseleur O Welch M Spring DR 《Organic & biomolecular chemistry》2008,6(22):4120-4124
The antibacterial drug azithromycin has clinically beneficial effects at sub-inhibitory concentrations for the treatment of conditions characterized by chronic Pseudomonas aeruginosa infection, such as cystic fibrosis. These effects are, in part, the result of inhibition of bacterial biofilm formation. Herein, the efficient synthesis of azithromycin in 4 steps from erythromycin and validation of the drug's ability to inhibit biofilm formation at sub-MIC (minimum inhibitory concentration) values are reported. Furthermore, the synthesis of immobilized and biotin-tagged azithromycin analogues is described. These chemical probes were used in pull-down assays in an effort to identify azithromycin's binding partners in vivo. Results from these assays revealed, as expected, mainly ribosomal-related protein binding partners, suggesting that this is the primary target of the drug. This was further confirmed by studies using a P. aeruginosa strain containing plasmid-encoded ermC, which expresses a protein that modifies 23S rRNA and so blocks macrolide entry to the ribosome. In this strain, no biofilm inhibition was observed. This work supports the hypothesis that the sub-inhibitory effects of azithromycin are mediated through the ribosome. Moreover, the synthesis of these chemical probes, and proof of their utility, is of value in global target identification in P. aeruginosa and other species. 相似文献
82.
Jalal Ghilane Olivier Fontaine Pascal Martin Jean-Christophe Lacroix Hyacinthe Randriamahazaka 《Electrochemistry communications》2008,10(8):1205-1209
The electrochemical reduction of noble metal electrodes in the presence of redox ionic liquid, 1-ferrocenylethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, [FcEMIM][TFSI], was investigated by cyclic voltammetry. Our experiments suggest the formation of metal with negative oxidation states, in the cases of platinum and gold electrodes [Mn−, FcEMIM+]. By analogy with the previous work, the formation of these phases is concomitant with the insertion of the supporting electrolyte; which correspond in our experimental condition to the redox cation of the ionic liquid. As an exciting result, the electrochemical investigations of the reduced electrode in electrolytic solution, containing solvent and supporting electrolyte, evidence the presence of the ferrocene groups at the electrode surface. Moreover, the reduced electrode exhibits the presence of the ferrocene even after, contact with air, after ultrasound, and after physical polishing, highlighting the large stability of this organo-metallic phases formed in this media. The AFM investigations demonstrate the morphological change of the platinum surface after the reduction process. Finally, our works bring a formal electrochemical proof of the presence of the ionic liquid cation inside the electrode material after the cathodic treatment in this media. 相似文献
83.
Water-in-Oil high internal phase emulsions (HIPEs) whose continuous phase is polymerizable gave access to highly porous polymeric
materials (polyHIPEs). These emulsions were prepared with a laboratory-made homogenizer whose shear frequency and time could
be varied to study the influence of the emulsification conditions on the polyHIPEs morphology. Intensive and/or long shear
induced a reduction of the cell and connection diameters without any modification of the material global porosity. The mechanical
properties were evaluated by estimating the Young’s modulus from compression tests. The mechanical behavior was analogous
for all materials possessing a characteristic polyHIPE structure, even if cell sizes were different between samples. 相似文献
84.
Baker KL Stappaerts EA Gavel D Wilks SC Tucker J Silva DA Olsen J Olivier SS Young PE Kartz MW Flath LM Kruelevitch P Crawford J Azucena O 《Optics letters》2004,29(15):1781-1783
Results of atmospheric propagation for a high-speed, large-actuator-number adaptive optics system are presented. The system uses a microelectromechanical system- (MEMS-) based spatial light modulator correction device with 1024 actuators. Tests over a 1.35-km path achieved correction speeds in excess of 800 Hz and Strehl ratios close to 0.5. The wave-front sensor was based on a quadrature interferometer that directly measures phase. This technique does not require global wave-front reconstruction, making it relatively insensitive to scintillation and phase residues. The results demonstrate the potential of large-actuator-number MEMS-based spatial light modulators to replace conventional deformable mirrors. 相似文献
85.
