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排序方式: 共有520条查询结果,搜索用时 15 毫秒
91.
Andreiadis ES Imbert D Pécaut J Demadrille R Mazzanti M 《Dalton transactions (Cambridge, England : 2003)》2012,41(4):1268-1277
Two tridentate pyridine-tetrazolate ligands (H(2)pytz and H(2)pytzc), analogues of the well-known dipicolinate (H(2)dpa) ligand, have been synthesized in a straightforward manner and used for lanthanide(III) coordination. The structures of the resulting tris-ligand complexes were determined in solution ((1)H-NMR), where they remain undissociated, as well as in the solid state (X-ray diffraction). The solubility of these anionic complexes can be easily tuned by changing the countercation. The bis-tetrazolate-pyridine ligand H(2)pytz sensitizes very efficiently both the visible and near-IR emission of the lanthanides, with unusually high luminescence quantum yields in solid state (61% and 65% for Eu and Tb, respectively, and 0.21% for Nd) and in water (63% for Tb and 18% for Eu). Furthermore, the absorption window of the complexes is significantly extended towards the visible region up to 330 nm. The results show that the bis-tetrazolate-pyridine ligand provides a very attractive alternative to the classic dipicolinate ligand. 相似文献
92.
Renaud Millet 《Tetrahedron letters》2009,50(26):3474-1750
The desymmetrization of oxabenzonorbornadienes with aluminum reagents and SimplePhos as chiral ligand is described. The corresponding homoallylic alcohols are obtained in high yield, diastereoselectivity, and enantiomeric excess. Furthermore the first anti enantioselective desymmetrization with aromatic nucleophiles is reported. 相似文献
93.
Renaud Belin Monique Tillard Laure Monconduit 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(3):267-268
In iron tridecazinc, the FeZn13 unit cell contains two Zn12 icosahedra which are Fe‐centred and two Zn2 dumb‐bells coordinated by eight icosahedra. Zn12 icosahedra form chains along the c axis by vertex‐sharing, and are further interlinked through octahedra‐sharing and vertex‐to‐vertex bonds. 相似文献
94.
95.
Sharon Curtis Justin Renaud John L. Holmes Paul M. Mayer 《Journal of the American Society for Mass Spectrometry》2010,21(11):1944-1946
A brief search in Sci Finder for oxalic acid and oxalates will reward the researcher with a staggering 129,280 hits. However,
the generation of alkali metal and silver anions via collision-induced dissociation of the metal oxalate anion has not been
previously been reported, though Tian and coworkers recently investigated the dissociation of lithium oxalate [18]. The exothermic
decomposition of alkali metal oxalate anion to carbon dioxide in the collision cell of a triple quadrupole mass spectrometer
leaves no place for the electron to reside, resulting in a double electron-transfer reaction to produce an alkali metal anion.
This reaction is facilitated by the negative electron affinity of carbon dioxide and, as such, the authors believe that metal
oxalates are potentially unique in this respect. The observed dissociation reactions for collision with argon gas (1.7−1.8
× 10−3 mbar) for oxalic acid and various alkali metal oxalates are discussed and summarized. Silver oxalate is also included to
demonstrate the propensity of this system to generate transition-metal anions, as well. 相似文献
96.
A. Zebda L. Renaud M. Cretin F. Pichot C. Innocent R. Ferrigno S. Tingry 《Electrochemistry communications》2009,11(3):592-595
A Y-shaped microfluidic channel is applied for the first time to the construction of a glucose/O2 biofuel cell, based on both laminar flow and biological enzyme strategies. During operation, the fuel and oxidant streams flow parallel at gold electrode surfaces without convective mixing. At the anode, the glucose oxidation is performed by the enzyme glucose oxidase whereas at the cathode, the oxygen is reduced by the enzyme laccase, in the presence of specific redox mediators. Such cell design protects the anode from an interfering parasite reaction of O2 at the anode and offers the advantage of using different streams of oxidant and fuel for optimal performance of the enzymes. Electrochemical characterizations of the device show the influence of the flow rate on the output potential and current density. The maximum power density delivered by the assembled biofuel cell reached 110 μW cm?2 at 0.3 V with 10 mM glucose at 23 °C. The microfluidic approach reported here demonstrates the feasibility of advanced microfabrication techniques to build an efficient microfluidic glucose/O2 biofuel cell device. 相似文献
97.
