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131.
Z-configured 1,4-diene or β, γ-unsaturated carbonyl systems are readily available by the Wittig reaction. Isomerization required for access into the E-series can easily be accomplished by irradiation using an ordinary tungsten lamp and diphenyl disulphide sensitizer. There is very little formatation of conjugated isomers (less than 1%). 相似文献
132.
Suni NM Lindfors P Laine O Ostman P Ojanperä I Kotiaho T Kauppila TJ Kostiainen R 《Analytica chimica acta》2011,699(1):73-80
We have studied the matrix effect within direct analysis of benzodiazepines and opioids from urine with desorption electrospray ionization-mass spectrometry (DESI-MS) and desorption atmospheric pressure photoionization-mass spectrometry (DAPPI-MS). The urine matrix was found to affect the ionization mechanism of the opioids in DAPPI-MS favoring proton transfer over charge exchange reaction. The sensitivity for the drugs in solvent matrix was at the same level with DESI-MS and DAPPI-MS (LODs 0.05–6 μg mL−1) but the decrease in sensitivity due to the urine matrix was higher with DESI (typically 20–160-fold) than with DAPPI (typically 2–15-fold) indicating better matrix tolerance of DAPPI over DESI. Also in MS/MS mode, DAPPI provided better sensitivity than DESI for the drugs in urine. The feasibility of DAPPI-MS/MS was then studied in screening the same drugs from five authentic, forensic post mortem urine samples. A reference measurement with gas chromatography-mass spectrometry (GC–MS) (including pretreatment) revealed 16 findings from the samples, whereas with DAPPI-MS/MS after sample pretreatment, 15 findings were made. Sample pretreatment was found necessary, since only eight findings were made from the same samples untreated. 相似文献
133.
For the first time, the equilibrium composition of chemical dissociation-recombination reaction is simulated from first-principles, only. Furthermore, beyond the conventional ab initio Born-Oppenheimer quantum chemistry the effects from the thermal and quantum equilibrium dynamics of nuclei are consistently included, as well as, the nonadiabatic coupling between the electrons and the nuclei. This has been accomplished by the path integral Monte Carlo simulations for full NVT quantum statistics of the H(3)(+) ion. The molecular total energy, partition function, free energy, entropy, and heat capacity are evaluated in a large temperature range: from below room temperature to temperatures relevant for planetary atmospheric physics. Temperature and density dependent reaction balance of the molecular ion and its fragments above 4000 K is presented, and also the density dependence of thermal ionization above 10,000 K is demonstrated. 相似文献
134.
Nordman N Sikanen T Moilanen ME Aura S Kotiaho T Franssila S Kostiainen R 《Journal of chromatography. A》2011,1218(5):739-745
Monolithically integrated, polymer (SU-8) microchips comprising an electrophoretic separation unit, a sheath flow interface, and an electrospray ionization (ESI) emitter were developed to improve the speed and throughput of metabolism research. Validation of the microchip method was performed using bufuralol 1-hydroxylation via CYP450 enzymes as the model reaction. The metabolite, 1-hydroxybufuralol, was easily separated from the substrate (R(s)=0.5) with very good detection sensitivity (LOD=9.3nM), linearity (range: 50-500nM, r(2)=0.9997), and repeatability (RSD(Area)=10.3%, RSD(Migrationtime)=2.5% at 80nM concentration without internal standard). The kinetic parameters of bufuralol 1-hydroxylation determined by the microchip capillary electrophoresis (CE)-ESI/mass spectrometry (MS) method, were comparable to the values presented in literature as well as to the values determined by in-house liquid chromatography (LC)-UV. In addition to enzyme kinetics, metabolic profiling was demonstrated using authentic urine samples from healthy volunteers after intake of either tramadol or paracetamol. As a result, six metabolites of tramadol and four metabolites of paracetamol, including both phase I oxidation products and phase II conjugation products, were detected and separated from each other within 30-35s. Before analysis, the urine samples were pre-treated with on-chip, on-line liquid-phase microextraction (LPME) and the results were compared to those obtained from urine samples pre-treated with conventional C18 solid-phase extraction (SPE, off-chip cartridges). On the basis of our results, the SU-8 CE-ESI/MS microchips incorporating on-chip sample pre-treatment, injection, separation, and ESI/MS detection were proven as efficient and versatile tools for drug metabolism research. 相似文献
135.