Rotthaus O Thomas F Jarjayes O Philouze C Saint-Aman E Pierre JL 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(26):6953-6962
The two tetradentate ligands H(2)L and H(2)L(Me) afford the slightly distorted square-planar low-spin Ni(II) complexes 1 and 2, which comprise two coordinated phenolate groups. Complex 1 has been electrochemically oxidized into 1(+), which contains a coordinated phenoxyl radical, with a contribution from the nickel orbital. In the presence of pyridine, 1(+) is converted into 1(Py) (+), an octahedral phenolate nickel(III) complex with two pyridines axially coordinated: An intramolecular electron transfer (valence tautomerism) is promoted by the geometrical changes, from square planar to octahedral, around the metal center. The tetradentate ligand H(2)L(Me), in the presence of pyridine, and the hexadentate ligand H(2)L(Py) in CH(2)Cl(2) afford, respectively, the octahedral high-spin Ni(II) complexes 2(Py) and 3, which involve two equatorial phenolates and two axially coordinated pyridines. At 100 K, the one-electron-oxidized product 2(Py) (+) comprises a phenoxyl radical ferromagnetically coupled to the high-spin Ni(II) ion, with large zero-field splitting parameters, while 3(+) involves a phenoxyl radical antiferromagnetically coupled to the high-spin Ni(II) ion. 相似文献
86.
Johannes Karges Uttara Basu Olivier Blacque Hui Chao Gilles Gasser 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(40):14472-14478
The use of photodynamic therapy (PDT) to treat cancer has received increasing attention over the last years. However, the clinically used photosensitisers (PSs) have some limitations that include poor aqueous solubility, hepatotoxicity, photobleaching, aggregation, and slow clearance from the body, so the design of new classes of PSs is of great interest. We present the use of bis(dipyrrinato)zinc(II) complexes with exceptionally long lifetimes as efficient PDT PSs. Based on the heavy‐atom effect, intersystem crossing of these complexes changes the excited state from singlet to a triplet state, thereby enabling singlet oxygen generation. To overcome the limitation of quenching effects in water and improve water solubility, the lead compound 3 was encapsulated in a polymer matrix. It showed impressive phototoxicity upon irradiation at 500 nm in various monolayer cancer cells as well as 3D multicellular tumour spheroids, without observed dark toxicity. 相似文献
87.
Cerruti CD Touboul D Guérineau V Petit VW Laprévote O Brunelle A 《Analytical and bioanalytical chemistry》2011,401(1):75-87
Mass spectrometry imaging of lipids using MALDI–TOF/TOF mass spectrometers is of growing interest for chemical mapping of
organic compounds at the surface of tissue sections. Many efforts have been devoted to the best matrix choice and deposition
technique. Nevertheless, the identification of lipid species desorbed from tissue sections remains problematic. It is now
well-known that protonated, sodium- and potassium-cationized lipids are detected from biological samples, thus complicating
the data analysis. A new sample preparation method is proposed, involving the use of lithium salts in the matrix solution
in order to simplify the mass spectra with only lithium-cationized molecules instead of a mixture of various cationized species.
Five different lithium salts were tested. Among them, lithium trifluoroacetate and lithium iodide merged the different lipid
adducts into one single lithium-cationized species. An optimized sample preparation protocol demonstrated that the lithium
trifluoroacetate salt slightly increased desorption of phosphatidylcholines. Mass spectrometry images acquired on rat brain
tissue sections by adding lithium trifluoroacetate showed the best results in terms of image contrast. Moreover, more structurally
relevant fragments were generated by tandem mass spectrometry when analyzing lithium-cationized species. 相似文献
88.
