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841.
Sanz D Pérez-Torralba M Alarcón SH Claramunt RM Foces-Foces C Elguero J 《The Journal of organic chemistry》2002,67(5):1462-1471
To study systems able to sustain intramolecular proton-transfer, we have prepared a series of six aminofulvene aldimines including several labeled with (15)N and (2)H. These compounds show coupling constants through the hydrogen bond, (1h)J((15)N- (1)H) and (2h)J((15)N-(15)N). The position of the tautomeric equilibria, i.e., on what nitrogen atom is the proton, was determined in the solid state and in solution. The crystal structure of N[[5-[(phenylamino)methylene]-1,3-cyclopentadien-1-yl]methylene]pyrrole-1-amine (3) has been determined by X-ray analysis. In solution, both N-H and C-H tautomers were observed and their structures assigned by NMR spectroscopy. Particularly useful is the value of the (1)J((15)N-(1)H) coupling constant. 相似文献
842.
Albrecht H Zbinden P Rizzi A Villetti G Riccardi B Puccini P Catinella S Imbimbo BP 《Combinatorial chemistry & high throughput screening》2004,7(8):745-756
A cell-based assay using homogeneous time-resolved fluorescence has been developed for high throughput screening of putative beta-amyloid (Abeta)production inhibitors. In this assay, total Abeta is detected by simply adding two commercially available antibody complexes. The first was a biotinylated monoclonal antibody (4G8), specifically recognizing an epitope comprising the residues 17-24 of the Abetapeptide, complexed with europium cryptate-streptavidin conjugate. The second was a polyclonal antibody (BioS-N), raised against the N-terminus of the Abeta peptide, complexed with an allophycocyanin-anti rabbit antibody conjugate. Binding of the two complexes to the Abeta peptide brought europium cryptate (fluorescence donor) and allophycocyanin (fluorescence acceptor) into close proximity, consequently a fluorescent resonance energy transfer signal was produced upon excitation at 337 nm. The resulting fluorescence signal (665 nm) was then detected using a Discovery or a ViewLux reader. Detection of Abeta by the proposed method is possible at concentrations of approximately 1 nM. The method was employed for the detection of Abeta secreted from a stable transfected human neuroglioma cell line (H4) overexpressing a mutated form of the human amyloid precursor protein (APP695NL) and developed for robotic automation. At optimized conditions, signal-to-background ratios exceeding 5 and Z' factors around 0.7 were achieved in a 384-well format. High throughput screening of 56,913 potential Abeta production inhibitors led to identification of new non-cytotoxic and cell permeable compounds with potencies in the submicromolar range. 相似文献
843.
In this paper isothermal, isoperibolic and adiabatic calorimeters and a Power-Compensating DSC are compared by determining kinetic data of a simple test reaction. First, the kinetic parameters were analyzed using a conventional isothermal method, based on the analytic determination of the course of reaction. Subsequently, the kinetic data of the performed reaction were determined for the different types of calorimeters by simultaneously evaluating several measurements with identical initial conditions but different temperature courses. The kinetic parameters obtained by the different calorimeters agree reasonable well, indicating the reliability of kinetic data derived from thermokinetic methods.The authors are thankful for the financial support by the Department of Education and Research of the Federal Republic of Germany (BMBF). 相似文献
844.
Arroyo Maribel Bernès Sylvain Meléndez Lidia Richards Raymond L. Torrens Hugo 《Transition Metal Chemistry》2001,26(6):608-612
Treatment of the coordinative unsaturated complexes [M(SRF)3(PMe2Ph)2] (M = Os or Ru; RF = C6F5 or C6F4H-4) with MS2Z (M = Na, S2Z = S2CNEt2; M = K, S2Z = S2COEt) and [Os(SRF)3(PMe2Ph)2] (RF = C6F5 or C6F4H-4) with MS2Z [M = Na; S2Z = S2P(OEt)2] in Me2CO solution, gave the paramagnetic OsIII and RuIII derivatives, [M(SRF)2(S2Z)(PMe2Ph)2]. X-ray crystallography shows that [Os(SC6F5)2(S2CNEt2)(PMe2Ph)2] has an octahedral geometry with trans-fluorothiolates, cis-phosphines and a chelating N,N-diethyldithiocarbamate ligand. 相似文献
845.
Débora de Oliveira Irajá do Nascimento Filho Marco di Luccio Carina Faccio Clarissa Dalla Rosa João Paulo Bender Nádia Lipke Cristiana Amroginski Cláudio Dariva José Vladimir de Oliveira 《Applied biochemistry and biotechnology》2005,121(1-3):231-241
This work investigated the production of fatty acid ethyl esters (FAEEs) from soybean oil using n-hexane as solvent and two commercial lipases as catalysts, Novozym 435 and Lipozyme IM. A Taguchi experimental design was
adopted considering the variables temperature (35–65°C), addition of water (0–10 wt/wt%), enzyme (5–20 wt/wt%) concentration,
and oil-to-ethanol molar ratio (1:3–1:10). It is shown that complete conversion in FAEE is achieved for some experimental
conditions. The effects of process variables on reaction conversion and kinetics of the enzymatic reactions are presented
for all experimental conditions investigated in the factorial design. 相似文献
846.
Summary The pentafluorophenylthiolate anion [C6F5S]– reacts with chloro-bridged binuclear complexes of RuII, RhI and PdII to give the compounds [(N-N)(PPh3)2Ru(SC6F5)]2Cl2 (1) (N-N = bipyridine), [LRh(SC6F5)]n (L = cycloocta-1,5-diene (2) or norbornadiene (3), n = 2 and L = dicyclopentadiene (4) for which n is probably 4), [(PPh3)Pd(SC6F5)Cl]2 (5) and (MeS-CHMeCHMeSMe)Pd(SC6F5), (6).19F n.m.r. spectroscopy shows a variable number of isomers depending on the compound considered. 相似文献
847.