A very efficient technique to drastically reduce the number of multipliers and adders in narrow transition-band linear-phase
finite-impulse response digital filters is to use the one-stage or multistage frequency-response masking (FRM) approach, which
has been originally introduced by Lim and further improved by Lim and Lian. In these original synthesis techniques, the subfilters
in the overall implementation are separately designed. As shown earlier by the authors of this contribution together with
Johansson, the arithmetic complexity in one-stage FRM filter designs can be considerably reduced by using the following two-step
technique for simultaneously optimizing all the subfilters. First, a suboptimal solution is found by using a simple design
scheme. Second, this solution is used as a start-up solution for further optimization, which is carried out with the aid of
an efficient nonlinear optimization algorithm. This paper exploits this approach to synthesizing multistage FRM filters. An
example taken from the literature illustrates that both the number of multipliers and the number of adders for the resulting
optimized multistage FRM filters are approximately 70 percent compared with those of the filters synthesized using the original
multistage FRM filter design schemes. Additional examples are included in order to show the benefits provided by the proposed
synthesis scheme over other recently published design techniques, in terms of an improved performance of the resulting solution,
a higher accuracy of the solution, and a faster speed required to arrive at the best solution. 相似文献
136.
Kortelainen J Väyrynen E Seppänen T 《IEEE transactions on bio-medical engineering》2011,58(5):1216-1223
General anesthesia is usually induced with a combination of drugs. In addition to the hypnotic agent, such as propofol, opioids are often used due to their synergistic hypnotic and analgesic properties. However, the effects of opioids on the EEG changes and the clinical state of the patient during anesthesia are complex and hinder the interpretation of the EEG-based depth of anesthesia indexes. In this paper, a novel technology for separating the anesthetic effects of propofol and an ultrashort-acting opioid, remifentanil, using the spectral features of EEG is proposed. By applying a floating search method, a well-performing feature set is achieved to estimate the effects of propofol during induction of anesthesia and to classify whether or not remifentanil has been coadministered. It is shown that including the detection of the presence of opioids to the estimated effect of propofol significantly improves the determination of the clinical state of the patient, i.e., if the patient will respond to a painful stimulation. 相似文献
137.
Kauppila TJ Kotiaho T Kostiainen R Bruins AP 《Journal of the American Society for Mass Spectrometry》2004,15(2):203-211
The ionization mechanism in the novel atmospheric pressure photoionization mass spectrometry (APPI-MS) in negative ion mode was studied thoroughly by the analysis of seven compounds in 17 solvent systems. The compounds possessed either gas-phase acidity or positive electron affinity, whereas the solvent systems had different polarities and gas-phase acidities and some of them positive electron affinities. The analytes that possessed gas-phase acidity formed deprotonated ions in proton transfer; in addition, fragments and solvent adducts were observed. The compounds of positive electron affinity formed negative molecular ions by electron capture or charge exchange and substitution products of form [M - X + O](-) by substitution reactions. The efficiency of deprotonation was decreased if the solvent used possessed higher gas-phase acidity than the analyte. Solvents of positive electron affinity captured thermal electrons and deteriorated the ionization of all the analytes. Also, the proportion of substitution products was affected by the solvent. Finally, the performances of negative ion APPI and negative ion APCI were compared. The sensitivity for the studied compounds was better in APPI, but the formation of substitution products was lower in APCI. 相似文献
138.
Multi-centered nature of adsorption as well as adsorbate-adsorbate interactions is addressed. A discussed reaction mechanism includes adsorption of a bulky molecule A, which requires several sites for adsorption, and two successive reaction steps of Eley type. Numerical treatment is performed for a special case of this mechanism. 相似文献
139.
Lasse-Pekka Tiainen P?ivi M?ki-Arvela Ahmad Kalantar Neyestanaki Tapio Salmi Dmitry Yu. Murzin 《Reaction Kinetics and Catalysis Letters》2003,78(2):251-257
Selective hydrogenation of citral was investigated at 70 °C over Ru/Al2O3. Activity changes in a series of consecutive experiments were described by a mathematical model, which included reaction
kinetics and deactivation.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
140.