Bourlès E Isaac M Lebrun C Latour JM Sénèque O 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(49):13762-13772
The reactivity of a series of Zn(Cys)(4) zinc finger model peptides towards H(2)O(2) and O(2) has been investigated. The oxidation products were identified by HPLC and ESI-MS analysis. At pH<7.5, the zinc complexes and the free peptides are oxidised to bis-disulfide-containing peptides. Above pH 7.5, the oxidation of the zinc complexes by H(2)O(2) also yields sulfinate- and sulfonate-containing overoxidised peptides. At pH 7.0, monitoring of the reactions between the zinc complexes and H(2)O(2) by HPLC revealed the sequential formation of two disulfides. Several techniques for the determination of the rate constant for the first oxidation step corresponding to the attack of H(2)O(2) by the Zn(Cys)(4) site have been compared. This rate constant can be reliably determined by monitoring the oxidation by HPLC, fluorescence, circular dichroism or absorption spectroscopy in the presence of excess ethyleneglycol bis(2-aminoethyl ether)tetraacetic acid. In contrast, monitoring of the release of zinc with 4-(2-pyridylazo)resorcinol or of the thiol content with 5,5'-dithiobis(2-nitrobenzoate) did not yield reliable values of this rate constant for the case in which the formation of the second disulfide is slower than the formation of the first. The kinetic measurements clearly evidence a protective effect of zinc on the oxidation of the cysteines by both H(2)O(2) and O(2), which points to the fact that zinc binding diminishes the nucleophilicity of the thiolates. In addition, the reaction between the zinc finger and H(2)O(2) is too slow to consider zinc fingers as potential sensors for H(2)O(2) in cells. 相似文献
89.
NIR‐to‐NIR Two‐Photon Scanning Laser Microscopy Imaging of Single Nanoparticles Doped by YbIII Complexes 下载免费PDF全文
Dr. Adrien Bourdolle Dr. Anthony D'Aléo Dr. Cécile Philippot Dr. Patrice L. Baldeck Dr. Yannick Guyot Dr. Fabien Dubois Dr. Alain Ibanez Dr. Chantal Andraud Dr. Sophie Brasselet Dr. Olivier Maury 《Chemphyschem》2016,17(1):128-135
The photophysical and nonlinear optical properties of water‐soluble chromophore‐functionalised tris‐dipicolinate complexes [LnL3]3? (Ln=Yb and Nd) are thoroughly studied, revealing that only the YbIII luminescence can be sensitized by a two‐photon excitation process. The stability of the complex in water is strongly enhanced by embedding in dispersible organosilicate nanoparticles (NPs). Finally, the spectroscopic properties of [NBu4]3[YbL3] are studied in solution and in the solid state. The high brightness of the NPs allows imaging them as single objects using a modified two‐photon microscopy setup in a NIR‐to‐NIR configuration. 相似文献
90.
Thirion D Poriel C Métivier R Rault-Berthelot J Barrière F Jeannin O 《Chemistry (Weinheim an der Bergstrasse, Germany)》2011,17(37):10272-10287
Two series of DiSpiroFluorene-IndenoFluorene (DSF-IF) positional isomers, namely dispiro[2,7-diarylfluorene-9',6,9',12-indeno[1,2-b]fluorenes], (1,2-b)-DSF-IFs 1 and dispiro[2,7-diarylfluorene-9',6,9',12-indeno[2,1-a]fluorenes], (2,1-a)-DSF-IFs 2 have been synthesized. These violet-to-blue fluorescent emitters possess a 3π-2spiro architecture, which combines via two spiro links two different indenofluorene cores, that is, (1,2-b)-IF or (2,1-a)-IF and 2,7-substituted-diaryl-fluorene units. Due to their different geometric profiles, the two families of positional isomers present drastically different properties. The marked difference observed between the properties of (1,2-b)-DSF-IF (1) and (2,1-a)-DSF-IF (2) is discussed in terms of intramolecular π-π interactions occurring in (2,1-a)-DSF-IF (2) leading to conformationally-controllable intramolecular excimer formation. Indeed, the original geometry of the (2,1-a)-DSF-IF (2) family, with face-to-face "aryl-fluorene-aryl" moieties, leads to remarkable excimer emission through intramolecular π-π interactions in the excited state. Furthermore, the emission wavelengths can be gradually modulated by the control of the steric hindrance between the adjacent substituted phenyl rings. Thus, through a comparative and detailed study of the (1)H NMR, electrochemical and photophysical properties of DSF-IFs 1 and 2, we have evidenced the intramolecular π-π interactions occurring between the two "aryl-fluorene-aryl" moieties in the ground state and in the excited state. These properties have been finally correlated to the spectacular conformational change modeled by density functional theory (DFT) calculations. Indeed, the two "aryl-fluorene-aryl" moieties switch from a staggered conformation in the ground state to an eclipsed conformation in the first excited state. 相似文献