Baruah M Qin W Flors C Hofkens J Vallée RA Beljonne D Van der Auweraer M De Borggraeve WM Boens N 《The journal of physical chemistry. A》2006,110(18):5998-6009
Steady-state and time-resolved fluorescence techniques have been used to study the photophysical properties of the fluorescent BODIPY-derived dye 3-{2-[4-(dimethylamino)phenyl]ethenyl}-4,4-difluoro-8-(4-methoxyphenyl)-1,5,7-trimethyl-3a,4a-diaza-4-bora-s-indacene. This compound has been synthesized via a microwave-assisted condensation of p-N,N-dimethylaminobenzaldehyde with the appropriate 1,3,5,7-tetramethyl substituted borondipyrromethene unit. The fluorescence properties of the dye are strongly solvent dependent: increasing the solvent polarity leads to lower fluorescence quantum yields and lifetimes, and the wavelength of maximum fluorescence emission shifts to the red. The Catalán solvent scales are found to be the most suitable for describing the solvatochromic shifts of the fluorescence emission. These are dominated by polarity/polarizability effects, as confirmed by quantum-chemical calculations performed in the dielectric continuum approximation. Fluorescence decay profiles of the dye can be described by a single-exponential fit in most solvents investigated, while two decay times are found in alcohols. The dye undergoes a reversible protonation-deprotonation reaction in the acidic pH range with a pK(a) of 2.25 in acetonitrile solution. Fluorimetric titrations as a function of pH produce fluorescence emission enhancements at lower pH. The fluorescence excitation spectra show a hypsochromic shift from 600 nm for the neutral amine to 553 nm for the ammonium form, so that ratiometric measurements can be used to determine pK(a). 相似文献
98.
Totally dissipative measures for the shift and conformal σ-finite measures for the stable holonomies
In this paper we investigate some results of ergodic theory with infinite measures for a subshift of finite type. We give
an explicit way to construct σ-finite measures which are quasi-invariant by the stable holonomy and equivalent to the conditional measures of some σ-invariant measure. These σ-invariant measures are totally dissipative, σ-finite but satisfy a Birkhoff Ergodic-like Theorem. The constructions are done for the symbolic case, but can be extended
for uniformly hyperbolic flows or diffeomorphisms. 相似文献
99.
Hania Hebbache Thomas Jerphagnon Christian Bruneau Jean-Luc Renaud 《Journal of organometallic chemistry》2010,695(6):870-874
β-Aminoesters were prepared in two simple steps from β-ketoesters derivatives and primary amines under mild conditions. Their hydrogenation was performed at 50 °C in the presence of several organometallic catalysts under acidic conditions. The new β-N-substituted aminoesters were isolated in moderate to good yields. 相似文献
100.
1H NMR-based metabolomics approach for exploring urinary metabolome modifications after acute and chronic physical exercise 总被引:1,自引:0,他引:1
C. Enea F. Seguin J. Petitpas-Mulliez N. Boildieu N. Boisseau N. Delpech V. Diaz M. Eugène B. Dugué 《Analytical and bioanalytical chemistry》2010,396(3):1167-1176
Metabolomics is a comprehensive method for metabolite assessment that involves measuring the overall metabolic signature of
biological samples. We used this approach to investigate biochemical changes due to acute and chronic physical exercise. Twenty-two
women using identical oral contraceptives were segregated into an untrained (n = 10) or trained (n = 12) group depending on their physical training background. The subjects performed two exercises in a randomized order:
a prolonged exercise test (75% of their
\mathop V· \textO2 max \mathop V\limits^\cdot {{\text{O}}_{2\,\;\max }} until exhaustion) and a short-term, intensive exercise test (short-term, intensive exercise anaerobic test). Urine specimens
were collected before and 30 min after each test. The samples were analyzed by 1H NMR spectroscopy, and multivariate statistical techniques were utilized to process the data. Distinguishing characteristics
were observed only in the urine profiles of specimens collected before vs. 30 min after the short-term, intensive exercise
test. The metabolites responsible for such changes were creatinine, lactate, pyruvate, alanine, β-hydroxybutyrate, acetate,
and hypoxanthine. In both groups, the excretion of lactate, pyruvate, alanine, β-hydroxybutyrate, and hypoxanthine increased
similarly after the completion of the short-term, intensive exercise test (p < 0.03). However, acetate excretion increased to a lesser extent in trained than in untrained subjects (p < 0.05). In conclusion, metabolomics is a promising tool in order to gain insight into physiological status and to clarify
the changes induced by short-term, intense physical exercise. 相似文献