Liliana Mogni Hugo Ascolani Mario S. Moreno Alberto Caneiro 《Journal of solid state chemistry》2005,178(5):1559-1568
The crystal chemistry, electronic structure, and electrical and magnetic properties of the novel perovskite-related nickel oxides Sr3Fe2−xNixO7−δ with 0?x?1.0 have been studied. X-ray diffraction and selected area electron diffraction (ED) data indicate that the samples have a tetragonal (Space group I4/mmm) structure. ED patterns and high-resolution images reveal the presence of a regular stacking along the c-axis for the x=1.0 sample. The lattice parameters, oxygen content, and average oxidation state of iron and nickel decrease with increasing Ni content. The electronic structure of the x=1.0 sample was studied by M 2p X-ray photoelectron spectroscopy (XPS). An analysis of the spectra using the cluster model indicates that this material is in the negative charge-transfer regime and the ground state is dominated by the 3dn+1L configuration with 2p holes (L) in the oxygen band. The insulator states are stabilized due to a p-p type band gap that arises because the p-d transfer integral Tσ dominates over the O 2p bandwith. Although magnetic measurements reveal the presence of ferromagnetic interactions that lead to magnetic frustration at , no long-range magnetic order was observed for the samples with x?0.3. The electrical resistivity decreases with increasing Ni content as the p-p band gap tend to close due to the reduction of the Tσ value. Negative magnetoresistance (∼−24% for x=0.6 and −7% for x=1.0 at 20 K and 9 T) was observed for the Ni containing samples. 相似文献
848.
Optimization of alkaline transesterification of soybean oil and castor oil for biodiesel production 总被引:3,自引:0,他引:3
Débora de Oliveira Marco Di Luccio Carina Faccio Clarissa Dalla Rosa João Paulo Bender Nádia Lipke Cristiana Amroginski Cláudio Dariva José Vladimir de Oliveira 《Applied biochemistry and biotechnology》2005,122(1-3):553-560
This article reports experimental data on the production of fatty acid ethyl esters from refined and degummed soybean oil
and castor oil using NaOH as catalyst. The variables investigated were temperature (30–70°C), reaction time (1–3 h), catalyst
concentration (0.5–1.5 w/wt%), and oil-to-ethanol molar ratio (1:3–1:9). The effects of process variables on the reaction
conversion as well as the optimum experimental conditions are presented. The results show that conversions >95% were achieved
for all systems investigated. In general, an increase in reaction temperature, reaction time, and in oil-to-ethanol molar
ratio led to an enhancement in reaction conversion, whereas an opposite trend was verified with respect to catalyst concentration. 相似文献
849.
Bravo M Lespes G De Gregori I Pinochet H Gautier MP 《Analytical and bioanalytical chemistry》2005,383(7-8):1082-1089
A method based on Headspace solid-phase microextraction (HS-SPME, with a 100 μm PDMS-fiber) in combination with gas-chromatography
and pulsed flame-photometric detection (GC-PFPD) has been investigated for simultaneous determination of eight organotin compounds.
Monobutyltin (MBT), dibutyltin (DBT), tributyltin (TBT), monophenyltin (MPhT), and the semi-volatile diphenyltin (DPhT), triphenyltin
(TPhT), monooctyltin (MOcT), and dioctyltin (DOcT) were determined after derivatization with sodium tetraethylborate. The
conditions used for the extraction and preconcentration step were optimised by experimental design methodology. Tripropyltin
(TPrT) and diheptyltin (DHepT) were used as internal standards for quantification of volatile and semi-volatile organotin
compounds, respectively. The analytical precision (RSD) for ten successive injections of a standard mixture containing all
the organic tin compounds ranged between 2 and 11%. The limits of detection for all the organotin compounds were sub ng (Sn)
L−1 in water and close to ng (Sn) kg−1 in sediments. The accuracy of the method was evaluated by analysis of two certified reference material (CRM) sediment samples.
The HS-SPME–GC–PFPD was then applied to the analysis of three harbour sediment samples. The results showed that headspace
SPME is an attractive tool for analysis of organotin compounds in solid environmental matrices. 相似文献
850.
Abstract
I measured the induction of cytosine-cytosine dimer (C-C) densities after UV-C (< 290 nm) and UV-B irradiation (290–320 nm) in the 2'-deoxy-[3 H]cytidine labeled DNA of Cloudman S91 mouse melanoma cells using a new, sensitive high pressure liquid chromatography procedure. UV-B exposure resulted in 0.000034% C-C/J m-2 of the total cytosine radioactivity which is 10 times less than the rate during UV-C irradiation. Previous work with these melanoma cells showed a 4-fold lower rate of induction of thymine-containing pyrimidine dimers by UV-B than UV-C light (Niggli Photochem. Photobiol . 52 , 519–524, 1990). Based on these results, the calculated ratios for the pyrimidine dimer subspecies showed no significant difference following UV-C and UV-B exposure. However, UV-C and UV-B light induce 10–20 times more thymine-containing pyrimidine dimers than C-C in the DNA of S91 cells. 相似文献
I measured the induction of cytosine-cytosine dimer (C-C) densities after UV-C (< 290 nm) and UV-B irradiation (290–320 nm) in the 2'-deoxy-[